V692 Coronae Australis

V692 Coronae Australis (HD 166596; HR 6804; 3 G. CrA), or simply V692 CrA, is a whitish-blue hued variable star located in the southern constellation Corona Australis. It has a maximum apparent magnitude of 5.46,^[2] making it faintly visible to the naked eye. The object is located relatively far at a distance of approximately 1,900 light years based on Gaia DR3 parallax measurements,^[1] but it is approaching the Solar System with a fairly constrained heliocentric radial velocity of −15.3 km/s.^[8] At its current distance, V692 CrA's brightness is heavily diminished by 0.46 magnitudes due to extinction due to interstellar dust.^[18] Its absolute magnitude depends on the source: Westin (1985) gave a value of −6.44^[9] while the extended Hipparcos catalogue gave a value of −2.26.^[10]

A light curve for V692 Coronae Australis, plotted from Hipparcos data^[19]

V692 Coronae Australis

Location of V692 CrA (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Corona Australis
Right ascension	18h 13m 12.69843s[1]
Declination	−41° 20′ 09.9972″[1]
Apparent magnitude (V)	5.46[2] (5.46 - 5.51)[3]
Characteristics
Spectral type	B2 III[4] or B1.5 IIIp[5]
B−V color index	−0.17[6]
Variable type	SX Arietis[7]
Astrometry
Radial velocity (Rv)	−15.3±2.8[8] km/s
Proper motion (μ)	RA: −2.050 mas/yr[1] Dec.: −6.210 mas/yr[1]
Parallax (π)	1.7423±0.0977 mas[1]
Distance	1,900 ± 100 ly (570 ± 30 pc)
Absolute magnitude (MV)	−6.44[9] or −2.26[10]
Details
Mass	7.35±0.48[11] M☉
Radius	12.6±0.7[12] R☉
Luminosity (bolometric)	4,181[11] L☉
Surface gravity (log g)	3.52+0.33 −0.14[1] cgs
Temperature	17,061+1,474 −1,357[13] K
Rotational velocity (v sin i)	212±9[14] km/s
Age	31.6±5.1[15] Myr
Other designations
3 G. Corona Australis[16], V692 CrA, CD−41°12534, CPD−41°8620, GC 24824, HD 166596, HIP 89290, HR 6804, SAO 228815[17]
Database references
SIMBAD	data

Astronomers Carlos and Mercedes Jaschek along with a colleague listed HD 166596 as a Be star in 1964.^[20] However, its status as an Ap star was not observed until 1979 by astronomers N. Vogt and A.M Faundez.^[21] A year later, HD 166596 was observed to be variable and it had a period of 1.67 days.^[22] In 1981, its variability was confirmed and it was given the variable star designation V692 Coronae Australis—the 692nd variable star in Corona Australis.^[23] The star might have a shorter period of 49.8 hours.^[7]

V692 CrA has a stellar classification of B2 III^[4] or B1.5 IIIp,^[5] both indicating that it is a slightly evolved B-type giant star. The second classification indicates that V692 CrA has peculiarities in its spectrum. It has 7.35 times the mass of the Sun^[11] and 12.6 times the Sun's radius.^[12] It radiates at a bolometric luminosity 4,181 times that of the Sun^[11] from its photosphere at an effective temperature of 17,061 K.^[13] V692 CrA is estimated to be 31.6 million years old^[15] and it spins rapidly with a projected rotational velocity of 212 km/s.^[14]