Astronomy:V Sagittae
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Sagitta |
| Right ascension | 20h 20m 14.691s[1] |
| Declination | +21° 06′ 10.44″[1] |
| Apparent magnitude (V) | 8.6-13.9[2] |
| Characteristics | |
| Evolutionary stage | White dwarf (primary)[3] |
| Spectral type | Be[4] |
| 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[1] mas |
| Distance | 9,900 ± 600 ly (3,000 ± 200 pc) |
| Absolute magnitude (MV) | −2.2[5] |
| Orbit | |
| Period (P) | 12.34[3] hours |
| Semi-major axis (a) | 4.36 R☉[6] |
| Inclination (i) | 65–80[3]° |
| Semi-amplitude (K1) (primary) | 320[6] km/s |
| Semi-amplitude (K2) (secondary) | 85[6] km/s |
| Details | |
| White dwarf (primary) | |
| Mass | 1.0[3] M☉ |
| Donor (secondary) | |
| Mass | 0.8–1.0[3] M☉ |
| Other designations | |
AAVSO 1015+20, V Sge, GSC 01643-01764 | |
| Database references | |
| SIMBAD | data |
V Sagittae or V Sge is a cataclysmic variable in the constellation Sagitta. It is the only super soft X-ray source non-magnetic cataclysmic variable found so far. Lidiya Tseraskaya discovered the variability of this star, in 1902.[7] It appeared with its variable star designation in Annie Jump Cannon's 1907 work Second catalogue of variable stars.[8]
Characteristics
There are two models that have been proposed to explain V Sagittae's properties. One says that the system is composed of a white dwarf accreting mass from a companion via an accretion disk, while the other model says that the system is composed of two hot stars (nearly) forming a contact binary. Both models have been disputed. Smak (2022) notes that the primary component shows similarities with Wolf-Rayet stars and the model with a white dwarf and its accretion disk does not explain many aspects of the system, including orbital period variations and mass loss from the primary, supporting a configuration with a Wolf-Rayet star and a main sequence star.[10] However, a 2025 study by Hakala, Charles and Rodríguez-Gil found that the 'hot binary' model fails to explain multiple properties of V Sagittae, such as the system's variability, strong Hα emission and presence of stationary, double-peaked narrow emission lines, while the white dwarf model explains nearly all of them.[3]
Material from the donor is accreting onto the primary 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.[5] 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.[11][12]
References
- ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 Samus, N. N. 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.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Hakala, Pasi; Charles, Phil; Rodríguez-Gil, Pablo (2025-10-06). "V Sge: supersoft source or exotic hot binary? – I. An X-Shooter campaign in the high state" (in en). Monthly Notices of the Royal Astronomical Society 543 (3): 2058–2077. doi:10.1093/mnras/staf1284. ISSN 0035-8711. Bibcode: 2025MNRAS.543.2058H.
- ↑ Iriarte, B.; Chavira, E. (1955). "Nuevas estrellas de tipos espectrales tempranos con Hα en emisión entre l=339° y l=33°". Boletín de los Observatorios de Tonantzintla y Tacubaya 2: 19. Bibcode: 1955BOTT....2m..19I.
- ↑ 5.0 5.1 "V Sagittae technical details". https://www.lsu.edu/physics/files/v_sagittae/vsge_technical-details.pdf.
- ↑ 6.0 6.1 6.2 Smak, Jozef I.; Belczynski, K.; Zola, S. (2001). "V Sge: A Hot, Peculiar Binary System". Acta Astronomica 51: 117. Bibcode: 2001AcA....51..117S.
- ↑ Ryves, P. M. (May 1932). "A remarkable variable star (V Sagittæ)". Monthly Notices of the Royal Astronomical Society 92: 715. doi:10.1093/mnras/92.7.715. Bibcode: 1932MNRAS..92..715R.
- ↑ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory 55: 1–94. Bibcode: 1907AnHar..55....1C.
- ↑ 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. doi:10.1051/aas:1999381. Bibcode: 1999A&AS..139...75S.
- ↑ Smak, J. (2022). "On the Orbital Period and Models of V Sge" (in en). Acta Astronomica 72 (1): 21–29. doi:10.32023/0001-5237/72.1.2. ISSN 0001-5237. Bibcode: 2022AcA....72...21S.
- ↑ "Binary star V Sagittae to explode as very bright nova by century's end" (in en-us). https://phys.org/news/2020-01-binary-star-sagittae-bright-nova.html.
- ↑ "CNN - Breaking News, Latest News and Videos". http://m.cnn.com/en/article/h_f7a7fda778b24834ac5316152cc63433.
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