4,658 research outputs found
Cooling of Hybrid Stars with Spin Down Compression
We study the cooling of hybrid stars coupling with spin-down. Due to the
spin-down of hybrid stars, the interior density continuously increases,
different neutrino reactions may be triggered(from the modified Urca process to
the quark and nucleon direct Urca process) at different stages of evolution. We
calculate the rate of neutrino emissivity of different reactions and simulate
the cooling curves of the rotational hybrid stars. The results show the cooling
curves of hybrid stars clearly depend on magnetic field if the direct urca
reactions occur during the spin-down. Comparing the results of the rotational
star model with the transitional static model, we find the cooling behavior of
rotational model is more complicated, the temperature of star is higher,
especially when direct urca reactions appear in process of rotation. And then
we find that the predicted temperatures of some rotating hybrid stars are
compatible with the pulsar's data which are contradiction with the results of
transitional method.Comment: 8 pages, 5figures, accepted by RA
Tentative evidence of spatially extended GeV emission from SS433/W50
We analyze 10 years of Fermi-LAT data towards the SS433/W50 region. With the
latest source catalog and diffuse background models, the gamma-ray excess from
SS433/W50 is detected with a significance of 6{\sigma} in the photon energy
range of 500 MeV - 10 GeV. Our analysis indicates that an extended flat disk
morphology is preferred over a point-source description, suggesting that the
GeV emission region is much larger than that of the TeV emission detected by
HAWC. The size of the GeV emission is instead consistent with the extent of the
radio nebula W50, a supernova remnant being distorted by the jets, so we
suggest that the GeV emission may originate from this supernova remnant. The
spectral result of the GeV emission is also consistent with an supernova
remnant origin. We also derive the GeV flux upper limits on the TeV emission
region, which put moderate constrains on the leptonic models to explain the
multiwavelength data.Comment: 7 pages, 4 figures, accepted for publication in A&
Carbon monoxide in an extremely metal-poor galaxy
Extremely metal-poor galaxies with metallicity below 10% of the solar value
in the local universe are the best analogues to investigating the interstellar
medium at a quasi-primitive environment in the early universe. In spite of the
ongoing formation of stars in these galaxies, the presence of molecular gas
(which is known to provide the material reservoir for star formation in
galaxies, such as our Milky Way) remains unclear. Here, we report the detection
of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with
7% solar metallicity, with additional detections in two galaxies at higher
metallicities. Such detections offer direct evidence for the existence of
molecular gas in these galaxies that contain few metals. Using archived
infrared data, it is shown that the molecular gas mass per CO luminosity at
extremely low metallicity is approximately one-thousand times the Milky Way
value.Comment: 12 pages, 3 figures, 1 table. Supplementary data at
http://www.nature.com/article-assets/npg/ncomms/2016/161209/ncomms13789/extref/ncomms13789-s1.pd
Mitigating Pooling Bias in E-commerce Search via False Negative Estimation
Efficient and accurate product relevance assessment is critical for user
experiences and business success. Training a proficient relevance assessment
model requires high-quality query-product pairs, often obtained through
negative sampling strategies. Unfortunately, current methods introduce pooling
bias by mistakenly sampling false negatives, diminishing performance and
business impact. To address this, we present Bias-mitigating Hard Negative
Sampling (BHNS), a novel negative sampling strategy tailored to identify and
adjust for false negatives, building upon our original False Negative
Estimation algorithm. Our experiments in the Instacart search setting confirm
BHNS as effective for practical e-commerce use. Furthermore, comparative
analyses on public dataset showcase its domain-agnostic potential for diverse
applications.Comment: Submitted to WWW'24 Industry Trac
- …