V407 Lupi

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
SIMBADdata
The light curve of V407 Lupi, plotted from AAVSO data

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 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]

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