12,915 research outputs found
A third HI 21-cm absorption system in the sight-line of MG J0414+0534: A redshift for Object X?
We report the detection of a third HI 21-cm absorber in the sight-line
towards the z=2.64 quasar MG J0414+0534 (4C +05.19). In addition to the
absorption at the host redshift and in the z=0.96 gravitational lens, we find,
through a decimetre-wave spectral scan towards this source, strong absorption
at z=0.38. We believe this may be associated with "Object X", an additional
feature apparent in the field of the lensing galaxy and lensed images, on the
basis of its close proximity to the quasar images and the possible detection of
the [OIII] doublet in a published optical spectrum. If real, the strength of
the [OIII] emission would suggest the presence of an active galactic nucleus,
or a gas-rich galaxy undergoing rapid star formation, either of which is
consistent with the strong outflows apparent in the 21-cm spectrum. Although
this is the strongest intervening 21-cm absorber yet found, simultaneous
observations failed to detect any of the 18-cm OH lines at the 21-cm redshift.
This suggests that, as for the lensing galaxy, this is not the primary location
of the intervening material responsible for the very red colour of MG
J0414+0534.Comment: 5 pages, accepted by MNRAS Letter
NIR and optical observations of the failed outbursts of black hole binary XTE J1550-564
A number of low mass X-ray binaries (LMXBs) undergo "failed outbursts" in
which, instead of evolving through the canonical states, they remain in a hard
state throughout the outburst. While the sources of X-ray and radio emission in
the hard state are relatively well understood, the origin of the near infrared
(NIR) and optical emission is more complex though it likely stems from an
amalgam of different emission processes, occurring as it does, at the
intersecting wavelengths of those processes. We aim to identify the NIR/optical
emission region(s) during a number of failed outbursts of one such low mass
X-ray binary and black hole candidate, XTE J1550-564, in order to confirm or
refute their classification as hard-state, failed outbursts. We present unique
NIR/optical images and spectra, obtained with the ESO-New Technology Telescope,
during the failed outbursts of 2001 and 2000. We compare the NIR/optical
photometric, timing, and spectral properties with those expected for the
different emission mechanisms in the various LMXB states. The NIR/optical data
are consistent with having come from reprocessing of X-rays in the accretion
disk, with no evidence of direct thermal emission from the disk itself.
However, the observed variability in high-cadence NIR light curves suggest that
the radio jet extends and contributes to the NIR wavelengths. We find that
these failed outbursts did not transition to an intermediate state but remained
in a true, hard state where there was no sign of jet quenching or deviation
from the observed hard state correlations.Comment: Accepted to Astronomy & Astrophysics (8 pages
Space Ultrareliable Modular Computer (SUMC) instruction simulator
Simulator has been constructed as set of quasi-independent modules, regulated by one control module. All machine-dependent functions have been resolved such that simulation package is as machine independent as possible
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
CN and HNC Line Emission in IR Luminous Galaxies
We have observed HNC 1-0, CN 1-0 and 2-1 line emission in a sample of 13 IR
luminous (LIRGs, L_IR > 10E11 Lo) starburst and Seyfert galaxies. HNC 1-0 is
detected in 9, CN 1-0 is detected in 10 and CN 2-1 in 7 of the galaxies. We
also report the first detection of HC3N (10-9) emission in Arp220. The
excitation of HNC and CN emission requires densities n > 10E4 cm-3. We compare
their intensities to that of the usual high density tracer HCN. The
I(HCN)/I(HNC}) and I(HCN)/I(CN) 1-0 line intensity ratios vary significantly,
from 0.5 to >6, among the galaxies. This implies that the actual properties of
the dense gas is varying among galaxies who otherwise have similar I(CO)/I(HCN)
line intensity ratios. We suggest that the HNC emission is not a reliable
tracer of cold (10 K) gas at the center of LIRGs, as it often is in the disk of
the Milky Way. Instead, the HNC abundance may remain substantial, despite high
gas temperatures, because the emission is emerging from regions where the HCN
and HNC formation and destruction processes are dominated by ion-neutral
reactions which are not strongly dependent on kinetic temperature. We find five
galaxies (four AGNs and one starburst) where the I(HCN)/I(HNC) intensity ratio
is close to unity. In other AGNs, however, I(HCN)/I(HNC}) is >4. The CN
emission is on average a factor of two fainter than HCN, but the variation is
large and there seems to be a trend of reduced relative CN luminosity with
increasing IR luminosity. One galaxy, NGC3690, has a CN luminosity twice that
of HCN and its ISM is thus strongly affected by UV radiation. We discuss the
I(HCN)/I(HNC) and I(HCN)/I(CN) line ratios as indicators of starburst
evolution.Comment: 12 pages, 4 figures. Accepted for publication in Astronomy and
Astrophysic
Harms and benefits associated with psychoactive drugs: findings of an international survey of active drug users.
There have been several recent efforts in the UK and the Netherlands to describe the harms of psychoactive substances based on ratings of either experts or drug users. This study aimed to assess the perceived benefits as well as harms of widely used recreational drugs, both licit and illicit, in an international sample of drug users. The survey was hosted at https://www.internationaldrugsurvey.org/ and was available in three languages. Residents reported their experience of 15 commonly used drugs or drug classes; regular users then rated their harms and benefits. In all, 5791 individuals from over 40 countries completed the survey, although the majority were from English speaking countries. Rankings of drugs differed across 10 categories of perceived benefits. Skunk and herbal cannabis were ranked consistently beneficial, whilst alcohol and tobacco fell below many classified drugs. There was no correlation at all between users' harm ranking of drugs and their classification in schedules of the USA or ABC system in the UK. Prescription analgesics, alcohol and tobacco were ranked within the top 10 most harmful drugs. These findings suggest that neither the UK nor US classification systems act to inform users of the harms of psychoactive substances. It is hoped the results might inform health professionals and educators of what are considered to be both the harms and benefits of psychoactive substances to young people
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