Strömgren <i>uvby</i> photometry of the magnetic Chemically 
Peculiar stars HD 32633, 25 Sex, HR 7224, and HD 200311

Adelman, Saul J.

doi:10.1051/aas:1997132

Cited by 18 publications

(16 citation statements)

References 3 publications

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“…Its photometric variability ephemeris: JD(u min ) = 2 445 659.000 + 4.37900 E were established by Manfroid & Renson (1994). The validity of this period is confirmed by Adelman (1997) and also by Hipparcos photometry: a fitting of the Hipparcos and Adelman's b-filter variations with Eq. (1) shows that the primary maxima are the phase 0.776 and 0.774 respectively (Fig.…”

Section: Sex = Hd 90044 = Hr 4082 = Hip 50885mentioning

confidence: 56%

“…According to Adelman's (1997) observations (Fig. 3): u variation shows the absolute maximum around the 0.3 phase and a secondary maximum around the 0.8 phase; b shows the primary maximum at the 0.8 phase and the secondary maximum at 0.3 phase; v and y light curves resemble the b variation even if with a very small (∼ 0.01 mag) amplitude.…”

Section: Sex = Hd 90044 = Hr 4082 = Hip 50885mentioning

confidence: 75%

“…2). Adelman (1997) and Hipparcos light curve of 25 Sex. Near infrared light curves are from Catalano et al (1998).…”

Section: (Triangles) Crosses Represent the Ten Colourmentioning

confidence: 99%

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Spectropolarimetric measurements of the mean longitudinal magnetic field of chemically peculiar stars

Leone

Catanzaro

2001

A&A

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Abstract. For a sample of chemically peculiar stars, we report time-resolved measurements of the effective magnetic field which were obtained with the spectropolarimetry operating at the Catania Astrophysical Observatory. These observations are combined with data from the literature for better pointing out that periodic magnetic variability which characterises this class of stars. Periods given in the literature have been checked and, if possible, redetermined, not only by means of the magnetic measurements but referring also to the Hipparcos photometry. The variability of the effective magnetic field of the already known magnetic star 25 Sex is pointed out for the first time. As to the suspected magnetic chemically peculiar star EP UMa, our measurements confirm that this is really a magnetic star and we indicate a possible variability period. The accuracy of the variability period for CS Vir and FF Vir is improved. The suggestion that light variability is due to the re-distribution of ultraviolet flux towards the visible wavelengths in metal rich regions, which are not homogeneously distributed on the stellar surface, appears not always and straightly valid. Local line-blocking is certainly important in the case of CS Vir and a direct influence of the magnetic field on the infrared photometric variability cannot be ruled out for 25 Sex.

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Section: Sex = Hd 90044 = Hr 4082 = Hip 50885mentioning

confidence: 56%

Section: Sex = Hd 90044 = Hr 4082 = Hip 50885mentioning

confidence: 75%

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Spectropolarimetric measurements of the mean longitudinal magnetic field of chemically peculiar stars

Leone

Catanzaro

2001

A&A

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“…The photometric variability of HR 7224 is known since a long time (Winzer 1974). The light curve shows a double wave (Adelman 1997) over the rotation period. A more detailed description of the history of HR 7224 observations is given in Lehmann et al (2006, Paper I).…”

Section: Introductionmentioning

confidence: 97%

The helium weak silicon star HR 7224

Lehmann¹,

Tkachenko²,

Tsymbal

et al. 2007

A&A

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Aims. We investigate the abundance distributions of silicon and iron on the surface of HR 7224 and check for the presence of magnetic fields. We try further to find an explanation for the observed Balmer line variations, alternative to that by surface temperature gradients given in a previous article. Methods. Based on time series of more than 570 high-resolution spectra we investigate the abundance distribution of silicon and iron using the Doppler Imaging technique applying two independent program codes and using single and multiple components atmosphere models. We further calculate the combined effect of abundance changes of Si, Fe, and He on the H β line profile and compare it with the observations. The mean longitudinal magnetic field strength of HR 7224 is measured spectropolarimetrically. Results. The Doppler Imaging analysis of HR 7224 shows the presence of large silicon and iron spots on the star's surface, large gradients of the abundances of these elements, and hints to enhanced line strengths near the visible pole of the star. The explanation of the observed Balmer line variations by inhomogeneous abundance distributions alone requires unrealistic large gradients of the helium abundance. Magnetic field measurements gave no definite results, a field strength of the order of +400 G is likely. Conclusions. We can exclude the hypothesis that the hydrogen line profile variations of HR 7224 are caused by inhomogeneous abundance distributions of Fe, Si, and He alone or by pressure gradients like in the case of Ap stars. Still the observed variations can be described only by the combined effect of abundance and temperature gradients. In this case, the derived Doppler imaging maps will reflect also the temperature gradients and the surface will be cooler in regions of enhanced line strength like at the visible pole. At present state, the physical origin of possible surface temperature gradients remains unknown.

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“…It was used by Adelman (1997) whose 109 uvby measurements were obtained in 1992-95. The star was observed by Hipparcos ESA (1997) (83 measurements).…”

Section: Light Curves and Improvement Of The Period Of Hd 90044mentioning

confidence: 99%