TESS first look at evolved compact pulsators

Abstract

Context. We present our findings on 18 previously known ZZ Ceti stars observed by the TESS space telescope in 120 s cadence mode during the survey observation of the southern ecliptic hemisphere. Aims. We focus on the frequency analysis of the space-based observations, comparing the results with findings of previous ground-based measurements. The frequencies detected by the TESS observations can serve as inputs for future asteroseismic analyses. Methods. We performed standard pre-whitening of the data sets to derive the possible pulsation frequencies of the different targets. In some cases, we fit Lorentzians to the frequency groups that emerged as the result of short-term amplitude or phase variations that occurred during the TESS observations. Results. We detected more than 40 pulsation frequencies in seven ZZ Ceti stars observed in the 120 s cadence by TESS, with precision better than 0.1 μHz. We found that HE 0532−5605 may be a new outbursting ZZ Ceti. Ten targets do not show any significant pulsation frequencies in their Fourier transforms, due to a combination of their intrinsic faintness and/or crowding on the large TESS pixels. We also detected possible amplitude or phase variations during the TESS observations in some cases. Such behaviour in these targets was not previously identified from ground-based observations.

Year 1 of the ZTF high-cadence Galactic plane survey: strategy, goals, and early results on new single-mode hot subdwarf B-star pulsators

“…8, which highlights ZTF J2339+5124, a new ZZ Ceti identified originally in Guidry et al (2020). The typical diurnal mean sampling rate of ZTF is too short to resolve the pulsations for many pulsating white dwarfs (ZZ Ceti pulsation modes range from 100-1500 sec Mukadam et al 2013;Bognár et al 2020). However, the Galactic plane survey's 40-s sampling over the span of hours is sufficient to capture consecutive pulsation peaks in ZZ Cetis.…”

Pulsating hydrogen-deficient white dwarfs and pre-white dwarfs observed with TESS: I. Asteroseismology of the GW Vir stars RX J2117+3412, HS 2324+3944, NGC 6905, NGC 1501, NGC 2371, and K 1-16

“…In this work, we have performed a detailed asteroseismological analysis of the formerly known GW Vir stars RX J2117, HS 2324, NGC 6905, NGC 1501, NGC 2371, and K 1−16 on the basis of the new TESS observations of these stars. TESS primary mission is to search for exoplanets around bright targets, although the high-precision photometry capabilities of the mission are also allowing us to study low-amplitude stellar variability, including WD pulsations (Bell et al 2019;Bognár et al 2020). We studied the pulsation spectrum of these stars, and, in one case (RX J2117), we estimated the rotation period on the basis of frequency-splitting multiplets.…”

“…The mission-data products of TESS also allow us to study stellar variability, including pulsations. Thanks to nearly continuous, stable photometry, as well as its expansive sky coverage, TESS has made a significant contribution to the study of stellar pulsations in evolved compact objects (Bell et al 2019;Wang et al 2020;Althaus et al 2020;Bognár et al 2020).…”

Exploring the pulsational properties of two ZZ Ceti stars

“…Hermes et al 2017a,b;Bell et al 2017b;Córsico 2020). In addition, published results have already demonstrated the value of the TESS data, focussing on a DBV star (Bell et al 2019), several ZZ Ceti stars (Bognár et al 2020;Althaus et al 2020), and GW Vir variables (Córsico et al 2021).…”