A search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy

Morel, Thierry; Briquet, Maryline; Auvergne, M.; Alecian, G.; Ghazaryan, S.; Niemczura, E.; Fossati, L.; Lehmann, H.; Hubrig, S.; Ulusoy, C.; Damerdji, Y.; Rainer, M.; Poretti, E.; Borsa, F.; Scardia, M.; Schmid, V. S.; Winckel, H. Van; Smedt, K. De; Pápics, P. I.; Gameiro, J. F.; Waelkens, C.; Fagas, M.; Kamiński, K.; Dimitrov, W.; Baglin, A.; Michel, E.; Dumortier, L.; Frémat, Y.; Hensberge, H.; Jorissen, A.; Eck, S. Van

doi:10.1051/0004-6361/201322289

Cited by 25 publications

(12 citation statements)

References 82 publications

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“…Among main-sequence CP stars, pulsations are found at least in roAp stars, and possibly in HgMn stars which partly share the region of slowly pulsating B type (SPB) stars in the HR-diagram (Alecian et al 2009;Morel et al 2014); for roAp stars, pulsations seem to coexist with vertical abundance stratifications (see for instance Freyhammer et al 2009). It is not yet known how these pulsations interact with the atmospheric structure, and whether or not they induce weak mixing.…”

Section: Other Processesmentioning

confidence: 99%

Abundance distributions over the surfaces of magnetic ApBp stars: theoretical predictions: Figure 1.

Alecian

2015

Mon. Not. R. Astron. Soc.

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Recently published empirical abundance maps, obtained through (Zeeman) Doppler mapping (ZDM), do not currently agree with the abundance structures predicted by means of numerical models of atomic diffusion in magnetic atmospheres of ApBp stars. In a first step towards the resolution of these discrepancies, we present a state of the art grid of equilibrium abundance stratifications in the atmosphere of a magnetic Ap star with T eff = 10000 K and log g = 4.0. A description of the behaviour of 16 chemical elements including predictions concerning the over-and/or under-abundances over the stellar surface is followed by a discussion of the possible influence of presently neglected physical processes.

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Section: Other Processesmentioning

confidence: 99%

Abundance distributions over the surfaces of magnetic ApBp stars: theoretical predictions: Figure 1.

Alecian

2015

Mon. Not. R. Astron. Soc.

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“…9 and 10. For the fit performed to determine the stellar radii, we took into account the fastwind synthetic fluxes and the TD1 (for HD 47777), Johnson, and 2MASS photometry (note that we did not consider the TD1 flux value at ∼2800 Å, which is affected by systematics; see e.g., Morel et al 2014). We excluded the far-IR photometry from the fit to highlight infrared excess.…”

Section: Spectral Energy Distributionmentioning

confidence: 99%

Two spotted and magnetic early B-type stars in the young open cluster NGC 2264 discovered by MOST and ESPaDOnS

Fossati

Zwintz

Castro

et al. 2014

A&A

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Star clusters are known as superb tools for understanding stellar evolution. In a quest for understanding the physical origin of magnetism and chemical peculiarity in about 7% of the massive main-sequence stars, we analysed two of the ten brightest members of the ∼10 Myr old Galactic open cluster NGC 2264, the early B-dwarfs HD 47887 and HD 47777. We find accurate rotation periods of 1.95 and 2.64 days, respectively, from MOST photometry. We obtained ESPaDOnS spectropolarimetric observations, through which we determined stellar parameters, detailed chemical surface abundances, projected rotational velocities, and the inclination angles of the rotation axis. Because we found only small (<5 km s −1 ) radial velocity variations, most likely caused by spots, we can rule out that HD 47887 and HD 47777 are close binaries. Finally, using the least-squares deconvolution technique, we found that both stars possess a large-scale magnetic field with an average longitudinal field strength of about 400 G. From a simultaneous fit of the stellar parameters we determine the evolutionary masses of HD 47887 and HD 47777 to be 9.4 +0.6 −0.7 M and 7.6 +0.5 −0.5 M . Interestingly, HD 47777 shows a remarkable helium underabundance, typical of helium-weak chemically peculiar stars, while the abundances of HD 47887 are normal, which might imply that diffusion is operating in the lower mass star but not in the slightly more massive one. Furthermore, we argue that the rather slow rotation, as well as the lack of nitrogen enrichment in both stars, can be consistent with both the fossil and the binary hypothesis for the origin of the magnetic field. However, the presence of two magnetic and apparently single stars near the top of the cluster mass-function may speak in favour of the latter.

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“…Generally, CP1 stars are not expected to show rotational light variability; in relation to CP3 stars, this is still a matter of debate (Paunzen et al 2013;Morel et al 2014). Interestingly, in a recent study using ultra-precise Kepler photometry, Balona et al (2015) have found that most of the investigated Am stars exhibit light curves indicative of rotational modulation due to star spots.…”

Section: Introductionmentioning

confidence: 99%

A search for photometric variability in magnetic chemically peculiar stars using ASAS-3 data

Bernhard

Hümmerich

Otero

et al. 2015

A&A

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Context. The (magnetic) chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of magnetic fields on the stellar surface because they produce abundance inhomogeneities (spots), which results in photometric variability that is explained in terms of the oblique rotator model. CP stars exhibiting this phenomenon are normally classified as α 2 Canum Venaticorum (ACV) variables. It is important to increase the sample of known rotational periods among CP stars by discovering new ACV variables. An increased sample size will contribute to the understanding of the CP stars' evolution in time. Aims. We aim at discovering new ACV variables in the public data of the third phase of the All Sky Automated Survey (ASAS-3). Furthermore, by analysis of the available photometric data, we intend to derive rotational periods of the stars. Methods. The ASAS-3 data were cross-correlated with the Catalogue of Ap, HgMn, and Am stars in order to analyse the light curves of bona fide CP and related stars. The light curves were downloaded and cleaned of outliers and data points with a flag indicating bad quality. Promising candidates showing a larger scatter than observed for constant stars in the corresponding magnitude range were searched for periodic signals using a standard Fourier technique. Objects exhibiting periodic signals well above the noise level were considered and visually inspected, whereas borderline cases were rejected. Results. In total, we found 323 variables, from which 246 are reported here for the first time, and 77 were probably wrongly classified before. The observed variability pattern of most stars is in accordance with an ACV classification. For some cases, it is difficult to distinguish between the light curves of double-waved ACVs and the variability induced by orbital motion (ellipsoidal variables/eclipsing variables), especially for objects exhibiting very small amplitudes and/or significant scatter in their light curves. Thus, some eclipsing or rotating ellipsoidal variables might be present. However, we are confident that the given periods are the correct ones. There seems to be a possible weak correlation between the rotational period and colour, in the sense that cooler magnetic CP stars rotate more slowly. However, this correlation seems to disappear when correcting for the interstellar reddening. Conclusions. The next steps have to include a compilation of all available rotational periods from the literature and a detailed investigation of the astrophysical parameters of these stars. This includes a determination of the individual masses, luminosities, ages, and inclination angles. However, this information cannot be straightforwardly determined from photometric data alone.

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A search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy

Cited by 25 publications

References 82 publications

Abundance distributions over the surfaces of magnetic ApBp stars: theoretical predictions: Figure 1.

Abundance distributions over the surfaces of magnetic ApBp stars: theoretical predictions: Figure 1.

Two spotted and magnetic early B-type stars in the young open cluster NGC 2264 discovered by MOST and ESPaDOnS

A search for photometric variability in magnetic chemically peculiar stars using ASAS-3 data

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