The population of hot subdwarf stars studied with<i>Gaia</i>

Geier, S.

doi:10.1051/0004-6361/202037526

Cited by 84 publications

(95 citation statements)

References 69 publications

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“…No further literature studies on this object are available. The star's location in the CMD would qualify it as a hot subdwarf (Pelisoli et al 2019, Geier 2020). These objects are considered to be core heliumburning stars located at the blueward extension of the Horizontal Branch, the so called Extreme or Extended Horizontal Branch (EHB).…”

Section: Colour-magnitude Diagrammentioning

confidence: 99%

New mercury-manganese stars and candidates from LAMOST DR4

Paunzen

Hümmerich

Bernhard

2021

A&A

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Aims. The present work presents our efforts at identifying new mercury-manganese (HgMn/CP3) stars using spectra obtained with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Methods. Suitable candidates were searched for among pre-selected early-type spectra from LAMOST DR4 using a modified version of the MKCLASS code that probes several Hg ii and Mn ii features. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry from Gaia DR2, we investigated magnitudes, distances from the Sun, and the evolutionary status of our sample stars. We also searched for variable stars using diverse photometric survey sources. Results. We present 99 bona fide CP3 stars, 19 good CP3 star candidates, and seven candidates. Our sample consists of mostly new discoveries and contains, on average, the faintest CP3 stars known (peak distribution 9.5 ≤ G ≤ 13.5 mag). All stars are contained within the narrow spectral temperature-type range from B6 to B9.5, in excellent agreement with the expectations and the derived mass estimates (2.4 ≤ M ⊙ ≤ 4 for most objects). Our sample stars are between 100 Myr and 500 Myr old and cover the whole age range from zero-age to terminal-age main sequence. They are almost homogeneously distributed at fractional ages on the main sequence ≤ 80 %, with an apparent accumulation of objects between fractional ages of 50 % to 80 %. We find a significant impact of binarity on the mass and age estimates. Eight photometric variables were discovered, most of which show monoperiodic variability in agreement with rotational modulation. Conclusions. Together with the recently published catalogue of APOGEE CP3 stars, our work significantly increases the sample size of known Galactic CP3 stars, paving the way for future in-depth statistical studies.

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Section: Colour-magnitude Diagrammentioning

confidence: 99%

New mercury-manganese stars and candidates from LAMOST DR4

Paunzen

Hümmerich

Bernhard

2021

A&A

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“…We found another five objects showing HW Vir variations among spectroscopically unclassified, bringing the final number of new HW Vir systems to seven (if all of them are confirmed to be sds). Comparing the number of new sdB variable objects, we can notice that even though the number of all objects, available in Geier (2020), and consequently the total number of new variables, was larger in the southern ecliptic hemisphere, we found more variable sdBs, including sdBVs, in the northern ecliptic hemisphere. Since, we rejected objects observed in the short cadence mode, we cannot conclude on the larger number of them in the north, but it clearly means there was still more to find.…”

Section: Discussionmentioning

confidence: 83%

“…Our search is not subject to any pre-approval since we use FFI images E-mail: andrzej.baran@up.krakow.pl that are stored automatically and all targets in those images are available for data processing. Handling all objects detectable in the FFIs, although desirable, is technically difficult (processing would take months if not years), hence we focus on targets listed in the sdB catalogue described by Geier (2020).…”

Section: Introductionmentioning

confidence: 99%

A search for variable subdwarf B stars in TESS Full Frame Images – II. Variable objects in the northern ecliptic hemisphere

Baran

Sahoo

Sanjayan

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We report the results of our search for pulsating subdwarf B stars in Full Frame Images collected during Year 2 of the TESS mission and covering the northern ecliptic hemisphere. This is a continuation of our effort we presented in Paper I. We found 13 likely new pulsating subdwarf B stars, 10 pulsating candidates that are identified as other hot subdwarfs, and 30 spectroscopically unclassified objects that show amplitude spectra typical of pulsating subdwarf B stars. We found 506 variable objects, most of them spectroscopically unclassified, hence their specific variability class yet to be confirmed. Eclipsing binaries with sharp eclipses sample comprises 33 systems. For 12 of them we derived precise orbital periods and checked their stabilities. We identified one known and five new candidate HW Vir systems. The amplitude spectra of the 13 likely sdB pulsators are not rich in modes, hence any further analysis is not possible. However, we selected three candidates for pulsating subdwarf B stars that show the richest amplitude spectra and we performed a mode identification deriving modal degrees of most of the detected modes. In total, in both ecliptic hemispheres, we found 15 likely pulsating pulsating subdwarf B stars, additional 10 candidates for pulsating subdwarf B stars, 66 other variable subdwarf B stars, 2076 spectroscopically unconfirmed variable stars, and 123 variable non-sdB stars.

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“…This limits the study of sdBVs to individual cases only and it does not allow for inferring how pulsation properties depend on a stellar population. We undertook a search for sdBVs candidates selected from a sdB database Geier (2020) and based on an all-sky photometry collected during the TESS mission in the LC mode. This data still limits our search to g-mode sdBVs, which is a consequence of a 30 min.…”

Section: Discussionmentioning

confidence: 99%

A search for variable subdwarf B stars in TESS full frame images – I. Variable objects in the southern ecliptic hemisphere

Sahoo

Baran

Sanjayan

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We report the results of our search for pulsating subdwarf B stars in Full Frame Images, sampled at 30 min cadence and collected during Year 1 of the TESS mission. Year 1 covers most of the southern ecliptic hemisphere. The sample of objects we checked for pulsations was selected from a subdwarf B stars database available to public. Only two positive detections have been achieved, however, as a by-product of our search we found 1807 variable objects, most of them not classified, hence their specific variability class cannot be confirmed at this stage. Our preliminary discoveries include: two new subdwarf B (sdB) pulsators, 26 variables with known sdB spectra, 83 non-classified pulsating stars, 83 eclipsing binaries (detached and semi-detached), a mix of 1535 pulsators and non-eclipsing binaries, two novae, and 77 variables with known (non-sdB) spectral classification. Among eclipsing binaries we identified two known HW Vir systems and four new candidates. The amplitude spectra of the two sdB pulsators are not rich in modes, but we derive estimates of the modal degree for one of them. In addition, we selected five sdBV candidates for mode identification among 83 pulsators and describe our results based on this preliminary analysis. Further progress will require spectral classification of the newly discovered variable stars, which hopefully include more subdwarf B stars.

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The population of hot subdwarf stars studied withGaia

Cited by 84 publications

References 69 publications

New mercury-manganese stars and candidates from LAMOST DR4

New mercury-manganese stars and candidates from LAMOST DR4

A search for variable subdwarf B stars in TESS Full Frame Images – II. Variable objects in the northern ecliptic hemisphere

A search for variable subdwarf B stars in TESS full frame images – I. Variable objects in the southern ecliptic hemisphere

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