Two new candidate ultra-compact X-ray binaries
Abstract
We present the identification of the optical counterparts to the low-mass X-ray binaries 1A 1246-588 and 4U 1812-12. We determine the X-ray position of 1A 1246-588 from ROSAT/PSPC observations and find within the error circle a blue star with V=19.45, B-V=0.22 and R-I=0.22 which we identify as the counterpart. Within the Chandra error circle of 4U 1812-12, a single star is present which appears blue with respect to the stars in the vicinity. It has R=22.15, R-I=1.53. Distance estimates for both systems indicate that the optical counterparts are intrinsically faint, suggesting that they are ultra-compact X-ray binaries. These identifications would increase the number of candidate ultra-compact X-ray binaries from 2 to 4, whereas orbital periods are measured for only 7 systems in the Galactic disk.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 2006
- DOI:
- 10.1051/0004-6361:200500229
- arXiv:
- arXiv:astro-ph/0601045
- Bibcode:
- 2006A&A...446L..17B
- Keywords:
-
- X-rays: binaries;
- X-rays: individual: 1A 1246-588;
- 4U 1812-12;
- Astrophysics
- E-Print:
- 5 pages, 3 figures, accepted for publication in A&