A Decade of Radial-velocity Monitoring of Vega and New Limits on the Presence of Planets

Hurt, Spencer A. and Quinn, Samuel N. and Latham, David W. and Vanderburg, Andrew and Esquerdo, Gilbert A. and Calkins, Michael L. and Berlind, Perry and Angus, Ruth and Latham, Christian A. and Zhou, George ORCID: https://orcid.org/0000-0002-4891-3517 (2021) A Decade of Radial-velocity Monitoring of Vega and New Limits on the Presence of Planets. The Astronomical Journal, 161 (4):157. pp. 1-14. ISSN 0004-6256


Abstract

We present an analysis of 1524 spectra of Vega spanning 10 yr, in which we search for periodic radial-velocity variations. A signal with a periodicity of 0.676 day and a semi-amplitude of ∼10 m s-1 is consistent with the rotation period measured over much shorter time spans by previous spectroscopic and spectropolarimetric studies, confirming the presence of surface features on this A0 star. The activity signal appears to evolve on long timescales, which may indicate the presence of failed fossil magnetic fields on Vega. TESS data reveal Vega’s photometric rotational modulation for the first time, with a total amplitude of only 10 ppm. A comparison of the spectroscopic and photometric amplitudes suggests that the surface features may be dominated by bright plages rather than dark spots. For the shortest orbital periods, transit and radial-velocity injection recovery tests exclude the presence of transiting planets larger than 2 R and most non-transiting giant planets. At long periods, we combine our radial velocities with direct imaging from the literature to produce detection limits for Vegan planets and brown dwarfs out to distances of 15 au. Finally, we detect a candidate radial-velocity signal with a period of 2.43 days and a semi-amplitude of 6 m s-1. If caused by an orbiting companion, its minimum mass would be ∼20 M; because of Vega’s pole-on orientation, this would correspond to a Jovian planet if the orbit is aligned with the stellar spin. We discuss the prospects for confirmation of this candidate planet.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 07 Mar 2022 03:59
Last Modified: 07 Mar 2022 04:18
Uncontrolled Keywords: Exoplanet astronomy; Exoplanet detection methods; Exoplanets; Stellar; activity; Stellar magnetic fields; Photometry; Radial velocity; Circumstellar disks; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.3847/1538-3881/abdec8
URI: http://eprints.usq.edu.au/id/eprint/44995

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