The Discovery of Pulsating Hot Subdwarfs in NGC 2808

Brown, Thomas M.; Landsman, W. B.; Randall, S. K.; Sweigart, A. V.; Lanz, T.

doi:10.1088/2041-8205/777/2/l22

Cited by 19 publications

(16 citation statements)

References 39 publications

(45 reference statements)

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“…These p-mode pulsations are consistent with theoretical predictions and a consequence of radiativelydriven diffusion in the interior enhancing the the iron-bump opacities, just as in the case of V499 Ser. Six short-period (85 -150 s) pulsating hot subdwarfs have been detected in the globular cluster NGC 2808 (Brown et al 2013), but are not strongly constrained in T eff .…”

Section: Variabilitymentioning

confidence: 99%

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Jeffery

Baran

Behara

et al. 2016

Mon. Not. R. Astron. Soc.

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UVO 0825+15 is a hot bright helium-rich subdwarf which lies in K2 Field 5 and in a sample of intermediate helium-rich subdwarfs observed with Subaru/HDS. The K2 light curve shows low-amplitude variations, whilst the Subaru spectrum shows Pbiv absorption lines, indicative of a very high lead overabundance. UVO 0825+15 also has a high proper motion with kinematics typical for a thick disk star. Analyses of ultraviolet and intermediate dispersion optical spectra rule out a short-period binary companion, and provide fundamental atmospheric parameters of T eff = 38 900±270 K, log g/cm s −2 = 5.97 ± 0.11, log n He /n H = −0.57 ± 0.01, E B−V ≈ 0.03, and angular radius θ = 1.062±0.006×10−11 radians (formal errors). The high-resolution spectrum shows that carbon is > 2 dex subsolar, iron is approximately solar and all other elements heavier than argon are at least 2 -4 dex overabundant, including germanium, yttrium and lead. Approximately 150 lines in the blue-optical spectrum remain unidentified. The chemical structure of the photosphere is presumed to be determined by radiatively-dominated diffusion. The K2 light curve shows a dominant period around 10.8 h, with a variable amplitude, its first harmonic, and another period at 13.3 h. The preferred explanation is multi-periodic non-radial oscillation due to g-modes with very high radial order, although this presents difficulties for pulsation theory. Alternative explanations fail for lack of radial-velocity evidence. UVO 0825+15 represents the fourth member of a group of hot subdwarfs having helium-enriched photospheres and 3-4 dex overabundances of trans-iron elements, and is the first lead-rich subdwarf to show evidence of pulsations.

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Section: Variabilitymentioning

confidence: 99%

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Jeffery

Baran

Behara

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Surprisingly, this star remains so far the unique member of this class found among the field sdO stars, despite significant efforts to search for pulsations in such objects (Rodríguez-López et al 2008). More pulsating sdO stars have however been found, but in the globular clusters ω Cen (Randall et al 2011) and NGC 2808 (Brown et al 2013). However, it is not clear if those cluster objects belong to the same class of pulsators as the star discovered by Woudt et al (2006) because they do not seem to occupy the same region in the log g − T eff plane (Figure 1).…”

Section: Pulsations In Hot Subdwarfsmentioning

confidence: 99%

Pulsations in hot subdwarf stars: recent advances and prospects for testing stellar physics

et al. 2015

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Abstract. The evolved, core helium burning, extreme horizontal branch stars (also known as hot B subdwarfs) host several classes of pulsators showing either p-or g-modes, or both. They offer particularly favorable conditions for probing with asteroseismology their internal structure, thus constituting arguably the most interesting seismic window for this intermediate stage of stellar evolution. G-modes in particular have the power to probe deep inside these stars, down to the convective He-burning core boundary where uncertain physics (convection, overshooting, semi-convection) is at work. Space data recently obtained with CoRoT and Kepler are offering us the possibility to probe these regions in detail and possibly shed new light on how these processes shape the core structure. In this short paper, we present the most recent advances that have taken place in this field and we provide hints of the foreseen future achievements of hot subdwarf asteroseismology.

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“…GALEX images available in the MAST archive are the result of pipeline reconstruction by integrating each photon event recorded over the length of the observation. Most variability studies so far have been based on comparing measurements between different observations (e.g., Conti et al 2014 and references therein), with a few exceptions (e.g., Welsh et al 2006, 2007, 2011; Browne et al 2009; Wheatley et al 2012; Browne et al 2013). The exposure times of GALEX individual observations (“visits”) range from about 100 secs up to ∼30 minutes, the duration of an “eclipse” (i.e., the useful observing time) during each orbit.…”

Section: Uv Time-domain Sciencementioning

confidence: 99%

New UV-source catalogs, UV spectral database, UV variables and science tools from the GALEX surveys

Bianchi

Vega

Shiao

et al. 2018

Astrophys Space Sci

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We present a new, expanded and improved catalog of Ultraviolet (UV) sources from the GALEX All-Sky Imaging survey: GUVcat_AIS (Bianchi et al. in Astrophys. J. Suppl. Ser. 230:24, 2017 ). The catalog includes 83 million unique sources (duplicate measurements and rim artifacts are removed) measured in far-UV and near-UV. With respect to previous versions (Bianchi et al. in Mon. Not. R. Astron. Soc. 411:2770 2011a , Adv. Space Res. 53:900–991, 2014 ), GUVcat_AIS covers a slightly larger area, 24,790 square degrees, and includes critical corrections and improvements, as well as new tags, in particular to identify sources in the footprint of extended objects, where pipeline source detection may fail and custom-photometry may be necessary. The UV unique-source catalog facilitates studies of density of sources, and matching of the UV samples with databases at other wavelengths. We also present first results from two ongoing projects, addressing respectively UV variability searches on time scales from seconds to years by mining the GALEX photon archive, and the construction of a database of ∼120,000 GALEX UV spectra (range ∼1300–3000 Å), including quality and calibration assessment and classification of the grism, hence serendipitous, spectral sources.

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The Discovery of Pulsating Hot Subdwarfs in NGC 2808

Cited by 19 publications

References 39 publications

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Discovery of a variable lead-rich hot subdwarf: UVO 0825+15

Pulsations in hot subdwarf stars: recent advances and prospects for testing stellar physics

New UV-source catalogs, UV spectral database, UV variables and science tools from the GALEX surveys

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