Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 10, 2013 | Submitted + Published
Journal Article Open

Keck Observations of the Galactic Center Source G2: Gas Cloud or Star?

Abstract

We present new observations and analysis of G2—the intriguing red emission-line object which is quickly approaching the Galaxy's central black hole. The observations were obtained with the laser guide star adaptive optics systems on the W. M. Keck I and II telescopes (2006-2012) and include spectroscopy (R ~ 3600) centered on the hydrogen Brγ line as well as K' (2.1 μm) and L' (3.8 μm) imaging. Analysis of these observations shows the Brγ line emission has a positional offset from the L' continuum. This offset is likely due to background source confusion at L'. We therefore present the first orbital solution derived from Brγ line astrometry, which, when coupled with radial velocity measurements, results in a later time of closest approach (2014.21 ± 0.14), closer periastron (130 AU, 1600 R_s), and higher eccentricity (0.9814 ± 0.0060) compared to a solution using L' astrometry. It is shown that G2 has no K' counterpart down to K' ~ 20 mag. G2's L' continuum and the Brγ line emission appears unresolved in almost all epochs, which implies that the bulk of the emission resides in a compact region. The observations altogether suggest that while G2 has a gaseous component that is tidally interacting with the central black hole, there is likely a central star providing the self-gravity necessary to sustain the compact nature of this object.

Additional Information

© 2013 The American Astronomical Society. Received 2013 April 17; accepted 2013 July 7; published 2013 July 29. The authors acknowledge the invaluable feedback from the referee and conference attendees at workshops where this work has been presented (AAS 221st Meeting, Keck 20th Anniversary Celebration, Galactic Nuclei Ringberg Workshop). Support for this work was provided by NSF grant AST-0909218. Data presented herein were taken at the Keck Observatory, which is operated as a scientific partnership among Caltech, UC, and NASA; the Observatory was made possible by the generous financial support of the Keck Foundation. Facilities: Keck:II (LGS AO, NIRC2, OSIRIS), Keck:I (LGS AO, OSIRIS)

Attached Files

Published - 2041-8205_773_1_L13.pdf

Submitted - 1304.5280v2.pdf

Files

1304.5280v2.pdf
Files (876.2 kB)
Name Size Download all
md5:303893395bfeac93b1b866c3dfd5b4af
288.7 kB Preview Download
md5:278e68aae3fd3c029f0123d7c2ce613d
587.5 kB Preview Download

Additional details

Created:
August 19, 2023
Modified:
October 24, 2023