Rotational periods of four roAp stars

Ryabchikova, T.; Wade, G. A.; Aurière, M.; Bagnulo, S.; Donati, J.‐F.; Jeffers, S. V.; Johnson, N.; Landstreet, J. D.; Lignières, F.; Lueftinger, T.; Marsden, S. C.; Mouillet, D.; Paletou, F.; Petit, P.; Reegen, P.; Silvester, J.; Strasser, S.; Toqué, N.

doi:10.1051/0004-6361:200400112

Cited by 24 publications

(47 citation statements)

References 23 publications

(29 reference statements)

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“…The variability period found by Preston (1972) was confirmed by photometric observations by Wolff & Morrison (1973). Many studies of the magnetic field of HD 24712 have been carried out (Preston 1972;Brown & Landstreet 1981;Mathys 1991Mathys , 1994Mathys & Hubrig 1997;Ryabchikova et al 1997;Leone et al 2000;Wade et al 2000a;Leone & Catanzaro 2004;Ryabchikova et al 2005Ryabchikova et al , 2007. Below we will use some of these measurements for improving the rotational period of the star.…”

Section: Hd 24712mentioning

confidence: 63%

“…The most recent determination of the rotational period of HD 24712 was done by Ryabchikova et al (2005). They combined their Fe-Cr line longitudinal magnetic field measurements with other data from the literature, finding P rot = 12.45902 ± 0.00044 d. They also obtained an independent period estimate, P rot = 12.45853 ± 0.00018 d, from the variability of equivalent widths of REE lines.…”

Section: Rotational Periodmentioning

confidence: 99%

“…They combined their Fe-Cr line longitudinal magnetic field measurements with other data from the literature, finding P rot = 12.45902 ± 0.00044 d. They also obtained an independent period estimate, P rot = 12.45853 ± 0.00018 d, from the variability of equivalent widths of REE lines. The final period recommended by Ryabchikova et al (2005), P rot = 12.45877±0.00016, represents a formal weighted mean of the periods found using the magnetic and equivalent width data. A significantly smaller period, P rot = 12.4572 ± 0.0003 d, was inferred from the photometric pulsational analysis of HD 24712 (Kurtz & Marang 1987;Kurtz et al 2005).…”

Section: Rotational Periodmentioning

confidence: 99%

“…For the period search we compiled a list of all published longitudinal magnetic field measurements derived from the spectral lines of Fe-peak elements, which should be among the least variable lines in the spectrum of HD 24712. This list includes the TiCrFe B z data published by Preston (1972), measurements from the Fe i lines by Mathys (1991) and Mathys & Hubrig (1997), longitudinal field derived from the LSD Stokes V profiles of Fe-peak elements by Wade et al (2000a) and Ryabchikova et al (2005), measurements by Leone & Catanzaro (2004) and, finally, measurements from the recent spectroscopic study of pulsations in the atmosphere of HD 24712 performed by Ryabchikova et al (2007). Photopolarimetric longitudinal magnetic field measurements from the Hβ line by Ryabchikova et al (1997) were also included.…”

Section: Rotational Periodmentioning

confidence: 99%

“…However, these measurements show systematically higher values of B z than those derived from metallic lines. Therefore, these measurements were reduced by 400 G following the analysis by Ryabchikova et al (2005). A similar correction of −300 G was applied to the data from Preston (1972).…”

Section: Rotational Periodmentioning

confidence: 99%

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Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Rusomarov

Kochukhov

Piskunov

et al. 2013

A&A

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Context. High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. High-quality spectra in the Stokes IQUV parameters are currently available for very few early-type magnetic chemically peculiar stars. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712 with a recently commissioned spectropolarimeter. Aims. The goal of our work is to examine the circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Methods. HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO telescope over a period of 2010-2011. We achieved full rotational phase coverage with 43 individual Stokes parameter observations. The resulting spectra have a signal-to-noise ratio of 300-600 and resolving power exceeding 10 5 . The multiline technique of least-squares deconvolution (LSD) was applied to combine information from the spectral lines of Fe-peak and rare earth elements. Results. We used the HARPSPol spectra of HD 24712 to study the morphology of the Stokes profile shapes in individual spectral lines and in LSD Stokes profiles corresponding to different line masks. From the LSD Stokes V profiles we measured the longitudinal component of the magnetic field, B z , with an accuracy of 5-10 G. We also determined the net linear polarization from the LSD Stokes Q and U profiles. Combining previous B z measurements with our data allowed us to determine an improved rotational period of the star, P rot = 12.45812 ± 0.00019 d. We also measured the longitudinal magnetic field from the cores of Hα and Hβ lines. The analysis of B z measurements showed no evidence for a significant radial magnetic field gradient in the atmosphere of HD 24712. We used our B z and net linear polarization measurements to determine parameters of the dipolar magnetic field topology. We found that magnetic observables can be reasonably well reproduced by the dipolar model, although significant discrepancies remain at certain rotational phases. We discovered rotational modulation of the Hα core and related it to a non-uniform surface distribution of rare earth elements.

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Section: Hd 24712mentioning

confidence: 63%

Section: Rotational Periodmentioning

confidence: 99%

Section: Rotational Periodmentioning

confidence: 99%

Section: Rotational Periodmentioning

confidence: 99%

Section: Rotational Periodmentioning

confidence: 99%

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Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Rusomarov

Kochukhov

Piskunov

et al. 2013

A&A

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Anomalous abundance of lithium in the roAp star HD 12098 recently discovered in the northern hemisphere of the sky

et al. 2008

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of Sciences) using the NES echelle spectrometer have revealed several stars with an anomalous lithium abundance. The oscillating star HD 12098, which is the first roAp star in the northern hemisphere of the sky, merits special attention. Strong, variable LiI 6708 Å line was observed in the spectrum of this star. There are not enough observations for a reliable analysis by Doppler mapping, but there are enough to indicate the presence of lithium spots on the surface of this star similar to the roAp stars HD 83368 and HD 60435, on whose surfaces spots with a high lithium abundance have been reliably detected. Parameters for a model of its atmosphere have been chosen using the method of synthetic spectra based on atmospheric models including lines from the VALD list and several additional blended REE lines calculated by the authors. The profile of the lithium LiI 6708 Å blend has been calculated taking the magnetic field into account using the SYNTHM code. A lithium abundance has been determined for two phases of the rotation of HD 12098 that is anomalously high compared to the solar and meteoritic abundances. The large difference in the lithium abundance in the two phases (in two different regions on the star's surface) exceeds 0.5 dex and is very close to that which we have found by analyzing the spectra of the roAp stars HD 83368 and HD 60435. Thus, we have discovered yet another roAp star, HD 12098, with lithium spots on its surface.

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Magnetic Doppler imaging of the roAp star HD 24712

Lüftinger¹,

Kochukhov

Ryabchikova

et al. 2009

A&A

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Aims. We present the first magnetic Doppler images of a rapidly oscillating Ap (roAp) star. Methods. We deduce information about magnetic field geometry and abundance distributions of a number of chemical elements on the surface of the hitherto best studied roAp star, HD 24712, using the magnetic Doppler imaging (MDI) code, invers10, which allows us to reconstruct simultaneously and consistently the magnetic field geometry and elemental abundance distributions on a stellar surface. For this purpose we analyse time series spectra obtained in Stokes I and V parameters with the SOFIN polarimeter at the Nordic Optical Telescope and recover surface abundance structures of sixteen different chemical elements, respectively ions, including Mg, Ca, Sc, Ti, Cr, Fe, Co, Ni, Y, La, Ce, Pr, Nd, Gd, Tb, and Dy. For the rare earth elements (REE) Pr and Nd separate maps were obtained using lines of the first and the second ionization stage. Results. We find and confirm a clear dipolar structure of the surface magnetic field and an unexpected correlation of elemental abundance with respect to this field: one group of elements accumulates solely where the positive magnetic pole is visible, whereas the other group avoids this region and is enhanced where the magnetic equatorial region dominates the visible stellar surface. We also observe relative shifts of abundance enhancement-or depletion regions between the various elements exhibiting otherwise similar behaviour.

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Rotational periods of four roAp stars

Cited by 24 publications

References 23 publications

Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Anomalous abundance of lithium in the roAp star HD 12098 recently discovered in the northern hemisphere of the sky

Magnetic Doppler imaging of the roAp star HD 24712

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