V4641 Sagittarii

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V4641 Sagittarii
Accretion disk.jpg
Graphic representation of an X-ray binary star
Position
EpochJ2000.0    EquinoxJ2000.0
Constellation Sagittarius
Right ascension 18 h 19 m 21.6 s
declination 1747574−25 ° 24 ′ 26 ″
Double star system
Type Low-mass X-ray binary star, microquasar
distance > 3 kpc
Period of circulation 2.817 d
Optical / stellar component
Apparent brightness (V-band) changeable, approx. 13.8 mag in the resting stage, regular optical outbursts up to 11 mag, nova outbreak in 1999: 8.8 mag
Spectral class B9 III
Dimensions 6.5 +1.6−1.0 M
radius approx 7.47 +0.53−0.47 M
Compact component
Type Black hole
Dimensions 9.6 +2.1−0.9 M
History and other names
discovery optically, as an irregular variable: Goransky, June 1978
as an X-ray source: February 1999
Designations V4641 Sagittarii • XTE J1819-254 • INTREF 898 • SAX J1819.3-2525 • GSC 06848-03786 • 2MASS J18192163-2524258

V4641 Sagittarii, or V4641 Sgr for short , is a microquasar in the constellation Sagittarius that contains a black hole about 10 solar masses.

history

This single star and compact component duo was discovered on September 15, 1999 after an X-ray burst was observed. Calculations resulted in a mass of approx. 10 solar masses for the compact, not directly observable component. This value is far above the limit for a stable neutron star of approx. 5 solar masses. Therefore, only a black hole comes into question.

The exact distance from V4641 Sagittarii is not known; earlier estimates of about 0.5 kpc, which would have made the object the closest known black hole, turned out to be way too low.

The name follows the rules of naming variable stars and states that V4641 Sagittarii is the 4641st variable star discovered in the constellation Sagittarius .

Individual evidence

  1. a b c d Orosz et al: A Black Hole in the Superluminal Source SAX J1819.3-2525 (V4641 Sgr). In: The Astrophysical Journal. Vol. 555, No. 1, pp. 489 ff., 2001, bibcode : 2001ApJ ... 555..489O .
  2. Chaty et al .: Optical and near-infrared observations of the microquasar V4641 Sgr during the 1999 September outburst. In: Monthly Notice of the Royal Astronomical Society. Vol. 343, No. 1, pp. 169 ff., 2003, bibcode : 2003MNRAS.343..169C .
  3. Goransky et al.: Recent activity of the black hole binary V4641 Sgr. In: The Astronomer's Telegram. No. 1134, 2007, bibcode : 2007ATel.1134 .... 1G .
  4. Goransky et al: Photometry and spectroscopy of the system V4641 sagittarii in quiescence. In: Astronomy Reports. Vol. 47, No. 9, pp. 740 ff., 2003, bibcode : 2003ARep ... 47..740G .

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