112 research outputs found
The Variable X-ray and Near-IR Behavior of the Particularly Anomaloux X-ray Pulsar 1E 1048.1-5937
We present the results of X-ray and near-IR observations of the anomalous
X-ray pulsar 1E 1048.1-5937, believed to be a magnetar. This AXP underwent a
period of extreme variability during 2001-2004, but subsequently entered an
extended and unexpected quiescence in 2004-2006, during which we monitored it
with RXTE, CXO, and HST. Its timing properties were stable for >3 years
throughout the quiescent period. 1E 1048.1-5937 again went into outburst in
March 2007, which saw a factor of >7 total X-ray flux increase which was
anti-correlated with a pulsed fraction decrease, and correlated with spectral
hardening, among other effects. The near-IR counterpart also brightened
following the 2007 event. We discuss our findings in the context of the
magnetar and other models.Comment: 3 pages, 4 figures. To appear in the proceedings of the "40 Years of
Pulsars: Millisecond Pulsars, Magnetars and More" conference, held 12-17
August 2007, in Montreal QC (AIP, in press, eds: C. Bassa, Z. Wang, A.
Cumming, V. Kaspi
X-ray Sources and their Optical Counterparts in the Globular Cluster M4
We report on the Chandra X-ray Observatory ACIS-S3 imaging observation of the
Galactic globular cluster M4 (NGC 6121). We detect 12 X-ray sources inside the
core and 19 more within the cluster half-mass radius. The limiting luminosity
of this observation is Lx~10e29 erg/sec for sources associated with the
cluster, the deepest X-ray observation of a globular cluster to date. We
identify 6 X-ray sources with known objects and use ROSAT observations to show
that the brightest X-ray source is variable. Archival data from the Hubble
Space Telescope allow us to identify optical counterparts to 16 X-ray sources.
Based on the X-ray and optical properties of the identifications and the
information from the literature, we classify two (possibly three) sources as
cataclysmic variables, one X-ray source as a millisecond pulsar and 12 sources
as chromospherically active binaries. Comparison of M4 with 47 Tuc and NGC 6397
suggests a scaling of the number of active binaries in these clusters with the
cluster (core) mass.Comment: 11 pages, 6 figures, accepted for publication in ApJ. Figure 1 and 5
are of reduced qualit
Detection of quasi-periodic micro-structure in three millisecond pulsars with the Large European Array for Pulsars
Contains fulltext :
250587.pdf (Publisher’s version ) (Open Access
A detailed study of giant pulses from PSR B1937-1-21 using the Large European Array for Pulsars
Contains fulltext :
202558.pdf (Publisher’s version ) (Open Access
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