64 research outputs found
Fermi pulsar revolution
2009 has been an extraordinary year for gamma-ray pulsar astronomy and 2010
promises to be equally good. Not only have we registered an extraordinary
increase in the number of pulsars detected in gamma rays, but we have also
witnessed the birth of new sub-families: first of all, the radio-quiet gamma
pulsars and later an ever growing number of millisecond pulsars, a real
surprise. We started with a sample of 7 gamma-ray emitting neutron stars (6
radio pulsars and Geminga) and now the Fermi-LAT harvest encompasses 24
"Geminga-like" new gamma-ray pulsars, a dozen millisecond pulsars and about
thirty radio pulsars. Moreover, radio searches targeted to LAT unidentified
sources yielded 18 new radio millisecond pulsars, several of which have been
already detected also in gamma rays. Thus, currently the family of gamma-ray
emitting neutron stars seems to be evenly divided between classical radio
pulsars, millisecond pulsars and radio quiet neutron stars.Comment: High Time Resolution Astrophysics IV - The Era of Extremely Large
Telescopes-HTRA-IV Agios Nikolaos, Crete, Greece May 5-7 2010 to be published
in Po
HST Proper Motion confirms the optical identification of the nearby pulsar PSR 1929+10
We report on the proper motion measurement of the proposed optical
counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with
the HST/STIS (average epoch 2001.73) we computed a yearly displacement of +97
+/- 1 mas yr^{-1} in RA and +46 +/- 1 mas yr^{-1} in Dec since the epoch
(1994.52) of the original HST/FOC detection. Both the magnitude and direction
of the optical proper motion components are found to be fully consistent with
the most recent VLBA radio measurements. This result provides an unambiguous
confirmation of the pulsar optical identification. In addition, we have used
the combined STIS/FOC datasets to derive information on the pulsar spectrum,
which seems characterized by a power law component, apparently unrelated to the
X-ray emission.Comment: 12 pages, 3 figures, submitted to ApJ Letter
A MULTIWAVELENGTH STUDY ON THE HIGH-ENERGY BEHAVIOR OF THE FERMI/LAT PULSARS
ABSTRACT Using archival as well as freshly acquired data, we assess the X-ray behavior of the Fermi/Large Area Telescope γ -ray pulsars listed in the First Fermi source catalog. After revisiting the relationships between the pulsars' rotational energy losses and their X-ray and γ -ray luminosities, we focus on the distance-independent γ -to-X-ray flux ratios. When plotting our F γ /F X values as a function of the pulsars' rotational energy losses, one immediately sees that pulsars with similar energetics have F γ /F X spanning three decades. Such spread, most probably stemming from vastly different geometrical configurations of the X-ray and γ -ray emitting regions, defies any straightforward interpretation of the plot. Indeed, while energetic pulsars do have low F γ /F X values, little can be said for the bulk of the Fermi neutron stars. Dividing our pulsar sample into radio-loud and radio-quiet subsamples, we find that, on average, radio-quiet pulsars do have higher values of F γ /F X , implying an intrinsic faintness of their X-ray emission and/or a different geometrical configuration. Moreover, despite the large spread mentioned above, statistical tests show a lower scatter in the radio-quiet data set with respect to the radio-loud one, pointing to a somewhat more constrained geometry for the radio-quiet objects with respect to the radio-loud ones
A multiwavelength study on the high-energy behaviour of Fermi/LAT pulsars
Using archival as well as freshly acquired data, we assess the X-ray
behaviour of the Fermi/LAT gamma-ray pulsars listed in the First Fermi source
catalog. After revisiting the relationships between the pulsars' rotational
energy losses and their X and gamma-ray luminosities, we focus on the
distance-indipendent gamma to X-ray flux ratios. When plotting our Fgamma/Fx
values as a function of the pulsars' rotational energy losses, one immediately
sees that pulsars with similar energetics have Fgamma/Fx spanning 3 decades.
Such spread, most probably stemming from vastly different geometrical
configurations of the X and gamma-ray emitting regions, defies any
straightforward interpretation of the plot. Indeed, while energetic pulsars do
have low Fgamma/Fx values, little can be said for the bulk of the Fermi neutron
stars. Dividing our pulsar sample into radio-loud and radio-quiet subsamples,
we find that, on average, radio-quiet pulsars do have higher values of
Fgamma/Fx, implying an intrinsec faintness of their X-ray emission and/or a
different geometrical configuration. Moreover, despite the large spread
mentioned above, statistical tests show a lower scatter in the radio-quiet
dataset with respect to the radio-loud one, pointing to a somewhat more
constrained geometry for the radio-quiet objects with respect to the radio-loud
ones.Comment: 39 pages, 5 figures, 3 tables. To be published in Astrophysical
Journa
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