1,738 research outputs found
A search for near infrared counterparts of 3 pulsar wind nebulae
While pulsar wind nebulae (PWNe) and their associated isolated pulsars are
commonly detected at X-ray energies, they are much rarer at near infrared (nIR)
and optical wavelengths. Here we examine three PWN systems in the Galactic
plane - IGR J14003-6326, HESS J1632-478 and IGR J18490-0000 - in a bid to
identify optical/nIR emission associated with either the extended PWNe or their
previously detected X-ray point sources. We obtain optical/nIR images of the
three fields with the ESO - New Technology Telescope and apply standard
photometric and astrometric calibrations. We find no evidence of any extended
emission associated with the PWNe in any of the fields; neither do we find any
new counterparts to the X-ray point sources, except to confirm the magnitude of
the previously identified counterpart candidate of IGR J18490-0000. Further
observations are required to confirm the association of the nIR source to IGR
J18490-0000 and to detect counterparts to IGR J14003-6326 and HESS J1632-478,
while a more accurate X-ray position is required to reduce the probability of a
chance superposition in the field of the latter.Comment: Accepted to A&A (4 pages, 1 figure
Bayesian reweighting of nuclear PDFs and constraints from proton-lead collisions at the LHC
New hard-scattering measurements from the LHC proton-lead run have the
potential to provide important constraints on the nuclear parton distributions
and thus contributing to a better understanding of the initial state in heavy
ion collisions. In order to quantify these constraints, as well as to assess
the compatibility with available nuclear data from fixed target experiments and
from RHIC, the traditional strategy is to perform a global fit of nuclear PDFs.
This procedure is however time consuming and technically challenging, and
moreover can only be performed by the PDF fitters themselves. In the case of
proton PDFs, an alternative approach has been suggested that uses Bayesian
inference to propagate the effects of new data into the PDFs without the need
of refitting. In this work, we apply this reweighting procedure to study the
impact on nuclear PDFs of low-mass Drell-Yan and single-inclusive
hadroproduction pseudo-data from proton-lead collisions at the LHC as
representative examples. In the hadroproduction case, in addition we assess the
possibility of discriminating between the DGLAP and CGC production frameworks.
We find that the LHC proton-lead data could lead to a substantial reduction of
the uncertainties on nuclear PDFs, in particular for the small-x gluon PDF
where uncertainties could decrease by up to a factor two. The Monte Carlo
replicas of EPS09 used in the analysis are released as a public code for
general use. It can be directly used, in particular, by the experimental
collaborations to check, in a straightforward manner, the degree of
compatibility of the new data with the global nPDF analyses.Comment: 21 pages, 10 figure
Infrared identification of high-mass X-ray binaries discovered by INTEGRAL
Since it started observing the sky, the INTEGRAL satellite has discovered new
categories of high mass X-ray binaries (HMXB) in our Galaxy. These observations
raise important questions on the formation and evolution of these rare and
short-lived objects. We present here new infrared observations from which to
reveal or constrain the nature of 15 INTEGRAL sources, which allow us to update
and discuss the Galactic HMXB population statistics. After previous photometric
and spectroscopic observing campaigns in the optical and near-infrared, new
photometry and spectroscopy was performed in the near-infrared with the SofI
instrument on the ESO/NTT telescope in 2008 and 2010 on a sample of INTEGRAL
sources. These observations, and specifically the detection of certain features
in the spectra, allow the identification of these high-energy objects by
comparison with published nIR spectral atlases of O and B stars. We present
photometric data of nine sources (IGR J10101-5654, IGR J11187-5438, IGR
J11435-6109, IGR J14331-6112, IGR J16328-4726, IGR J17200-3116, IGR
J17354-3255, IGR J17404-3655, and IGR J17586-2129) and spectroscopic
observations of 13 sources (IGR J10101-5654, IGR J11435-6109, IGR J13020-6359,
IGR J14331-6112, IGR J14488-5942, IGR J16195-4945, IGR J16318-4848, IGR
J16320-4751, IGR J16328-4726, IGR J16418-4532, IGR J17354-3255, IGR
J17404-3655, and IGR J17586-2129). Our spectroscopic measurements indicate
that: five of these objects are Oe/Be high-mass X-ray binaries (BeHMXB), six
are supergiant high-mass X-ray binaries (sgHMXB), and two are sgB[e]. From a
statistical point of view, we estimate the proportion of confirmed sgHMXB to be
42% and that of the confirmed BeHMXB to be 49%. The remaining 9% are peculiar
HMXB.Comment: Accepted for publication in A&A (in press
Doppler Tomography of XTE J2123-058 and Other Neutron Star LMXBs
We describe Doppler tomography obtained in the 1998 outburst of the neutron
star low mass X-ray binary (LMXB) XTE J2123-058. This analysis, and other
aspects of phase-resolved spectroscopy, indicate similarities to SW Sex
systems, except that anomalous emission kinematics are seen in HeII, whilst
phase 0.5 absorption is confined to H alpha. This separation of these effects
may provide tighter constraints on models in the LMXB case than is possible for
SW Sex systems. We will compare results for other LMXBs which appear to show
similar kinematics and discuss how models for the SW Sex phenomenon can be
adapted to these systems. Finally we will summarise the limited Doppler
tomography performed on the class of neutron star LMXBs as a whole, and discuss
whether any common patterns can yet be identified.Comment: 8 pages, 5 postscript figures. To appear in Proceedings of
Astro-Tomography Workshop, Brussels, July 2000, Eds. H. Boffin, D. Steeghs,
Springer-Verlag Lecture Notes in Physic
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