Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra
We present a technique to extract radial velocity (RV) measurements from echelle spectrograph observations of rapidly rotating stars (V sin i ≳ 50 kms^(−1)). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the RV shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract RV measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute RVs with a precision ranging from 0.5–2.0 kms^(−1) per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with RV scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly rotating stars.
© 2015 American Astronomical Society. Received 2014 November 3; accepted 2015 March 12; published 2015 April 15. We thank Emily Rauscher for her careful review of the manuscript and helpful suggestions. J.B. thanks Philip Muirhead for useful conversations and Iryna Butsky for useful comments on the manuscript. We thank the referee, Davide Gandolfi, for his extremely helpful suggestions that led to a vastly improved paper, as well as his suggestions for future directions to take this work. J.B. and A.V. are supported by the National Science Foundation Graduate Research Fellowship, Grants No. DGE 1256260 and DGE 1144152, respectively. J.B. would like to thank Mr. and Mrs. Kenneth Adelman for providing funding for her 2012 Alain Porter Memorial SURF Fellowship, during which this research was begun. J.A.J. is supported by generous grants from the David and Lucile Packard and Alfred P. Sloan Foundations. This research has made use of NASA's Astrophysics Data System, the SIMBAD database and VizieR catalog access tool, operated at CDS, Strasbourg, France. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Published - 0067-0049_217_2_29.pdf
Submitted - 1503.03874v1.pdf