On‐line database of photometric observations of magnetic chemically peculiar stars

Krtička²,

Henry

et al. 2008

A&A

Self Cite

Context. Light and spectrum variations of the magnetic chemically peculiar (mCP) stars are explained by the oblique rigid rotator model with a rotation period usually assumed to be stable on a long time scale. A few exceptions, such as CU Vir or 56 Ari, have been reported as displaying an increase in their rotation period. A possible increase in the period of light and spectrum variations has also been suggested from observations of the helium-strong mCP star HD 37776 (V901 Ori). Aims. In this paper we attempt to confirm the possible period change of HD 37776 and discuss a possible origin of this change as a consequence of i) duplicity; ii) precession; iii) evolutionary changes; and iv) continuous/discrete/transient angular momentum loss. Results. We confirm the previously suspected gradual increase in the 1. d 5387 period of HD 37776 and find that it has lengthened by a remarkable 17.7 ± 0.7 s over the past 31 years. We also note that a decrease in the rate of the period change is not excluded by the data. The shapes of light curves in all colours were found to be invariable. Conclusions. After ruling out light-time effects in a binary star, precession of the rotational axis, and evolutionary changes as possible causes for the period change, we interpret this ongoing period increase as a braking of the star's rotation, at least in its surface layers, due to the momentum loss through events or processes in the extended stellar magnetosphere.

Section: Published Photometric Datamentioning

confidence: 99%

“…For the purpose of exploiting the outliers we introduced "robust weights" (Mikulášek et al 2003) as follows…”

Section: Robust Regression Proceduresmentioning

confidence: 99%

The extremely rapid rotational braking of the magnetic helium-strong star HD 37776

Krtička²,

Henry

et al. 2008

A&A

Self Cite

“…Mikulášek et al 2007b) of the steady light variations due to the ellipticity of the primary component, a 1e and a 2e are partial effective semi-amplitudes describing the shape of the transient component of the light curve. The linear orbital phase is f = (t−M 0 )/P, where time of observation t is counted in JD hel , M 0 is the time of the basic light minimum and P the period in days, c and e in subscript indicate passband and era respectively.…”

Section: Photometry and Radial Velocitymentioning

confidence: 99%

“…in Mikulášek et al (2007b), the seasonal A Se and "steady" A Ce components of the light curves, and the average magnitudes in UBVHp m ce in individual eras e (see Table 2). It seems that the semiamplitude of the steady component remains constant, while the semiamplitude of the seasonal component varies considerably.…”

Section: Pca Disentangling Of Light Curvesmentioning

confidence: 99%

“…As an example we use HD 119213, the cool CP star of SrCrEu type with an amplitude in Strömgreen's v, A v = 0.089 mag (Mikulášek et al 2007b), the period P = 2.4499 d and effective magnetic field B eff varying from -0.5 to 1.2 kGs , the SrCrEu star HD 188041, A v = 0.090 mag, P = 223.81 d (Mikulášek et al 2007b), and a magnetic field varying from -0.2 to 1.5 kGs , the SiCr star HD 32633 with amplitude in u, A u = 0.048 mag, P = 6.4300 d (Mikulášek et al 2007b), and magnetic field varying from -5.7 to +3.5 kG.…”

Section: Effective Magnetic Fieldmentioning

confidence: 99%

See 1 more Smart Citation

The puzzling binary HD 143418

Zverko¹,

Ziznovsky²,

et al. 2009

A&A

Self Cite

Context. HD 143418 was discovered recently to be a double-lined spectroscopic binary with a primary designated as a CP star. Its light displays an orbital phase coupled variability with a peak-to-peak amplitude up to 0.04 mag. Aims. The photometry available and new high dispersion spectra were investigated from a point of view of CP characteristics.Methods. A series of high resolution high S/N coudé spectra was acquired from which 25 weak to strong unblended lines of Fe i and ii, Ti ii, Cr ii, Zr ii, and Ba ii were selected to study spectral line variability. Two Zeeman spectra were obtained to search for a possible magnetic field of the star, and one echelle spectrum in a wide spectral region was analysed for abundance determination by means of synthetic spectra. The photometric observations were subjected to a PCA disentangling of the complex photometric behaviour. Results. We identified spectral lines of the secondary in the yellow region on the echelle as well as on two coudé spectra, whose occurence belongs to an F6V star and the intensity corresponds to the luminosity ratio 0.06. Equivalent widths of the selected spectral lines of the primary component do not change within the errors of measurements. The spectra taken with a Zeeman analyser do not indicate a magnetic field. The abundance pattern does not correspond to characteristics of a variable CP2 star. The only remarkable deviation is a more than 1.1 dex deficit of scandium, one of the properties of non-variable Am stars. The photometric variability is tied to the orbital period and is due to ellipticity of the primary component and not to a putatively structured surface of the primary that is confirmed to rotate subsynchronously. The seasonal component of the light curve changes in amplitude as well as in shape. Conclusions. We conclude that the primary is a normal, mildly evolved A5V main sequence star. The seasonal variability of the orbitally modulated light curves may be related to an expected incidence of circumstellar matter originating in the tidally spinning up primary component. HD 143418 may be a prototype of a rare detached interacting close binary containing a subsynchronously rotating primary passing through its synchronisation stage.

Preliminary Analysis of Photometric Variations of the Central Star of the Planetary Nebula Sh 2–71

Zdeněk Kopal’s Binary Star Legacy

Kohoutek

Zejda

et al.