1,662 research outputs found
Polyunsaturated fatty acid-derived lipid mediators and T cell function
Copyright © 2014 Nicolaou, Mauro, Urquhart and Marelli-Berg . This is an open-
access article distributed under the terms of the
Creative Commons Attribution License
(CC BY)
. The use, distribution or reproduction in other forums is permitted, provided
the original author(s) or licensor are credited and that the original publication in this
journal is cited, in accordance with accepted academic practice. No use, distribution or
reproduction is permitted which does not comply with these terms
Polyunsaturated fatty acid-derived lipid mediators and T cell function
Copyright © 2014 Nicolaou, Mauro, Urquhart and Marelli-Berg . This is an open-
access article distributed under the terms of the
Creative Commons Attribution License
(CC BY)
. The use, distribution or reproduction in other forums is permitted, provided
the original author(s) or licensor are credited and that the original publication in this
journal is cited, in accordance with accepted academic practice. No use, distribution or
reproduction is permitted which does not comply with these terms
New VLT observations of the Fermi pulsar PSR J1048-5832
PSR J1048-5832 is a Vela-like (P=123.6 ms; tau~20.3 kyr) gamma-ray pulsar
detected by Fermi, at a distance of ~2.7 kpc and with a rotational energy loss
rate dot{E}_{SD} ~2 x 10^{36} erg/s. The PSR J1048-5832 field has been observed
with the VLT in the V and R bands. We used these data to determine the colour
of the object detected closest to the Chandra position (Star D) and confirm
that it is not associated with the pulsar. For the estimated extinction along
the line of sight, inferred from a re-analysis of the Chandra and XMM-Newton
spectra, the fluxes of Star D (V~26.7; R~25.8) imply a -0.13 < (V-R)_0 < 0.6.
This means that the PSR J1048-5832 spectrum would be unusually red compared to
the Vela pulsar.Moreover, the ratio between the unabsorbed optical and X-ray
flux of PSR J1048-5832 would be much higher than for other young pulsars. Thus,
we conclude that Star D is not the PSR J1048-5832 counterpart. We compared the
derived R and V-band upper limits (R>26.4; V>27.6) with the extrapolation of
the X and gamma-ray spectra and constrained the pulsar spectrum at
low-energies. In particular, the VLT upper limits suggest that the pulsar
spectrum could be consistent with a single power-law, stretching from the
gamma-rays to the optical.Comment: 5 pages, 2 figures, accepted for publication on Monthly Notices of
the Royal Astronomical Society Main Journa
Supergiant Fast X-ray Transients uncovered by the EXTraS project: flares reveal the development of magnetospheric instability in accreting neutron stars
The low luminosity, X-ray flaring activity, of the sub-class of high mass
X-ray binaries called Supergiant Fast X-ray Transients, has been investigated
using XMM-Newton public observations, taking advantage of the products made
publicly available by the EXTraS project. One of the goals of EXTraS was to
extract from the XMM-Newton public archive information on the aperiodic
variability of all sources observed in the soft X-ray range with EPIC (0.2-12
keV). Adopting a Bayesian block decomposition of the X-ray light curves of a
sample of SFXTs, we picked out 144 X-ray flares, covering a large range of soft
X-ray luminosities (1e32-1e36 erg/s). We measured temporal quantities, like the
rise time to and the decay time from the peak of the flares, their duration and
the time interval between adjacent flares. We also estimated the peak
luminosity, average accretion rate and energy release in the flares. The
observed soft X-ray properties of low-luminosity flaring activity from SFXTs is
in qualitative agreement with what is expected by the application of the
Rayleigh-Taylor instability model in accreting plasma near the neutron star
magnetosphere. In the case of rapidly rotating neutron stars, sporadic
accretion from temporary discs cannot be excluded.Comment: Accepted for publication in MNRAS (accepted 2019 May 1; received 2019
April 30; in original form 2019 February 25). 22 pages, 16 figures, 3 tables
Large Binocular Telescope observations of PSR J2043+2740
We present the results of deep optical imaging of the radio/-ray
pulsar PSR J2043+2740, obtained with the Large Binocular Telescope (LBT). With
a characteristic age of 1.2 Myr, PSR J2043+2740 is one of the oldest (non
recycled) pulsars detected in -rays, although with still a quite high
rotational energy reservoir ( erg
s). The presumably close distance (a few hundred pc), suggested by the
hydrogen column density ( cm),
would make it a viable target for deep optical observations, never attempted
until now. We observed the pulsar with the Large Binocular Camera of the LBT.
The only object (V=25.440.05) detected within ~3" from the pulsar radio
coordinates is unrelated to it. PSR J2043+2740 is, thus, undetected down to
V~26.6 (3-), the deepest limit on its optical emission. We discuss the
implications of this result on the pulsar emission properties.Comment: 4 pages, 3 figures, accepted for publication on MNRA
A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054
We carried out deep optical observations of the middle-aged -ray
pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two
objects, of magnitudes and , at positions
consistent with the very accurate Chandra coordinates of the pulsar, the
faintest of which is more likely to be its counterpart. From the VLT images we
also detected the known bow-shock nebula around PSR J1741-2054. The nebula is
displaced by \sim 0\farcs9 (at the confidence level) with respect
to its position measured in archival data, showing that the shock propagates in
the interstellar medium consistently with the pulsar proper motion. Finally, we
could not find evidence of large-scale extended optical emission associated
with the pulsar wind nebula detected by Chandra, down to a surface brightness
limit of magnitudes arcsec. Future observations are needed
to confirm the optical identification of PSR J1741-2054 and characterise the
spectrum of its counterpart.Comment: 8 pages, 3 figures, Astrophysical Journal, in pres
X-ray pulsations from the radio-quiet gamma-ray pulsar in CTA 1
Prompted by the Fermi LAT discovery of a radio-quiet gamma-ray pulsar inside
the CTA 1 supernova remnant, we obtained a 130 ks XMM-Newton observation to
assess the timing behavior of this pulsar. Exploiting both the unprecedented
photon harvest and the contemporary Fermi LAT timing measurements, a 4.7 sigma
single peak pulsation is detected, making PSR J0007+7303 the second example,
after Geminga, of a radio-quiet gamma-ray pulsar also seen to pulsate in
X-rays. Phase-resolved spectroscopy shows that the off-pulse portion of the
light curve is dominated by a power-law, non-thermal spectrum, while the X-ray
peak emission appears to be mainly of thermal origin, probably from a polar cap
heated by magnetospheric return currents, pointing to a hot spot varying
throughout the pulsar rotation.Comment: 19 pages, 4 figures. Accepted for publication in ApJ Letter
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