8,017 research outputs found
"Soft X-ray transient" outbursts which aren't soft
We have accumulated multiwavelength (X-ray, optical, radio) lightcurves for
the eight black hole X-ray binaries which have been observed to enter a
supposed `soft X-ray transient' outburst, but remained in the low/hard state
throughout the outburst. Comparison of the lightcurve morphologies, spectral
behaviour, properties of the quasi-periodic oscillations and the radio jet
provides the first study of such objects as a sub-class of X-ray transients.
However rather than assuming that these hard state X-ray transients are
different from the `canonical' soft X-ray transient, we prefer to consider the
possibility that new analysis of both soft and hard state X-ray transients in a
spectral context will provide a model capable of explaining the outburst
mechanisms of (almost) all black hole X-ray binaries.Comment: Accepted for publication in New Astronom
The Hard Truth about Some "Soft" X-ray Transients
We have accumulated multiwavelength lightcurves for eight black hole X-ray
binaries which have been observed to enter a supposed ``soft X-ray transient''
outburst, but which in fact remained in the low/hard state throughout the
outburst. Comparison of the lightcurve morphologies, spectral behaviour,
properties of the QPOs and the radio jet provides the first study of such
objects as a subclass of X-ray transients (XRTs). However, rather than assuming
that these hard state XRTs are different from ``canonical'' soft XRTs, we
prefer to consider the possibility that a new analysis of both soft and hard
state XRTs in a spectral context will provide a model capable of explaining the
outburst mechanisms for the majority of black hole X-ray binaries.Comment: 3 pages, 2 figures; to appear in the Proceedings of the 4th
Microquasar Workshop, 2002, eds. Durouchoux, Fuchs & Rodriguez, published by
the Center for Space Physics: Kolkat
Spectroscopic Identification of the Infrared Counterpart to GX5-1
Using CGS4 on UKIRT, we have obtained a 1.95-2.45 micron infrared spectrum of
the primary candidate counterpart to the bright Z LMXB GX5-1. IR photometry by
Naylor, Charles, & Longmore (1992) and the astrometry of Jonker et al. (2000)
had previously identified this star as the most likely counterpart to GX5-1.
The spectrum presented here clearly shows Brackett gamma and He lines in
emission, for the first time confirming the identity of the counterpart.
Similar to our previous spectroscopy of the Z source LMXBs Sco X-1 and Sco X-2
(Bandyopadhyay et al. 1999), the K-band spectrum of GX5-1 shows emission lines
only. We briefly discuss the implications of this spectrum for the nature of
the Z sources.Comment: accepted for publication as a Letter in MNRA
Displaced Higgs production in type III seesaw
We point out that the type III seesaw mechanism introducing fermion triplets
predicts peculiar Higgs boson signatures of displaced vertices with two b jets
and one or two charged particles which can be cleanly identified. In a
supersymmetric theory, the scalar partner of the fermion triplet contains a
neutral dark matter candidate which is almost degenerate with its charged
components. A Higgs boson can be produced together with such a dark matter
triplet in the cascade decay chain of a strongly produced squark or gluino.
When the next lightest supersymmetric particle (NLSP) is bino/wino-like, there
appears a Higgs boson associated with two charged tracks of a charged lepton
and a heavy charged scalar at a displacement larger than about 1 mm. The
corresponding production cross-section is about 0.5 fb for the squark/gluino
mass of 1 TeV. In the case of the stau NLSP, it decays mainly to a Higgs boson
and a heavy charged scalar whose decay length is larger than 0.1 mm for the
stau NLSP mixing with the left-handed stau smaller than 0.3. As this process
can have a large cascade production pb for the squark/gluino mass
TeV, one may be able to probe it at the early stage of the LHC
experiment.Comment: 10 pages, 5 figure
Counterparts to the Nuclear Bulge X-ray source population
We present an initial matching of the source positions of the Chandra Nuclear
Bulge X-ray sources to the new UKIDSS-GPS near-infrared survey of the Nuclear
Bulge. This task is made difficult by the extremely crowded nature of the
region, despite this, we find candidate counterparts to ~50% of the X-ray
sources. We show that detection in the J-band for a candidate counterpart to an
X-ray source preferentially selects those candidate counterparts in the
foreground whereas candidate counterparts with only detections in the H and
K-bands are more likely to be Nuclear Bulge sources. We discuss the planned
follow-up for these candidate counterparts.Comment: 5 pages, 2 figures, 1 table, published in the proceedings of "A
population Explosion", AIP Conference Proceedings Volume 1010, pp. 117-12
The Nuclear Bulge extinction
We present a new, high resolution (5" per pixel) near-infrared extinction map
of the Nuclear Bulge using data from the UKIDSS-GPS. Using photometry from the
J, H and K-bands we show that the extinction law parameter is also highly
variable in this region on similar scales to the absolute extinction. We show
that only when this extinction law variation is taken into account can the
extinction be measured consistently at different wavelengths.Comment: 3 pages, 2 figures, published in the proceedings of "A population
Explosion", AIP Conference Proceedings Volume 1010, pp. 168-17
LOCC distinguishability of unilaterally transformable quantum states
We consider the question of perfect local distinguishability of mutually
orthogonal bipartite quantum states, with the property that every state can be
specified by a unitary operator acting on the local Hilbert space of Bob. We
show that if the states can be exactly discriminated by one-way LOCC where
Alice goes first, then the unitary operators can also be perfectly
distinguished by an orthogonal measurement on Bob's Hilbert space. We give
examples of sets of N<=d maximally entangled states in for
d=4,5,6 that are not perfectly distinguishable by one-way LOCC. Interestingly
for d=5,6 our examples consist of four and five states respectively. We
conjecture that these states cannot be perfectly discriminated by two-way LOCC.Comment: Revised version, new proofs added; to appear in New Journal of
Physic
Infrared Photometric Variability of GX13+1 and GX17+2
We present infrared photometry of the Galactic Bulge X-ray binary systems
GX13+1 and GX17+2 obtained in 1997 July and August using OSIRIS on the 1.8m
Perkins Telescope at Lowell Observatory. GX13+1 clearly varies over ~0.6
magnitudes in the K-band. Our light curve suggests a modulation on a timescale
of ~20 days, which is in agreement with previously proposed orbital periods for
the system. The IR counterpart of GX17+2 is also variable in the K-band over
\~0.8 magnitudes on a timescale of days to weeks, extending the variability
first seen by Naylor, Charles, & Longmore (1991). We discuss the implications
our data have for Deutsch et al's (1999) identification of ``star A'' as the
true IR counterpart of GX17+2. The variability observed in our photometry of
the blend of star A and the foreground star NP Ser implies a ~4 magnitude
intrinsic variation in the K-band for GX17+2.Comment: Accepted for publication in ApJ, 5 pages, 4 figure
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