Abstract

We present XMM-Newton and Chandra observations of two low-metallicity cometary blue compact dwarf (BCD) galaxies, Mrk 59 and Mrk 71. The first BCD, Mrk 59, contains two ultraluminous X-ray sources (ULXs), IXO 72 and IXO 73, both associated with bright massive stars and H ii complexes, as well as one fainter extended source associated with a massive H ii complex at the head of the cometary structure. The low metallicity of Mrk 59 appears to be responsible for the presence of the two ULXs. IXO 72 has varied little over the last 10 yr, while IXO 73 has demonstrated a variability factor of similar to 4 over the same period. The second BCD, Mrk 71, contains two faint X-ray point sources and two faint extended sources. One point source is likely a background AGN, while the other appears to be coincident with a very luminous star and a compact H ii region at the 'head' of the cometary structure. The two faint extended sources are also associated with massive H ii complexes. Although both BCDs have the same metallicity, the three sources in Mrk 71 have X-ray luminosities similar to 1-2 orders of magnitude fainter than those in Mrk 59. The age of the starburst may play a role.