- Swift observations of the ultra-compact binary 4U 1850-087
- The astronomer's telegram
- Document type
- Faculty of Science (FNWI)
- Anton Pannekoek Institute for Astronomy (API)
We report on six observations of the ultra-compact X-ray binary 4U 1850-087 (P_orb = 21 min) in a rare high flux state, taken by Swift. Observations were made on 12, 14, 15, 16, 18, and 20 May 2008. Fits to the XRT spectra were made over the 0.5-10 keV band, assuming a column density of 2.4 E +21. The distance was assumed to be 6.8 kpc (Sidoli et al. 2004). The photon index ranged from 2.09 to 2.30, the unabsorbed flux ranged from 2.55 E-10 to 6.0 E-10 cgs, and the luminosity ranged from 1.1 E+36 to 3.4 E+36 erg/s. A blackbody component was not required by the spectra, with an upper limit flux of 1.5 E-10 cgs.