10,146 research outputs found
The X-ray Transient XTE J2012+381
We present optical and infrared observations of the soft X-ray transient
(SXT) XTE J2012+381 and identify the optical counterpart with a faint red star
heavily blended with a brighter foreground star. The fainter star is coincident
with the radio counterpart and appears to show weak H alpha emission and to
have faded between observations. The RXTE/ASM lightcurve of XTE J2012+381 is
unusual for an SXT in that after an extended linear decay, it settled into a
plateau state for about 40 days before undergoing a weak mini-outburst. We
discuss the nature of the object and suggest similarities to long orbital
period SXTs.Comment: 5 pages, 7 postscript figures included, uses mn.sty. Accepted for
publication in MNRA
Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418
We present near-infrared and millimeter investigations of the nucleus of the
infrared luminous galaxy NGC 4418, which previous observations suggest
possesses a powerful buried AGN. We found the following main results: (1) The
infrared K-band spectrum shows CO absorption features at 2.3-2.4 micron owing
to stars and very strong H2 emission lines. The luminosity ratios of H2
emission lines are suggestive of a thermal origin, and the equivalent width of
the H2 1-0 S(1) line is the second largest observed to date in an external
galaxy, after the well-studied strong H2-emitting galaxy NGC 6240. (2) The
infrared L-band spectrum shows a clear polycyclic aromatic hydrocarbon (PAH)
emission feature at 3.3 micron, which is usually found in star-forming
galaxies. The estimated star-formation luminosity from the observed PAH
emission can account for only a small fraction of the infrared luminosity. (3)
Millimeter interferometric observations of the nucleus reveal a high HCN (1-0)
to HCO+ (1-0) luminosity ratio of 1.8, as has been previously found in pure
AGNs. (4) The measurements of HCN (1-0) luminosity using a single-dish
millimeter telescope show that the HCN (1-0) to infrared luminosity ratio is
slightly larger than the average, but within the scattered range, for other
infrared luminous galaxies. All of these results can be explained by the
scenario in which, in addition to energetically-insignificant, weakly-obscured
star-formation at the surface of the nucleus, a powerful X-ray emitting AGN
deeply buried in dust and high density molecular gas is present.Comment: 31 pages, 9 figures, Accepted for publication in Astronomical Journal
(2004 November issue
Very low shot noise in carbon nanotubes
We have performed noise measurements on suspended ropes of single wall carbon
nanotubes (SWNT) between 1 and 300 K for different values of dc current through
the ropes. We find that the shot noise is suppressed by more than a factor 100
compared to the full shot noise 2eI. We have also measured an individual SWNT
and found a level of noise which is smaller than the minimum expected. Another
finding is the very low level of 1/f noise, which is significantly lower than
previous observations. We propose two possible interpretations for this strong
shot noise reduction: i) Transport within a rope takes place through a few
nearly ballistic tubes within a rope and possibly involves non integer
effective charges. ii) A substantial fraction of the tubes conduct with a
strong reduction of effective charge (by more than a factor 50).Comment: Submitted to Eur. Phys. J. B (Jan. 2002) Higher resolution pictures
are posted on http://www.lps.u-psud.fr/Collectif/gr_07/publications.htm
Magnetic Insulator-Induced Proximity Effects in Graphene: Spin Filtering and Exchange Splitting Gaps
We report on first-principles calculations of spin-dependent properties in
graphene induced by its interaction with a nearby magnetic insulator (Europium
oxide, EuO). The magnetic proximity effect results in spin polarization of
graphene orbitals by up to 24 %, together with large exchange splitting
bandgap of about 36 meV. The position of the Dirac cone is further shown to
depend strongly on the graphene-EuO interlayer. These findings point towards
the possible engineering of spin gating by proximity effect at relatively high
temperature, which stands as a hallmark for future all-spin information
processing technologies.Comment: 5 pages, 4 figure
Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane
Context. In 2015, Barman et al. (ApJ, 804, 61) presented detections of
absorption from water, carbon monoxide, and methane in the atmosphere of the
directly imaged exoplanet HR8799b using integral field spectroscopy (IFS) with
OSIRIS on the Keck II telescope. We recently devised a new method to analyse
IFU data, called molecule mapping, searching for high-frequency signatures of
particular molecules in an IFU data cube.
Aims. The aim of this paper is to use the molecule mapping technique to
search for the previously detected spectral signatures in HR8799b using the
same data, allowing a comparison of molecule mapping with previous methods.
Methods. The medium-resolution H- and K-band pipeline-reduced archival data
were retrieved from the Keck archive facility. Telluric and stellar lines were
removed from each spectrum in the data cube, after which the residuals were
cross-correlated with model spectra of carbon monoxide, water, and methane.
Results. Both carbon monoxide and water are clearly detected at high
signal-to-noise, however, methane is not retrieved.
Conclusions. Molecule mapping works very well on the OSIRIS data of exoplanet
HR8799b. However, it is not evident why methane is detected in the original
analysis, but not with the molecule mapping technique. Possible causes could be
the presence of telluric residuals, different spectral filtering techniques, or
the use of different methane models. We do note that in the original analysis
methane was only detected in the K-band, while the H-band methane signal could
be expected to be comparably strong. More sensitive observations with the JWST
will be capable of confirming or disproving the presence of methane in this
planet at high confidence.Comment: 5 pages, 5 figures and 2 tables, accepted by A&
Assessing the sociology of sport: On sports mega-events and capitalist modernity
On the 50th anniversary of the ISSA and IRSS, one of the leading international scholars on sport and consumer culture, John Horne, considers the trajectory and challenges of research on sports mega-events and their place in capitalist modernity. In anchoring work on this topic in Roche’s definition of mega-events, Horne notes that sports mega-events are important symbolic, economic, and political elements in the orientation of nations to stake their place in global society. Fundamental issues about the concept of ‘mega-event’ pose challenges for scholars as questions remain over what qualifies as a sports mega-event and how ‘lived experience’ with such events transacts with media spectacularization and characterization. The essay closes by posing broader questions for further investigation about the economic, political, and social risks and benefits of sports mega-events and how these events may portend and relate to changing relations of economic and political power on a global scale
Tuning decoherence with a voltage probe
We present an experiment where we tune the decoherence in a quantum
interferometer using one of the simplest object available in the physic of
quantum conductors : an ohmic contact. For that purpose, we designed an
electronic Mach-Zehnder interferometer which has one of its two arms connected
to an ohmic contact through a quantum point contact. At low temperature, we
observe quantum interference patterns with a visibility up to 57%. Increasing
the connection between one arm of the interferometer to the floating ohmic
contact, the voltage probe, reduces quantum interferences as it probes the
electron trajectory. This unique experimental realization of a voltage probe
works as a trivial which-path detector whose efficiency can be simply tuned by
a gate voltage
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