A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era

Schaffenroth V, Casewell SL, Schneider D, Kilkenny D, Geier S, Heber U, Irrgang A, Przybilla N, Marsh TR, Littlefair SP, Dhillon VS (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Monthly Notices of the Royal Astronomical Society Oxford University Press

Book Volume: 501

Pages Range: 3847-3870

Journal Issue: 3

DOI: 10.1093/mnras/staa3661

Abstract

Subdwarf B stars are core-helium-burning stars located on the extreme horizontal branch (EHB). Extensive mass loss on the red giant branch is necessary to form them. It has been proposed that substellar companions could lead to the required mass loss when they are engulfed in the envelope of the red giant star. J08205+0008 was the first example of a hot subdwarf star with a close, substellar companion candidate to be found. Here, we perform an in-depth re-analysis of this important system with much higher quality data allowing additional analysis methods. From the higher resolution spectra obtained with ESO-VLT/XSHOOTER, we derive the chemical abundances of the hot subdwarf as well as its rotational velocity. Using the Gaia parallax and a fit to the spectral energy distribution in the secondary eclipse, tight constraints to the radius of the hot subdwarf are derived. From a long-term photometric campaign, we detected a significant period decrease of -3.2(8) x 10(-12) dd(-1). This can be explained by the non-synchronized hot subdwarf star being spun up by tidal interactions forcing it to become synchronized. From the rate of period decrease we could derive the synchronization time-scale to be 4 Myr, much smaller than the lifetime on EHB. By combining all different methods, we could constrain the hot subdwarf to a mass of 0.39-0.50 M-circle dot and a radius of R-sdB = 0.194 +/- 0.008 R-circle dot, and the companion to 0.061-0.071 M-circle dot with a radius of R-comp = 0.092 +/- 0.005 R-circle dot, below the hydrogen-burning limit. We therefore confirm that the companion is most likely a massive brown dwarf.

Authors with CRIS profile

David Schneider Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut Ulrich Heber Naturwissenschaftliche Fakultät Andreas Irrgang Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut

Involved external institutions

Universität Potsdam DE Germany (DE) Leopold-Franzens-Universität Innsbruck / University of Innsbruck AT Austria (AT) University of Leicester GB United Kingdom (GB) University of the Western Cape (UWC) ZA South Africa (ZA) University of Sheffield GB United Kingdom (GB) University of Warwick GB United Kingdom (GB)

How to cite

APA:

Schaffenroth, V., Casewell, S.L., Schneider, D., Kilkenny, D., Geier, S., Heber, U.,... Dhillon, V.S. (2021). A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era. Monthly Notices of the Royal Astronomical Society, 501(3), 3847-3870. https://doi.org/10.1093/mnras/staa3661

MLA:

Schaffenroth, V., et al. "A quantitative in-depth analysis of the prototype sdB plus BD system SDSS J08205+0008 revisited in the Gaia era." Monthly Notices of the Royal Astronomical Society 501.3 (2021): 3847-3870.

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