EIGHT γ-RAY PULSARS DISCOVERED IN BLIND FREQUENCY SEARCHES OF FERMI LAT DATA

We report the discovery of eight gamma-ray pulsars in blind frequency searches of similar to 650 source positions using the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. We present the timing models, light curves, and detailed spectral parameters of the new pulsars. PSRs J1023-5746, J1044-5737, J1413-5205, J1429-5911, and J1954+2836 are young (tau(c) < 100 kyr), energetic ((E) over dot greater than or similar to 10(36) erg s(-1)), and located within the Galactic plane (vertical bar b vertical bar < 3 degrees). The remaining three pulsars, PSRs J1846+0919, J1957+5033, and J2055+25, are less energetic, and located off the plane. Five pulsars are associated with sources included in the Fermi-LAT bright gamma-ray source list, but only one, PSR J1413-6205, is clearly associated with an EGRET source. PSR J1023-5746 has the smallest characteristic age (tau(c) = 4.6 kyr) and is the most energetic ((E) over dot = 1.1 x 10(37) erg s(-1)) of all gamma-ray pulsars discovered so far in blind searches. By analyzing > 100 ks of publicly available archival Chandra X-ray data, we have identified the likely counterpart of PSR J1023-5746 as a faint, highly absorbed source, CXOU J102302.8-574606. The large X-ray absorption indicates that this could be among the most distant gamma-ray pulsars detected so far. PSR J1023-5746 is positionally coincident with the TeV source HESS J1023-575, located near the young stellar cluster Westerlund 2, while PSR J1954+2836 is coincident with a 4.3 sigma excess reported by Milagro at a median energy of 35 TeV. PSRs J1957+5033 and J2055+25 have the largest characteristic ages (tau(c) similar to 1 Myr) and are the least energetic ((E) over dot similar to 5 x 10(33) erg s(-1)) of the newly discovered pulsars. We used recent XMM observations to identify the counterpart of PSR J2055+25 as XMMU J205549.4+253959. Deep radio follow-up observations of the eight pulsars resulted in no detections of pulsations and upper limits comparable to the faintest known radio pulsars, indicating that these pulsars can be included among the growing population of radio-quiet pulsars in our Galaxy being uncovered by the LAT, and currently numbering more than 20.