- ID:
- ivo://CDS.VizieR/J/A+A/545/A119
- Title:
- Stromgren v photometry of {sigma} Lup
- Short Name:
- J/A+A/545/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic early B-type stars are rare. Indirect indicators are needed to identify them before investing in time-intensive spectropolarimetric observations. We use the strongest indirect indicator of a magnetic field in B stars, which is periodic variability of ultraviolet (UV) stellar wind lines occurring symmetric about the approximate rest wavelength. Our aim is to identify probable magnetic candidates which would become targets for follow-up spectropolarimetry to search for a magnetic field. From the UV wind line variability the B1/B2V star sigma Lupi emerged as a new magnetic candidate star. AAT spectropolarimetric measurements with SEMPOL were obtained. The longitudinal component of the magnetic field integrated over the visible surface of the star was determined with the least- squares deconvolution method. The UV line variations of sigma Lupi are similar to what is known in magnetic B stars, but no periodicity could be determined. We detected a varying longitudinal magnetic field with amplitude of about 100G with error bars of typically 20G, which supports an oblique magnetic-rotator configuration. The equivalent width variations of the UV lines, the magnetic and the optical-line variations are consistent with the photometric period of 3.02d, which we identify with the rotation period of the star. Additional observations with ESPaDOnS attached to the CFHT confirmed this discovery, and allowed the determination of a precise magnetic period. Analysis revealed that sigma Lupi is a helium-strong star, with an enhanced nitrogen abundance and an underabundance of carbon, and has a chemically spotted surface. Conclusions. sigma Lupi is a magnetic oblique rotator, and is a He-strong star. Like in other magnetic B stars the UV wind emission appears to originate close to the magnetic equatorial plane, with maximum emission occurring when a magnetic pole points towards the Earth. The 3.01972+/-0.00043d magnetic rotation period is consistent with the photometric period, with maximum light corresponding to maximum magnetic field.
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- ID:
- ivo://CDS.VizieR/J/A+A/561/A63
- Title:
- The chemically peculiar binary HD 161701
- Short Name:
- J/A+A/561/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a complete study of the HgMn binary HD 161701, including the determination of physical parameters and photospheric chemical abundances. We analyzed time series of high-resolution FEROS and HARPS spectroscopic observations in addition to a near-IR spectrum obtained with CRIRES. Radial velocity curves were combined with additional spectroscopic information to estimate absolute stellar parameters. A spectral separation technique was applied, which enabled us to conduct a detailed spectral analysis of both components. The primary is a HgMn star with overabundances of P, Mn, Ga, Y, Xe, and Hg. The secondary is an Ap star showing strong (2-5dex) overabundances of Sr, Y, and rare-earth elements. We detected line profile variations in both stellar companions, indicating a non uniform surface distribution of chemical composition. The secondary presents a remarkable chemical pattern with Ti and rare-earths pemanently facing the binary companion, and Fe concentrated on the far side. The primary star shows weak profile variations in Mn and Cr spectral lines. The coincidence of chemical spots with the position of the binary companion suggests a possible connection between the presence of the companion and the origin of chemical anomalies.
- ID:
- ivo://CDS.VizieR/J/ApJS/212/6
- Title:
- The McGill magnetar catalog
- Short Name:
- J/ApJS/212/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of the 26 currently known magnetars and magnetar candidates. We tabulate astrometric and timing data for all catalog sources, as well as their observed radiative properties, particularly the spectral parameters of the quiescent X-ray emission. We show histograms of the spatial and timing properties of the magnetars, comparing them with the known pulsar population, and we investigate and plot possible correlations between their timing, X-ray, and multiwavelength properties. We find the scale height of magnetars to be in the range of 20-31pc, assuming they are exponentially distributed. This range is smaller than that measured for OB stars, providing evidence that magnetars are born from the most massive O stars. From the same fits, we find that the Sun lies ~13-22pc above the Galactic plane, consistent with previous measurements. We confirm previously identified correlations between quiescent X-ray luminosity, L_X_, and magnetic field, B, as well as X-ray spectral power-law indexes, {Gamma} and B, and show evidence for an excluded region in a plot of L_X_ versus {Gamma}. We also present an updated kT versus characteristic age plot, showing that magnetars and high-B radio pulsars are hotter than lower-B neutron stars of similar age. Finally, we observe a striking difference between magnetars detected in the hard X-ray and radio bands; there is a clear correlation between the hard and soft X-ray fluxes, whereas the radio-detected magnetars all have low, soft X-ray flux, suggesting, if anything, that the two bands are anticorrelated.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A44
- Title:
- Tr16-22. V and V/I Stokes parameters
- Short Name:
- J/A+A/596/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/3604
- Title:
- Variability of the PGa star HD 19400
- Short Name:
- J/MNRAS/442/3604
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study is to carry out an abundance determination, to search for spectral variability and for the presence of a weak magnetic field in the typical PGa star HD19400. High-resolution, high signal-to-noise HARPS spectropolarimetric observations of HD19400 were obtained at three different epochs in 2011 and 2013. For the first time, we present abundances of various elements determined using an ATLAS12 model, including the abundances of a number of elements not analysed by previous studies, such as NeI, GaII, and XeII. Several lines of As II are also present in the spectra of HD19400. To study the variability, we compared the behaviour of the line profiles of various elements. We report on the first detection of anomalous shapes of line profiles belonging to Mn, and Hg, and the variability of the line profiles belonging to the elements Hg, P, Mn, Fe, and Ga. We suggest that the variability of the line profiles of these elements is caused by their non-uniform surface distribution, similar to the presence of chemical spots detected in HgMn stars. The search for the presence of a magnetic field was carried out using the moment technique and the SVD method. Our measurements of the magnetic field with the moment technique using 22 MnII lines indicate the potential existence of a weak variable longitudinal magnetic field on the first epoch. The SVD method applied to the MnII lines indicates B_z_=-76+/-25G on the first epoch, and at the same epoch the SVD analysis of the observations using the Fe II lines shows B_z_=-91+/-35G. The calculated false alarm probability values, 0.008 and 0.003, respectively, are above the value 10^-3^, indicating no detection.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/97
- Title:
- VLA rotation measures in the Galactic plane
- Short Name:
- J/ApJ/728/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined 194 Faraday rotation measures (RMs) of polarized extragalactic radio sources using new, multi-channel polarization observations at frequencies around 1.4GHz from the Very Large Array in the Galactic plane at 17{deg}<=l<=63{deg} and 205{deg}<=l<=253{deg}. This catalog fills in gaps in the RM coverage of the Galactic plane between the Canadian Galactic Plane Survey (CGPS; Taylor et al. 2003, Cat. VI/128; Brown et al. 2003, Cat. J/ApJS/145/213) and Southern Galactic Plane Survey (SGPS; Haverkorn et al. 2006ApJS..167..230H; Brown et al. 2007, Cat. J/ApJ/663/258).
- ID:
- ivo://CDS.VizieR/J/A+A/538/A136
- Title:
- VLBA SiO maser maps of the star OH 44.8-2.3
- Short Name:
- J/A+A/538/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SiO maser emission occurs in the extended atmosphere of evolved stars and can be studied at high angular resolution. As compact, high-brightness components they can be used as important tracers of the dynamics at distances close to the central star. The masers also serve as probes of the evolutionary path from spherically symmetric AGB stars to aspherical PNe. Very long baseline interferometry (VLBI) observations of Mira variables indicate that SiO masers are significantly linearly polarized with linear polarization fractions up to 100%. However, no information is available at high angular resolution for SiO masers in higher mass loss OH/IR stars. Theory indicates a different SiO pumping mechanism in higher mass loss evolved stars. We extend the VLBI SiO maser studies to OH/IR stars. The observations enable us to understand the SiO pumping mechanisms in higher mass-loss evolved objects and to compare them with Mira variables. Additionally, polarimetric observations of SiO masers help us to understand the magnetic field strength and morphology and to distinguish between conflicting polarization theories.
- ID:
- ivo://CDS.VizieR/J/A+A/410/671
- Title:
- X-ray emission in cool main sequence stars
- Short Name:
- J/A+A/410/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The maximum amplitude A_max_ of spot-induced brightness variations from long-term V-band photometry and the ratio L_X_/L_bol_ between X-ray and bolometric luminosities are suitable indicators of the level of magnetic activity in the photosphere and in the corona of late-type stars, respectively. By using these activity indicators we investigate the dependence of coronal X-ray emission on the level of photospheric starspot activity in a homogeneous sample of low mass main-sequence field and cluster stars of different ages (IC 2602, IC 4665, IC 2391, {alpha} Per, Pleiades and Hyades).
- ID:
- ivo://CDS.VizieR/J/PAZh/29/571
- Title:
- X-ray fluxes of radio pulsars
- Short Name:
- J/PAZh/29/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the correlations between the luminosities of radio pulsars in various frequency ranges and the magnetic fields of the light cylinder.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A71
- Title:
- ZDI maps of five young solar-type stars
- Short Name:
- J/A+A/659/A71
- Date:
- 09 Mar 2022 16:47:36
- Publisher:
- CDS
- Description:
- The magnetic activity of the Sun changes with the solar cycle. Similar cycles are found in other stars as well, but their details are not known to a similar degree. Characterising stellar magnetic cycles is important for the understanding of the stellar and solar dynamos that are driving the magnetic activity. We present spectropolarimetric observations of five young, solar-type stars and compare them to previous observations, with the aim to identify and characterise stellar equivalents of the solar cycle. We use Zeeman-Doppler imaging (ZDI) to map the surface magnetic field and brightness of our targets. The magnetic field is decomposed into spherical harmonic expansions, from which we report the strengths of the axisymmetric versus non-axisymmetric and poloidal versus toroidal components, and we compare them to the Rossby numbers of the stars. We present five new ZDI maps of young, solar-type stars from December 2017. Of special interest is the case of V1358 Ori, which had gone through a polarity reversal between our observations and earlier ones. A less evident polarity reversal might also have occurred in HD 35296. There is a preference for a more axisymmetric field, and possibly a more toroidal field, for the more active stars with lower Rossby number, but a larger sample should be studied to draw any strong conclusions from this. For most of the individual stars, the amounts of toroidal and poloidal field have stayed on levels similar to those in earlier observations. We find evidence for a magnetic polarity reversal having occurred in V1358 Ori. An interesting target for future observations is {chi}^1^ Ori, which may have a short magnetic cycle of a few years. The correlation between the brightness maps and the magnetic field is mostly poor, which could indicate the presence of small-scale magnetic features of different polarities that cancel one another out and are thus not resolved in our maps.
