Phase-resolved spectroscopy and Kepler photometry of the ultracompact AM CVn binary SDSS J190817.07+394036.4
Abstract
Kepler satellite photometry and phase-resolved spectroscopy of the ultracompact AM CVn type binary SDSS J190817.07+394036.4 are presented. The average spectra reveal a variety of weak metal lines of different species, including silicon, sulphur and magnesium as well as many lines of nitrogen, beside the strong absorption lines of neutral helium. The phase-folded spectra and the Doppler tomograms reveal an S-wave in emission in the core of the He I 4471 Å absorption line at a period of P_(orb) = 1085.7 ± 2.8 s identifying this as the orbital period of the system. The Si II, Mg II and the core of some He I lines show an S-wave in absorption with a phase offset of 170° ± 15° compared to the S-wave in emission. The N II, Si III and some helium lines do not show any phase variability at all. The spectroscopic orbital period is in excellent agreement with a period at P_(orb) = 1085.108(9) s detected in the 3 yr Kepler light curve. A Fourier analysis of the Q6–Q17 short-cadence data obtained by Kepler revealed a large number of frequencies above the noise level where the majority shows a large variability in frequency and amplitude. In an Observed-minus-computed analysis, we measured a |P˙| ∼1.0 |P˙|∼1.0× 10^(−8) s s^(−1) for some of the strongest variations and set a limit for the orbital period to be |P˙| < 10^(−10) |P˙| < 10^(−10) s s^(−1). The shape of the phase-folded light curve on the orbital period indicates the motion of the bright-spot. Models of the system were constructed to see whether the phases of the radial velocity curves and the light-curve variation can be combined to a coherent picture. However, from the measured phases neither the absorption nor the emission can be explained to originate in the bright-spot.
Additional Information
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 July 14. Received 2015 July 9; in original form 2015 May 12. TK acknowledges support by the Netherlands Research School of Astronomy (NOVA). TRM and DS acknowledge the support from the Science and Technology Facilities Council (STFC) during the course of this work. PJG wishes to thank the California Institute of Technology its hospitality and support during a sabbatical leave. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias, in the island of La Palma. Based on observations with the William Herschel Telescope operated by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias on the island of La Palma, Spain. Some of 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. This paper includes data collected by the Kepler mission. The authors gratefully acknowledge the Kepler team and all who have contributed to enabling the mission. The Kepler data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). Funding for the Kepler Mission is provided by NASAs Science Mission Directorate. This research has made use of NASA's Astrophysics Data System.Attached Files
Published - MNRAS-2015-Kupfer-483-96.pdf
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- Eprint ID
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- CaltechAUTHORS:20160108-124025927
- W. M. Keck Foundation
- NASA
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2016-01-09Created from EPrint's datestamp field
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2021-11-10Created from EPrint's last_modified field
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