No close companions to a sample of bright sdB stars

Silvotti, Roberto; Ostensen, Roy H.; Telting, John H.

doi:10.48550/arxiv.2002.04545

Cited by 9 publications

(7 citation statements)

References 3 publications

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“…Among these phenomena, macro turbulence caused by pulsations should be a minor effect. Indeed, g-mode pulsations in sdB stars produce typical RV variations of less than 1 km/s (Silvotti et al 2020). In HD 4539, that has pulsation amplitudes of the main peaks very similar to TIC 137608661, the RV variations do not exceed 200-300 m/s (Silvotti et al 2019).…”

Section: High-resolution Spectroscopy: Sdb Surface Rotation and Metal...mentioning

confidence: 99%

Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well-defined rotational splitting

Silvotti

Németh

Telting

et al. 2022

Monthly Notices of the Royal Astronomical Society

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TIC 137608661/TYC 4544-2658-1/FBS 0938+788 is a new sdBV+dM reflection-effect binary discovered by the TESS space mission with an orbital period of 7.21 hours. In addition to the orbital frequency and its harmonics, the Fourier transform of TIC 137608661 shows many g-mode pulsation frequencies from the sdB star. The amplitude spectrum is particularly simple to interpret as we immediately see several rotational triplets of equally spaced frequencies. The central frequencies of these triplets are equally spaced in period with a mean period spacing of 270.12 s, corresponding to consecutive l=1 modes. From the mean frequency spacing of 1.25 μHz we derive a rotation period of 4.6 days in the deep layers of the sdB star, significantly longer than the orbital period. Among the handful of sdB+dM binaries for which the sdB rotation was measured through asteroseismology, TIC 137608661 is the non-synchronized system with both the shortest orbital period and the shortest core rotation period. Only NY Vir has a shorter orbital period but it is synchronized. From a spectroscopic follow-up of TIC 137608661 we measure the radial velocities of the sdB star, determine its atmospheric parameters, and estimate the rotation rate at the surface of the star. This measurement allows us to exclude synchronized rotation also in the outer layers and suggests a differential rotation, with the surface rotating faster than the core, as found in few other similar systems. Furthermore, an analysis of the spectral energy distribution of TIC 137608661, together with a comparison between sdB pulsation properties and asteroseismic models, gives us further elements to constrain the system.

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Section: High-resolution Spectroscopy: Sdb Surface Rotation and Metal...mentioning

confidence: 99%

Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well-defined rotational splitting

Silvotti

Németh

Telting

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…Using the RV method, Geier et al (2009) announced the discovery of a close-in (P orb " 2.4 days) planet of several Jupiter masses around HD 149382, but it was ruled out by high-precision RV measurements obtained with the Hobby-Eberly Telescope spectrograph, excluding the presence of almost any substellar companion with P orb ă 28 days and M sin i Á 1M Jup (Norris et al 2011). No close massive planets (down to a few Jupiter masses) were found from a mini RV survey carried out with the HARPS-N spectrograph on 8 apparently single hot subdwarfs (Silvotti et al 2020).…”

Section: Search For Planets Around Hot Subdwarfs: Current Statusmentioning

confidence: 99%

A transit survey to search for planets around hot subdwarfs: I. methods and performance tests on light curves from Kepler, K2, TESS, and CHEOPS

Van Grootel,

Pozuelos,

Thuillier

et al. 2021

Preprint

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Context. Hot subdwarfs experienced strong mass loss on the Red Giant Branch (RGB) and are now hot and small He-burning objects. Such stars constitute excellent opportunities to address the question of the evolution of exoplanetary systems directly after the RGB phase of evolution. Aims. In this project we aim to perform a transit survey in all available light curves of hot subdwarfs from space-based telescopes (Kepler, K2, TESS, and CHEOPS), with our custom-made pipeline SHERLOCK, in order to determine the occurrence rate of planets around these stars, as a function of orbital period and planetary radius. We also aim to determine whether planets previously engulfed in the envelope of their red giant host star can survive, even partially, as a planetary remnant. Methods. In this first paper, we perform injection-and-recovery tests of synthetic transits for a selection of representative Kepler, K2 and TESS light curves, to determine which transiting bodies, in terms of object radius and orbital period, we will be able to detect with our tools. We also provide such estimates for CHEOPS data, which we analyze with the pycheops package. Results. Transiting objects with a radius À 1.0 R C can be detected in most of Kepler, K2 and CHEOPS targets for the shortest orbital periods (1 d and below), reaching values as small as "0.3 R C in the best cases. Reaching sub-Earth-sized bodies is achieved only for the brightest TESS targets, and the ones observed during a significant number of sectors. We also give a series of representative results for farther and bigger planets, for which the performances strongly depend on the target magnitude, the length and the quality of the data. Conclusions. The TESS sample will provide the most important statistics for the global aim of measuring the planet occurrence rate around hot subdwarfs. The Kepler, K2 and CHEOPS data will allow us to search for planetary remnants, i.e. very close and small (possibly disintegrating) objects, which would have partly survived the engulfment in their red giant host.

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“…We adopted the mean values as listed in Table 1, which agree with the published values to within respective error limits. PG 0342+026 was observed in November-December 2012 with Harps-N at the Telescopio Nazionale Galileo (TNG, La Palma) in the context of a program to search for sdB low-mass companions (see Silvotti et al (2020) for more details). Four high-resolution spectra were collected with a mean signal-to-noise ratio of 71 at 4700 Å.…”

Section: Spectroscopic Analysismentioning

confidence: 99%

Mode identification in three pulsating hot subdwarfs observed with TESS satellite

Sahoo,

Baran,

Heber

et al. 2020

Preprint

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We report on the detection of pulsations of three pulsating subdwarf B stars observed by the TESS satellite and our results of mode identification in these stars based on an asymptotic period relation. SB 459 (TIC 067584818), SB 815 (TIC 169285097) and PG 0342+026 (TIC 457168745) have been monitored during single sectors resulting in 27 days coverage. These datasets allowed for detecting, in each star, a few tens of frequencies, which we interpreted as stellar oscillations. We found no multiplets, though we partially constrained mode geometry by means of period spacing, which recently became a key tool in analyses of pulsating subdwarf B stars. Standard routine that we have used allowed us to select candidates for trapped modes that surely bear signatures of non-uniform chemical profile inside the stars. We have also done statistical analysis using collected spectroscopic and asteroseismic data of previously known subdwarf B stars along with our three stars. Making use of high precision trigonometric parallaxes from the Gaia mission and spectral energy distributions we converted atmospheric parameters to stellar ones. Radii, masses and luminosities are close to their canonical values for extreme horizontal branch stars. In particular, the stellar masses are close to the canonical one of 0.47 M for all three stars but uncertainties on the mass are large. The results of the analyses presented here will provide important constrains for asteroseismic modelling.

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No close companions to a sample of bright sdB stars

Cited by 9 publications

References 3 publications

Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well-defined rotational splitting

Filling the gap between synchronized and non-synchronized sdBs in short-period sdBV+dM binaries with TESS: TIC 137608661, a new system with a well-defined rotational splitting

A transit survey to search for planets around hot subdwarfs: I. methods and performance tests on light curves from Kepler, K2, TESS, and CHEOPS

Mode identification in three pulsating hot subdwarfs observed with TESS satellite

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