1,431 research outputs found
Pulsar Counterparts of Gamma-Ray Sources
The EGRET catalogue of unidentified X-ray sources has more objects along the
galactic disk than at high galactic latitude, where identifications are
comparatively easier. On the other hand, the Egret/GRO mission has already
identified several known radio pulsars as gamma-ray sources as well as
discovering Geminga's nature as a pulsar. If Geminga is not a unique case, as
it is very likely not to be, than other galactic sources could, in fact, be
radio quiet isolated neutron stars. For these, the identification work is
extremely difficult and should anyway start from high resolution X-ray/optical
data.Comment: 6 pages, LaTeX, macro aipproc.st
Is the Fuzziness of GRB970228 constant?
In view of the data gathered in September 1997, we review the flux values
collected so far for the "fuzziness" seen in the optical counterpart of
GRB970228. Comparison between the ground based data collected in March and the
data of September 1997 suggests a fading of the fuzz. Given the diversity of
the data in hand, the magnitude of the effect and its significance are not easy
to quantify. Only new images, both from the ground and with the Space
Telescope, directly comparable to the old ones could settle this problem.Comment: 6 pages, Latex, 6 postscript figures, 1 postscript table Proceedings
of the 4th Huntsville Gammma-Ray Burst Symposiu
A long-period, violently-variable X-ray source in a young SNR
Observations with the Newton X-ray Multimirror Mission (XMM) show a strong
periodic modulation at 6.67+/-0.03 hours of the X-ray source at the centre of
the 2,000-year-old supernova remnant RCW 103. No fast pulsations are visible.
If genetically tied to the supernova remnant, the source could either be an
X-ray binary, comprising a compact object and a low-mass star in an eccentric
orbit, or an isolated neutron star. In the latter case, its age-period
combination would point to a peculiar magnetar, dramatically slowed-down,
possibly by a supernova debris disc. Both scenarios require non-standard
assumptions on the formation and evolution of compact objects in supernova
explosions.Comment: Accepted for publication in Science. Published online via Science
Express on 2006, July 6. 17 pages, 7 figure
On the local birth place of Geminga
Using estimates of the distance and proper motion of Geminga and the
constraints on its radial velocity posed by the shape of its bow shock, we
investigate its birth place by tracing its space motion backwards in time. Our
results exclude the lambda Ori association as the origin site because of the
large distance between both objects at any time. Our simulations place the
birth region at approximately 90-240 pc from the Sun, between 197 degrees and
199 degrees in Galactic longitude and -16 degrees and -8 degrees in latitude,
most probably inside the Cas-Tau OB association or the Ori OB1a association. We
discard the possibility of the progenitor being a massive field star. The
association of Geminga with either stellar association implies an upper limit
of M = 15 Msun for the mass of its progenitor. We also propose new members for
the Cas-Tau and Ori OB1 associations.Comment: 6 pages, 5 figures. Accepted for publication in Astronomy &
Astrophysic
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