1,405 research outputs found
Discovery of X-ray pulsations in the Be/X-ray binary LS992/ RX J0812.4-3114
We report on the discovery of X-ray pulsations from the Be/X-ray system LS
992/RX J0812.4-3114 during an RXTE observation. From a timing analysis of the
source we obtained a barycentric pulse period of 31.8851 \pm 0.0004 s. The
pulse profile is highly structured and departs from a pure sinusoidal shape. It
shows a sharp dip that may indicate absorption by the accretion flow. The
energy spectrum from 3-30 keV can be fitted by a power-law model with an
exponential cut-off in accordance with other X-ray pulsars. The X-ray
luminosity is estimated to be in the energy
range 3-30 keV, assuming a distance of .Comment: 5 pages, 6 fgures, 2 tables, to appear in MNRA
Discovery of two new persistent Be/X-ray pulsar systems
We present RXTE observations of two recently identified massive X-ray
binaries. RX J0440.9+4431/BSD 24-491 and RX J1037.5-564/LS 1698 are confirmed
as accreting Be/X-ray systems following the discovery of X-ray pulsations, with
barycentric pulse periods of 202.50.5 s and 8602 s respectively. The
X-ray spectral analysis shows that the energy spectra of the pulsars can be
represented by a power-law, modified at low energy by an absorption component
and at high energy by a cut-off. Very weak Fe lines may be present. Both
sources appear to display a low cut-off energy when compared to typical X-ray
pulsars, low X-ray variability (factor of < 10), and no dependence of the X-ray
spectrum with energy. Given the similarity of these X-ray properties with those
of the other persistent BeXRB pulsars, 4U0352+309/X Per and RX J0146.9+6121/LS
I +61 235, we suggest that RX J0440.9+4431/BSD 24-491 and RX J1037.5-564/LS
1698 are also members of this subclass.Comment: 8 pages 7 figures, accepted for publication in MNRA
Robotic Astronomy with the Faulkes Telescopes and Las Cumbres Observatory Global Telescope
We present results from ongoing science projects conducted by members of the
Faulkes Telescope (FT) team and Las Cumbres Observatory Global Telescope
(LCOGT). Many of these projects incorporate observations carried out and
analysed by FT users, comprising amateur astronomers and schools.
We also discuss plans for the further development of the LCOGT network.Comment: 8 pages, 2 figures, conference proceedings from "Workshop on Robotic
Autonomous Observatories", held at Malaga, Spain from 18-21 May 2009,
acccepted for publication in Advances in Astronom
The X-Ray Position and Infrared Counterpart of the Eclipsing X-Ray Pulsar OAO 1657-415
We have measured the precise position of the 38-s eclipsing X-ray pulsar OAO
1657-415 with the Chandra X-Ray Observatory: RA = 17h00m48.90s, Dec =
-41d39m21.6s, equninox J2000, error radius = 0.5 arcsec. Based on the
previously measured pulsar mass function and X-ray eclipse duration, this
10.4-d high-mass X-ray binary is believed to contain a B supergiant companion.
Deep optical imaging of the field did not detect any stars at the Chandra
source position, setting a limit of V>23. However, near-IR imaging revealed a
relatively bright star (J=14.1, H=11.9, K_s=10.7) coincident with the Chandra
position, and we identify this star as the IR counterpart of OAO 1657-415. The
IR colors and magnitudes and the optical non-detections for this star are all
consistent with a highly reddened B supergiant (A_V= 20.4 +/- 1.3) at a
distance of 6.4 +/- 1.5 kpc. This implies an X-ray luminosity of 3e36 erg/s
(2-10 keV). IR spectroscopy can verify the spectral type of the companion and
measure its radial velocity curve, yielding a neutron star mass measurement.Comment: 4 pages. ApJ in press (Vol. 573, July 10 issue
Bioactivity in Whey Proteins Influencing Energy Balance
Peer-reviewedObesity develops due to energy (food) intake exceeding energy expenditure. Nutrients that reduce the positive energy balance are thus being considered as therapies to combat obesity. Here, we review the literature related to the physiological, cellular and endocrine effects of intake of whey proteins, namely α-lactalbumin, ÎČ-lactoglobulin, glycomacropeptide and lactoferrin. Moreover, we discuss how dietary composition and obesity may influence whey protein effects on the above parameters. Evidence suggests that intake of whey proteins causes a decrease in energy
intake, increase in energy expenditure, influence insulin sensitivity and glucose homeostasis and alter lipid metabolism
in the adipose, liver and muscle. These physiological changes are accompanied by alterations in the plasma levels of
energy balance related hormones (cholecystokinin, ghrelin, insulin and glucagon-like peptide-1) and the expression of catabolic and anabolic genes in the above tissue in the direction to cause a negative energy balance
Continued monitoring of LMXBs with the Faulkes Telescopes
The Faulkes Telescope Project is an educational and research arm of the Las Cumbres Observatory Global Telescope Network (LCOGTN). It has two 2-metre robotic telescopes, located at Haleakala on Maui (FT North) and Siding Spring in Australia (FT South). It is planned for these telescopes to be complemented by a research network of eighteen 1-metre telescopes, along with an educational network of twenty-eight 0.4-metre telescopes, providing 24 hour coverage of both northern and southern hemispheres.
We have been conducting a monitoring project of 13 low-mass X-ray binaries (LMXBs) using FT North since early 2006. The introduction of FT South has allowed us to extend this to monitor a total of 30 LMXBs (see target list, Section 4). New instrumentation will allow us to expand this project to include both infrared wavelengths (z and y band) and spectroscopy. Brighter targets (~ 16 - 18 mag.) are imaged weekly in V, R and iâ bands (SNR ~ 50), while fainter ones (> 18 mag.) are observed only in iâ band (SNR ~ 20). We alter this cadence in response to our own analysis or Astronomers Telegrams (ATels)
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