16h47m7.503s, −45° 52′ 29.152″
Credit: ESO | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ara |
| Right ascension | 16h47m 7.5041s[1] |
| Declination | −45° 52′ 29.123″[1] |
| Apparent magnitude (V) | 15.807[2] |
| Characteristics | |
| Spectral type | A3Ia+[3] |
| Apparent magnitude (J) | 6.407[4] |
| Apparent magnitude (H) | 5.271[4] |
| Apparent magnitude (K) | 4.632[4] |
| Astrometry | |
| Proper motion (μ) | RA: −1.574[1] mas/yr Dec.: −4.036[1] mas/yr |
| Parallax (π) | 0.0119 ± 0.0812 mas[1] |
| Distance | 13,400 ly (4,120[5] pc) |
| Details[3] | |
| Mass | 40 M☉ |
| Radius | 376.9 R☉ |
| Luminosity | 730,000 L☉ |
| Surface gravity (log g) | ~0.65 cgs |
| Temperature | ~8,500 K |
| Rotational velocity (v sin i) | 10 km/s |
| Age | 10.4+1.3 −1.2[5] Myr |
| Other designations | |
Westerlund 1 W 243, Westerlund 1 BKS G, 2MASS J16470749-4552290, Gaia DR3 5940105830990286208 | |
| Database references | |
| SIMBAD | data |
Westerlund 1-243orWd 1-243 is a luminous blue variable (LBV) star undergoing an eruptive phase located within the outskirts of the super star cluster Westerlund 1.[6] Located about 13,400 ly (4,100 pc) from Earth,[5] it has a luminosity of 0.73 million L☉ making it one of the most luminous stars known.[3]
Westerlund 1-243 is the second brightest star in Westerlund 1, behind only Westerlund 1-4.[2] It is one of several different hypergiant stars in Westerlund 1. It may also have a companion star, possibly an O-type supergiant.[7]
Westerlund 1-243 displays a complex, time-varying spectrum with emission linesofhydrogen, helium and Lyman-α pumped metals, forbidden linesofnitrogen and iron, and a large number of absorption lines from neutral and singly-ionized metals. Many lines are complex emission/absorption blends, with significant spectral evolution occurring on timescales of just a few days.[3]
Westerlund 1-243 has a temperature of ~8,500 K determined from modelling the absorption line spectrum. It has expanded to a radius of 376.9 R☉, and a Rosseland radius of 450 R☉. It is radiating at a luminosity of 730,000 L☉. It is losing mass at a rate of 6.1×10−7 M☉/yr.[3]
Westerlund 1-243 is believed to be either in an advanced pre-red supergiant LBV phase, or has evolved through the RSG phase and returned to the blue side of the HR diagram. In the future it is expected to evolve toward a WR phase. The K-band spectrum also implies a higher temperature than that of a typical yellow hypergiant and suggests that Westerlund 1-243 may be evolving back towards a hotter state.[3]
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