V Sagittae

V Sagittae
Location of V Sagittae (circled) in Sagitta
Observation data
Epoch J2000      Equinox J2000
Constellation Sagitta
Right ascension 20h 20m 14.691s[1]
Declination +21° 06′ 10.44″[1]
Apparent magnitude (V) 8.6-13.9[2]
Characteristics
Spectral type B1[3]
Variable type eclipsing and cataclysmic[2]
Astrometry
Proper motion (μ) RA: −2.133[1] mas/yr
Dec.: −6.489[1] mas/yr
Parallax (π)0.3310±0.0206 mas[1]
Distance9,900 ± 600 ly
(3,000 ± 200 pc)
Absolute magnitude (MV)−2.2[4]
Orbit[5]
Semi-major axis (a)4.36 R☉
Inclination (i)71°
Semi-amplitude (K1)
(primary)		320 km/s
Semi-amplitude (K2)
(secondary)		85 km/s
Details
White dwarf
Mass0.9[5] M☉
Radius1.2[5] R☉
Luminosity30,000[5] L☉
Temperature70,000[5] K
Donor
Mass3.3[5] M☉
Radius2.1[5] R☉
Temperature12,000[5] K
Other designations
AAVSO 1015+20, V Sge, GSC 01643-01764
Database references
SIMBADdata

V Sagittae or V Sge is a cataclysmic variable in the constellation Sagitta. The system is composed of a main sequence star of about 3.3 solar masses and a white dwarf of about 0.9 solar masses; the fact that the white dwarf is less massive than its companion is highly unusual for a cataclysmic variable,[6] and V Sge is the only super soft X-ray source nonmagnetic cataclysmic variable found so far.

A visual band light curve for V Sagittae, adapted from Šimon and Mattei (1999)[7]

Material from the larger star is accreting onto the white dwarf at an exponentially increasing rate, generating a huge stellar wind. The doubling time for the accretion rate, and hence for the system luminosity, is about 89±11 years.[4] It is predicted that the system will erupt as a nova some time between 2067 and 2099, at which point it will become one of the brightest stars in the sky.[6][8]

References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  3. ↑ Iriarte, B.; Chavira, E. (1955). "Nuevas estrellas de tipos espectrales tempranos con Hα en emisión entre l=339° y l=33°". Boletin de los Observatorios Tonantzintla y Tacubaya. 2: 19. Bibcode:1955BOTT....2m..19I.
  4. 1 2 "V Sagittae technical details" (PDF). Retrieved 2021-10-03.
  5. 1 2 3 4 5 6 7 8 Smak, Jozef I.; Belczynski, K.; Zola, S. (2001). "V Sge: A Hot, Peculiar Binary System". Acta Astronomica. 51: 117. Bibcode:2001AcA....51..117S.
  6. 1 2 "Binary star V Sagittae to explode as very bright nova by century's end". phys.org. Retrieved 2020-01-09.
  7. ↑ Šimon, V.; Mattei, J. A. (October 1999). "The peculiar binary V Sagittae: Properties of its long-term light changes". Astronomy and Astrophysics Supplement Series. 139: 75–88. Bibcode:1999A&AS..139...75S. doi:10.1051/aas:1999381.
  8. ↑ "CNN - Breaking News, Latest News and Videos". m.cnn.com. Archived from the original on 2020-01-13. Retrieved 2020-01-09.


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