- ID:
- ivo://CDS.VizieR/J/A+A/622/A199
- Title:
- Fit parameters & ephemerides of 650 mCP stars
- Short Name:
- J/A+A/622/A199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic, chemically peculiar stars are known for exhibiting surface abundance inhomogeneities (chemical spots) that lead to photometric and spectroscopic variability with the rotation period. It is commonly assumed that the surface structures are causally connected with the global magnetic field that dominates the photospheric and subphotospheric layers of these stars. As a rule, the observed magnetic fields show a simple dipole-like geometry, with the magnetic axis being noncollinear to the rotational one. The present study aims at detecting underlying patterns in the distribution of photometric spots in a sample of 650 magnetic, chemically peculiar stars and examines their link to the magnetic field topology. Photometric time-series observations from the ASAS-3 archive were employed to inspect the light-curve morphology of our sample stars and divide them into representative classes described using a principal component analysis. Theoretical light curves were derived from numerous simulations assuming different spot parameters and following the symmetry of a simple dipole magnetic field. These were subsequently compared with the observed light curves. The results from our simulations are in contradiction with the observations and predict a much higher percentage of double-wave light curves than is actually observed. We thereby conclude that the distribution of the chemical spots does not follow the magnetic field topology, which indicates that the role of the magnetic field in the creation and maintenance of the surface structures may be more subsidiary than what is predicted by theoretical studies.
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- ID:
- ivo://CDS.VizieR/J/A+A/628/A81
- Title:
- Gaia DR2-based catalogue of 237 Ap stars
- Short Name:
- J/A+A/628/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Knowing the distribution of strongly magnetic Ap stars in the Hertzsprung-Russell diagram (HRD) allows us to study the evolution of their magnetic fields across the main sequence (MS). With a newly extended Ap star sample from APOGEE and available Gaia DR2 data, we can now critically review the results of previous studies based on Hipparcos data. To investigate our targets in the Gaia DR2 HRD, we need to define astrometric and photometric quality criteria to remove unreliable data from the HRD. We used the Gaia DR2 renormalised unit weight error RUWE as our main quality criterion. We considered known (close) binaries in our sample compared to their (partly affected) astrometry and used the Gaia DR2 data to find common parallax and proper motion (CPPM) wide companions and open cluster members. We studied G, BP and RP variability amplitudes and their significance as a function of magnitude. In colour-magnitude diagrams (CMDs) with absolute G magnitude (determined from inverted parallax) versus BP-RP colour and HRDs, where BP-RP is replaced by effective temperature, we studied the appearance of outliers with respect to their astrometric quality, binarity, and variability. We present a catalogue of 83 previously known and 154 new strongly magnetic Ap stars with Gaia DR2 data, including astrometric quality parameters, binary flags, information on cluster membership, variability amplitudes, and data from Hipparcos. Our astrometrically cleaned subsamples include 47 and 46 old and new Ap stars with parallaxes >2mas. Most of the known 26 binaries among all 237 stars and 14 out of 15 CMD/HRD outliers were excluded by astrometric criteria. The remaining 11 known binaries and a few highly variable objects mainly appear in the bright and red CMD/HRD parts. A CMD based on Hipparcos photometry and Gaia DR2 parallaxes shows a much more narrow distribution in the absolute V magnitudes of 75 common Ap stars over the full B-V colour range than the corresponding CMD based on Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A106
- Title:
- GO And, 84 UMa, kappa Psc ESPaDOnS spectra
- Short Name:
- J/A+A/655/A106
- Date:
- 11 Mar 2022 13:28:01
- Publisher:
- CDS
- Description:
- The aim of this work is to determine fundamental parameters of three Ap stars, GO And (HD 4778), {kappa} Psc (HD 220825), and 84 UMa (HD 120198), using spectroscopic techniques. By analysing these stars, we complete the sample of Ap stars for which fundamental parameters have additionally been derived by means of interferometry. This enables a cross-comparison of results derived by direct and indirect methods. Our study is based on the analysis of high-resolution spectra with a high signal-to-noise ratio that were obtained with ESPaDOnS spectrograph. We used an iterative method of fundamental parameter determinations that includes self-consistent modelling of the stellar atmosphere, taking individual abundances of chemical elements into account and subsequently fitting a theoretical spectral energy distribution to the observed distribution. The quality of the spectroscopic determinations was evaluated through a comparison with the interferometric results. For all investigated stars we determined fundamental parameters and derived chemical abundances that turn to be typical for Ap stars and are characterised mainly by gradual increase of heavy elements atmospheric abundance from an order of magnitude for iron peak elements up to very significant excesses of 3-4dex of the rare-earth elements relative to the solar values. The only exception is Ba which abundance is close to the solar one. There is also a significant He deficiency in the atmospheres of HD 120198 and HD 220825, whereas He abundance in HD 4778 is close to the solar one. We do not find significant Fe and Cr stratification. Using these abundances we constructed self-consistent atmospheric models for each star. The effect of the surface chemical inhomogeneity on the derived fundamental parameters did not exceed +/-100K in effective temperature which lies within a range of errors in similar self-consistent analyses of Ap stars. Finally, we compared spectroscopically derived effective temperatures, radii, and luminosity for 13 out of 14 Ap stars in benchmarking sample with the interferometric results. While radii and luminosity agree within the quoted errors of both determinations, spectroscopic effective temperatures are higher than the interferometric ones for stars with Teff>9000K. The observed hydrogen line profiles favour the spectroscopically derived temperatures.
- ID:
- ivo://CDS.VizieR/J/A+A/347/164
- Title:
- HD 59435 Geneva photometry
- Short Name:
- J/A+A/347/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The SB2 binary HD 59435 hosts a yellow giant and a magnetic Ap star, the latter being the secondary (Wade et al., 1996, Cat. <J/A+A/314/491>) and exhibiting spectral lines resolved into their magnetically-split components. Additional measurements of the magnetic field modulus of the Ap secondary are reported, as well as additional radial velocities for both components and photometric magnitudes and colours in the Geneva system. The magnetic field modulus varies with a period of about 1360 days. For a general description of the Geneva photometric system, see e.g. <GCPD/13>
- ID:
- ivo://CDS.VizieR/J/A+A/542/A89
- Title:
- Hvar survey for roAp stars. I.
- Short Name:
- J/A+A/542/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapidly oscillating Ap (roAp) stars exhibit short time scale photometric and/or radial velocity variations, which are most important to test current pulsation models as well as our assumptions of the atmospheric structure characteristics. In addition, their chemical peculiarity makes them very interesting for probing stellar formation and evolution in the presence of a global magnetic field. To date, only a limited number of about 45 roAp stars are known. In order to increase the sample, we obtained photometric time series of 20 good roAp candidates to search for pulsations. We present the time series analysis of about 60 hours of CCD photometry taken at the 1 meter Austrian-Croatian Telescope (Hvar Observatory) and derive effective temperatures for the programme objects. The upper amplitude limits of the Fourier spectra are typically below 2mmag in Bessell B with one good candidate for follow-up observations to find possible pulsation. In addition, we present a list of further roAp candidates, worth to be (re)investigated.
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/1804
- Title:
- Magnetic fields of chem. peculiar stars
- Short Name:
- J/MNRAS/372/1804
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectropolarimetric observations of 96 chemically peculiar (CP) main-sequence stars have been carried out at the 6-m telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) with the aim of searching for the presence of stellar magnetic fields. The stars selected for investigation were CP stars known to have strong anomalies in the wavelength region of the continuum flux depression around {lambda} 5200{AA}. This selection was conducted with the aid of low-resolution spectral observations, made with the SAO RAS 1-m telescope, and of published differential photometric data. Magnetic fields have been successfully detected in 72 stars of which only three stars were previously known to have magnetic fields. For two stars, the longitudinal component of the magnetic field B_e_exceeds 5kG: HD178892 - 7.4kG, and HD258686 - 6.7kG. We failed to reliably detect the magnetic field in the other 24 CP stars. These stars are mostly fast rotators, a feature which hampers accurate measurements of B_e_. It is demonstrated in this paper that selecting candidate magnetic stars by considering their photometric indices Z or {Delta}alpha}, or alternatively, by inspecting low-resolution spectra around the {lambda}5200{AA} flux depression, considerably increases the detection rate.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/73.178
- Title:
- Magnetic fields of CP stars (2011)
- Short Name:
- J/other/AstBu/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of measuring longitudinal magnetic fields (B_e_), rotation velocities (v_e_sini), and radial velocities (V_r_) of 92 stars observed with the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope of the Special Astrophysical Observatory in 2010. Observations of standard stars without magnetic fields confirm the absence of systematic errors capable of introducing distortions into the longitudinal-field measurement results.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/75.294
- Title:
- Magnetic fields of CP stars (2012)
- Short Name:
- J/other/AstBu/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of measuring longitudinal magnetic fields (Be), rotation velocities (v_esini), and radial velocities (VR) of 163 stars observed with the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope of the Special Astrophysical Observatory in 2012. Observations of standard stars without magnetic fields confirm the absence of systematic errors capable of introducing distortions into the longitudinal-field measurement results.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A40
- Title:
- 1002 mCP stars from LAMOST DR4
- Short Name:
- J/A+A/640/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present work is aimed at identifying new mCP stars using spectra collected by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Suitable candidates were selected by searching LAMOST DR4 spectra for the presence of the characteristic 5200{AA} flux depression. Spectral classification was carried out with a modified version of the MKCLASS code and the accuracy of the classifications was estimated by comparison with results from manual classification and the literature. Using parallax data and photometry from Gaia DR2, we investigated the space distribution of our sample stars and their properties in the colour-magnitude diagram. Our final sample consists of 1002 mCP stars, most of which are new discoveries (only 59 common entries with the Catalogue of Ap, HgMn and Am stars). Traditional mCP star peculiarities have been identified in all but 36 stars, highlighting the efficiency of the code's peculiarity identification capabilities. The derived temperature and peculiarity types are in agreement with manually derived classifications and the literature. Our sample stars are between 100Myr and 1Gyr old, with the majority having masses between 2M_{sun}_ and 3M_{sun}_. Our results could be considered as strong evidence for an inhomogeneous age distribution among low-mass (M<3M_{sun}_) mCP stars; however, we caution that our sample has not been selected on the basis of an unbiased, direct detection of a magnetic field. We identified several astrophysically interesting objects: the mCP stars LAMOST J122746.05+113635.3 and LAMOST J150331.87+093125.4 have distances and kinematical properties in agreement with halo stars; LAMOST J034306.74+495240.7 is an eclipsing binary system (Porb=5.1435+/-0.0012d) hosting an mCP star component; and LAMOST J050146.85+383500.8 was found to be an SB2 system likely comprising of an mCP star and a supergiant component. With our work, we significantly increase the sample size of known Galactic mCP stars, paving the way for future in-depth statistical studies.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/353
- Title:
- Mean magnetic field modulus of Ap stars
- Short Name:
- J/A+AS/123/353
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper reports about a systematic study of the mean magnetic field modulus of Ap stars with magnetically resolved split lines. Tables 2a and 2b present the main properties of all such stars presently known. The results about their mean magnetic field modulus derived in this study are summarized in Table 3, while the individual field measurements are given in Table 4.
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