V630 Sagittarii

V630 Sagittarii

Location of V630 Sagittarii (circled in red)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	18^h 08^m 48.25^s
Declination	−34° 20′ 21.4″
Apparent magnitude (V)	4.5 - 21.3[1]
Characteristics
Variable type	Nova,[2] VY Scl, and eclipsing[1]
Astrometry
Distance	2000[3] pc
Other designations
Nova Sgr 1936c HD 321353 AAVSO 1802-34
Database references
SIMBAD	data

The light curve for V630 Sgr. Data from the AAVSO, Warner (2006)^[4] and Gaposchkin (1955)^[5] are plotted.

V630 Sagittarii (Nova Sagittarii 1936) was a nova visible to the naked eye in 1936. It was discovered on 3 October 1936 by Shigeki Okabayashi of Kobe, Japan when it had an apparent magnitude of 4.5.^[4]

There is disagreement within the astronomical literature about what this nova's peak brightness was. Both Warner^[4] and Downes et al.^[6] report a peak brightness of magnitude 1.6 but Duerbeck reports 4.0^[3] in rough agreement with the Harrison and Gehrz value of 4.5.^[7] The AAVSO database contains no magnitude estimates for this star brighter than 6.5 (on 8 October 1936), indicating that whatever the peak brightness was, the star was barely visible to the naked eye just five days after its discovery. Its light curve shows it to be one of the most rapidly fading novae on record.^[5]

Duerbeck estimated that the star's absolute magnitude at peak brightness was −9.3.^[3] Diaz and Steiner list it as a possible magnetic nova, due to its short decay time (< 20 days) and large amplitude outburst.^[8]

All classical novae are binary systems, with a donor star losing mass onto the surface of a white dwarf. Mróz et al. report that in the case of V630 Sagittarii, the donor star is a main sequence star.^[9] Since all classical novae are very close binary systems, they are frequently also eclipsing binaries. Woudt and Warner detected these eclipses, which are 0.4 to 0.6 magnitudes deep, allowing them to derive an orbital period of 2.831 hours.^[10] Mróz et al. report the presence of superhumps.^[9]

References

1. "V630 Sgr". International Variable Star Index. American Association of Variable Star Observers. Retrieved 2020-12-01.
2. Warner, B. (1 July 1987). "Absolute magnitudes of cataclysmic variables". Monthly Notices of the Royal Astronomical Society. 227: 23–73. Bibcode:1987MNRAS.227...23W. doi:10.1093/mnras/227.1.23.
3. Duerbeck, H.W. (April 1981). "Light curve types, absolute magnitudes, and physical properties of galactic novae". Publications of the Astronomical Society of the Pacific. 93 (552): 165. Bibcode:1981PASP...93..165D. doi:10.1086/130799. S2CID 121397724.
4. Warner, B. (February 2006). "Where have all the novae gone?". Astronomy & Geophysics. 47 (1): 29–32. Bibcode:2006A&G....47a..29W. doi:10.1111/j.1468-4004.2006.47129.x.
5. Gaposchkin, S. (1955). "Notes and observations: Nova Sagittarii 1936". Astronomical Journal. 60: 454. Bibcode:1955AJ.....60..454G. doi:10.1086/107259.
6. Downes, Ronald; Webbink, Ronald F.; Shara, Michael M. (April 1997). "A Catalog and Atlas of Cataclysmic Variables-Second Edition". Publications of the Astronomical Society of the Pacific. 109 (734): 345–440. Bibcode:1997PASP..109..345D. doi:10.1086/133900. S2CID 120396435.
7. Harrison, T.E.; Gehrz, R.D. (February 1991). "IRAS observations of classical novae. II - Modeling the detections". Astronomical Journal. 101: 587–599. Bibcode:1991AJ....101..587H. doi:10.1086/115708.
8. Diaz, M.P.; Steiner, J.E. (September 1991). "UBVRI photometry of CP Puppis - A magnetic nova?". Publications of the Astronomical Society of the Pacific. 103: 964–968. Bibcode:1991PASP..103..964D. doi:10.1086/132913.
9. Mróz, P.; Udalski, A.; Poleski, R.; Soszyński, I.; Szymański, M.K.; Pietrzyński, G.; Wyrzykowski, L.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J. (August 2015). "Ogle Atlas of Classical Novae. I. Galactic Bulge Objects". The Astrophysical Journal Supplement Series. 219 (2): 26. arXiv:1504.08224. Bibcode:2015ApJS..219...26M. doi:10.1088/0067-0049/219/2/26.
10. Woudt, Patrick A.; Warner, Brian (November 2001). "High-speed photometry of faint cataclysmic variables - I. V359 Cen, XZ Eri, HY Lup, V351 Pup, V630 Sgr, YY Tel, CQ Vel and CE-315". Monthly Notices of the Royal Astronomical Society. 328 (1): 159–166. arXiv:astro-ph/0107505. Bibcode:2001MNRAS.328..159W. doi:10.1046/j.1365-8711.2001.04857.x.