WR 128

WR 128

A visual band light curve for QT Sagittae, adapted from Antokhin and Cherepashchuk (1985)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Sagitta
Right ascension	19h 48m 32.19686s[2]
Declination	+18° 12′ 03.69399″[2]
Apparent magnitude (V)	10.51
Characteristics
Evolutionary stage	Wolf-Rayet
Spectral type	WN4(h)-w[3]
U−B color index	−0.89[4]
B−V color index	-0.02[4]
Astrometry
Radial velocity (Rv)	100.00[5] km/s
Parallax (π)	0.3129 ± 0.0417 mas[2]
Distance	2,900+540 −390[6] pc
Absolute magnitude (MV)	−3.27[3]
Details
Mass	11[3] M☉
Radius	2.69[3] R☉
Luminosity	166,000[3] L☉
Temperature	70,800[3] K
Other designations
QT Sagittae, HD 187282, WR 128, HIP 97456, 2MASS J19483219+1812036
Database references
SIMBAD	data

WR 128 is a Wolf–Rayet star located about 9,500 light years away in the constellation of Sagitta. A member of the WN class, WR 128's spectrum resembles that of a WN4 star, but hydrogen is clearly present in the star (hence the h in its spectrum), making it the only known hydrogen-rich WN4 star in the galaxy. However, similar H-rich very early WN stars can be found in the LMC and especially in the SMC, but the only other galactic examples of this are WR 3 and WR 152.^[7]

Properties

Analysis of WR 128's spectrum with PoWR shows that it has a temperature of around 70,800 K and is losing mass at a very slow pace (in Wolf-Rayet terms), at 10^-5.4 M_☉/year, or in other words, 1 solar mass every 250,000 years.^[3] All this mass is being carried by a very strong stellar wind with a terminal velocity of 2,050 kilometres per second. Taking its distance into account, WR 128 has a luminosity of 166,000 L_☉, or 10^5.22 L_☉,^[3] making it one of the dimmest galactic WN stars. Using the Stefan-Boltzmann Law, we can calculate a radius of 2.69 R_☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is at about 13 R_☉.^[3]

References

This page was last edited on 14 May 2023, at 12:14