THE sdB+M ECLIPSING SYSTEM HW VIRGINIS AND ITS CIRCUMBINARY PLANETS

By Jae Woo Lee, Seung-Lee Kim, Chun-Hwey Kim, R. Koch, Chung-Uk Lee, Ho‐Il Kim, Jang-Ho Park. 2008

183 citations recorded by the source corpus.

For the very short period subdwarf B eclipsing binary HW Vir, we present new CCD photometry made from 2000 through 2008. In order to obtain consistency of the binary parameters, our new light curves, showing sharp eclipses and a striking reflection effect, were analyzed simultaneously with previously published radial velocity data. The secondary star parameters of M2 = 0.14 M☉, R2 = 0.18 R☉, and T2 = 3084 K are consistent with those of an M6-7 main-sequence star. A credibility issue regarding bolometric corrections is emphasized. More than 250 times of minimum light, including our 41 timings and spanning more than 24 yr, were used for a period study. From a detailed analysis of the O − C diagram, it emerged that the orbital period of HW Vir has varied as a combination of a downward-opening parabola and two sinusoidal variations, with cycle lengths of P3 = 15.8 yr and P4 = 9.1 yr and semiamplitudes of K3 = 77 s and K4 = 23 s, respectively. The continuous period decrease with a rate of −8.28 × 10−9 days yr−1 may be produced by angular momentum loss due to magnetic stellar wind braking but not by gravitational radiation. Of the possible causes of the cyclical components of the period change, apsidal motion and magnetic period modulation can be ruled out. The most reasonable explanation of both cyclical variations is a pair of light-travel-time effects driven by the presence of two substellar companions with projected masses of M3sin i3 = 19.2 MJup and M4sin i4 = 8.5 MJup. The two objects are the first circumbinary planets known to have been formed in a protoplanetary disk as well the first ones discovered by using the eclipse-timing method. The detection implies that planets could be common around binary stars just as are planets around single stars and demonstrates that planetary systems formed in a circumbinary disk can survive over long timescales. Depending on the thermal inertia of their massive atmospheres, the hemispheres of the planets turned toward the stars can experience substantial reciprocating temperature changes during the minutes-long primary eclipse intervals.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/95c68644d4f36d46ebf858e8990da1f32c5bfdab

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Citations in the corpus

• The great escape: how exoplanets and smaller bodies desert dying stars (2011, background): “…a giant planet orbiting the extreme horizontal branch star V 391 Pegasi, Geier et al. (2009) found a planet around the hot subdwarf star HD 149382, Lee et al. (2009) reported circumbinary planets to the sdB+M eclipsing system HW Virginis, and Setiawan et al. (2010) suggested that the planet…”
• Simulations of two-planet systems through all phases of stellar evolution: implications for the instability boundary and white dwarf pollution (2013, background): “…systems (Wolszczan & Frail 1992; Wolszczan 1994; Sigurdsson et al. 2003; Silvotti et al. 2007; Mullally et al. 2008, 2009; Geier et al. 2009; Lee et al. 2009, 2012; Setiawan et al. 2010; Wickramasinghe et al. 2010; Charpinet et al. 2011; Adamów et al. 2012; Farihi et al. 2012c; Lee, Han &…”
• High‐inclination orbits in the secular quadrupolar three‐body problem (2009, background): “The outer restricted problem and its generalization to the non restricted case provide an interesting starting point in the study of circumbinary planetary systems, such as the one discovered recently around the eclipsing sdB+M system HW Virginis (Lee et al. 2009).”
• PLANET HUNTERS: A TRANSITING CIRCUMBINARY PLANET IN A QUADRUPLE STAR SYSTEM (2012, background): “Although planets have previously been suspected to be orbiting both stars in a binary star system before Kepler (Bennett et al. 1999; Deeg et al. 2008; Lee et al. 2009; Beuermann et al. 2012), the Kepler era ushered in the first confirmed identification of such systems.”