NGC 2139 (also IC 2154, ESO 488-54, MCG -4-15-5, AM 0559-234, IRAS 05590-2340 and PGC 18258) is a magnitude +11.6 barred spiral galaxy located 84 million light-years away in the constellation Lepus.
The galaxy was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire, on the 17th November 1784.
Right Ascension 06h 01m 08.0s, Declination -23° 40' 22"
Title: Chandra Observations of the Nuclear Star Cluster and Ultraluminous X-ray Sources in NGC 2139 Authors: Joseph C. Shields, Torsten Boeker, Luis C. Ho, Hans-Walter Rix, Roeland P. van der Marel, C. Jakob Walcher
We report Chandra observations of the Scd galaxy NGC 2139, which is known to host a recently formed (10^7.6 yrs) nuclear star cluster. The star cluster is undetected in X-rays, with an upper bound on 0.5-7 keV luminosity of L_X < 7.1 x 10^37 erg/s. This bound implies a bolometric accretion luminosity 10^39 erg/s. We use archival Hubble Space Telescope images to identify candidate optical counterparts for seven Chandra sources, which in most cases have optical luminosities and spatial profiles consistent with star clusters. Compared with other galaxies, the number of luminous X-ray sources in NGC 2139 is larger by a factor of 4 - 10 than expected based on its present star formation rate and stellar mass. This finding can be understood if NGC 2139 has concluded a burst of star formation in the recent past, and suggests that this galaxy could be important for testing the use of X-ray source populations as a chronometer of star formation history.