2004A&A...420..993V


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.07CET04:45:51

2004A&A...420..993V - Astronomy and Astrophysics, volume 420, 993-1007 (2004/6-4)

The influence of magnetic fields on the hydrostatic structure of the atmospheres of chemically peculiar stars.

VALYAVIN G., KOCHUKHOV O. and PISKUNOV N.

Abstract (from CDS):

We discuss the properties of atmospheres of chemically peculiar magnetic stars. The slow evolution of global magnetic fields leads to the development of an induced electric current in all conductive atmospheric layers. The Lorentz force, which results from the interaction between a magnetic field and the induced current, may change the atmospheric structure and provide insight into the formation and evolution of stellar magnetic fields. We developed a model atmosphere code that takes into account the Lorentz force in the equation of hydrostatic equilibrium, and computed a number of model atmospheres for magnetic A and B stars. The surface distribution of a magnetic field was assumed to be a dipole, slightly distorted by the induced atmospheric electric current. The interaction between the magnetic field and electric current is modelled in detail, taking into account microscopic properties of the stellar plasma. The presence of a significant Lorentz force leads to substantial modification of the atmospheric structure and in particular the pressure stratification, which in turn influences the formation of absorption spectral features, especially hydrogen Balmer lines. Furthermore, we find that rotational modulation of the disk-average parameters of a global stellar magnetic field causes characteristic rotational variability of hydrogen lines. With our model, observable effects correspond to induced electric currents of the order of 10–11cgs, which requires characteristic field evolution times 2-3 orders of magnitude shorter than the field decay time estimated for magnetic A and B stars assuming fossil dipolar field topology in the stellar interior. Using the computations of our model atmospheres we consider an observational aspect of the problem and attempt to interpret photometric data on the variability of hydrogen lines within the framework of simplest model of the evolution of global magnetic fields. With the hydrogen line data we find tentative support for the presence of a non-negligible Lorentz force in the atmospheres of some magnetic chemically peculiar stars.

Abstract Copyright:

Journal keyword(s): stars: chemically peculiar - stars: magnetic fields - stars: atmospheres

Simbad objects: 1

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Number of rows : 1

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 * 56 Ari a2* 03 12 14.2459541239 +27 15 25.093114957 5.22 5.64 5.76     B6IV-V 251 0

    Equat.    Gal    SGal    Ecl

C.D.S. - SIMBAD4 rel 1.7 - 2021.03.07CET04:45:51

Available data : Basic data  •  Identifiers  •  Plot & images  •  Bibliography  •  Measurements  •  External archives  •  Notes  •  Annotations


Basic data :
* 56 Ari -- Variable Star of alpha2 CVn type
Origin of the objects types :

(Ref) Object type as listed in the reference "Ref"
(acronym) Object type linked to the acronym according to the original reference
() Anterior to 2007, before we can link the objet type to a reference, or given by the CDS team in some particular cases

Other object types:
a2* (), * (*,AG,...), UV (CEL,TD1), V* (V*), IR (2MASS)
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
ICRS coord. (ep=J2000) :
03 12 14.2459541239 +27 15 25.093114957 (Optical) [ 0.1460 0.1220 90 ] A 2018yCat.1345....0G
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
FK4 coord. (ep=B1950 eq=1950) :
03 09 15.1043830522 +27 04 11.408547883 [ 0.1460 0.1220 90 ]
Syntax of coordinates is : "ra dec (wtype) [error ellipse] quality bibcode" :
  • ra dec : right ascension and declination (unit and frame defined according to your Output Options)
    Grey values are increasing the original precision due to the computation of frame transformations
  • (wtype) : wavelength class for the origin of the coordinates (Rad, mm, IR, Optical, UV, Xray, Gam)
  • [error ellipse] : measurement uncertainty, on (ra,dec) if the positional angle is 90 degrees, on (majaxis,minaxis) otherwise (in mas at defined epoch in the original catalogue),
    position angle (in degrees North celestial pole to East)
  • quality : flag of quality
    • E ≥ 10"
    • D : 1-10" (and some old data)
    • C : 0.1-1"
    • B : 0.01-0.1" + 2MASS, Tyc
    • A : VLBI, Hipparcos
  • bibcode : bibcode of the coordinates reference
Gal coord. (ep=J2000) :
157.6756262467517 -25.9549963752849 [ 0.1460 0.1220 90 ]
Syntax of proper motions is : "pm-ra pm-dec [error ellipse] quality bibcode"
  • pm-ra : mu-ra*cos(dec) (expressed in the ICRS system in mas/yr)
  • pm-dec : mu-dec (expressed in the ICRS system in mas/yr)
  • [error ellipse] : error major axis and minor axis (in mas), orientation angle (in deg)
  • quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the proper motion reference
Proper motions mas/yr :
12.035 -18.791 [0.349 0.271 90] A 2018yCat.1345....0G
Syntax of radial velocity (or/and redshift) is : "value [error] (wavelength) quality bibcode"
  • value : radial velocity or/and redshift (Heliocentric frame) according to your Output Options
    (redshift may be not displayed if the data value is <0 and the database inside value is a radial velocity)
  • [error] : error of the corresponding value displayed before
  • (wavelength) : wavelength range of the measurement : Rad, mm, IR, Opt, UV, Xray, Gam or  '∼'(unknown)
  • quality : flag of quality ( A=best quality -> E=worst quality, {� } =unknown quality)
  • bibcode : bibcode of the value's origin
Radial velocity / Redshift / cz :
V(km/s) 16.00 [2] / z(~) 0.000053 [0.000007] / cz 16.00 [2.00]
   B 2006AstL...32..759G
Syntax of parallax is : 'value quality [error] bibcode'
  • value : parallax value
  • quality : flag of quality (A=best quality -> E=worst quality, {� } =unknown quality)
  • [error] : mean error
  • bibcode : bibcode of the parallax reference
Parallaxes (mas):
8.0413 [0.1723] A 2018yCat.1345....0G
Spectral type is made of 3 parts: %coding is composed of 4 parts :
  • the spectral type, which is made of a temperature class, eventually a luminosity class (roman number) and/or spectral peculiarities;
  • a quality letter: A=best quality→E=worst quality, {� } =unknown quality %
  • a quality letter: A=best quality -> E=worst quality, {� } =unknown quality
  • bibcode : bibcode of the spectral type reference
Spectral type:
B6IV-V C ~
Syntax of fluxes (or magnitudes) is : "filter-name (System) flux-value [error] quality MultVarFlags bibcode"
  • filter-name : U, B, V, R, I, G, J, H, K, u, g, r, i, z
  • (System) : may be AB (default is Vega)
  • flux-value : value of flux or magnitude
  • [error] : error value
  • quality : flag of quality of the flux value ( A=best quality -> E=worst quality, {� } =unknown quality)
  • MultVarFlags : Mult is zero or one char (J) for joined photometry ; Var can be zero or two chars (V[0-4])
  • bibcode : bibcode of the flux reference
Fluxes (7) :
U 5.22 [~] C 2002yCat.2237....0D
B 5.64 [~] C 2002yCat.2237....0D
V 5.76 [~] C 2002yCat.2237....0D
G 5.7522 [0.0015] C 2018yCat.1345....0G
J 5.929 [0.018] C 2003yCat.2246....0C
H 5.993 [0.016] C 2003yCat.2246....0C
K 6.011 [0.016] C 2003yCat.2246....0C
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Suggestions are: crowded field: 0.5 to 1.5 arcsec, 3 arcsec otherwise; uncertain coordinates (SIMBAD quality E or coordinates without reference): 5 to 30 arsec (risky!).


The link on the acronym of the identifiers give access to the information for this acronym in the dictionary of nomenclature.
Identifiers (28) :
An access of full data is available using the icon Vizier near the identifier of the catalogue

* 56 Ari GSC 01791-01519 Renson 4910 UBV M 9378
AG+27 324 HD 19832 SAO 75788 uvby98 100019832
BD+26 523 HIC 14893 SKY# 4798 V* SX Ari
CEL 304 HIP 14893 TD1 1964 WEB 2874
GC 3821 HR 954 TIC 34978817 YPAC 312
GCRV 1765 2MASS J03121424+2715250 TYC 1791-1519-1 YZ 27 1600
GEN# +1.00019832 PPM 92289 UBV 21410 Gaia DR2 118591610481186688

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References (251 between 1850 and 2021) (Total 251)
Simbad bibliographic survey began in 1850 for stars (at least bright stars) and in 1983 for all other objects (outside the solar system).
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Collections of Measurements


distance : 1    diameter : 1    velocities : 6    ROT : 3    PM : 5    PLX : 3    MK : 5   

   

Observing logs


IUE : 113   

   


External archives :

Archive data at HEASARC - High-Energy Astrophysics Science Archive Research Center

Link by name to the catalogue in VizieR :

AG+27 324 BD+26 523 CEL 304 GSC 01791-01519 HD 19832
HIC 14893 HIP 14893 HR 954 2MASS J03121424+2715250 PPM 92289
SAO 75788 TD1 1964 TYC 1791-1519-1 uvby98 100019832 V* SX Ari
Gaia DR2 118591610481186688

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2021.03.07-04:45:51

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