Three new pulsating sdB stars discovered with SuperWASP

Holdsworth, Daniel Luke; Østensen, R. H.; Smalley, B.; Telting, J. H.

doi:10.1093/mnras/stx077

Cited by 25 publications

(36 citation statements)

References 93 publications

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“…In this paper, we have shown that EC 03089−6421 is a very rapid pulsator with two frequencies near 32.1 and 29.2 mHzperiods of 31.1 and 34.2 s, much shorter than observed in the other sdOV stars, or in any pulsating subdwarf (see table 1 of Holdsworth et al 2017). Both frequencies have quite variable amplitudesbetween about 0.2 and 2 per cent on a time-scale of a few days and also varying on a time-scale of hours.…”

Section: Discussionmentioning

confidence: 78%

EC 03089-6421: a new, very rapidly pulsating sdO star

Kilkenny

Worters

Østensen

2017

Mon. Not. R. Astron. Soc.

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EC 03089−6421, classified sdO in the Edinburgh-Cape (EC) blue object survey, is shown to have unusually rapid pulsations with a dominant frequency near 32 mHz (amplitude ∼0.02 mag; period 31.1 s)-which appears to be strongly variable in amplitude on timescales of hours and days-and a generally weaker frequency near 29 mHz (amplitude ∼0.004 mag; period 34.2 s), which is also variable in amplitude. This star varies at twice the frequency of any known hot subdwarf pulsator. Although the low-resolution EC spectrogram appears very similar to those of DAO stars, our analysis derives T eff = 40 200 ± 1600 K; log g = 6.25 ± 0.23 and log N(He)/N(H) = −1.63 ± 0.55; more recent spectrograms give T eff = 37 400 ± 1000 K; log g = 5.70 ± 0.13 and log N(He)/N(H) = −2.02 ± 0.17, both of which indicate that the gravity is too low for a white dwarf star, although the low temperature derived from the Balmer lines is at odds with the absence of neutral Helium and the strength of He II 4686. It is possible that EC 03089−6421 is a field analogue of the ω Cen sdO variables.

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Section: Discussionmentioning

confidence: 78%

EC 03089-6421: a new, very rapidly pulsating sdO star

Kilkenny

Worters

Østensen

2017

Mon. Not. R. Astron. Soc.

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“…It also produces excellent data for the study of stellar variability. For full details of the SuperWASP project, see Pollacco et al (2006); for examples of stellar variability studies that have been conducted with the data, we refer the reader to the following papers: Maxted et al (2008); Thomas et al (2010); Norton et al (2011Norton et al ( , 2016; Smalley et al (2011Smalley et al ( , 2014Smalley et al ( , 2017; Holdsworth et al (2014aHoldsworth et al ( , 2017; Bowman et al (2015); Greer et al (2017).…”

Section: Superwasp Datamentioning

confidence: 99%

Suppressed phase variations in a high amplitude rapidly oscillating Ap star pulsating in a distorted quadrupole mode

Holdsworth

Saio

Bowman

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present the results of a multisite photometric observing campaign on the rapidly oscillating Ap (roAp) star 2MASS 16400299-0737293 (J1640; V = 12.7). We analyse photometric B data to show the star pulsates at a frequency of 151.93 d −1 (1758.45 µHz; P = 9.5 min) with a peak-to-peak amplitude of 20.68 mmag, making it one of the highest amplitude roAp stars. No further pulsation modes are detected. The stellar rotation period is measured at 3.6747 ± 0.0005 d, and we show that rotational modulation due to spots is in anti-phase between broadband and B observations. Analysis and modelling of the pulsation reveals this star to be pulsating in a distorted quadrupole mode, but with a strong spherically symmetric component. The pulsational phase variation in this star is suppressed, leading to the conclusion that the contribution of ℓ > 2 components dictate the shape of phase variations in roAp stars that pulsate in quadrupole modes. This is only the fourth time such a strong pulsation phase suppression has been observed, leading us to question the mechanisms at work in these stars. We classify J1640 as an A7 Vp SrEu(Cr) star through analysis of classification resolution spectra.

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“…Indeed, many of these projects have been employed for that purpose (e.g. Pepper et al 2008;Hartman et al 2011;Ulaczyk et al 2013;Holdsworth et al 2014a;Smalley et al 2017;Holdsworth et al 2017). The ability of these surveys to achieve mmag precision provides an extensive all-sky database in which to search for low-amplitude stellar variability, which can then be observed at much higher precision by space-based missions such as K2 (Howell et al 2014) and the upcoming Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Whole Earth Telescope discovery of a strongly distorted quadrupole pulsation in the largest amplitude rapidly oscillating Ap star

Holdsworth

Kurtz

Saio

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J19400781 − 4420093 (J1940; V = 13.1). The star was discovered using SuperWASP broadband photometry to have a frequency of 176.39 d −1 (2041.55 µHz; P = 8.2 min; Holdsworth et al. 2014a) and is shown here to have a peak-to-peak amplitude of 34 mmag. J1940 has been observed during three seasons at the South African Astronomical Observatory, and has been the target of a Whole Earth Telescope campaign. The observations reveal that J1940 pulsates in a distorted quadrupole mode with unusual pulsational phase variations. A higher signal-to-noise ratio spectrum has been obtained since J1940's first announcement, which allows us to classify the star as A7 Vp Eu(Cr). The observing campaigns presented here reveal no pulsations other than the initially detected frequency. We model the pulsation in J1940 and conclude that the pulsation is distorted by a magnetic field of strength 1.5 kG. A difference in the times of rotational maximum light and pulsation maximum suggests a significant offset between the spots and pulsation axis, as can be seen in roAp stars.

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Three new pulsating sdB stars discovered with SuperWASP

Cited by 25 publications

References 93 publications

EC 03089-6421: a new, very rapidly pulsating sdO star

EC 03089-6421: a new, very rapidly pulsating sdO star

Suppressed phase variations in a high amplitude rapidly oscillating Ap star pulsating in a distorted quadrupole mode

Whole Earth Telescope discovery of a strongly distorted quadrupole pulsation in the largest amplitude rapidly oscillating Ap star

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