AAS meeting, January 2010, Washington, DC
The Stellar Mass-Exoplanet Correlation
Kimberly Aller (University of California, Berkeley & IfA), J. Johnson (Caltech)

We have derived an empirical relation between stellar mass and planet occurrence by measuring the occurrence rate of planets from Doppler surveys spanning a wide range of stellar masses. We used Bayesian parameter estimation to fit a parametric model to the sample of detections and non-detections in our data set, while simultaneously correcting for the effects of metallicity. Remarkably, we find no correlation between stellar metallicity and planet occurrence for stars with masses greater than 1.5 M_sun. We see a slow increase in the measured planet occurrence for stars with masses less than 1.5 M_sun which rises steeply thereafter. There is a much higher chance of finding a gas giant planet around an A-type star, regardless of its metallicity, than around either an M-dwarf or Sun-like star.

DPS meeting, October 2009, Ithaca, NY
Detectability of Low-Mass Trojans in Transiting Systems Using Transit Timing Variations
Stephanie Capen (Eastern Nazarene College), N. Haghighipour (IfA & NASA astrobiology Institute, University of Hawai), S. Kirste (IfA & NASA astrobiology Institute, University of Hawai)

We present the results of a study of the feasibility of detecting small, terrestrial-sized planets in a transiting system consisting of a Jupiter-like planet and an M-dwarf using the variations in the transit timing of the larger body. Specifically, we studied the case where the two planets are in 1:1 mean-motion resonance. To determine the detectability of such Trojan planets, a number of systems with different masses, eccentricities, and periods were numerically integrated and the amplitudes of their TTV signals were calculated. Results indicate that Trojan planets in 3 to 10 day orbits and with eccentricities ranging from 0 to 0.15 have a high probability for detection. We present the results of our study and discuss the applicability of our analysis to the probability of the detection of such planets with the recently launched Kepler space telescope. Support for S.C. through the NSF funded REU program at the Institute for Astronomy, University of Hawaii is acknowledged.

AAS meeting, January 2010, Washington, DC
Color Analysis of Local (U)LIRGs
Michele Dufault (Yale University & IfA), D. Sanders (IfA), V. U (IfA & Harvard-Smithsonian Center for Astrophysics)

Luminous and ultra-luminous galaxies, galaxies with L_IR > 10¹¹L_sol and 10¹²L_sol respectively, are critical in understanding galaxy interaction and evolution; however, the local population (z < 0.088) as a class has been understudied. We present a color analysis of a subset of 22 local (U)LIRGs from the Great Observatory All-sky LIRG Survey (GOALS) sample. We examine the g – r color distribution for both global and localized regions within each system in order to understand what physical mechanisms give rise to the appearance and color of these sources. The 2 kpc regions surrounding the K-band centroid of each object are redder and optically fainter than the corresponding hosts, which are aligned with the luminous end of the blue cloud. We compare the total photometry colors with pipeline data from the SDSS archives and find the database color distribution to differ significantly. Finally, two color profiles of the ULIRGs Mrk 231, host of a known QSO, and Arp 220, host of a heavily obscured AGN, show that despite their differences, their host colors are very similar. This result suggests that the vast difference between the two objects might be dominated by the amount of dust obscuration in the central regions. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai’i’s Institute for Astronomy and funded by the NSF.

AAS meeting, January 2010, Washington, DC
Evidence for a Composite Starburst-AGN Class of Infrared Galaxies
Francesca Fornasini (College of William and Mary), L. J. Kewley (IfA)

In order to determine whether composite starburst-AGN galaxies demonstrate any radio properties distinct from starbursts and AGNs, we studied 156 infrared objects for which spectroscopic and VLBI or LBA radio data was available. We found that 19 of 28 (68%) optically classified AGN had a compact radio core, 16 of 55 (29%) optically classified starburst had a compact radio core, and only 8 of 52 (15%) optically classified composites had a compact radio core. Thus, there appears to be a depletion of compact radio cores among composites, an unexpected result considering that in previous classification schemes, composites were often classified as LINERs. We calculate that there is &lt
;1% chance that such an uneven distribution of compact radio cores would randomly occur if composites were AGNs, and that there is a 7% chance that this distribution would occur if composites were starbursts. The latter is a small but significant percentage, and it is probably a lower bound, considering that some of the optically classified starbursts with compact radio cores may actually be obscured AGN. In addition, we find that the compact radio core luminosity of composites tends to be in between that of starbursts and AGNs, supporting the hypothesis that composites may possess a mixture of starburst and AGN phenomena. Thus, these results, though not enough to decisively confirm the existence of composites as a distinct class, certainly lend support to such a conclusion, and suggest that composite galaxies may be an interesting area of future research. This research was undertaken at the Institute for Astronomy at the University of Hawaii as part of a Research Experience for Undergraduates (REU) program funded by the National Science Foundation.

American Geophysical Union, Fall Meeting 2009, San Francisco, California
Determining CME Azimuthal Properties from Stereoscopic Heliospheric Observations
N. Lugaz (IfA), J. N. Hernandez (Universidad de los Andes, Bogota, Colombia), I. I. Roussev (IfA), A. Vourlidas (Naval Research Laboratory, Washington, DC)

We discuss how remote-sensing observations by multiple white-light imagers can provide some information about the azimuthal deflection and azimuthal expansion of Coronal Mass Ejections (CMEs) as they propagate in the heliosphere. Our analysis focuses on one CME which was well observed by the SECCHI/HIs onboard STEREO-A and B on April 26-28, 2008. By considering two simple models of CME geometry and using simultaneous observations from the two different viewpoints, we show that the observations can be best understood by modeling the CME as a propagating sphere of expanding radius on a fixed radial trajectory. Preliminary analysis shows that the CME expansion is self-similar from 0.2 AU until 0.5 AU and slows down afterwards. An alternative explanation of the observations is a deflection towards the east of a bubble CME. While observational effects may play a role, the results from these two models are corroborated by the non-detection of the CME at L1, where a CME hit was expected based on its initial width and direction.

AAS meeting, May 2010, Miami, Florida
Double Lobed Radio Sources in Cl1604 at z~.9
Stephen Sirisky (Rutgers University), R. Gal (Institute for Astronomy)                 

We present findings from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) super cluster survey. The super cluster Cl1604 residing at z ~ 9 is one of only a few such large scale structures discovered at high redshift. The structure has been imaged in a variety of wavelengths, including radio, optical, infrared, and x-ray, and spectroscopic measurements have been taken using DEIMOS and LRIS on Keck. Using the 1.4 GHz VLA maps and HST optical imaging of Cl 1604 to visually inspect for double radio sources with associated optical host galaxies, we have confirmed three double lobed radio sources within the large scale structure. From the observations of these sources, we calculate radio luminosities and lobe separations using data from previously discovered double lobes at similar redshifts in the VVDS and FIRST surveys. Furthermore, we examine the host galaxy properties, including optical colors, morphologies, spectra, and each of their specific locations within the constituent cluster and the broader super cluster. Although the low number of sources limits statistical analysis, we find that the double lobes only appear in the large scale structure, and within the large scale structure only in areas of high galactic density.

AAS meeting, January 2010, Washington, DC
The Stellar Mass-Exoplanet Correlation
Kimberly Aller (University of California, Berkeley & IfA), J. Johnson (Caltech)
We have derived an empirical relation between stellar mass and planet occurrence by measuring the occurrence rate of planets from Doppler surveys spanning a wide range of stellar masses. We used Bayesian parameter estimation to fit a parametric model to the sample of detections and non-detections in our data set, while simultaneously correcting for the effects of metallicity. Remarkably, we find no correlation between stellar metallicity and planet occurrence for stars with masses greater than 1.5 M_sun. We see a slow increase in the measured planet occurrence for stars with masses less than 1.5 M_sun which rises steeply thereafter. There is a much higher chance of finding a gas giant planet around an A-type star, regardless of its metallicity, than around either an M-dwarf or Sun-like star.

DPS meeting, October 2009, Ithaca, NY
Detectability of Low-Mass Trojans in Transiting Systems Using Transit Timing Variations
Stephanie Capen (Eastern Nazarene College), N. Haghighipour (IfA & NASA astrobiology Institute, University of Hawai), S. Kirste (IfA & NASA astrobiology Institute, University of Hawai)
We present the results of a study of the feasibility of detecting small, terrestrial-sized planets in a transiting system consisting of a Jupiter-like planet and an M-dwarf using the variations in the transit timing of the larger body. Specifically, we studied the case where the two planets are in 1:1 mean-motion resonance. To determine the detectability of such Trojan planets, a number of systems with different masses, eccentricities, and periods were numerically integrated and the amplitudes of their TTV signals were calculated. Results indicate that Trojan planets in 3 to 10 day orbits and with eccentricities ranging from 0 to 0.15 have a high probability for detection. We present the results of our study and discuss the applicability of our analysis to the probability of the detection of such planets with the recently launched Kepler space telescope. Support for S.C. through the NSF funded REU program at the Institute for Astronomy, University of Hawaii is acknowledged.

AAS meeting, January 2010, Washington, DC
Color Analysis of Local (U)LIRGs
Michele Dufault (Yale University & IfA), D. Sanders (IfA), V. U (IfA & Harvard-Smithsonian Center for Astrophysics)
Luminous and ultra-luminous galaxies, galaxies with L_IR > 10¹¹L_sol and 10¹²L_sol respectively, are critical in understanding galaxy interaction and evolution; however, the local population (z < 0.088) as a class has been understudied. We present a color analysis of a subset of 22 local (U)LIRGs from the Great Observatory All-sky LIRG Survey (GOALS) sample. We examine the g – r color distribution for both global and localized regions within each system in order to understand what physical mechanisms give rise to the appearance and color of these sources. The 2 kpc regions surrounding the K-band centroid of each object are redder and optically fainter than the corresponding hosts, which are aligned with the luminous end of the blue cloud. We compare the total photometry colors with pipeline data from the SDSS archives and find the database color distribution to differ significantly. Finally, two color profiles of the ULIRGs Mrk 231, host of a known QSO, and Arp 220, host of a heavily obscured AGN, show that despite their differences, their host colors are very similar. This result suggests that the vast difference between the two objects might be dominated by the amount of dust obscuration in the central regions. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawai’i’s Institute for Astronomy and funded by the NSF.

AAS meeting, January 2010, Washington, DC
Evidence for a Composite Starburst-AGN Class of Infrared Galaxies
Francesca Fornasini (College of William and Mary), L. J. Kewley (IfA)
In order to determine whether composite starburst-AGN galaxies demonstrate any radio properties distinct from starbursts and AGNs, we studied 156 infrared objects for which spectroscopic and VLBI or LBA radio data was available. We found that 19 of 28 (68%) optically classified AGN had a compact radio core, 16 of 55 (29%) optically classified starburst had a compact radio core, and only 8 of 52 (15%) optically classified composites had a compact radio core. Thus, there appears to be a depletion of compact radio cores among composites, an unexpected result considering that in previous classification schemes, composites were often classified as LINERs. We calculate that there is <1% chance that such an uneven distribution of compact radio cores would randomly occur if composites were AGNs, and that there is a 7% chance that this distribution would occur if composites were starbursts. The latter is a small but significant percentage, and it is probably a lower bound, considering that some of the optically classified starbursts with compact radio cores may actually be obscured AGN. In addition, we find that the compact radio core luminosity of composites tends to be in between that of starbursts and AGNs, supporting the hypothesis that composites may possess a mixture of starburst and AGN phenomena. Thus, these results, though not enough to decisively confirm the existence of composites as a distinct class, certainly lend support to such a conclusion, and suggest that composite galaxies may be an interesting area of future research. This research was undertaken at the Institute for Astronomy at the University of Hawaii as part of a Research Experience for Undergraduates (REU) program funded by the National Science Foundation.

American Geophysical Union, Fall Meeting 2009, San Francisco, California
Determining CME Azimuthal Properties from Stereoscopic Heliospheric Observations
N. Lugaz (IfA), J. N. Hernandez (Universidad de los Andes, Bogota, Colombia), I. I. Roussev (IfA), A. Vourlidas (Naval Research Laboratory, Washington, DC)
We discuss how remote-sensing observations by multiple white-light imagers can provide some information about the azimuthal deflection and azimuthal expansion of Coronal Mass Ejections (CMEs) as they propagate in the heliosphere. Our analysis focuses on one CME which was well observed by the SECCHI/HIs onboard STEREO-A and B on April 26-28, 2008. By considering two simple models of CME geometry and using simultaneous observations from the two different viewpoints, we show that the observations can be best understood by modeling the CME as a propagating sphere of expanding radius on a fixed radial trajectory. Preliminary analysis shows that the CME expansion is self-similar from 0.2 AU until 0.5 AU and slows down afterwards. An alternative explanation of the observations is a deflection towards the east of a bubble CME. While observational effects may play a role, the results from these two models are corroborated by the non-detection of the CME at L1, where a CME hit was expected based on its initial width and direction. 

AAS meeting, May 2010, Miami, Florida
Double Lobed Radio Sources in Cl1604 at z~.9
Stephen Sirisky (Rutgers University), R. Gal (Institute for Astronomy)
We present findings from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) super cluster survey. The super cluster Cl1604 residing at z ~ 9 is one of only a few such large scale structures discovered at high redshift. The structure has been imaged in a variety of wavelengths, including radio, optical, infrared, and x-ray, and spectroscopic measurements have been taken using DEIMOS and LRIS on Keck. Using the 1.4 GHz VLA maps and HST optical imaging of Cl 1604 to visually inspect for double radio sources with associated optical host galaxies, we have confirmed three double lobed radio sources within the large scale structure. From the observations of these sources, we calculate radio luminosities and lobe separations using data from previously discovered double lobes at similar redshifts in the VVDS and FIRST surveys. Furthermore, we examine the host galaxy properties, including optical colors, morphologies, spectra, and each of their specific locations within the constituent cluster and the broader super cluster. Although the low number of sources limits statistical analysis, we find that the double lobes only appear in the large scale structure, and within the large scale structure only in areas of high galactic density. 

AAS Winter 2008, Austin
Implementation of the Pan-STARRS Image Processing Pipeline
Julia Fang (Northwestern University & IfA) and C. Aspin (IfA)

Pan-STARRS, or the Panoramic Survey Telescope and Rapid Response System, is a wide-field imaging facility that combines small mirrors with gigapixel cameras. It surveys the entire available sky several times a month, which ultimately requires large amounts of data to be processed and stored right away. Accordingly, the Image Processing Pipeline–the IPP–is a collection of software tools that is responsible for the primary image analysis for Pan-STARRS. It includes data registration, basic image analysis such as obtaining master images and detrending the exposures, mosaic calibration when applicable, and lastly, image sum and difference. In this paper I present my work of the installation of IPP 2.1 and 2.2 on a Linux machine, running the Simtest, which is simulated data to test your installation, and finally applying the IPP to two different sets of UH 2.2m Tek data. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

DPS October 2007 Orlando
Dynamical Stability of Terrestrial and Giant Planets in the HD 155358 Planetary System 
James Haynes (IfA)

We present the results of a study of the dynamical evolution and the habitability of the system HD 155358. This system is unique in that it is one of the two low metallicity stars discovered to host a multiple planet system. HD 155358 is host to two Jupiter-sized planets, with minimum masses of 0.86 and 0.50 Jupiter-masses. The orbit of the lower mass planet of this system is located at the inner edge of the system’s habitable zone. To determine whether this system can harbor terrestrial-type planets, we numerically integrated the orbits of its planets and an Earth-like object for different values of their masses and orbital eccentricities. Results indicate that this system could potentially host stable orbits for terrestrial-sized planets in its habitable zone, but the stability of these orbits is very sensitive to the precise characteristics of the giant planets of the system. We also studied the long term stability of larger bodies (Neptune- and Saturn-mass) in the system. Our results show that a Neptune- or Saturn-mass body could exist in stable orbits in this system fairly close in, potentially within the range of present detection techniques, again depending on the precise configurations of the giant planets.

AAS Winter 2008, Austin
Beryllium Abundances in Solar Mass Stars
Julie A. Krugler (Michigan State Univ) and A. M. Boesgaard  (IfA)

Light element abundance analysis allows for a deeper understanding of the chemical composition of a star beneath its surface. Beryllium provides a probe down to 3.5×10^6 K, where it fuses with protons. In this study, Be abundances were determined for 52 F and G dwarfs selected from a sample of local thin disc stars. These stars were selected by their mass to be in a mass range of 0.9 to 1.1 solar masses as determined by Lambert & Reddy (2004). They have effective temperatures from 5600 to 6400 K, and their metallicities [Fe/H] -0.65 to +0.11. The data were taken over several nights, with forty-six spectra taken with the Keck HIRES instrument and six spectra on the Canada France Hawaii Telescope (CFHT) using the Gecko spectrograph. The abundances were calculated via spectral synthesis, fitting a 4Å region around the resonance lines of Be II. The data were then analyzed to investigate the Be abundance as a function of age, temperature, and metallicity and its relation to the lithium abundance for this narrow mass range. Be is found to increase with metallicity and the linear relationship evident when extended to metallicities down to -4.0 dex with slope 0.86 ± 0.02. The relation of the Be abundance to effective temperature is dependent upon metallicity, but when metallicity effects are taken into account, there is a spread 1.2 dex. We find a 1.5 dex spread in A(Be) when plotted against age, with the largest spread occurring from 6-8 Gyr. The relation with Li is found to be linear with slope 0.36
± 0.06 for the temperature regime of 5900-6300 K. This research was conducted through the Research Experiences for Undergraduate (REU) program at the University of Hawaii’s Institute for Astronomy and was funded by the NSF.

AAS Winter 2008, Austin
Theoretical Mid-Infrared Modeling of Starburst Galaxies
Kirsten Larson (The College of Wooster) and L. Kewley (IfA)

We investigated the ability of the stellar models Starburst99 and MappingsIII to model starburst galaxies using infrared diagnostics and Spitzer data. The infrared diagnostics were useful for distinguishing between starforming galaxies and AGN. The theoretical starburst models indicate that the infrared emission-line ratios are largely degenerate and are extremely sensitive to the age of the stellar population and the star formation history prescription (instantaneous versus continuous). Additional information from the near-infrared or optical spectra are required to resolve the degeneracies encountered in the infrared emission-line ratios. This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS Winter 2008, Austin
Cloud Structure and the Origins of the Stellar Initial Mass Function in ρ Ophiuchus
Dylan R. Nelson (UC Berkeley & IfA), J. J. Swift (IfA), J. P. Williams (IfA)

We explore the relationship between dense molecular cores and young, pre-main sequence stars in rho-Ophiuchus, an active star-forming region. Our analyses synthesize multi-wavelength data, including dust extinction maps, dust emission at 1.2mm, mid-infrared images, and molecular line emission from several species. Following the investigation of several core identification algorithms – including a new technique based on Bayesian statistics – we select a final sample of dense cores from a hybrid of techniques applied to the 1.2mm dust emission. The spatial distribution of these cores appears scale free over two orders of magnitude, following the spatial distribution of young stars over a wide dynamic range. However, measured velocity dispersions of the dense gas in cores imply that a vast majority are stable against gravitational collapse. The average column density of cores systematically decreases with core size suggesting that some of the larger cores may be transient or fragment into multiple star systems. Several cores harbor multiple embedded sources, while other cores previously thought to be “starless” are found to contain newly identified sources. In light of these results, we find it unlikely that cores identified through dust emission or extinction have a one-to-one mapping with the subsequent generation of stars arising from them. Furthermore, simple modeling suggests that the similarity between the observed core mass function and the stellar IMF does not necessitate a one-to-one mapping between members of the two distributions. Understanding the similarities between ensembles of dense cores and the stellar initial mass function will require in depth studies that consider the distribution of dust, molecular line emission, and deep near and mid-infrared imaging from nearby regions of active star formation. This work received funding from the NSF as part of the REU program at the Institute for Astronomy, University of Hawaii.

DPS October 2007 Orlando
Olivine-Pyroxene Distribution of S-type Asteroids in the Main Belt 
Shaye Storm, S. J Bus, and R. P. Binzel

The mineralogical composition of asteroids can be constrained using visible and near-IR (VNIR) spectroscopy. The most prominent spectral features observed over this wavelength range are due to olivine and pyroxene, the two most abundant minerals in both chondritic and achondritic meteorites. The observed ratio of these two minerals is highly dependent on the amount of heating that an asteroid has undergone. The 1-micron band minimum and the band area ratio between the 2- and 1-micron bands (BAR) reveal relative abundances of olivine and/or pyroxene on an asteroid surface (Gaffey et al. 1993, Icarus 106:573). A large sample of S-, A-, V-, and R-type asteroid spectra was collected over the visible and near-IR wavelengths during the second phase of the Small Main-belt Asteroid Spectroscopic Survey (Bus and Binzel 2002, Icarus 158:106) and using the low-resolution SpeX spectrograph (Rayner et al. 2003, PASP 115:362) at NASA’s Infrared Telescope Facility (IRTF). Here we present a methodology for calculating the location of the 1-micron band minimum and BAR with appropriate 1- sigma uncertainties. This method was used to characterize approximately 200 S-type asteroids throughout the main belt. We will also present the distribution of olivine / pyroxene throughout the main belt by measuring how the S-type mineralogy varies with heliocentric distance. This will provide a better understanding of both the thermal processing across the main belt and subsequent mixing of asteroids through collisional and dynamical processes. This work was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS Winter 2008, Austin
Mass Determinations of Population II Binary Stars
Kathryn Williamson (University of Georgia and IfA) and J. N. Heasley (IfA)

Accurate mass determinations of Population II stars are essential to understanding the metallicity effects in stellar evolutionary models of the old stars in the Galactic halo. This research contributes accurate mass estimates for the three dwarf Population II binary systems HD 157948, HD 195987, and HD 200580. Results were obtained via a simultaneous least-squares adjustment of double-line spectroscopic and astrometric data to find the best fit orbital parameters and masses with error estimates. Monte Carlo simulations of theoretical data sets were used to test the consistency and accuracy of the optimization techniques in order to gauge the reliability of results. These theoretical data were designed to match orbital parameters that likely describe the three binary systems of this study. The results of the Monte Carlo analysis imply that reported mass estimates and error bars are indeed reliable for each particular orbit and given set of observation times. 

AAS Summer 2007, Honolulu
Earth-like Planets around GJ 876
Joseph Castro and N. Haghighipour (IfA, University of Hawaii)

GJ 876 is a 0.32 solar-mass M4 dwarf currently hosting three known planets. The inner planet of this star is a 7.5 Earth-masses body at 0.02 AU with an unknown orbital eccentricity. The two outer planets of this system are Jovian-type and located at 0.130 AU and 0.208 AU from the central star. We have studied the possibility of the existence of other Earth-like objects between the two inner planets of this system. We carried out numerical simulations of the dynamical stability of test particles in the region between 0.03 AU and 0.12 AU, for different values of the orbital eccentricity of the currently known Earth-sized object. We also studied the orbital dynamics of additional Earth-like planets in this region. Results indicate that additional terrestrial bodies may only exist in a small region between 0.04 AU and 0.05 AU from the central star. The inner region of the planetary system of GJ 876 seems to be dynamically full.

AAS Winter 2007, Seattle
Earth-like Planets around GJ 876
Joseph Castro and N. Haghighipour (IfA, University of Hawaii)

Gamma Cephei is a spectroscopic binary consisting of a 1.59 solar-mass K1 IV subgiant primary star and a 0.34-0.92 solar-mass red giant secondary star. The primary of this system is host to a 1.7 Jupiter-mass planet at approximately 2.1 AU and with an eccentricity of 0.12. Numerical simulations were carried out on the dynamical stability of additional hypothetical planets located 3 to 5 AU from the primary star. To ensure a comprehensive search, various values for the mass, eccentricity, and inclination of the additional Jupiter-like planets were used. Similar simulations were also carried out for possible Saturn and Neptune-like planets within the same range. Results indicate that Gamma Cephei appears to be dynamically full and no stable orbits of any additional planets were found.

AAS Winter 2007, Seattle
Conditional Density Analysis of the Hubble Deep Field
Brittany L. Dames and P. H. Coleman (IfA, University of Hawaii)

The Hubble Deep Field galaxy data set is reanalyzed using conditional density methods which are more suitable for distributions of unknown correlation structure than n-point correlation statistics or the related power spectrum analyses. The large-scale distribution of galaxies is known to exhibit power-law correlation on small scales (perhaps up to tens of megaparsecs) and is thought to become uncorrelated (homogeneous) on large enough scales. This sample is used to probe much larger scales, and the initial angular analysis presented here shows no evidence for a change in correlation structure. This implies that the large-scale distribution of luminous matter may in fact be power-law correlated on all scales. This has strong implications for current cosmological models based on the Robertson-Walker metric which describes a homogeneous space of constant curvature.

AAS Winter 2007, Seattle
New and Improved Ephemerides of Nix and Hydra during the 1985 to 1990 Mutual Events between Pluto and Charon
Garrett Elliott (Ohio State University) and D. J. Tholen (IfA, Hawaii)

Acknowledging the non-Keplerian orbits for the Plutonian moons Nix and Hydra due to significant perturbations by Charon, new ephemeris positions were calculated to assist with their detection in previous observations of the Pluto system. To compensate for unknown albedo and density, we varied their masses from 1.0 x 10¹⁶ kg to 2.5 x10¹⁸ kg to allow for extremes of Pluto-like albedo and a water-ice density to comet-like albedo and Pluto-like density, respectively. New ephemeris positions of Nix and Hydra should allow us to identify them in stacked images from archival Hubble Space Telescope data. Also, the coplanar orbits of Nix, Hydra, and Charon result in a shared season of mutual events. In Pluto and Charon mutual event observations made between 1985 and 1990, Nix or Hydra mutual events with Pluto may have been unknowingly observed. Although mutual events between Nix or Hydra and Charon did occur, the focus of the observations during this time was on the events between Charon and Pluto. This situation makes the possibility that there were observations of one of these Nix or Hydra and Charon events very remote.

AAS Winter 2007, Seattle
The Composition of the Old, Metal-Rich Open Cluster, NGC 6791
Elizabeth Jensen (Smith College), A. M. Boesgaard (IfA, Hawaii), and C. P. Deliyannis (Indiana University)

The populous open cluster, NGC 6791, has pre
sented an anomaly as it appears to be very old (8-10 Gyr), yet metal-rich. We have made high resolution (45,000) spectroscopic observations of two turn-off stars (V = 17.4) with HIRES on the Keck I telescope on Mauna Kea. We have determined the stellar parameters for these two stars spectroscopically. The high metallicity of NGC 6791 is confirmed by our results, [Fe/H] = +0.40. In addition we have found elemental abundances for Na, Si, Ca, Ti, Ni, Cr, and Y. We compare our results with those of field star samples that are both old and metal-rich: a) six dwarf stars with [Fe/H] > +0.01 and age > 8.5 Gyr from Edvardsson et al. (1993), b) nine old dwarf stars with [Fe/H] from +0.05 to +0.39 from Chen et al. (2003), and c) four old dwarf stars with [Fe/H] from +0.15 to +0.47 from Feltzing & Gonzalez (2001). The abundances of these elements are in agreement in the field and in the cluster with the possible exception of Ti which appears higher in the cluster stars; it is not clear why Ti would be enhanced when Si and Ca are not. We discuss the possible interpretations of the cluster peculiarities.

AAS Winter 2007, Seattle
Planetary Nebulae and Stellar Kinematics in Interacting Spiral Galaxy M82
Lent C. Johnson (Colby College), R. H. Mendez, and A. M. Teodorescu (IfA, Hawaii)

Using an on-band/off-band filter technique, we identify 114 planetary nebulae (PNs) in the edge-on spiral galaxy M82 using the FOCAS instrument at the 8.2m Subaru Telescope. Radial velocities were determined for 100 of these PNs using a method of slitless spectroscopy, from which we obtain a clear picture of the galaxy’s rotation. We find evidence for a Keplerian decline in M82s rotation curve, in agreement with results derived by CO(2-1) and HI measurements (Sofue 1998). These results affirm the use of PN as effective, accurate kinematic probes of galaxies. 

AAS Summer 2007, Honolulu
Coronal Mass Ejections: A Study of Structural Evolution and Classification
Chris Lowder (Georgia Tech), S. R. Habbal, and H. Morgan (IfA, Hawaii)

Coronal mass ejections (or CMEs) are known for their majestic, yet explosive, outflow from the Sun. Although different criteria are often used for their classification, this paper seeks to classify them based on the following factors: (1) The velocity of the CME; (2) the structure of the CME itself, and (3) the angular separation of the “legs” of the CME as it expands. Given that the outer edge and the inner core of the CME move at different velocities, this difference can track the structural evolution of the outburst. Using data from solar minimum and maximum, CMEs will be analyzed and a new classification scheme will be developed based on the characteristics outlined above. 

AAS Winter 2007, Seattle
A Correlative Study between Coronal Mass Ejections, Prominences and Flares
Anthony Rasca (Carroll College), S. R. Habbal, and H. Morgan (IfA, Hawaii)

The exact cause of coronal mass ejections (CMEs) remains unsettled despite three decades of observations since their discovery in the early 1970s. Their association with events at the Sun, such as prominence eruptions and solar flares, is often established from a near-time and -position angle coincidence on the solar disk and limb. Using a list from randomly chosen CMEs in the LASCO/C2 catalog, a comparison is made of the number of associated events from observations at solar maximum (1999-2000) and during the declining phase of the solar cycle (2004-05). Images of the Fe XII and He II lines from SOHO/EIT are used to locate events associated with the CMEs. The results show solar maximum CMEs having four times more associated prominence eruptions, without an associated flare, than at solar minimum (12% vs. 3%). CMEs at solar minimum have five times the number of flare-associated prominences (11% vs. 2%), and twice the number of flare-associated active regions (29% vs. 14%). A histogram of the CMEs speed distribution shows a trend with a skewed peak in the range of 200-399 km/s at both phases of the solar cycle. When separated into event-associated cases, a similar distribution with speed is found with the flare-associated events, whereas a peak in the percent of CME-associated prominence eruptions appears in the range of 600-799 km/s. Using this information and the fact that prominence eruptions were most commonly observed at the solar limb, we estimate that the mean prominence-associated CME speed lies within the range of 600-799 km/s and the mean flare-only associated speed lies in the 200-399 km/s range. Such results point to the importance of prominence eruptions in fast-propagating CMEs.

AAS Summer 2007, Honolulu
Habitable Planets in the Planetary System of HD 69830
Sarah Rugheimer (Calgary) and N. Haghighipour (IfA, Hawaii)

We present the results of a study of the dynamical evolution and habitability of HD 69830 planetary system. Being the first multiplanet extrasolar planetary system with three Neptune-sized objects, HD 69830 provides new grounds for testing the possibility of the existence of smaller objects, such as terrestrial planets, particularly in its habitable zone. We numerically integrated the orbits of the planets of this system for different values of their masses, and also studied the long-term stability of many Earth-like objects in its habitable zone. Results indicate that the planetary system of HD 69830 is dynamically stable and its habitable zone can harbor terrestrial planet for long times. The only exception is at 0.735 AU inside this region where an island of stability appears.

AAS Winter 2007, Seattle
Using Fe and Mg in Olivine as an Indicator of Asteroidal Hydrothermal Alteration
Anne Sweet (Macalaster College) and L. Chizmadia (IfA, Hawaii)

Amoeboid olivine aggregates (AOAs) found in CO3 meteorites are sensitive indicators of parent body alteration. Because chondritic meteorites are considered to be some of the most primordial material of the early solar system, studying these features reveals information about the hydrothermal alteration undergone after the time of their formation. As water encounters the AOAs, the Mg-rich olivine, forsterite (Mg₂SiO₄), is replaced with Fe-rich olivine, creating fayalite (Fe₂SiO₄). The calculation of the Fe/Mg ratio of the AOAs, along with a visual examination of the ferroan veins and diffusive halos in these features, allows for a classification of the petrologic subtype (3.0-3.8) of the meteorite. By using a scanning electron microscope for meteorite mapping, feature identification, and element mapping, as well as an electron microprobe for accurate elemental abundance calculation, we were able to accomplish this classification. In this work we present the subtype classification of six previously unclassified meteorites (ALH83108, A-882094, MET00694, MET00711, MET00747, QUE97416, and Y-82094) along with the analysis of two previously studied meteorites as standards (Lance and ALH77003). We found that on the basis of the distribution of the mol% Fe/(Mg+Fe) that Y-82094 is a CO3.3, QUE97416 is a CO3.5, ALH83108, MET00694, MET00711 and MET00747 are CO3.8, and that A-882094 is probably a breccia since the AOAs show different levels of alteration ranging from CO3.4 to CO3.6.

n.

AAS 207th Meeting, 8-12 January 2006
[4.16] Using AOAs to Document Aqueous Alteration in the CO3 Parent Asteroid
C. Bendersky (Mount Holyoke College), L. Chizmadia (Institute for Astronomy, University of Hawaii)

Chondritic meteorites are considered to be among the most primitive materials remaining from the early solar system. Chondritic meteorites have experienced few changes since their formation; only subtle changes are observed, due to aqueous and thermal alteration. CO3 carbonaceous chondrites are of particular interest for studying incipient alteration because they show a clear metamorphic sequence, designated 3.0 (least altered) to 3.8 (most altered). Amoeboid olivine aggregates (AOAs) are fine grained, irregularly shaped objects composed dominantly of olivine with minor amounts of anorthite, diopside and spinel. The fine grained and porous nature of AOAs make them very sensitive to hydrothermal alteration.

We used established procedures of measuring the size, shape and distribution of relict Mg-rich olivine patches, and the Fe content and distribution of the olivine to assign petrologic subtypes to seven CO3 chondrites which had not previously been assigned a petrologic subtype (metamorphic stage).

ALH85003 and ALH82101 are 3.5. There is an even volume of Mg-rich olivine and Fe-rich olivine. Their Fe-rich olivine veins have widened into 10-15 micron channels. ~0.8 micron halos around relic Mg-rich olivine cores separate the cores from the Fe-rich veins.

A-881632 is a 3.6. The inclusions are dominated by Fe-rich olivine. Veins are no longer apparent; instead Mg-rich olivine cores remain. These Mg-rich cores have 2-3 micron halos.

DaG 055 is a 3.7. There is no remnant Mg-rich olivine. The Fe contents of the AOAs and matrix have not equilibrated.

Finally, Y-790992, EET92126 and Y-791717 are 3.8. Only Fe-rich olivine remains in the AOAs. The Fe content of the matrix and the AOAs have fully equilibrated.

AAS 207th Meeting, 8-12 January 2006
[74.02] Habitable Extrasolar Planetary Systems: The Case of rho Cancri
D. Cotto-Figueroa (University of P.R. at Humacao), N. Haghighipour (Institute for Astronomy, University of Hawaii)

Having the largest number of extrasolar planets, a Neptune-mass object on a 2.8 days orbit, and an outer planet that orbits at 5.3 AU which is comparable to Jupiter’s distance from the Sun, rho Cancri has become an interesting system for study of habitability. In this paper, we present the results of a study of the orbital evolution and dynamical stability of Earth-like planets in this system. Numerical integrations of the system, using the orbital parameters reported by McArthur et al. (2004), indicate that the system may not be stable. In search of stable planetary orbits, an extensive search of the parameter-space of the system was carried out, and a stable region was identified. Within this region, dynamical stability of an Earth-like planet in the habitable zone of the system was studied and two regions of stability were recognized.

This research took place at the University of Hawaii’s Institute for Astronomy during a Research Experience for Undergraduates (REU) internship funded by the National Science Foundation (NSF).

AAS 207th Meeting, 8-12 January 2006
[74.01] Habitability in the Upsilon Andromedae System 
A. Dove (University of Missouri – Columbia), N. Haghighipour (Institute for Astronomy, University of Hawaii)

Upsilon Andromedae is an F8 V star with a stellar companion orbiting at about 750 AU. Doppler velocity measurements have revealed the presence of three planets orbiting the star, with periods of about 4.6 days, 241 days, and 1267 days (Butler et al., 1999). Like many extrasolar planets orbiting at radii greater than 0.2 AU, the outer two planets of Ups And exhibit high eccentricities (greater than 0.1). Planet-planet scattering is one mechanism that has been suggested to cause perturbations that excite the eccentricities of these planets (Ford et al., 2005). We investigate the habitability of the Ups And planetary system as it undergoes planet-planet scattering and evolves from a hypothetical four-planet system into its observed state. We present the results of the numerical integrations of the system with a fourth planet at a distance of 4.76 AU from the central star. Our results demonstrate that an Earth-like planet could not remain stable in the HZ of this system. We also show, through an extensive survey of the parameter-space of this system, that it is important to include the inner planet of this system in the simulations of its dynamical evolution, and in the study of its habitability.

This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS 207th Meeting, 8-12 January 2006
[177.04] Chandra Analysis of a Possible Cooling Core Cluster at z = 1.03 
K. Dolan (Lawrence University), H. Ebeling (Institute for Astronomy, University of Hawaii at Manoa)

We present an analysis of Chandra observations of a massive cluster of galaxies at high redshift, Cl J1415+3612 at z = 1.03, investigating whether the cluster possesses a cooling core. If the cluster does possess a cooling core, it will be the earliest known example of a massive cooling core cluster. We find Cl J1415+3612 to be of a relaxed morphology through the use of a two-dimensional X-ray surface brightness model, and we use spectral fitting to find that the temperature of the cluster is kT = 5.7 ± 0.49 keV. Spectral fitting gives a temperature of 7.03 ± 0.01 keV for the core and 4.45 ±
0.58 keV for the outer cluster, which suggests that the core is warmer than the rest of the cluster, but too few counts are available for the spectral fits to be definitive. We find through one-dimensional spatial modeling that the radial surface brightness profile of the cluster cannot be satisfactorily modeled without some strong central peak in addition to the standard beta model, which is suggestive of the presence of a cooling core.

The use of spectrally normalized exposure maps is also discussed, and we mention the importance of correcting for the degradation of the Chandra ACIS low-energy quantum efficiency when performing spectral fits to energies below 1 keV.

AAS 207th Meeting, 8-12 January 2006
[68.03] A Wide-Field Optical and Near-Infrared Search for Brown Dwarf Candidates
J. S. Katz (Columbia University), E. Magnier (Institute for Astronomy, University of Hawaii)

The Two Micron All Sky Survey (2MASS) has been a great resource for astronomers in search of low-mass objects. J, H, and K photometry from 2MASS has been used to pinpoint brown dwarf candidates by their distinctive near-infrared colors. We present a study which utilizes this resource in conjunction with overlapping I-band photometry from the Canada-France-Hawaii Telescope’s 12,288 by 8,192 pixel mosaic CCD to isolate previously unidentified brown dwarf candidates based on their optical and near-infrared colors. Our selection criteria included a high signal to noise ratio in detections from both sources and a color range of 4 < I – J < 10 and J – K <= 1.5. This range corresponds to published estimates of the colors of late-type dwarfs and also excludes reddened background giants. This analysis produces 217 candidates that meet these criteria; their attributes and credibility are discussed. The group, representing spectral types from M9 to L6 or later, could contribute greatly to the current understanding of brown dwarfs if spectroscopically confirmed. Additionally, this study provides insight into the expectations of brown dwarf discoveries from the upcoming 3π steradian Pan-STARRS survey.

This work was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS 207th Meeting, 8-12 January 2006
[69.15] Beryllium: A Cosmic Chronometer? 
C. Peruta (University of Arizona), A.M. Boesgaard (Institute for Astronomy, University of Hawaii)

The process spallation, by which beryllium is formed, is the key to understanding many topics in astronomy today. It is still not certain whether spallation occurs within the local vicinity of supernovae where C N O is excited into interstellar gas or conversely on a global scale by high energy protons bombarding C N O in the interstellar gas. If global, the instantaneous abundance can be characterized by a scatter around the mean value significantly smaller than for Fe or O. Beryllium would therefore be a more reliable chronometer than [Fe/H] or [O/H]. I present Be abundances from 20 metal poor stars ([Fe/H] < -1.5). The stars were observed with high resolution/high S/N spectroscopy and abundances were determined by fitting synthesized spectra. These abundances are plotted against [Fe/H] and combined with results from previous Be studies to confirm whether or not there is an intrinsic spread in Be at low metallicities. If there is a spread, we can infer the most likely mechanism for Be formation is spallation in the vicinity of supernovae and therefore A(Be) is not a good chronometer. This study shows that there is a spread around [Fe/H] = -1.5 and -2.5 with a typical error of 0.10 dex for all Be abundances.

This work was conducted by a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS 207th Meeting, 8-12 January 2006
[21.02] Metallicity and Star Formation in High EW(H-alpha) Galaxies 
J. E. Pollack (New College of Florida), L. J. Kewley, D. Sanders (Institute for Astronomy, University of Hawaii), M. J. Geller (Smithsonian Astrophysical Observatory)

We present an investigation into the chemical abundances and star formation properties of the central regions in ~330 Updated Zwicky Catalog (UZC) galaxies at cz > 5000 km/s. These galaxies were selected to have strong bursts of recent star formation by constraining the sample to galaxies with high EW(H-alpha) and detectable 60-micron IRAS fluxes. Spectra were obtained for the 330 galaxies with the CfA FAST spectrograph. We calculate metallicities using Kewley and Dopita’s (2000) metallicity and ionization parameter diagnostics using the [NII], [OII], [OIII], [SII], and the Balmer emission lines. We use stellar population synthesis models to derive the age of the recent bursts of star formation. Finally, we investigate the metallicity and burst age in terms of morphology and the presence of companions.

Funding for this research was provided by the National Science Foundation Research Experience for Undergraduates program hosted by the Institute for Astronomy at University of Hawaii-Manoa.

AAS 207th Meeting, 8-12 January 2006
[10.07] New Debris Disks Around Low-Mass Stars 
J. J. Wray (Princeton University), M. C. Liu (Institute for Astronomy, University of Hawaii), I. N. Reid (STScI)

Debris disks provide an opportunity to learn about the planet formation process in other solar systems as well as our own. To date, most studies have focused on disks around early or mid-type stars, excluding the much more common low-mass dwarfs either by choice or simply because any disks they may have are too low luminosity to be detected. We have conducted the largest and most thorough search for K and M dwarf debris disks to date, and have found several new candidate disks. The candidates include both warm, asteroid belt-type rings and cold disks more nearly analogous to the Kuiper belt. The candidates were identified from a sample of 1,400 dwarf stars within a 25 pc radius, cross-matched with IRAS flux densities compiled from a number of sources. The completeness and reliability of the matches have been tested rigorously and found to be high.

This work was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy and funded by the NSF.

AAS 205th Meeting, San Diego, January 2005
[140.10] Self-Similarity in the Rosette Molecular Cloud
A. M. Hughes (Yale University) and J. P. Williams (IfA)
The Rosette Molecular Cloud is an active region of star formation in the Milky Way. We present a study of the cloud using a large scale ¹²CO and ¹³CO map of the cloud obtained at the Five College Radio Astronomy Observatory. The map covers 6 square degrees at a resolution of 50” (0.3 pc). Using a clump deconvolution algorithm, we divided the cloud into discrete regions of emission and calculated their physical properties including mass, size, linewidth, temperature, aspect ratio and degree of virialization. Clumps with embedded IRAS sources tend to be hotter and somewhat denser than average. The HII region at the cloud’s edge produces a pronounced temperature gradient in the cloud (temperature decreasing as the inverse square root of distance) but does not significantly affect other clump properties. We also smoothed the data set to lower resolutions to study the dependence of the derived clump properties on size scale. The cloud structure was found to be self-similar but clump densities and their virialization parameter decreased with smoothing scale.

AAS 205th Meeting, San Diego, January 2005
[147.13] X-Ray Point Source Excesses around MACS Clusters
J. Ruderman (Stanford University) and H. Ebeling (IfA)
Chandra X-ray images of clusters of galaxies indicate an excess of X-ray point sources, believed to be AGN cluster members, above the background surface density. We study the point source content of the ACIS-I data for 47 clusters primarily from the MACS survey, which range in redshift from 0.3 to 1.0 and have similar x-ray luminosities, and 7 control fields that do not contain clusters.
We use the Celldetect algorithm, in the 0.5-2.0 keV range, to detect point sources with a three sigma signal-to-noise ratio above the X-ray background, resulting in 789 detections in the cluster fields and 235 point detections in the control fields. Source count rates are converted to unabsorbed energy fluxes (0.5-2.0 keV) using X-Spec software and a scaled power law source spectral model. Based on the resulting logN-logS graphs, we use a flux limit of completeness of 1.1 × 10¹⁴ erg/sec/cm². We separately analyze eight long-exposure fields in the 0.5 to 0.6 redshift range at a deeper flux limit of 5.9 × 10¹⁵ erg/sec/cm². Sources above the flux limit are binned into annuli extending 20 arcmin in radius, centered at the cluster center or observation aimpoints, for the cluster and control fields respectively.
The cluster observations exhibit a central excess at the 3-6 σ level over the densities observed at the edge of the field. No such excess is observed in the control fields. This point source density in the control fields is consistent with the one observed at the edge of the cluster fields.
Future work will focus on the optical counterparts of the X-ray point sources from a subset of the clusters. Color-magnitude diagrams combined with spectroscopic information will allow us to classify the sources as foreground stars, likely cluster members, or gravitationally lensed background galaxies.

AAS 205th Meeting, San Diego, January 2005
[13.05] Magnetic Feilds of Young Stars in NGC 752
C. Christensen (Carleton College) and T. Simon (IfA)
The magnetic fields of stars change in direction and strength not only over short time scales, as in the Sun’s twenty-two year cycle, but also as the star ages. As characteristics of a star like rotational velocity and depth of convection zone change, the magnetic field must alter as well. To shed light on this ageing process, we studied the magnetic flux of stars 1.78 gigayears old, an age between that of the Hyades and the Sun, both of which have been extensively studied. This study was done using data from a deep-field Chandra observation to find the coronal luminosity, a proxy for the magnetic flux, of a total of 130 stars, many of which are known to be members of NGC 752. Photon count rate was converted to luminosity using the Raymond-Smith model. Convective stars were found to have a range of coronal luminosities averaging only slightly higher then that of the Sun. Stars with B – V < 0.45, however showed a trend towards brighter luminosities. We determined the average coronal luminosity of G-type stars to be 2.98 × 10²⁸ ergs/sec with a range of plus or minus 2.21 × 10²⁸ ergs/sec, which corresponds to an exponential decline in coronal luminosities from those of the Hyades.

DPS 46th Meeting, Louisville, October 2004
[40.08] An Observational Upper Limit on the Number-Density of Interstellar Comets
B. Meinke (U.C. Berkeley), R. Jedicke (IfA), and J. A. Larsen (LPL, Arizona)
Current theories of Solar System formation predict that comets that acrete in a protostellar nebula are later ejected by interactions with the newly formed giant planets. In such a process a large fraction (>99%) of all comets would be ejected from the new planetary system, subsequently creating a large population of Interstellar Objects (ISO) in the interstellar medium. Due to the observational absence of such objects, Whipple (1975) determined the limit on their number-density to be ~10¹³ pc^-3, although he, and others since (e.g. Stern 1990) contend that this liberal upper limit could be reduced by several orders of magnitude given their continued observational absence in a survey covering large areas of sky to faint magnitudes. Since the early 1990s, the University of Arizona’s Spacewatch survey at Kitt Peak has conducted such wide-field observations to V ~ 21.7. In the period corresponding to this study Spacewatch covered about 4200 deg².
Given the amount of sky covered by Spacewatch observations, and the detection efficiency for objects as a function of their rates of motion and apparent magnitude, we determined the 97% upper confidence limit on the number of ISOs as a function of the slope parameter alpha . We have parameterized the number density of ISOs as ρ = ρ_o 10^{α(H – Ho)}, where H is the absolute magnitude of an object, α is the slope of the number density as a function of H, and ρ_o is the space density at H_o. We use H_o = 19.1 which corresponds to an ~1 km diameter object with a typical cometary albedo of p = 0.04.
At α = 0.5, corresponding roughly to the expected slope for accreting planetesimals, the 97% upper C.L. on the number density of ISOs is ~ 10¹⁴ pc^-3 or ~ 10^-2 AU^-3.

DPS 46th Meeting, Louisville, October 2004
[33.14] A Study of Jet Morphology and Outburst Evolution in the Coma of Schwassmann-Wachmann 1
C. E. Ellis (Redlands University), Y. R. Fernandez (IfA) and L. M. Woodney (University of Central Florida)
We present results from a continuing project to study the physical and rotational behavior of the comet Schwassmann-Wachmann 1 (SW-1). SW-1 is one of the most unusual comets known due to its orbit (at the edge of the Centaur region) and its activity behavior (with frequent stochastic outbursts). Studying SW-1 may tell us generally how outbursts are triggered and evolve. Our data consists of CCD imaging taken every few weeks over the summer of 2002. We observed SW-1 having two different outburst events, during which the coma showed a rich diversity of coma morphologies. Manipulating images enhances the faint jet features hidden within the coma, and we used 7 different image manipulation techniques to be sure of identifying features vs. artefacts. These enhancements allow us to obtain quantitative information on jet positions and relative brightnesses, and will let us eventually model the nucleus’s rotation state and the location of its active areas. Our data also show us different stages of outburst evolution, which has not been often done before. The outbursts lasted for several weeks, whith two jet features located approximately 180 degrees apart. Interestingly the two features did not always stay at a constant orientation, but rather their PAs seemed to vary slightly as the outburst progressed. We present (a) images that show the evolution of the outburst, (b) a description of the location and any apparent movement of the coma features, and (c) a discussion of possible explanations. The continued study of SW-1 will undoubtedly help us better understand the nature of this truly strange comet.
 
 

The REU students presented their summer research projects to the IfA on Friday, August 1, 2003, in a day long mini-conference held in the auditorium.

AAS 203rd Meeting, January 2004
[5.07] A Survey of Classical and Weak-line T Tauri Stars in the Young Cluster NGC 2264 
S. E. Dahm, T. Simon (U. of Hawaii), E. David (Xavier U.)

We present initial results from an Ha and X-ray emission survey of the young cluster NGC 2264 in the Mon OB1 association. Approximately 450 emission Ha stars were identified in a 25′ × 40′ field roughly centered between the O7V multiple star S Mon and the Cone Nebula. The Ha emission survey was carried out using the wide-field grism spectrograph on the University of Hawaii 2.2 meter telescope and the Gemini Multi-Object Spectrograph (GMOS). The XMM-EPIC observations of the cluster are discussed in detail in the accompanying poster by David et al. (2004). Additionally, we obtained optical (BVRCIC) and near infrared (JHK) photometry for selected fields in NGC 2264 to supplement published data from previous investigations and to ensure coverage for the majority of detected emission Ha stars and X-ray sources. Optical color-magnitude diagrams are presented and used to derive ages and masses from theoretical isochrones and evolutionary tracks for the candidate pre-main sequence stars. We analyze the X-ray luminosity functions of classical and weak-line T Tauri stars in NGC 2264 and seek correlations among LHa, LX, spectral type and theoretical age. Finally, the distribution and density of emission Ha stars in the cluster are discussed and compared with those found in other star forming regions including IC 348, IC 5146 and NGC 2362. This research was supported in part by the NASA XMM-Newton Guest Observer program and the NASA Graduate Student Research Program.

AAS 203rd Meeting, January 2004
[5.05] XMM Observations of the Star Forming Region NGC 2264
E. David (Xavier U.), T. Simon, S. E. Dahm (U. of Hawaii), B. M. Patten (Harvard-Smithsonian CfA)

X-ray images of the heavily-populated, young, star-forming region NGC 2264 were obtained with the XMM-Newton European Photon Imaging Cameras (EPIC). The region was observed in two 30′ fields of view; the southern field contains the Cone Nebula, while the northern field is centered near the bright O star, SMon. In all, 320 X-ray sources were detected above a 3 s detection level of L_x = 3 × 10²⁹ ergs s^-1 . The large majority of the sources have optical counterparts from earlier surveys of the pre-main sequence population of the cluster. A dozen sources have no identified optical counterpart and therefore are possible candidates for very young, deeply embedded protostars. We describe our procedures for extracting source count rates and pulse-height spectra, light curves, and X-ray luminosities. More detailed analysis of these results and a comparison with ground-based optical and infrared data appears in the accompanying poster by Dahm et al. (2004). This research was supported in part by the NASA XMM Guest Observer program and by the NSF Research Experience for Undergraduate Program.

AAS 203rd Meeting, January 2004
[7.05] A Comparison Between Observations and Simulations of Polarization in Star Forming Regions
A.K. Hernandez (U.Colorado), J.P. Williams (IfA, U.Hawaii), E.G. Zweibel (U.Wisconsin)

Previous research has hinted that magnetic fields play a key role in the formation of cores in star forming molecular clouds. However, the extent of that role is not fully understood. Here, we compare polarization data of observed cores with clumps formed in a simulated model of turbulent molecular clouds. Through an investigation of the polarized angle dispersion of both sets of data, it was found that the simulations were accurate in representing cores formed with either a low turbulence or within a relatively strong magnetic field. Also, through investigation of data’s polarized flux, the observed sources are found to have formed in fields that are more ordered than those modeled in the simulations. This finding is also supported by the calculated magnetic field strengths of the observed cores via the Chandrasekhar-Fermi method. This research will aid in understanding the conditions of star formation within turbulent molecular clouds. This work was funded by the National Science Foundation’s Research Experience for Undergraduates program.

AAS 203rd Meeting, January 2004
[18.03] Time-Evolution of a White Light Flare: Observations in Optical, Microwave, Soft X-Ray, Ha
E. Lee (Harvard Univ.), J. Li (IfA, Univ. of Hawaii)

Since Richard Carrington’s 1859 discovery of White Light Flares (WLFs), only fifty other WLFs have been observed. While the predicted frequency was 15.5 (± 4.5) per year for solar cycle 20, the lack of sensitive instruments makes WLFs extremely rare. Past observations suggest that WLFs do not accompany all high-energy events, and that some specific initial conditions and mechanisms produce WLFs. To analyze this claim, we found a WLF by combing through a list of X class events. This X5.6 flare occurred at AR 9415 on April 6th, 2001 (UT 19:14) and was accompanied by a halo CME. After confirming this event to be a WLF using Imaging Vector Magnetograph data, we found microwave, EUV, optical, soft X-ray, and magnetogram data. Our data suggests that this WLF erupted through the same mechanisms as the standard flare models, but was more energetic. This work was funded by the National Science Foundation’s Research Ex
perience for Undergraduates program.

AAS 203rd Meeting, January 2004
[17.06] Extra-Solar Planet Search Using Two 0.1-meter Diameter Telescopes 
Y.R. Torres (Institute for Astronomy, University of Hawaii)

The research project my mentor, Dr. Jim Heasley, and I worked on this summer involved a search for extra-solar planets. My research was supported by the National Science Foundation. The search was conducted using a drift scanning method with two 0.1-meter diameter telescopes. By using these small telescopes, we were capable of attaining over 2 million stars per night and over 30 million stars for data analysis. The telescopes are mounted on Haleakala, Maui at an altitude of 10,000 feet. Our main interest was to detect subtle decreases in the intensity of the measured stars. Sixteen nights of observations were used for our data analysis which covered a range in right ascension from 40 degrees to 200 degrees. For this particular data set, a Stellar Photometry Software package, written by Janes & Heasley (1993), produced information for each star such as the raw instrumental magnitudes, ID numbers, (x,y) coordinates, and an estimated error for each reported magnitude. In order to flag down these transits and detect time history of any measured object, it was in our best interest to establish a database. The database is useful to us in such a way that large numbers of stars can be stored and examined, we are allowed flexibility in examining the data in a number of ways, and incorporating additional observations as they become available will be much more simplified. The observing program on Haleakala is set to operate for a three year period. This work was funded by the National Science Foundation’s Research Experience for Undergraduates program.

AAS 201st Meeting, January, 2003
[44.01] The Chemical Composition of the Hyades
A. M. Boesgaard (U. Hawaii), J. L. Beard (Virginia Tech), J. R. King (UNLV)

The enrichment of various chemical elements with time in the Galaxy reveals the history of massive star formation and the production of supernovae. We have embarked on a study of elemental abundances in unevolved G stars in star clusters of a range in age to trace the evolution and mixing in the galactic disk.

We have obtained Keck/HIRES spectra of 17 Hyades stars with temperatures between 5000 and 6200 K and high signal-to-noise ratios (typically 500 – 700) in order to determine chemical abundances of G dwarfs in this 700 Myr old cluster. The spectra cover 5700 – 8100 A with some inter-order gaps. We have redetermined Fe and Li abundances and find good agreement with earlier results. Abundances for O and C and some other alpha-elements have been found as well as abundances of other light elements, Fe-peak elements, and rare earth elements. We compare the Hyades results with those from the old open cluster, M67. The Hyades at 700 Myr is metal-rich with [Fe/H] = +0.16 while M67 at 4.5 Gyr has solar metallicity of -0.04. Compared to M67, the Hyades has somewhat larger enhancements of C and O.

AAS 201st Meeting, January, 2003
[6.17U] Extremely Red Objects and Very Red Objects: A Wide Field Survey Around the Hubble Deep Field
E. Fernandez (New Mexico Institute of Mining and Technology), A. Barger (University of Hawaii)

We performed a deep, wide-field near-infrared survey of the Hubble Deep Field North region using the University of Hawaii’s 2.2-meter telescope. We obtained complementary Suprime-Cam I-band observations of the same area using the Subaru 8.2-meter telescope. From the I-K colors of the galaxy sources, we were able to identify a sizeable population of Extremely Red Objects (EROs; I-K>4) and Very Red Objects (VROs; I-K>3.5). We report on the surface densities of these unusual populations and compare our results with those of other surveys.Fernandez, E.; Barger, A. 
We performed a deep, wide-field near-infrared survey of the Hubble Deep Field North region using the University of Hawaii’s 2.2-meter telescope. We obtained complementary Suprime-Cam I-band observations of the same area using the Subaru 8.2-meter telescope. From the I-K colors of the galaxy sources, we were able to identify a sizeable population of Extremely Red Objects (EROs; I-K>4) and Very Red Objects (VROs; I-K>3.5). We report on the surface densities of these unusual populations and compare our results with those of other surveys.

AAS 201st Meeting, January, 2003
[46.05U] Potential Brown Dwarfs Discovered in IfA Deep Imaging Survey
M. Graham (Oklahoma State University)

Deep, wide-field imaging surveys in the red and near-infrared are ideal for discovering substellar objects like brown dwarfs. A few of these surveys, such as 2MASS and SDSS, have already been successful in these attempts. A new wide-field red plus near-infrared survey was conducted by astronomers at the University of Hawaii’s Institute for Astronomy (IfA) on the Subaru telescope. Five fields, each approximately 0.5 square degrees at varying galactic latitudes were observed in the Rc-, Ic-, and z’-bands.

Typical image quality of the survey is FWHM = 0.8″. The total integration times for the Rc-, Ic-, and z’-bands were approximately 4500, 6500, and 9500 sec, respectively, for each field. For a 2″ circular aperture the 5-sigma limiting magnitudes in Rc, Ic, and z’ were approximately 27.1, 26.7, and 26.0, respectively.

One of the goals of the survey is the study of brown dwarfs. T dwarfs (or methane dwarfs) are the coolest, faintest, and most difficult to observe of the brown dwarf types. One T dwarf with spectral type T3-T4, IfA 0230-Z1, has already been confirmed from the IfA survey. In total the survey is expected to yield about 40 such objects.

Evaluation of the data has led to a large number of brown dwarf candidates. From four of the five fields in the survey, concentrating on the brightest (z’-magnitude < 23.0) stellar objects, approximately 38 excellent brown dwarf candidates were discovered. These are thought to be mostly late-L and T dwarfs.

This project was undertaken at the IfA as part of the summer 2002 Research Experience for Undergraduates program sponsored by the The presenter wishes to thank his project advisor at the IfA, Dr. Richard Wainscoat, as well as Dr. Eduardo Martin, who proposed the project as part of the IfA Deep Imaging Survey.

DPS 35th Meeting, 1-6 September 2003
[14.06] Spectrum of MUSES-C target asteroid 1998 SF36 from TRISPEC observations
C. Salyk (MIT), D.J. Tholen (IfA)

A spectrum spanning 0.5 – 2.5 microns was obtained for the asteroid 1998 SF36, the target of Japanese sample-return mission MUSES-C, which is scheduled for launch at the end of 2002. The asteroid was observed with the UKIRT telescope on Mauna Kea, on 2001 March 2 and 3 UT using a new instrument called TRISPEC (Triple Range Imager and SPECtrograph), developed by Nagoya University graduate students H. Nakaya, M. Watanabe and T. Yamamuro. Using three optical channels, this instrument allows simultaneous observations in a visible and two infrared bands, each with its own detector. Preliminary spectra confirm results of Binzel et al. (2001, Meteoritics Plan. Sci., 36, 1167-1172) that 1998 SF36 is an S-type asteroid. Further analysis of band-depth ratios should reveal more detailed information about its composition and classification. This work was supported by the National Science Foundation Research Experience for Undergraduates Site grant AST99-87896 to the University of Hawaii.

AAS 199th meeting, Washington, DC, January 2002
[56.18] The Chemical Composition of the Globular Cluster M71 from Keck/HIRES Spectra of Turn-Off Stars
A. M. Boesgaard (U. Hawaii), A. M. Cody (Harvard U.), C. P. Deliyannis (Indiana U.), J. R. King (UNLV), A. Stephens (U. Hawaii)

It is important to determine the composition of unevolved stars in globular clusters in order to learn the original composition of the cluster and to learn about stellar evolution and the chemical history of the Galactic halo. We have made observations of five stars at the turn-off in M 71 with the Keck I 10-m telescope and HIRES at a spectral resolution of 45,000. Such stars have not undergone any mixing with the interior layers and can provide benchmark abundances to interpret the abundance results found in red giants and other evolved stars. These stars have V = 17.7 and integration times of 2.5-5 hours were needed to obtain signal-to-noise ratios of 50-60. We have determined abundances of Li, Na, the Fe-peak elements: Fe, Cr, Ni, alpha-fusion elements: Mg, Si, Ca, Ti, and neutron capture elements: Y and Ba. Except for Li, we have found no star-to-star abundance variations and derive [Fe/H] = -0.80 ±0.02. The alpha elements are enhanced with [<\alpha>/Fe] = 0.24. Both Y and Ba are enhanced relative to Fe also. We compare our results with those from giant stars in M71, with turn-off stars in the globular clusters M13 and M92, and with halo field stars.

This work has been supported by the National Science Foundation.

AAS 199th meeting, Washington, DC, January 2002
[63.03] Rotational Studies of MUSES-C Target Asteroid (25143) 1998 SF36
J.S. Lambert, D.J. Tholen (IFA, U. Hawaii)

The Apollo-type near-Earth asteroid (25143) 1998 SF36 has been selected as the target for the Japanese MUSES-C sample return mission. To assist with mission planning, we participated in a world-wide effort to acquire physical observations of this asteroid during its close approach to the Earth in 2001. The work being presented here deals with observations to determine the rotational state and shape of the asteroid. The 2001 apparition was particularly well-suited for the determination of the orientation of the spin axis, because the asteroid swung through 180 degrees of geocentric ecliptic longitude, though our observations will need to be combined with similar ones from other observatories made at different times during the apparition to realize the full potential of the data. Our observations do show a 12-hour rotation period, which is slower than average for asteroids. The brightness variation exceeds 0.7 mag, indicating an elongated shape with an axial ratio of at least 2 to 1. This research was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawaii’s Institute for Astronomy.

AAS 199th meeting, Washington, DC, January 2002
[54.01] Near-Infrared Spectroscopy of a Sample of Luminous Infrared Galaxies
R. D. Joseph (University of Hawaii), M. Pitts (Ohio State University)

We have obtained spectra from 0.95 to 2.35 micron at a spectral resolution of ~1,200 for a sample of luminous infrared-bright galaxies. The spectra were measured with SpeX, the new cross-dispersed medium-resolution infrared spectrometer at the NASA Infrared Telescope Facility. Since our goal was to investigate putative AGN or starburst activity in the centers of these galaxies, with as little dilution from the surrounding galaxy as possible, the spectra were taken with a 0.5 x 2 arcsec2 slit. We use these data: a) to search for broad hydrogen lines indicative of an underlying AGN, and b) to determine the stellar populations of underlying starbursts using stellar evolutionary synthesis models. These results will be compared with those found from previously-published 2 micron spectra for these galaxies obtained with a 3 x 9 arcsec2 slit.

This work was supported by NSF Grant AST 99-87896 and NASA Grants NAG 5-3370 and JPL 961566.

AAS 199th meeting, Washington, DC, January 2002
[96.08] The Stellar Population Associated with NGC7023
A. Urban, M. R. Meyer (Steward Obs., U. of Arizona), G. H. Herbig, S. Dahm (IfA, U. of Hawaii)

What is the richness of the stellar aggregate associated with the reflection nebula, NGC7023 and what is its star formation history? NGC7023 is located in the Cepheus Flare Region and numerous studies have been conducted on the properties of its nebulosity. However, there has been little investigation into the properties of its stars. HD200775 is the brightest star in NGC7023 and it is classified as a Herbig Be star, an intermediate mass analogue of solar-type pre-main sequence T Tauri stars. By sampling the full stellar population, the sequence of star formation and distribution of stellar masses can be investigated. To understand these properties, regions in and around NGC7023 were sampled for stars with H alpha emission, a reliable method of identifying active young stars. For five fields around NGC7023, 7.5 square arcminutes each, photometry was obtained in BVRI. Point spread function fitting was used in order to look for blended or binary stars. Color-magnitude diagrams were created and compared with pre-main sequence tracks to determine the age of the aggregate. With the knowledge of the distance, extinction, and age, the distribution of the H alpha emission stars can be compared with the distribution of the other members in the aggregate associated with NGC7023.
This research project was supported by the NSF REU program.