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