The discovery of pulsars is of great significance in the field of physics and astronomy. As the astronomical equipment produces a large amount of pulsar data, an algorithm for automatically identifying pulsars becomes urgent. We propose a deep learning framework for pulsar recognition. In response to the extreme imbalance between positive and negative examples and the hard negative sample issue presented in the HTRU Medlat Training Data,there are two coping strategies in our framework: the smart under-sampling and the improved loss function. We also apply the early-fusion strategy to integrate features obtained from different attributes before classification to improve the performance. To our best knowledge,this is the first study that integrates these strategies and techniques together in pulsar recognition. The experiment results show that our framework outperforms previous works with the respect to either the training time or F1 score. We can not only speed up the training time by 10X compared with the state-of-the-art work, but also get a competitive result in terms of F1 score.
9 pages. 5 figures, 2 tables, accept for publication in ApJ
Cyclotron line scattering features are detected in a few tens of X-ray pulsars (XRPs) and used as direct indicators of a strong magnetic field at the surface of accreting neutron stars (NSs). In a few cases, cyclotron lines are known to be variable with accretion luminosity of XRPs. It is accepted that the observed variations of cyclotron line scattering features are related to variations of geometry and dynamics of accretion flow above the magnetic poles of a NS. A positive correlation between the line centroid energy and luminosity is typical for sub-critical XRPs, where the accretion results in hot spots at the magnetic poles. The negative correlation was proposed to be a specific feature of bright super-critical XRPs, where radiation pressure supports accretion columns above the stellar surface. Cyclotron line in spectra of Be-transient X-ray pulsar GRO J1008-57 is detected at energies from ∼75−90 keV, the highest observed energy of cyclotron line feature in XRPs. We report the peculiar relation of cyclotron line centroid energies with luminosity in GRO J1008-57 during the Type II outburst in August 2017 observed by Insight-HXMT. The cyclotron line energy was detected to be negatively correlated with the luminosity at 3.2×1037\ergs<L<4.2×1037\ergs, and positively correlated at L≳. We speculate that the observed peculiar behavior of a cyclotron line would be due to variations of accretion channel geometry.
29 pages, 4 figures, accepted to ApJ
Young stellar objects are observed to have large X-ray fluxes and are thought to produce commensurate luminosities in energetic particles (cosmic rays). This particle radiation, in turn, can synthesize short-lived radioactive nuclei through spallation. With a focus on ^{26}Al, this paper estimates the expected abundances of radioactive nulcei produced by spallation during the epoch of planet formation. In this model, cosmic rays are accelerated near the inner truncation radii of circumstellar disks, r_{\scriptstyle X}\approx0.1 AU, where intense magnetic activity takes place. For planets forming in this region, radioactive abundances can be enhanced over the values inferred for the early solar system (from meteoritic measurements) by factors of \sim10-20. These short-lived radioactive nuclei influence the process of planet formation and the properties of planets in several ways. The minimum size required for planetesimals to become fully molten decreases with increasing levels of radioactive enrichment, and such melting leads to loss of volatile components including water. Planets produced with an enhanced radioactive inventory have significant internal luminosity which can be comparable to that provided by the host star; this additional heating affects both atmospheric mass loss and chemical composition. Finally, the habitable zone of red dwarf stars is coincident with the magnetic reconnection region, so that planets forming at those locations will experience maximum exposure to particle radiation, and subsequent depletion of volatiles.
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14 pages + appendix, to be submitted to ApJ
10 pages, 7 figures, accepted for publication in the Astrophysical Journal
Accepted for publication in ApJ Letters
22 pages, 15 figures (with 3 more figures in the Appendix), abstract abridged. Accepted for publication in A&A
Accepted for publication in A&A Letters. Data catalogue will be available via CDS and at this link this https URL
16 pages, 7 figures, 3 tables. Accepted for publication in ApJ
25 pages, 16 figures, 2 tables, code available at this https URL and this https URL
21 pages, 17 figures. Accepted for publication in the Astrophysical Journal. The full catalog is available from the publisher or from the corresponding author upon request
37 pages, 22 figures, 6 tables, accepted for publication in PASJ
15 pages, 8 figures, accepted for publication in ApJ
A mini review to apear in EPJST (18 pages, 4 figures)
17 pages, 7 figures, accepted for publication in ApJ
32 pages including 11 figures and 2 tables. To be submitted in Frontiers in Astronomy and Space Science
12 pages, 6 figures, accepted for publication in Astronomy and Astrophysics (A & A)
20 pages, 22 figures, submitted to MNRAS
8 pages, 3 figures
8 pages, 6 figures, Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021)
13 pages, 11 figures. Submitted to MNRAS
15 pages, 5 tables, 8 figures
24 pages, 7 figures, 2 tables, accepted for publication in ApJ
Author's version of a Letter published in Nature on July 8th, 2021
accepted 2021 July 5, to be published in MNRAS, 19 pages
18 pages, 1 appendix, 9 figures, 3 tables; accepted by Astronomy & Astrophysics
15 pages, 7 figures, accepted to MNRAS
Accepted by Science Bulletin. Note that the final version of the paper in the journal is formatted slightly differently from the one in astro-ph because of the journal's layout
Submitted to ApJ. 18 pages, 5 figures, 3 tables
8 pages, ICRC2021 proceeding
22 pages, 10 figures, 3 tables
Accepted for publication in Astronomy and Astrophysics
16 pages, 6 figures
24 pages, 9 figures, accepted for publication in Celestial Mechanics and Dynamical Astronomy
3 pages, 1 figure, accepted to the Journal of the American Association of Variable Star Observers
24 pages, 10 Figures, 5 Tables. Accepted to AJ. Co-First Authors
Accepted to ApJ
Accepted for the Planetary Science Journal
8 pages, 3 figures
21 pages, 11 Figures. Published in MNRAS on 07 June 2021
16 pages, 8 figures
7 pages, 3 figures, accepted to JBIS
13 pages, 2 figures, to appear in International Journal of Geometric Methods in Modern Physics
13 pages, 11 figures. Comments welcome
7 pages, 2 figures
50 pages, 30 figures. Submitted to Class. and Quantum Grav. (July 2021)