The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

Pulley, D.; Faillace, G.; Smith, D.; Watkins, Americo; Harrach, S. von

doi:10.1051/0004-6361/201731125

Cited by 14 publications

(15 citation statements)

References 49 publications

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“…The only possibility for our technique missing this planet would be an orbital inclination lower than 43 • . Our conclusion supplements the work by Pulley et al (2018) based on recent observations of seven sdB systems. The authors show that period variations of these stars cannot be explained simply on the basis of third bodies orbiting these systems.…”

Section: Discussionsupporting

confidence: 90%

The quest for planets around subdwarfs and white dwarfs fromKeplerspace telescope fields

Krzesiński

Blokesz

Siwak

et al. 2020

A&A

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Context. In this study, we independently test the presence of an exoplanet around the binary KIC 9472174, which is composed of a red dwarf and a pulsating type B subdwarf. We also present the results of our search for Jupiter-mass objects orbiting near to the eclipsing binary KIC 7975824, which is composed of a white dwarf and type B subdwarf, and the pulsating white dwarf KIC 8626021. Aims. The goal is to test analytical techniques and prepare the ground for a larger search for possible substellar survivors on tight orbits around post-common envelope binaries and stars at the end of their evolution, that is, extended horizontal branch stars and white dwarfs. We, therefore, mainly focus on substellar bodies orbiting these stars within the range of the host’s former red-giant or asymptotic-giant phase envelopes. Due to the methods we use, the quest is restricted to single-pulsating type B subdwarf and white dwarf stars and short-period eclipsing binaries containing a white dwarf or a subdwarf component. Methods. Our methods rely on the detection of exoplanetary signals hidden in photometric time series data from the Kepler space telescope, and they are based on natural clocks within the data itself, such as stellar pulsations and eclipse times. The light curves are analyzed using Fourier transforms, time-delays, and eclipse timing variations. Results. Based on the three objects studied in this paper, we demonstrate that these methods can be used to detect giant exoplanets orbiting around pulsating white dwarf or type B subdwarf stars as well as short-period binary systems, at distances which fall within the range of the former red-giant envelope of a single star or the common envelope of a binary. Using our analysis techniques, we reject the existence of a Jupiter-mass exoplanet around the binary KIC 9472174 at the distance and orbital period previously suggested in the literature. We also found that the eclipse timing variations observed in the binary might depend on the reduction and processing of the Kepler data. The other two objects analyzed in this work do not have Jupiter mass exoplanets orbiting within 0.7–1.4 AU from them, or larger-mass objects on closer orbits (the given mass limits are minimum masses). Conclusions. Depending on the detection threshold of the time-delay method and the inclination of the exoplanet orbit toward the observer, data from the primary Kepler mission allows for the detection of bodies with a minimum of ~1 Jupiter-mass orbiting these stars at ~1 AU, while data from the K2 mission extends the detection of objects with a minimum mass of ~7 Jupiter-mass on ~0.1 AU orbits. The exoplanet mass and orbital distance limits depend on the length of the available photometric time series.

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Section: Discussionsupporting

confidence: 90%

The quest for planets around subdwarfs and white dwarfs fromKeplerspace telescope fields

Krzesiński

Blokesz

Siwak

et al. 2020

A&A

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“…They concluded that these findings are in agreement with the so-called Applegate mechanism, which proposes that variability in the binary orbits can be driven by magnetic cycles in the secondary stars. In all published HW Vir systems with a longer observational baseline of several years quite large period variations on the order of minutes have been detected (see Zorotovic & Schreiber 2013;Pulley et al 2018, for an overview), with the exception of AA Dor (Kilkenny 2014), which still shows no sign of period variations after a baseline of about 40 years. Also the orbital period decrease in J08205+0008 is on the order of seconds and has only been found after 10 years of observation and no additional sinusoidal signals have been found as seen in many of the other systems.…”

Section: Orbital Period Variations In Hw Vir Systemsmentioning

confidence: 99%

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

Schaffenroth

Casewell

Schneider

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Subdwarf B stars are core-helium burning stars located on the extreme horizontal branch. 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 $-3.2(8)\cdot 10^{-12} \, \rm dd^{-1}$. This can be explained by the non-synchronised hot subdwarf star being spun up by tidal interactions forcing it to become synchronised. From the rate of period decrease we could derive the synchronisation timescale 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 $0.39-0.50\, \rm M_\odot$ and a radius of $R_{\rm sdB}=0.194\pm 0.008\, \rm R_\odot$, and the companion to $0.061-0.071\rm \, M_\odot$ with a radius of $R_{\rm comp}=0.092 \pm 0.005\, \rm R_\odot$, below the hydrogen burning limit. We therefore confirm that the companion is most likely a massive brown dwarf.

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“…Pulley et al (2015) showed that the more recent O-C timing data began to diverge from the Qian model. Later in 2018, they confirmed this departure by adding 65 more times of minima (Pulley et al 2018). Bogensberger et al (2017) proposed a new one planet model with a longer orbital 11.8 year period, eccentricity 0.38, and no quadratic term.…”

Section: Hw Virginismentioning

confidence: 94%

“…Almeida et al (2017) reported eight more eclipse times and updated the linear ephemeris. Most recently, Pulley et al (2018) extended the timing database with 26 more timing minima. They compared the quadratic ephemeris by Qian et al (2010) and linear ephemeris proposed by Lohr et al (2014) concluded there is no statistically significant difference between the two.…”

Section: Hs2231+2441mentioning

confidence: 99%

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Eclipse Timing Modeling of Three Post-Common Envelope Binaries: Hybrid Solutions

Mai,

Mutel

2021

Preprint

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We report 88 new observations of three post common envelope binaries at primary eclipse spanning between December 2018 to February 2021. We combine recent primary eclipse timing observations with previously published values to search for substellar circumbinary components consistent with timing variations from a linear ephemeris. We used a least-squares minimization fitting algorithm weighted by a Hill orbit stability function, followed by Bayesian inference, to determine best-fit orbital parameters and associated uncertainties. For HS2231+2441, we find that the timing data are consistent with a constant period and that there is no evidence to suggest orbiting components. For HS0705+6700, we find both two and three-component solutions that are stable for at least 10 Myr but have very different parameters. For HW Vir, we find multi-component solutions that fit the timing data but they are unstable on short timescale, and therefore highly improbable. Conversely, both the least-squares and Bayesian solutions provide a poor fit. In both systems, the best-fit stable solutions significantly deviate from the ensemble timing data.For both HS0705+6700 and HW Vir, substellar component solutions that fit all observed eclipse timing data are dynamically unstable, whereas best-fit solutions with stable orbits provide poor O-C fits. We speculate that the observed timing variations for these systems, and very possibly other sdB binaries, may result from a combination of substellar component perturbations and an Applegate-Lanza mechanism.

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The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries

Cited by 14 publications

References 49 publications

The quest for planets around subdwarfs and white dwarfs fromKeplerspace telescope fields

The quest for planets around subdwarfs and white dwarfs fromKeplerspace telescope fields

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

Eclipse Timing Modeling of Three Post-Common Envelope Binaries: Hybrid Solutions

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