V407 Lupi

V407 Lupi, also known as Nova Lupi 2016, was a bright nova in the constellation Lupus discovered by All Sky Automated Survey for SuperNovae (ASAS-SN) on 24.00 September 2016. At the time of its discovery, it had an apparent visual magnitude of 9.1. The ASAS-SN team reported that no object at the nova's location brighter than magnitude 17.5 was seen on images taken four days earlier.^[5] Wildly incorrect coordinates (in error by many degrees) were published in the announcement telegram,^[5] but corrected in a subsequent telegram.^[1] It reached a peak brightness of magnitude 5.6, faintly visible to the naked eye, on 25 September 2016.^{[6] [7]}

V407 Lupi

Location of V407 Lupi (circled in red)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Lupus
Right ascension	15h 29m 01.820s[1]
Declination	−44° 49′ 40.89″[1]
Apparent magnitude (V)	5.6 – 14.8 [2]
Characteristics
Variable type	Nova[3]
Other designations
Nova Lupi 2016, V407 Lup, PNV J15290182-4449409, ASASSN -16kt[4]
Database references
SIMBAD	data

The light curve of V407 Lupi, plotted from AAVSO data

V407 Lupi declined from its peak brightness very quickly, fading by 2 magnitudes in less than three days. That is one of the most rapid declines in brightness ever seen in a nova. It is therefore classified as a "very fast" nova in the classification scheme of Cecilia Payne-Gaposchkin.^[7][8]

All novae are binary stars, with a "donor" star orbiting a white dwarf. The two stars are so close to each other that matter is transferred from the donor to the white dwarf. Observations by the satellite TESS detected a variation in the light curve of V407 Lupi indicating an orbital period for the binary system of 3.513 days;^[9] it was previously thought to be 3.573 hours,^[10] but this has since been disproven.^[9] A second periodicity in the light curve was also detected by the Chandra X-ray Observatory^[7] and has a period of 591.27465 seconds (9.8545775 min), which appears to be the rotation period of the white dwarf.^[9][11] The very rapid decline from peak brightness indicates that the mass of the white dwarf is ≥ 1.25 M_☉, not far below the Chandrasekhar limit for white dwarf masses. The system is probably an intermediate polar nova.^[7]

References

1. Stanek, K.Z.; Team, ASAS-SN (September 2016). "Erratum to ATel 9538: ASAS-SN Discovery of A Likely Galactic Nova ASASSN-16kt at V=9.1". The Astronomer's Telegram. 9539: 1. Bibcode:2016ATel.9539....1S. Retrieved 10 January 2021.
2. "Download Data". aavso.org. AAVSO. Retrieved 9 January 2021.
3. Izzo, L.; Cano, Z.; de Ugarte Postigo, A.; Thoene, C.; Vanzi, L.; Zapata, A.; Espinoza, N.; Fernandez, D.; Prieto, J.L.; Bonifacio, P.; Della Valle, M.; Molaro, P. (October 2016). "Spectroscopic observations of Nova Lup 2016". The Astronomer's Telegram. 9587: 1. Bibcode:2016ATel.9587....1I. Retrieved 9 January 2021.
4. "V4407 Lup". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-09.
5. Stanek, K.Z.; Kochanek, C.S.; Brown, J.S.; Holoien, T.W.S.; Shields, J.; Shappee, B.J.; Prieto, J.L.; Bersier, D.; Dong, Subo; Bose, S.; Chen, Ping; Chomiuk, L.; Strader, J.; Brimacombe, J. (September 2016). "ASAS-SN Discovery of A Likely Galactic Nova ASASSN-16kt at V=9.1". The Astronomer's Telegram. 9538: 1. Bibcode:2016ATel.9538....1S. Retrieved 11 January 2021.
6. Watson, Christopher Watson, Christopher. "VSX : Detail for ASASSN-16kt".{{cite web}}: CS1 maint: multiple names: authors list (link)
7. Aydi, E.; Orio, M.; Beardmore, A.P.; Ness, J.U.; Page, K.L.; Kuin, N.P.M.; Walter, F.M.; Buckley, D.A.H.; Mohamed, S.; Whitelock, P.; Osborne, J.P.; Strader, J.; Chomiuk, L.; Darnley, M.J.; Dobrotka, A.; Kniazev, A.; Miszalski, B.; Myers, G.; Ospina, N.; Henze, M.; Starrfield, S.; Woodward, C.E. (October 2018). "Multiwavelength observations of V407 Lupi (ASASSN-16kt) - a very fast nova erupting in an intermediate polar". Monthly Notices of the Royal Astronomical Society. 480 (1): 572–609. arXiv:1807.00706. Bibcode:2018MNRAS.480..572A. doi:10.1093/mnras/sty1759.
8. Payne-Gaposchkin, Cecilia (1964). The galactic novae. New York: Dover. Bibcode:1964gano.book.....P. Retrieved 11 January 2021.
9. Schaefer, Bradley E. (2021). "Discovery of 13 New Orbital Periods for Classical Novae". Research Notes of the AAS. 5 (6): 150. arXiv:2106.13907. Bibcode:2021RNAAS...5..150S. doi:10.3847/2515-5172/ac0d5b. S2CID 235632263.
10. Beardmore, A.P.; Page, K.L.; Osborne, J.P.; Orio, M. (11 August 2021). "Swift observations of nova V407 Lup: detection of a UV period at 1.1 or 3.6 hours". The Astronomer's Telegram. 10632. Retrieved 11 January 2021.
11. Beardmore, Andy; Dobrotka, Andrej; Ness, Jan-Uwe; Orio, Marina; Osborne, Julian; Page, Kim (September 2017). "Detection of a 9.4 min periodicity in the XMM-Newton and Chandra X-ray light curves of V407 Lup (Nova Lup 2016)". The Astronomer's Telegram. 10749: 1. Bibcode:2017ATel10749....1B. Retrieved 11 January 2021.