HD 15144, a magnetic AP star with a possible intrinsic periodic variation of the magnetic field

Bonsack, W. K.

doi:10.1086/130922

Cited by 8 publications

(7 citation statements)

References 10 publications

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“…Our observations confirm the existence of a rather strong negative magnetic field at the surface of HD 15144 as already inferred by Babcock (1958) and Bonsack (1981). Figure 10 shows the LSD Stokes profiles when the longitudinal magnetic field was measured as B = −631 ± 15 G.…”

Section: Hd 15144supporting

confidence: 87%

Weak magnetic fields in Ap/Bp stars

Aurière¹,

Wade

Silvester

et al. 2007

A&A

306

342

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Aims. We investigated a sample of 28 well-known spectroscopically-identified magnetic Ap/Bp stars, with weak, poorly-determined or previously undetected magnetic fields. The aim of this study is to explore the weak part of the magnetic field distribution of Ap/Bp stars. Methods. Using the MuSiCoS and NARVAL spectropolarimeters at Télescope Bernard Lyot (Observatoire du Pic du Midi, France) and the cross-correlation technique Least Squares Deconvolution (LSD), we obtained 282 LSD Stokes V signatures of our 28 sample stars, in order to detect the magnetic field and to infer its longitudinal component with high precision (median σ = 40 G). Results. For the 28 studied stars, we obtained 27 detections of Stokes V Zeeman signatures from the MuSiCoS observations. Detection of the Stokes V signature of the 28th star (HD 32650) was obtained during science demonstration time of the new NARVAL spectropolarimeter at Pic du Midi. This result clearly shows that when observed with sufficient precision, all firmly classified Ap/Bp stars show detectable surface magnetic fields. Furthermore, all detected magnetic fields correspond to longitudinal fields which are significantly greater than some tens of G. To better characterise the surface magnetic field intensities and geometries of the sample, we phased the longitudinal field measurements of each star using new and previously-published rotational periods, and modeled them to infer the dipolar field intensity (B d , measured at the magnetic pole) and the magnetic obliquity (β). The distribution of derived dipole strengths for these stars exhibits a plateau at about 1 kG, falling off to larger and smaller field strengths. Remarkably, in this sample of stars selected for their presumably weak magnetic fields, we find only 2 stars for which the derived dipole strength is weaker than 300 G. We interpret this "magnetic threshold" as a critical value necessary for the stability of large-scale magnetic fields, and develop a simple quantitative model that is able to approximately reproduce the observed threshold characteristics. This scenario leads to a natural explanation of the small fraction of intermediate-mass magnetic stars. It may also explain the near-absence of magnetic fields in more massive B and O-type stars.

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Section: Hd 15144supporting

confidence: 87%

Weak magnetic fields in Ap/Bp stars

Aurière¹,

Wade

Silvester

et al. 2007

A&A

306

342

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“…Extensive observations by Babcock (1958) and Bonsack (1981) show that spectral variations in HR 710 are mild or absent. Nevertheless, abundance patches apparently influence the spectrum.…”

Section: The Atmosphere Of Hr 710mentioning

confidence: 99%

“…Values of v sin i have been published by Bonsack (1981) and Preston (1971): 7.7 and 13 km s −1 , respectively. We have made a new determination from our UVES spectra, using the magnetic null lines λλ3850, 4006, 4065 and 7090, all of Fe i .…”

Section: Hr 710aa and Its Companion Hr 710abmentioning

confidence: 99%

“…Extensive magnetic field measurements were made by Babcock (1958) and Bonsack (1981). The field varied between −0.45 and −1.10 kG – it did not reverse.…”

Section: Introductionmentioning

confidence: 98%

“…Tokovinin (1997) concludes that the system ADS 1849AB is a physical double, rather than a common proper motion pair, but the period must be very long. The primary, ADS 1849A (or is itself a spectroscopic binary (Aa and Ab) with a well‐determined period of 2.998 d (Bonsack 1981; Tokovinin 1997). This is a very short period for a magnetic Ap star.…”

Section: Introductionmentioning

confidence: 99%

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HR 710 (HD 15144): an ultra-Sr-rich, magnetic Ap star with a close companion

Cowley

Hubrig

2008

Monthly Notices RAS

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The magnetic, chemically peculiar A‐star HR 710 (HD 15144, ADS 1849A, AB Cet) has a close companion in a nearly circular orbit. Its 3‐d period is unusually short for such stars. The system emits moderately hard X‐rays, which likely come from a white dwarf secondary (ADS 1849Ab). The Sr ii spectrum is very strong, and the resonance lines show similar core‐nib structure to the stronger Ca K line. We place only loose constraints on a model. There are indications of a lower electron/gas pressure than expected from the star's parallax and brightness. Strong‐line profiles and anomalous excitation/ionization indicate significant deviations from traditional models, fixed by Teff, log g and abundances. Weak spectral‐line profiles and wavelength shifts probably indicate abundance patches rather than the presence of a secondary (ADS 1849Ab) spectrum. Our UV–Visual Echelle Spectrograph (UVES) spectra are from only one epoch. Additional low‐noise, high‐resolution spectra are needed. We discuss the spectrum within the context of abundance stratification.

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Catalogue of averaged stellar effective magnetic fields

Бычков

Бычкова

Madej

2003

A&A

114

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Abstract. This paper presents the catalogue and the method of determination of averaged quadratic effective magnetic fields B e for 596 main sequence and giant stars. The catalogue is based on measurements of the stellar effective (or mean longitudinal) magnetic field strengths B e , which were compiled from the existing literature. We analysed the properties of 352 chemically peculiar A and B stars in the catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, and all ApSr type stars. We have found that the number distribution of all chemically peculiar (CP) stars vs. averaged magnetic field strength is described by a decreasing exponential function. Relations of this type hold also for stars of all the analysed subclasses of chemical peculiarity. The exponential form of the above distribution function can break down below about 100 G, the latter value representing approximately the resolution of our analysis for A type stars.

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HD 15144, a magnetic AP star with a possible intrinsic periodic variation of the magnetic field

Cited by 8 publications

References 10 publications

Weak magnetic fields in Ap/Bp stars

Weak magnetic fields in Ap/Bp stars

HR 710 (HD 15144): an ultra-Sr-rich, magnetic Ap star with a close companion

Catalogue of averaged stellar effective magnetic fields

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