Open AccessOn the compact nature of the most luminous ULX in the Cartwheel ring
Author(s) -
Wolter Anna,
Trinchieri Ginevra,
Colpi Monica
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.11116.x
Subject(s) - physics , luminosity , astrophysics , galaxy , supernova , flux (metallurgy) , astronomy , materials science , metallurgy
We report the first detection of flux variability in the most luminous X‐ray source in the southern ring of the Cartwheel galaxy. XMM–Newton data show that the luminosity has varied over a time‐scale of 6 months from L 0.5−10 keV ∼ 1.3 × 10 41 erg s −1 , consistent with the previous Chandra observation, to L 0.5−10 keV ≲ 6.4 × 10 40 erg s −1 . This fact provides the first evidence that the source is compact in nature and is not a collection of individual fainter sources, such as supernova remnants. The source has been repeatedly observed at the very high‐luminosity level of L 0.5−10 keV ∼ 1.3 × 10 41 erg s −1 for a period of at least 4 yr before dimming at the current level. It represents then the first example of an accreting object revealed in a long‐lived state of extremely high luminosity.