AAS meeting, January 2009, Long Beach, California Host Galaxies of Long-Duration Gamma-Ray Bursts Megan Bagley (University of Wyoming), L. J. Kewley (IfA), E. M. Levesque (IfA)
Long-duration gamma-ray bursts (GRBs) are associated with the deaths of massive, short-lived stars, and thus may be useful in tracking star formation in the universe. However, GRB progenitor models suggest that they might occur only in low-metallicity environments, introducing a bias into star formation studies. Presented here are the high-resolution spectra of two GRB host galaxies, one at z ~ 0.03 and the other at z ~ 0.7. The nearby galaxy, the host of GRB 060218, has a low metallicity, but one that is comparable to local galaxies of similar luminosity. It has little to no extinction and a star formation rate of ~2 x 10-2 M yr-1. The metallicity of the more distant galaxy, the host of GRB 991208, is not well constrained because the Hα and [N II] lines are redshifted into the near infrared and were not observed. It has a star formation rate of 1–9 M yr-1 and, unlike the majority of GRB hosts, is dusty. These two galaxies will eventually be a part of a larger sample of GRB hosts. 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 2009, Long Beach, California V1647 Orionis: Accretion in an Eruptive Variable Star
Lori Beerman (University of Cincinnati & IfA), C. Aspin (IfA)
Eruptions in young stars are rare and can provide us with new insight into the mechanics of star formation. High-resolution near-IR observations were taken of the 2004-2006 outburst of V1647 Orionis, a young variable which illuminates what is now termed McNeil’s nebula. From these observations, we are able to follow the decrease in the mass accretion rate onto the star as the outburst subsides using Br-gamma and Pa-beta emission line fluxes. Accretion rates were found to range from 5 x 10-6 solar masses per year during the outburst to 3 x 10-7 solar masses per year one year following the outburst, showing that there is a definite relationship between accretion of circumstellar material onto the disk and the eruptive event. We present these results and consider their implications for pre-main sequence stellar evolution.
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 meeting, January 2009, Long Beach, California Photometric Follow-up of the Transiting Exoplanet HAT-P-7b Nicole Cabrera (Georgia Institute of Technology), J. A. Johnson (IfA), P. K. G. Williams (University of California)
HAT-P-7b is a recently discovered very hot Jupiter with a period of 2.2047299 days that transits a star in the Kepler field. We collected photometric data of HAT-P-7b using the 1-meter Nickel telescope at the Lick Observatory in order to refine the system parameters. We reduced the data using a pipeline created specifically to handle Nickel images. We present our data reduction method and two new light curves. This work was conducted as part of the Research Experience for Undergraduates (REU) at the University of Hawaii's Institute for Astronomy and funded by the NSF.
AAS meeting, January 2009, Long Beach, California Determining the Source of Neutral Helium in the Corona from Spectropolarimetric Observations with SOLARC
Meghan Cassidy (IfA REU)
On the summit of Haleakala, spectropolarimetic ground observations from the coronagraph of the Scattered-light Observatory for Limb Active Regions and Coronae (SOLARC) and infrared imaging spectropolarimeter detect a spectrally resolved surface brightness flux at the 10830 Å wavelength. The polarization signal indicates scattered light off of He I particles. Under investigation is the origin of this neutral helium. Its presence in the corona could be due to the local interstellar medium (LISM) helium wind (LISW) or a zodiacal dust related “inner source.”
AAS meeting, January 2009, Long Beach, California Commissioning a Robotic Telescope for Star Formation Studies Heather Cegla (Minnesota State University Moorhead,), J. Walawender (IfA), B. Reipurth (IfA)
We present an account of the commissioning of a small, wide field telescope (VYSOS-5) which is the first component of the VYSOS (Variable Young Stellar Objects Survey) telescope network to become operational. The VYSOS network will consist of four telescopes, two situated at Mauna Loa on the Big Island of Hawaii and two situated at Cerro Armazones in Chile's Atacama Desert. All four telescopes will make automated observations of star forming regions on a nightly basis in order to detect sudden outbursts in young stars, find young eclipsing binaries, determine rotation periods of young stars, and characterize the types of variability of pre-main sequence stars. Preliminary results from early observations with VYSOS-5 are also presented. 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 meeting, January 2009, Long Beach, California Spectropolarimetric Observations of the Helium 10830 Å Line: A Search for the Signature of Optical Pumping Nathan Jonathan Goldbaum (University of Colorado), J. R. Kuhn (IfA)
In order to characterize the center-to-limb and latitudinal variation of the polarization of the He I 10830 Å line we observed the limb of the sun at several position angles using the Scatter-Free Observatory for Limb Active Regions and Coronae (SOLARC), an imaging spectropolarimeter located on the summit of Haleakala, Maui. The data was reduced and analyzed to produce profiles of the magnitude of the Stokes Q/I and U/I signals as a function of latitude and solar radius. Modeling of the observed profiles should allow us to detect whether the observed linear polarization signal is due entirely to scattering polarization or possibly includes absorptively polarized light transmitted through an optically pumped gas. This work was conducted as part of a Research Experience for Undergraduates (REU) position at the University of Hawaii's Institute for Astronomy and funded by the NSF.
AAS meeting, January 2009, Long Beach, California X-ray Stacking Of 70µM Detected Sources In The C-COSMOS Field
Severin Knudsen (Yale), D. Sanders (IfA), M. Urry (Yale), J. Kartaltepe (IfA), S. Virani (Yale), V. U (IfA)
Sources detected at 70µm in the COSMOS field are infrared luminous galaxies predominantly in the range 0 < z 0.5 yields an average count rate of 1.624 counts/source, less than the average background count rate for the same size aperture of 2.151 counts/aperture. However, the very low RMS value on the background counts shows this to be a 11.85 s detection. Background analysis clearly indicates that our stacked images are a compilation of many very faint sources rather than a few stronger sources. The hardness ratio was significantly less negative for the z > 0.5 sources (H-S/H+S = -0.270) than for the z < 0.5 sources (H-S/H+S = -0.516). For the sources z > 0.5 the hard X-ray spectral shape indicates they are dominated by more intrinsically luminous AGN compared to the softer X-ray spectral shape of the nearby sources which is characteristic of star formation. The harder composite X-ray SED for the more distant objects suggests that luminous 70mm sources are a valuable way to find high-redshift obscured AGN.
DPS, October 2008, Ithaca, New York Artificial Neural Network Classification of Asteroids in the Sloan Digital Sky Survey
Amit Misra (Case Western Reserve University), S. J. Bus (University of Hawaii Institute for Astronomy)
There are currently only a few thousand asteroids with known classifications. Our aim is to increase this number to over 20,000 by classifying asteroids identified in the Sloan Digital Sky Survey (SDSS) Moving Object Catalogue using an artificial neural network that has been developed using the Neural Network Toolbox in Matlab. With this neural network, we are able to provide classifications for 22,847 asteroids based on normalized reflectances derived from the g', r', i', and z' SDSS magnitudes. The neural network was trained using a combination of previously classified asteroids, asteroids from known dynamical families, and asteroids we classified by hand from the SDSS reflectances. The previously classified asteroids were from the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) and the Small Solar System Objects Spectroscopic Survey (S3OS2). Asteroids were divided into 13 spectral classes (T, D, B, C, X, K, S, L, A, R, Q, V and O), based on the previous taxonomies of Tholen (1984) and Bus and Binzel (2002). A major advantage of the neural network approach is that it generates a set of possible classifications for each asteroid, along with associated probabilities that emulate the continuum between classes observed in asteroid taxonomy. Our neural network solution can be applied to any new asteroid observations made in the g', r', i', z' system. We anticipate that this network and any supporting algorithms will be made publicly available in the near future via the world wide web. We will present a description of this artificial neural network and the resulting classifications as well as a discussion of its accuracy and limitations. This work was conducted through a Research Experience for Undergraduates (REU) position at the University of Hawaii's Institute for Astronomy, funded by the NSF.