2003A&A...410..519C


Query : 2003A&A...410..519C

2003A&A...410..519C - Astronomy and Astrophysics, volume 410, 519-522 (2003/11-1)

Radio variability of Sagittarius A* due to an orbiting star.

CHANG H.-Y. and CHOI C.-S.

Abstract (from CDS):

Recently, unprecedentedly accurate data on the orbital motion of stars in the vicinity of Sgr A* have become available. Such information can be used not only to constrain the mass of the supermassive black hole (SMBH) in the Galactic center but also to study the source of the radio emission. Two major competing explanations of the radio spectrum of Sgr A* are based on two different models, that is, hot accretion disk and jet. Hence, independent observational constraints are required to resolve related issues. It has been suggested that a star passing by a hot accretion disk may cool the hot accretion disk by Comptonization and consequently cause the radio flux variation. We explore the possibility of using the observational data of the star S2, currently closest to the Galactic center, to distinguish physical models for the radio emission of Sgr A*, by applying the stellar cooling model to Sgr A* with the orbital parameters derived from the observation. The relative difference in the electron temperature due to stellar cooling by S2 is a few parts of a thousand and the consequent relative radio luminosity difference is of the order of 10–4. Therefore, one might expect to observe the radio flux variation with a periodic or quasi-periodic modulation in the frequency range ν≲100MHz if radiatively inefficient hot accretion flows are indeed responsible for the radio emission, contrary to the case of a jet. According to our findings, even though no periodic radio flux variations have been reported up to date a radiatively inefficient hot accretion disk model cannot be conclusively ruled out. This is because the current available sensitivity is insufficient and because the energy bands that have been studied are too high to observe the effect of the star S2 even if it indeed interacts with the hot disk.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - Galaxy: center - galaxies: active - black hole physics

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 - 2024
#notes
1 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 4260 3

Query : 2003A&A...410..519C

Basic data :
NAME Sgr A* -- X-ray Source
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:
gam (), X (AX,CXOGC,...), Rad (2014ApJ)
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) :
17 45 40.03599 -29 00 28.1699 (Radio) [ 2.65 1.42 0 ] B 2011AJ....142...35P
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) :
17 42 29.30683 -28 59 18.5584 [ 2.65 1.42 0 ]
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) :
359.94423568 -00.04616002 [ 2.65 1.42 0 ]
SIMBAD within arcmin
', {sourceSize:12, color:'#30a090'})); aladin.on('objectClicked', function(object) { var objName=object.data.MAIN_ID; aladin.showPopup(object.ra,object.dec,'',''+ objName+''); });" title="Show Simbad objects"> Overlay Simbad points in this preview
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The search radius has to be specified by the user. It is currently limited to a maximum of 30 arcsec. It depends mostly on the precision or quality of the coordinates (SIMBAD and VizieR catalogs), the resolution of the images from which the sources were extracted, source extent, and source crowding.
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Some important notes on this object about identifications and objects associations.
notes:


Hierarchy : number of linked objects
whatever the membership probability is (see description here ) :

: 1 Display criteria :

The link on the acronym of the identifiers give access to the information for this acronym in the dictionary of nomenclature.
Identifiers (14) :
An access of full data is available using the icon Vizier near the identifier of the catalogue

AX J1745.6-2900 NAME Sgr A*/L' NAME Sagittarius A [BGM2005] J174540.08-290028.48
CXOGC J174540.0-290027 NAME Sgr A* IR NAME Sagittarius A* [SKM2002] 28
NAME Sgr A* NAME Sgr A * SWIFT J1746.3-2850A
NAME SgrA*/IR NAME Sgr A [BGM2005] J174540.14-290028.40

References (4260 between 1850 and 2024) (Total 4260)
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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Observing logs


herschel : 188    ISO : 82    XMM : 5   

   


External archives :

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

Data at NED - NASA/IPAC Extragalactic Database : NAME Sgr A*

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2023.11.29-17:14:38

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