14 research outputs found
Pulsar Timing with the Parkes Radio Telescope for the Fermi Mission
We report here on two years of timing of 168 pulsars using the Parkes radio
telescope. The vast majority of these pulsars have spin-down luminosities in
excess of 10^34 erg/s and are prime target candidates to be detected in
gamma-rays by the Fermi Gamma-Ray Space Telescope. We provide the ephemerides
for the ten pulsars being timed at Parkes which have been detected by Fermi in
its first year of operation. These ephemerides, in conjunction with the
publicly available photon list, can be used to generate gamma-ray profiles from
the Fermi archive. We will make the ephemerides of any pulsars of interest
available to the community upon request. In addition to the timing ephemerides,
we present the parameters for 14 glitches which have occurred in 13 pulsars,
seven of which have no previously known glitch history. The Parkes timing
programme, in conjunction with Fermi observations, is expected to continue for
at least the next four years.Comment: Accepted for publication in PASA.12 page
The compact central source in the RX J0852-4622 supernova remnant
The central region of the recently discovered supernova remnant RX
J0852.0-4622 was observed with the ACIS detector aboard the Chandra X-ray
Observatory. We found only one relatively bright source, about 4' north of the
SNR center, with a flux of erg s cm in
the 0.5--10 keV band. The position of this point-like source, CXOU
J085201.4-461753, rules out its association with the two bright stars in the
field, HD 76060 and Wray 16-30. Observations of the field with the CTIO 0.9-m
telescope show a star (, ) at about 2\farcs4 from the
nominal X-ray position. We consider association of this star with the X-ray
source unlikely and estimate a limiting magnitude of the optical counterpart as
and . Based on the X-ray-to-optical flux ratio, we
argue that the X-ray source is likely the compact remnant of the supernova
explosion that created the RX J0852.0-4622 SNR. The observed X-ray spectrum of
the source is softer than spectra of magnetospheric radiation of
rotation-powered pulsars, but it is harder than spectra of cooling neutron
stars emitting thermal radiation from the entire surface, similar to the
central compact source of the Cas A SNR. We suggest that CXOU J085201.4-461753
belongs to the growing family of radio-quiet compact central sources,
presumably neutron stars, recently discovered in a number of SNRs.Comment: 4 pages (incl. 2 embedded PS figures), AASTEX, uses emulateapj5.sty.
Submitted to ApJ Letter
The identification of the optical companion to the binary millisecond pulsar J0610-2100 in the Galactic field
We have used deep V and R images acquired at the ESO Very Large Telescope to
identify the optical companion to the binary pulsar PSR J0610-2100, one of the
black-widow millisecond pulsars recently detected by the Fermi Gamma-ray
Telescope in the Galactic plane. We found a faint star (V~26.7) nearly
coincident (\delta r ~0".28) with the pulsar nominal position. This star is
visible only in half of the available images, while it disappears in the
deepest ones (those acquired under the best seeing conditions), thus indicating
that it is variable. Although our observations do not sample the entire orbital
period (P=0.28 d) of the pulsar, we found that the optical modulation of the
variable star nicely correlates with the pulsar orbital period and describes a
well defined peak (R~25.6) at \Phi=0.75, suggesting a modulation due to the
pulsar heating. We tentatively conclude that the companion to PSR J0610-2100 is
a heavily ablated very low mass star (~ 0.02Msun) that completely filled its
Roche Lobe.Comment: 17 pages, 5 figures - Accepted for pubblication in Ap
Establishing a high‐resolution stratigraphy in the Holocene marine sequence of the ancient Theodosian harbor of Istanbul with the help of dendrochronology
Salvage excavations in the Theodosian harbor (Yenikapi-Istanbul) have uncovered diverse archaeological objects including 36 shipwrecks and various Byzantine period wooden docks. The sequence of these docks provided a unique opportunity to obtain a high-resolution stratigraphy. The new approach is based on stratigraphic interpretation of deformation patterns created by the posts in soft sediments, combined with dendrochronological dating of the posts. Dendrochronology offers the potential to date the posts to within one calendar year of felling, a level of precision and accuracy rare in sedimentological analysis. The posts, most of them Quercus, were rammed during six different time periods. The first period is associated with posts cut in 528 AD. The second and third periods are dated by posts cut in 583 and 594 AD, respectively. The fourth-period dates within 8-10 years of 639 AD. The fifth period could be dated only roughly to between 690 and 770 AD. The last period produced a possible placement of after 778 AD. This new approach helps to establish a high-resolution stratigraphy. Furthermore, it provides information about sedimentation history and specific anthropogenic events