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A half-a-day long thermonuclear X-ray burst from KS 1731-260
E. Kuulkers, J. J. M. in 't Zand, M. H. van Kerkwijk +7
We report on an approximately twelve hour long X-ray flare from the low-mass X-ray binary KS 1731-260. The flare has a rise time of less than 13 min and declines exponentially with…
Identification of the optical and quiescent counterparts to the bright X-ray transient in NGC 6440
J. J. M. in 't Zand, M. H. van Kerkwijk, D. Pooley +3
After 3 years of quiescence, the globular cluster NGC 6440 exhibited a bright transient X-ray source turning on in August 2001, as noted with the RXTE All-Sky Monitor. We carried o…
The Parallax and Proper Motion of RX J1856.5-3754 Revisited
D. L. Kaplan, M. H. van Kerkwijk, J. Anderson
RX J1856.5-3754, a bright soft X-ray source believed to be the nearest thermally emitting neutron star, has commanded and continues to command intense interest from X-ray missions.…
A possible faint near-infrared counterpart to the AXP 1E~2259+58.6
F. Hulleman, A. F. Tennant, M. H. van Kerkwijk +3
We present near-infrared and optical observations of the field of the Anomalous X-ray Pulsar 1E 2259+58.6 taken with the Keck telescope. We derive a subarcsecond Chandra position a…
The mass of the neutron star in Vela X-1
O. Barziv, L. Kaper, M. H. van Kerkwijk +2
We measured the radial-velocity curve of HD77581, the B-supergiant companion of the X-ray pulsar Vela X-1, using 183 high-resolution optical spectra obtained in a nine-month campai…
The IR counterpart of the black-hole candidate 4U 1630-47
T. Augusteijn, E. Kuulkers, M. H. van Kerkwijk
We present K band photometry of the region including the radio error box of the soft X-ray transient 4U 1630-47 during its 1998 outburst. We detect a variable source at K=16.1 mag…
Deep Radio, Optical, and Infrared Observations of SGR 1900+14
D. L. Kaplan, S. R. Kulkarni, D. A. Frail +1
We present HST/STIS, Keck J- and K_s-band, and VLA 332-MHz and 1400-MHz images of the region around the Soft Gamma-ray Repeater SGR 1900+14. No non-stellar sources were detected at…
Optical spectroscopy and photometry of the isolated neutron star RX J1856.5-3754
M. H. van Kerkwijk, S. R. Kulkarni
We present spectroscopy and imaging with the Very Large Telescope (VLT) of the neutron star RX J1856.5-2754. Little is known about the nature of this source other than that it is a…