- ID:
- ivo://CDS.VizieR/J/A+A/430/1143
- Title:
- Stellar magnetic rotational phase curves
- Short Name:
- J/A+A/430/1143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetized stars usually exhibit periodic variations of the effective (longitudinal) magnetic field B_e_ caused by their rotation. We present a catalog of magnetic rotational phase curves, B_e_ vs. the rotational phase phi, and tables of their parameters for 136 stars on the main sequence and above it. Phase curves were obtained by the least squares fitting of sine wave or double wave functions to the available B_e_ measurements, which were compiled from the existing literature. Most of the catalogued objects are chemically peculiar A and B type stars (127 stars). For some stars we also improved or determined periods of their rotation. We discuss the distribution of parameters describing magnetic rotational phase curves in our sample.
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- ID:
- ivo://CDS.VizieR/J/A+A/652/A31
- Title:
- Stellar magnetic rotational phase curves. II
- Short Name:
- J/A+A/652/A31
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Some stars show periodic variability of the longitudinal (effective) global magnetic field B_e_ mainly due to rotation. We present the second version of the catalog of average magnetic phase curves, which are functions of B_e_ versus the rotational phase phi, tables of their parameters. The curves were obtained from literary data and as the result of observations from SAO RAS telescopes. A total of 357 stars of various spectral types were studied, data on which was published before the end of August 2020. Magnetic Ap and Bp stars make up the most numerous a subset in the catalog (224 objects). Phase curves were obtained by least squares fit of a simple sine wave or a double sine wave to the available B_e measurements. For some stars we also improved or determined periods of their rotation. Phase curves also are presented in 514 figures. In some cases several phase curves presented here correspond to the same star. This occurred when different observational techniques produced significantly different series of B_e_ values for that star. In a few cases the rotational phase curves of the surface field, B_s_, are given for stars where longitudinal magnetic field data were not available.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/2361
- Title:
- Stellar magnetism, age and rotation
- Short Name:
- J/MNRAS/441/2361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate how the observed large-scale surface magnetic fields of low-mass stars (~0.1-2M_{sun}_), reconstructed through Zeeman-Doppler imaging, vary with age t, rotation and X-ray emission. Our sample consists of 104 magnetic maps of 73 stars, from accreting pre-main sequence to main-sequence objects (1Myr<~t<~10Gyr). For non-accreting dwarfs we empirically find that the unsigned average large-scale surface field is related to age as t^-0.655+/-0.045^. This relation has a similar dependence to that identified by Skumanich, used as the basis for gyrochronology. Likewise, our relation could be used as an age-dating method ('magnetochronology'). The trends with rotation we find for the large-scale stellar magnetism are consistent with the trends found from Zeeman broadening measurements (sensitive to large- and small-scale fields). These similarities indicate that the fields recovered from both techniques are coupled to each other, suggesting that small- and large-scale fields could share the same dynamo field generation processes. For the accreting objects, fewer statistically significant relations are found, with one being a correlation between the unsigned magnetic flux and rotation period. We attribute this to a signature of star-disc interaction, rather than being driven by the dynamo.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A163
- Title:
- Stokes param. of Bok globules background stars
- Short Name:
- J/A+A/618/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of magnetic fields in the process of star formation is a matter of continuous debate. Clear observational proof of the general influence of magnetic fields on the early phase of cloud collapse is still pending. In an earlier study on Bok globules with simple structures, we find strong indications of dominant magnetic fields across large spatial scales. The aim of this study is to test the magnetic field influence across Bok globules with more complex density structures. We apply near-infrared polarimetry to trace the magnetic field structure on scales of 10^4^-10^5^au in selected Bok globules. The combination of these measurements with archival data in the optical and sub-mm wavelength range allows us to characterize the magnetic field on scales of 10^3^-10^6^au. We present polarimetric data in the near-infrared wavelength range for the three Bok globules CB34, CB56, and [OMK2002] 18, combined with archival polarimetric data in the optical wavelength range for CB34 and CB56, and in the sub millimeter wavelength range for CB34 and [OMK2002] 18. We find a strong polarization signal (P>2%) in the near-infrared for all three globules. For CB34, we detect a connection between the structure on scales of 10^4^-10^5^au to 10^5^-10^6^au. For CB56, we trace aligned polarization segments in both the near-infrared and optical data, suggesting a connection of the magnetic field structure across the whole globule. In the case of [OMK2002]18, we find ordered polarization structures on scales of 10^4^-10^5^au. We find strongly aligned polarization segments on large scales which indicate dominant magnetic fields across Bok globules with complex density structures. To reconcile our findings in globules, the lowest mass clouds known, and the results on intermediate (e.g. Taurus) and more massive (e.g. Orion) clouds, we postulate a mass dependent role of magnetic fields, whereby magnetic fields appear to be dominant on low and high mass but rather sub dominant on intermediate mass clouds.
- 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/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.
