Dynamical evolution of titanium, strontium, and yttrium spots on the surface of the HgMn star HD 11753

Briquet, Maryline; Korhonen, H.; González, J. F.; Hubrig, S.; Hackman, T.

doi:10.1051/0004-6361/200913775

Cited by 48 publications

(69 citation statements)

References 29 publications

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“…The rotational period of ϕ Phe, 9. d 54 (Briquet et al 2010), was recently revised to 9. d 531 (Korhonen et al 2011). This improvement corresponds to a negligible change of the rotational phases of our observations.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…Surface maps were reconstructed using the Doppler imaging code INVERS10 . Unlike the previous attempt to study chemical spots in ϕ Phe (Briquet et al 2010), our analysis is based on simultaneous modelling of multiple spectral lines, which significantly improves reliability of the DI maps. The maps of Y were reconstructed from nine spectral lines, Sr from three, Ti from nine, and Cr from eight spectral lines.…”

Section: Doppler Imagingmentioning

confidence: 99%

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Magnetism, chemical spots, and stratification in the HgMn starϕ Phoenicis

Makaganiuk

Kochukhov

Piskunov

et al. 2012

A&A

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Context. Mercury-manganese (HgMn) stars have been considered as non-magnetic and non-variable chemically peculiar (CP) stars for a long time. However, recent discoveries of the variability in spectral line profiles have suggested an inhomogeneous surface distribution of chemical elements in some HgMn stars. From the studies of other CP stars it is known that magnetic field plays a key role in the formation of surface spots. All attempts to find magnetic fields in HgMn stars have yielded negative results. Aims. In this study, we investigate the possible presence of a magnetic field in ϕ Phe (HD 11753) and reconstruct surface distribution of chemical elements that show variability in spectral lines. We also test a hypothesis that a magnetic field is concentrated in chemical spots and look into the possibility that some chemical elements are stratified with depth in the stellar atmosphere. Methods. Our analysis is based on high-quality spectropolarimetric time-series observations, covering a full rotational period of the star. Spectra were obtained with the HARPSpol at the ESO 3.6-m telescope. To increase the sensitivity of the magnetic field search, we employed the least-squares deconvolution (LSD) technique. Using Doppler imaging code INVERS10, we reconstructed surface chemical distributions by utilising information from multiple spectral lines. The vertical stratification of chemical elements was calculated with the DDAFit program. Results. Combining information from all suitable spectral lines, we set an upper limit of 4 G on the mean longitudinal magnetic field. For chemical spots, an upper limit on the longitudinal field varies between 8 and 15 G. We confirmed the variability of Y, Sr, and Ti and detected variability in Cr lines. Stratification analysis showed that Y and Ti are not concentrated in the uppermost atmospheric layers. Conclusions. Our spectropolarimetric observations rule out the presence of a strong, globally-organised magnetic field in ϕ Phe. This implies an alternative mechanism of spot formation, which could be related to a non-equilibrium atomic diffusion. However, the typical time scales of the variation in stratification predicted by the recent time-dependent diffusion models exceed significantly the spot evolution time-scale reported for ϕ Phe.

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Section: Observations and Data Reductionmentioning

confidence: 99%

Section: Doppler Imagingmentioning

confidence: 99%

Magnetism, chemical spots, and stratification in the HgMn starϕ Phoenicis

Makaganiuk

Kochukhov

Piskunov

et al. 2012

A&A

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“…However, some binary HgMn stars have been shown to display spectroscopic variations (Adelman et al 2002;Kochukhov et al 2005;Hubrig et al 2006a;Briquet et al 2010). The non-uniform surface abundances invoked to explain these variations appear to evolve with time (Kochukhov et al 2007).…”

Section: Hgmn Starsmentioning

confidence: 99%

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

Aurière

Wade

Lignières

et al. 2010

A&A

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Aims. We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am and HgMn stars. Methods. Using the NARVAL spectropolarimeter at the Télescope Bernard Lyot (Observatoire du Pic du Midi, France), we obtained high-resolution circular polarisation spectroscopy of 12 Am stars and 3 HgMn stars. Results. Using least squares deconvolution (LSD), no magnetic field is detected in any of the 15 observed stars. Uncertaintiies as low as 0.3 G (respectively 1 G) have been reached for surface-averaged longitudinal magnetic field measurements for Am (respectively HgMn) stars. Conclusions. Associated with the results obtained previously for Ap/Bp stars, our study confirms the existence of a magnetic dichotomy among A-type stars. Our data demonstrate that there is at least one order of magnitude difference in field strength between Zeeman detected stars (Ap/Bp stars) and non Zeeman detected stars (Am and HgMn stars). This result confirms that the spectroscopically-defined Ap/Bp stars are the only A-type stars harbouring detectable large-scale surface magnetic fields.

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“…A patchy surface distribution of some chemical species has first been firmly established from the detection of large, daily changes in the strength of Hg ii λ3984 in the primary component of α And (Adelman et al 2002), but has also been subsequently found in other HgMn stars (e.g., Kochukhov et al 2005;Briquet et al 2010;Hubrig et al 2011). To date, Doppler imaging techniques have been used to infer the distribution (and evolution) of chemical spots in four B stars with HgMn peculiarity: AR Aur A A35, page 11 of 14 A&A 561, A35 (2014) Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Among the processes invoked by these authors to explain these observations, they considered the time-dependent atomic diffusion scenario proposed by Alecian (1998). Line-profile variations have been detected during the last decade in several HgMn stars and interpreted in terms of abundance spots in the photosphere (e.g., Adelman et al 2002;Kochukhov et al 2005;Hubrig et al 2006;Briquet et al 2010). These kinds of patches generally concern elements that have low abundances in normal stars (Sr, Y, Pt, Zr, and Hg) and which are suspected of being concentrated in high-altitude (above log τ = -4) clouds.…”

Section: Introductionmentioning

confidence: 99%

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

Morel

Briquet

Auvergne

et al. 2013

A&A

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The existence of pulsations in HgMn stars is still being debated. To provide the first unambiguous observational detection of pulsations in this class of chemically peculiar objects, the bright star HD 45975 was monitored for nearly two months by the CoRoT satellite. Independent analyses of the light curve provide evidence of monoperiodic variations with a frequency of 0.7572 d −1 and a peak-topeak amplitude of ∼2800 ppm. Multisite, ground-based spectroscopic observations overlapping the CoRoT observations show the star to be a long-period, single-lined binary. Furthermore, with the notable exception of mercury, they reveal the same periodicity as in photometry in the line moments of chemical species exhibiting strong overabundances (e.g., Mn and Y). In contrast, lines of other elements do not show significant variations. As found in other HgMn stars, the pattern of variability consists in an absorption bump moving redwards across the line profiles. We argue that the photometric and spectroscopic changes are more consistent with an interpretation in terms of rotational modulation of spots at the stellar surface. In this framework, the existence of pulsations producing photometric variations above the ∼50 ppm level is unlikely in HD 45975. This provides strong constraints on the excitation/damping of pulsation modes in this HgMn star.

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Dynamical evolution of titanium, strontium, and yttrium spots on the surface of the HgMn star HD 11753

Cited by 48 publications

References 29 publications

Magnetism, chemical spots, and stratification in the HgMn starϕ Phoenicis

Magnetism, chemical spots, and stratification in the HgMn starϕ Phoenicis

No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars

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

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