HD 160529

HD 160529 (V905 Scorpii) is a luminous blue variable (LBV) star located in the constellation of Scorpius. With an apparent magnitude of around +6.8 it cannot be seen with the naked eye except under very favourable conditions, but it is easy to see with binoculars or amateur telescopes.

HD 160529

A visual band light curve for V905 Scorpii. The red points are from Sterken et al. (1997),[1] and the blue points are ASAS data.[2]
Observation data Epoch J2000      Equinox J2000
Constellation	Scorpius
Right ascension	17h 41m 59.025s[3]
Declination	−33° 30′ 13.71″[3]
Apparent magnitude (V)	6.66[4] (6.3–6.9[5])
Characteristics
Spectral type	LBV
U−B color index	+0.30[4]
B−V color index	+1.21[4]
Variable type	LBV[5]
Astrometry
Radial velocity (Rv)	−35[6] km/s
Proper motion (μ)	RA: −1.75[3] mas/yr Dec.: −1.49[3] mas/yr
Parallax (π)	0.54±0.54 mas[3]
Distance	2,500[7] pc
Absolute magnitude (MV)	−8.9[8]
Details
Mass	13[8] M☉
Radius	150–330[5] R☉
Luminosity	290,000[7] L☉
Surface gravity (log g)	0.55[8] cgs
Temperature	8,000–12,000[5] K
Rotational velocity (v sin i)	45[5] km/s
Other designations
V905 Sco, HD 160529, CD −33°12361, SAO 209151, HIP 86624
Database references
SIMBAD	data

Physical characteristics

V905 Sco in comparison to other LBVs and cool hypergiants

V905 Sco has a peculiar variable spectral type with emission lines and P Cygni profiles. At visual maximum it is similar to an A9 star and at minimum close to B8.^[5] The distance has been estimated at 2.5 kiloparsecs (8,200 light years) based on the assumption of an absolute magnitude of −8.9.^[8] However this distance is uncertain and values between 1.9 kiloparsecs and 3.5 kiloparsecs have been proposed.^[5]

Working with a distance of 2.5 kiloparsecs, the radius varies from 150 R_☉ when quiescent to 330 R_☉ in outburst. The temperature also varies, from 8,000K in outburst to 12,000K when quiescent. With these parameters, the apparent visual magnitude varies by 0.5 and the bolometric luminosity is constant at 180,000 L_☉.^[5]

Estimates of the surface gravity lead to a mass of 13 M_☉ and a probable initial mass of 25 M_☉ This suggests that V905 Sco is a former red supergiant star.^[8]