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21. Multiplicity among chemically peculiar stars II
ID:
ivo://CDS.VizieR/J/A+A/394/151
Title:
Multiplicity among chemically peculiar stars II
Short Name:
J/A+A/394/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new orbits for sixteen Ap spectroscopic binaries, four of which might in fact be Am stars, and give their orbital elements. Four of them are SB2 systems: HD 5550, HD 22128, HD 56495 and HD 98088. The twelve other stars are : HD 9996, HD 12288, HD 40711, HD 54908, HD 65339, HD 73709, HD 105680, HD 138426, HD 184471, HD 188854, HD 200405 and HD 216533. Rough estimates of the individual masses of the components of HD 65339 (53 Cam) are given, combining our radial velocities with the results of speckle interferometry and with Hipparcos parallaxes. Considering the mass functions of 74 spectroscopic binaries from this work and from the literature, we conclude that the distribution of the mass ratio is the same for cool Ap stars as for normal G dwarfs. Therefore, the only differences between binaries with normal stars and those hosting an Ap star lie in the period distribution: except for the case of HD 200405, all orbital periods are longer than (or equal to) 3 days. A consequence of this peculiar distribution is a deficit of null eccentricities. There is no indication that the secondary has a special nature, like e.g. a white dwarf.
22. Observations of the Ap Star HR 1217 from 1980-86
ID:
ivo://CDS.VizieR/II/146
Title:
Observations of the Ap Star HR 1217 from 1980-86
Short Name:
II/146
Date:
21 Oct 2021
Publisher:
CDS
Description:
This file contains magnitudes from nearly 50,000 40 second observations of the rapidly oscillating Ap star HR 1217 obtained during nearly 600 hours of observation at various observatories from 1980 to 1986. Most of the observations were made through Johnson B filters, but some were made through other filters. All data in this file were included in a paper entitled The high-overtone p-mode spectrum of the rapidly oscillating Ap star HR 1217 (HD 24712) by Kurtz et al. (1989MNRAS.240..881K) and described in the CDS Inf. Bull. (Kurtz 1989). Much of the information published in Kurtz et al. (1989) had been gathered from previously published literature, and some had been obtained by a team established for that paper. Each record holds one observation with the Heliocentric Julian Date given to 5 decimal accuracy and the magnitude given to 4 decimal accuracy. The observations are grouped so that all observations from a single night from each observatory are listed together. The data published in Kurtz et al. (1989) included observations previously published as follows: Julian Dates Source of data ------------ -------------- JD2444540-2444643 Kurtz (1982MNRAS.200..807K) JD2444849-2444953 Kurtz & Seeman (1983MNRAS.205...11K) JD2445661-2445664 H. J. Wood (unpublished) JD2445690-2445693 Kurtz, Schneider & Weiss (1985MNRAS.215...77K) JD2446712-2446784 original (Kurtz et al. 1989MNRAS.240..881K)
23. Observed Periods of Ap and Bp stars
ID:
ivo://CDS.VizieR/III/199A
Title:
Observed Periods of Ap and Bp stars
Short Name:
III/199A
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalogue of all the periods published up to 31 October 1996 on 364 CP stars is presented; it supersedes the previous version (catalog <III/152>). The paper version (catalog.tex) is arranged in three tables: the bulk of the data, i.e. those referring to CP2, CP3, and CP4 stars, are given in Table 1, while the data concerning He-strong stars are given in Table 2 and those for eclipsing or ellipsoidal variables are collected in Table 3. Notes are also provided at the end of each table, mainly about duplicities. The machine-readable version was arranged in two main parts: the main parameters of the 364 stars (identifiers and names, positions, spectral types, magnitudes and peculiarities) are tabulated in the file 'stars'; periods and the of the observed variations (light, spectrum, magnetic field, etc.) are listed in the 'periods' file. Two other files contains the notes and the references.
24. Ori OB1 CP stars magnetic fields. III.
ID:
ivo://CDS.VizieR/J/other/AstBu/74.55
Title:
Ori OB1 CP stars magnetic fields. III.
Short Name:
J/other/AstBu/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents results of magnetic field measurements of 10 chemically peculiar stars of subgroup (a) in the Orion OB1 association: HD33917, HD34859, HD35008, HD35039, HD35177, HD35575, HD35730, HD36549, HD38912, and HD294046. Observations were carried out with the circular polarization analyzer at the Main Stellar Spectrograph at the 6-m SAO RAS telescope.Magnetic fields were detected in four stars, six stars have magnetic fields below the detection threshold.
25. Ori OB1 CP stars magnetic fields. V.
ID:
ivo://CDS.VizieR/J/other/AstBu/76.163
Title:
Ori OB1 CP stars magnetic fields. V.
Short Name:
J/other/AstBu/76
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents the results of magnetic field measurements of 27 chemically peculiar stars in subgroups (c) and (d) of the Orion OB1 association. In total, more than 140 circularly polarized spectra were obtained and measured in the period from 2013 to 2020. An analysis of the results showed that 13 out of 24 CP stars in subgroup (c) have a magnetic field. At the same time, no field of a significant strength was found in any of the three CP stars in subgroup (d). We found that the occurrence of magnetic stars in subgroup (c), whose average age is approximately 5Myr, lies in the middle between the occurrence of magnetic stars in subgroups (a) with an age of 10 Myr and (b), whose age is about 2Myr. Our results indicate a sharp decrease in the occurrence of magnetic CP stars and a simultaneous decrease in their magnetic field with age. The data obtained with the example of the Orion OB1 association generally support the theory of the fossil origin of the magnetic field of chemically peculiar stars; however, the process of the field formation itself can have a number of features manifesting observationally.
26. Ori OB1 CP stars magnetic fields. V.
ID:
ivo://CDS.VizieR/J/other/AstBu/76.39
Title:
Ori OB1 CP stars magnetic fields. V.
Short Name:
J/other/AstBu/76
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents magnetic field measurements for 15 chemically peculiar (CP) stars of subgroup 1b in the Orion OB1 association. We have found that the proportion of stars with strong magnetic fields among these 15 CP stars is almost twice as large as in subgroup 1a. Along with this, the age of subgroup 1b is estimated as 2Myr, and the age of subgroup 1a is in the order of 10Myr. The average root-mean-square magnetic field <Be> (all) for stars in subgroup 1b is 2.3 times higher than that for stars in subgroup 1a. The conclusions obtained fall within the concept of the fossil origin of large-scale magnetic fields in B and A stars, but the rate of field weakening with age appears anomalously high. We present our results as an important observational test for calibrating the theory of stellar magnetic field formation and evolution.
27. Photometry of CU Vir
ID:
ivo://CDS.VizieR/J/A+A/625/A34
Title:
Photometry of CU Vir
Short Name:
J/A+A/625/A34
Date:
21 Oct 2021
Publisher:
CDS
Description:
CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. We used our own far-UV and visual photometric observations supplemented with the archival data to improve the parameters of the quasisinusoidal long-term variations of the rotational period. We predict the flux variations of CU Vir from surface abundance maps and compare these variations with UV flux distribution. We searched for wind, auroral, and interstellar lines in the spectra. The UV and visual light curves display the same long-term period variations supporting their common origin. New updated abundance maps provide better agreement with the observed flux distribution. The upper limit of the wind mass-loss rate is about 10^-12^M_{sun}_/yr. We do not find any auroral lines. We find rotationally modulated variability of interstellar lines, which is most likely of instrumental origin. Our analysis supports the flux redistribution from far-UV to near-UV and visual domains originating in surface abundance spots as the main cause of the flux variability in chemically peculiar stars. Therefore, UV and optical variations are related and the structures leading to these variations are rigidly confined to the stellar surface. The radio emission of CU Vir is most likely powered by a very weak presumably purely metallic wind, which leaves no imprint in spectra.
28. Photometry of HD 3831
ID:
ivo://CDS.VizieR/J/ApJ/459/278
Title:
Photometry of HD 3831
Short Name:
J/ApJ/459/278
Date:
21 Oct 2021
Publisher:
CDS
Description:
We demonstrate a new approach for probing the atmospheres of selected chemically peculiar magnetic stars. Using the Cerro Tololo Inter-American Observatory (CTIO) 1.0 and 1.5m telescopes simultaneously on two nights in 1991, we obtained optical and infrared high-speed photometry of the rapidly oscillating Ap (roAp) star HR 3831 (=HD 83368), which pulsates with a period of ~11.8 minutes. Oscillation amplitudes (or upper limits) in each of eight bandpasses were measured by Fourier analysis, revealing the very steep decline in amplitude with increasing wavelength characteristic of roAp stars. Matthews and coworkers have shown that this can be explained by the wavelength dependence of limb darkening and its filtering effect on the integrated amplitude of an (l,m)=(1,0) nonradial pulsation mode. Since the eigenfrequency spectrum of HR 3831 is dominated by just such a dipole mode, it is possible to infer limb-darkening coefficients beta(lambda) for its atmosphere from our amplitude measurements. These coefficients are used to derive a source function through the Eddington-Barber relation, which leads to a relation for temperature versus optical depth in the stellar photosphere. Our results show that the T-Tau(5000) curve is much steeper for HR 3831 than for the Sun (at least at the rotational phase when the star's magnetic pole dominates the visible hemisphere). We also calculate the gradient dT/dtau as a function of wavelength to compare with the curve expected for H- continuous opacity. This type of diagnostic may become a useful tool for checking the predictions of diffusion theory.
29. Photometry of magnetic CP stars
ID:
ivo://CDS.VizieR/J/A+AS/111/41
Title:
Photometry of magnetic CP stars
Short Name:
J/A+AS/111/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photometry in the Stroemgren and Geneva systems is used to improve the ephemerides of the magnetic CP stars 56 Tau, HD 111133, HD 126515 and HD 215441.
30. Polarimetry of Ap stars: general catalogue
ID:
ivo://CDS.VizieR/J/A+AS/114/79
Title:
Polarimetry of Ap stars: general catalogue
Short Name:
J/A+AS/114/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
A systematic program of broadband linear polarimetry, bearing on 55 Ap stars, has been developed during the 4 last years, at the Pic du Midi Observatory. While separate data have been already published, we present in this paper a complete catalogue of our observational material, including more than 400 measurements. We complement these data with another 100 measurements, obtained previously by other authors, so as to get a synthetic view of the phenomenon. Most of the observations have been dedicated to a small number (15) of stars, which show conspicuous changes of the linear polarization, so that it is possible to know accurately the time variation of the Stokes parameters: we expect that these new data will really improve our knowledge of the magnetic configuration, after a proper analysis which is currently being developed. For the other 40 stars, the polarization is either too small, or strongly contaminated by the interstellar polarization, so that broadband polarimetry is not very effective. Anyway, this first systematic investigation on the linear polarization of Ap stars will be a useful starting point for future measurements which should be made with higher spectral resolution. Finally, our measurements have provided new determinations of the rotation period for several stars.