We present new optical spectra and photometry plus the first infrared photometry of the optical counterpart to the X-ray transient system 4U 0728-25. Our spectral and photometrical analysis lead us to conclude that the primary is an O8-9Ve star with E(B-V)=0.75+/-0.02. This revised spectral classification places the star at a distance of 6.1+/-0.3 kpc. We also present evidence for an unusual faint, blue state that may represent a diskless phase in late 1991.
Astronomy and Astrophysics
- Pub Date:
- November 1996
- STARS: INDIVIDUAL: 4U 0728-25;
- X-RAY: STARS;