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Optical Counterpart of the Ultraluminous X-ray Source IC 342 X-1
Hua Feng, Philip Kaaret
We present Chandra and HST observations of the ultraluminous X-ray source (ULX) IC 342 X-1. The Chandra and HST images are aligned using two X-ray emitting foreground stars. The as…
Confirmation of the 62 Day X-Ray Periodicity from M82
Philip Kaaret, Hua Feng
Using 400 days of new X-ray monitoring of M82, we confirm the 62 day periodicity previously reported. In the full data set spanning 1124 days, we find a period of 62.0 +/- 0.3 days…
Origin of the X-ray Quasi-Periodic Oscillations and Identification of a Transient Ultraluminous X-Ray Source in M82
Hua Feng, Philip Kaaret
The starburst galaxy M82 contains two ultraluminous X-ray sources (ULXs), CXOM82 J095550.2+694047 (=X41.4+60) and CXOM82 J095551.1+694045 (=X42.3+59), which are unresolved by XMM-N…
Spectral Evolution of NGC 1313 X-2: Evidence Against The Cool Disk Model
Hua Feng, Philip Kaaret
The presence of a cool multicolor disk component with an inner disk temperature kT=0.1~0.3 keV at a luminosity L>10^40 erg/s has been interpreted as evidence that the ultraluminous…
Spectral State Transitions of the Ultraluminous X-ray Sources X-1 and X-2 in NGC 1313
Hua Feng, Philip Kaaret
X-ray spectral state transitions are a key signature of black hole X-ray binaries and follow a well-defined pattern. We examined 12 XMM-Newton observations of the nearby spiral gal…
A Comparison of Ultraluminous X-ray Sources in NGC 1399 and the Antennae Galaxies (NGC 4038/4039)
Hua Feng, Philip Kaaret
The temporal and spectral properties of ultraluminous X-ray sources (ULXs, L>2x10^39 ergs/s) and bright X-ray sources (L>3x10^38 ergs/s) are examined and compared in two extremely…