No evidence of a sudden change of spectral appearance or magnetic field strength of the O9.7V star HD 54879

Wade, G. A.; Bagnulo, S.; Keszthelyi, Z.; Folsom, C. P.; Alécian, E.; Castro, N.; David-Uraz, Alexandre; Fossati, L.; Petit, Véronique; Shultz, Matt; Sikora, J.

doi:10.1093/mnrasl/slz174

Cited by 4 publications

(2 citation statements)

References 13 publications

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“…We have seven stars with a clear magnetic field detection in the literature, namely HD 37061 (Shultz et al 2019a), HD 57682 (Grunhut et al 2009(Grunhut et al , 2012, HD 54879 (Castro et al 2015;Shenar et al 2017;Hubrig et al 2019;Wade et al 2020a), HD 37022 (Donati et al 2002;Wade et al 2006), HD 37742 (Bouret et al 2008;Blazère et al 2015), HD 46056 (Grunhut et al 2017;Petit et al 2019), and HD 37479 (Landstreet & Borra 1978;Oksala et al 2012;). In all LS-periodograms singular frequencies are visible in the low frequency regime (ranging between 0.31 and 1.67 d −1 , with amplitudes between 0.11 and 6.6 mmag).…”

Section: Magnetic O-and B-type Starsmentioning

confidence: 99%

“…Subsequent studies have shown that the magnetic and spectroscopic variability implies a long rotation period (Shenar et al 2017). A recent sudden change in magnetic field, accompanied by radial velocity variations on the time-scale of days was claimed by Hubrig et al (2019) but this has been contested by Wade et al (2020a). The one-sector TESS data set shows low amplitude stochastic variability.…”

Section: Appendix B42: Magnetic O-and B-type Starsmentioning

confidence: 99%

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Variability of OB stars from TESS southern Sectors 1–13 and high-resolution IACOB and OWN spectroscopy

Burssens

Simón‐Díaz

Bowman

et al. 2020

A&A

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Context. The lack of high-precision long-term continuous photometric data for large samples of stars has impeded the large-scale exploration of pulsational variability in the OB star regime. As a result, the candidates for in-depth asteroseismic modelling have remained limited to a few dozen dwarfs. The TESS nominal space mission has surveyed the southern sky, including parts of the galactic plane, yielding continuous data across at least 27 d for hundreds of OB stars. Aims. We aim to couple TESS data in the southern sky with ground-based spectroscopy to study the variability in two dimensions, mass and evolution. We focus mainly on the presence of coherent pulsation modes that may or may not be present in the predicted theoretical instability domains and unravel all frequency behaviour in the amplitude spectra of the TESS data. Methods. We compose a sample of 98 OB-type stars observed by TESS in Sectors 1–13 and with available multi-epoch, high-resolution spectroscopy gathered by the IACOB and OWN surveys. We present the short-cadence 2 min light curves of dozens of OB-type stars, which have one or more spectra in the IACOB or OWN database. Based on these light curves and their Lomb–Scargle periodograms, we performed variability classification and frequency analysis. We placed the stars in the spectroscopic Hertzsprung–Russell diagram to interpret the variability in an evolutionary context. Results. We deduce the diverse origins of the mmag-level variability found in all of the 98 OB stars in the TESS data. We find among the sample several new variable stars, including three hybrid pulsators, three eclipsing binaries, high frequency modes in a Be star, and potential heat-driven pulsations in two Oe stars. Conclusions. We identify stars for which future asteroseismic modelling is possible, provided mode identification is achieved. By comparing the position of the variables to theoretical instability strips, we discuss the current shortcomings in non-adiabatic pulsation theory and the distribution of pulsators in the upper Hertzsprung–Russell diagram.

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Section: Magnetic O-and B-type Starsmentioning

confidence: 99%

Section: Appendix B42: Magnetic O-and B-type Starsmentioning

confidence: 99%

Variability of OB stars from TESS southern Sectors 1–13 and high-resolution IACOB and OWN spectroscopy

Burssens

Simón‐Díaz

Bowman

et al. 2020

A&A

View full text Add to dashboard Cite

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WALLABY – an SKA Pathfinder H i survey

Koribalski

Staveley‐Smith

Westmeier

et al. 2020

Astrophys Space Sci

201

125

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The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of neutral hydrogen (H I) in the Local Universe. It uses the widefield, high-resolution capability of the Australian Square Kilometer Array Pathfinder (ASKAP), a radio interferometer consisting of 36 × 12-m dishes equipped with Phased-Array Feeds (PAFs), located in an extremely radioquiet zone in Western Australia. WALLABY aims to survey three-quarters of the sky (−90 • < δ < +30 • ) to a redshift of z 0.26, and generate spectral line image cubes at ∼30 arcsec resolution and ∼1.6 mJy beam −1 per 4 km s −1 channel sensitivity. ASKAP's instantaneous field of view at 1.4 GHz, delivered by the PAF's 36 beams, is about 30 sq deg. At an integrated signal-to-noise ratio of five, WALLABY is expected to detect around half a million galaxies with a mean redshift of z ∼ 0.05 (∼200 Mpc). The scientific goals of WALLABY include: (a) a census of gas-rich galaxies in the vicinity of the Local Group; (b) a study of the H I properties of galaxies, groups and clusters, in particular the influence of the environment on galaxy evolution; and (c) the refinement of cosmological parameters using the spatial and redshift distribution of low-bias gas-rich galaxies. For context we provide an overview of recent and planned large-scale H I surveys. Combined with existing and new multi-wavelength sky surveys, WALLABY will enable an exciting new generation of panchromatic studies of the Local Universe. -First results from the WALLABY pilot survey are revealed, with initial data products publicly available in the CSIRO ASKAP Science Data Archive (CASDA).

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Probing galaxy evolution through Hi 21-cm emission and absorption: current status and prospects with square kilometre array

et al. 2022

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One of the major science goals of square kilometre array (SKA) is to understand the role played by atomic hydrogen (Hi) gas in the evolution of galaxies throughout cosmic time. The hyperfine transition line of the hydrogen atom at 21-cm is one of the best tools to detect and study the properties of Hi gas associated with galaxies. In this paper, we review our current understanding of Hi gas and its relationship with galaxies through observations of the 21-cm line both in emission and absorption. In addition, we provide an overview of the Hi science that will be possible with SKA and its precursors and pathfinders, i.e., Hi 21-cm emission and absorption studies of galaxies from nearby to high redshifts that will trace various processes governing galaxy evolution.

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No evidence of a sudden change of spectral appearance or magnetic field strength of the O9.7V star HD 54879

Cited by 4 publications

References 13 publications

Variability of OB stars from TESS southern Sectors 1–13 and high-resolution IACOB and OWN spectroscopy

Variability of OB stars from TESS southern Sectors 1–13 and high-resolution IACOB and OWN spectroscopy

WALLABY – an SKA Pathfinder H i survey

Probing galaxy evolution through Hi 21-cm emission and absorption: current status and prospects with square kilometre array

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