297 research outputs found
The optical companion to the binary millisecond pulsar J1824-2452H in the globular cluster M28
We report on the optical identification of the companion star to the
eclipsing millisecond pulsar PSR J1824-2452H in the galactic globular cluster
M28 (NGC 6626). This star is at only 0.2" from the nominal position of the
pulsar and it shows optical variability (~ 0.25 mag) that nicely correlates
with the pulsar orbital period. It is located on the blue side of the cluster
main sequence, ~1.5 mag fainter than the turn-off point. The observed light
curve shows two distinct and asymmetric minima, suggesting that the companion
star is suffering tidal distortion from the pulsar. This discovery increases
the number of non-degenerate MSP companions optically identified so far in
globular clusters (4 out of 7), suggesting that these systems could be a common
outcome of the pulsar recycling process, at least in dense environments where
they can be originated by exchange interactions.Comment: accepted for publication on ApJ, 17 pages, 5 figure
Affine su(3) and su(4) fusion multiplicities as polytope volumes
Affine su(3) and su(4) fusion multiplicities are characterised as discretised
volumes of certain convex polytopes. The volumes are measured explicitly,
resulting in multiple sum formulas. These are the first polytope-volume
formulas for higher-rank fusion multiplicities. The associated threshold levels
are also discussed. For any simple Lie algebra we derive an upper bound on the
threshold levels using a refined version of the Gepner-Witten depth rule.Comment: 16 pages, LaTe
Dynamical Formation of Millisecond Pulsars in Globular Clusters
The cumulative luminosity distribution functions (CLFs) of radio millisecond
pulsars (MSPs) in globular clusters (GCs) and in the Galactic field at a
frequency of 1.4 GHz have been examined. Assuming a functional form, where is the number of MSPs and is the luminosity at 1.4 GHz, it
is found that the CLFs significantly differ with a steeper slope, , in GCs than in the Galactic field (), suggesting a
different formation or evolutionary history of MSPs in these two regions of the
Galaxy. To probe the production mechanism of MSPs in clusters, a search of the
possible relationships between the MSP population and cluster properties was
carried out. The results of an investigation of 9 GCs indicate positive
correlations between the MSP population and the stellar encounter rate and
metallicity. This provides additional evidence suggesting that stellar
dynamical interactions are important in the formation of the MSP population in
GCs.Comment: 18 pages, 3 figures, 4 tables, accepted for publication in Ap
A rare myoepithelioma of the sinonasal cavity: case report
Myoepithelioma is a rare benign neoplasm. Pure accounting for less than 1% of all salivary gland tumors. Only three cases of sinonasal myoepithelioma have been reported in the literature. Diagnosis of myoepithelioma through light microscopy is possible and immunohistochemistry is done to facilitate the diagnosis. The lesion is so rare that there are no specific indications/guidelines for its treatment. We report to you a rare case of sinonasal myoepithelioma in a 57 year old Asian female
Diffuse X-ray emission in globular cluster cores
The unresolved X-ray emission in the cores of 10 globular clusters hosting
millisecond pulsars is investigated. Subtraction of the known resolved point
sources leads to detectable levels of unresolved emission in the core region of
M28, NGC 6440, M62, and NGC 6752. The X-ray luminosities in the 0.3-8 keV
energy band of this emission component were found to lie in the range ergs s (NGC 6752) to ergs
s (M28). The lowest limiting luminosity for X-ray source detections
amongst these four clusters was ergs s for NGC
6752. The spectrum of the unresolved emission can be fit equally well by a
power-law, a thermal bremsstrahlung model, a black body plus power-law, or a
thermal bremsstrahlung model plus black body component. The unresolved emission
is considered to arise from the cumulative contribution of active binaries,
cataclysmic variables, and faint millisecond pulsars with their associated
pulsar wind nebulae. In examining the available X-ray data, no evidence for any
pulsar wind nebular emission in globular clusters is found. It is shown that
the X-ray luminosity contribution of a faint source population based on an
extrapolation of the luminosity function of detected point sources is
compatible with the unresolved X-ray emission in the cores of NGC 6440 and NGC
6752. Adopting the same slope for the luminosity function for M62 as for NGC
6440 and NGC 6752 leads to a similar result for M62. For M28, the contribution
from faint sources in the core can attain a level comparable with the observed
value if a steeper slope is adopted. The characteristics on the faint source
population as constrained by the properties of the unresolved X-ray emission
are briefly discussed.Comment: 25 pages, 4 figures, 3 tables, accepted for publication in Ap
Eight New Millisecond Pulsars in NGC 6440 and NGC 6441
Motivated by the recent discovery of 30 new millisecond pulsars in Terzan 5,
made using the Green Bank Telescope's S-band receiver and the Pulsar Spigot
spectrometer, we have set out to use the same observing system in a systematic
search for pulsars in other globular clusters. Here we report on the discovery
of five new pulsars in NGC 6440 and three in NGC 6441; each cluster previously
had one known pulsar. Using the most recent distance estimates to these
clusters, we conclude that there are as many potentially observable pulsars in
NGC 6440 and NGC 6441 as in Terzan 5. We present timing solutions for all of
the pulsars in these globular clusters. Four of the new discoveries are in
binary systems; one of them, PSR J1748-2021B (NGC 6440B), has a wide (P_b =
20.5 d) and eccentric (e = 0.57) orbit. This allowed a measurement of its rate
of advance of periastron: 0.00391(18) degrees per year. If due to the effects
of general relativity, the total mass of this binary system is 2.92 +/- 0.20
solar masses (1 sigma), implying a median pulsar mass of 2.74 +/- 0.21 solar
masses. There is a 1 % probability that the inclination is low enough that
pulsar mass is below 2 solar masses, and 0.10 % probability that it is between
1.20 and 1.44 solar masses. If confirmed, this anomalously large mass would
strongly constrain the equation of state for dense matter. The other highly
eccentric binary, PSR J1750-37A, has e = 0.71, and periastron advance of
0.0055(3) degrees per year, implying a total system mass of 1.97 +/-0.15 solar
masses and, along with the mass function, maximum and median pulsar masses of
1.65 and 1.26 solar masses respectively.Comment: Accepted for publication by the Astrophysical Journal. 14 pages in
emulate format, 6 tables, 7 figure
Plasma response to fish oil in the elderly
Little information is available concerning whether incorporation of dietary omega-3 fatty acids into plasma lipids changes during healthy aging. Elderly (74 ± 4 years old) and young (24 ± 2 years old) adults were given a fish oil supplement for 3 weeks that provided 680 mg/day of docosahexaenoic acid and 320 mg/day of eicosapentaenoic acid, followed by a 2 week wash-out period. Compliance was monitored by spiking the capsules with carbon-13 glucose, the excretion of which was measured in breath CO2. In response to the supplement, plasma docosahexaenoic acid rose 42% more in the elderly but eicosapentaenoic responded similarly in both groups. Despite raising docosahexaenoic acid intake by five to tenfold, the supplement did not raise plasma free docosahexaenoic acid (% or mg/dL) in either group. We conclude that healthy aging is accompanied by subtle but significant changes in DHA incorporation into plasma lipids
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