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تسجيل مستخدم جديدX-ray Through Very-High-Energy Intrabinary Shock Emission from Black Widows and Redbacks
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Black widow and redback systems are compact binaries in which a millisecond pulsar heats and may even ablate its low-mass companion by its intense wind of relativistic particles and radiation. In such systems, an intrabinary shock can form as a site of particle acceleration and associated non-thermal emission. We model the X-ray and gamma-ray synchrotron and inverse-Compton spectral components for select spider binaries, including diffusion, convection and radiative energy losses in an axially-symmetric, steady-state approach. Our new multi-zone code simultaneously yields energy-dependent light curves and orbital phase-resolved spectra. Using parameter studies and matching the observed X-ray spectra and light curves, and Fermi Large Area Telescope spectra where available, with a synchrotron component, we can constrain certain model parameters. For PSR J1723--2837 these are notably the magnetic field and bulk flow speed of plasma moving along the shock tangent, the shock acceleration efficiency, and the multiplicity and spectrum of pairs accelerated by the pulsar. This affords a more robust prediction of the expected high-energy and very-high-energy gamma-ray flux. We find that nearby pulsars with hot or flaring companions may be promising targets for the future Cherenkov Telescope Array. Moreover, many spiders are likely to be of significant interest to future MeV-band missions such as AMEGO and e-ASTROGAM.
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Black widows and redbacks are binary systems consisting of a millisecond pulsar in a close binary with a companion having matter driven off of its surface by the pulsar wind. X-rays due to an intra-binary shock have been observed from many of these s
ystems, as well as orbital variations in the optical emission from the companion due to heating and tidal distortion. We have been systematically studying these systems in radio, optical and X-rays. Here we will present an overview of X-ray and optical studies of these systems, including new XMM-Newton and NuStar data obtained from several of them, along with new optical photometry.
The wealth of detections of millisecond pulsars (MSPs) in $gamma$-rays by {em Fermi} has spurred searches for these objects among the several unidentified $gamma$-ray sources. Interesting targets are a sub-class of binary MSPs, dubbed Black Widows (B
Ws) and Redbacks (RBs), which are in orbit with low-mass non-degenerate companions fully or partially ablated by irradiation from the MSP wind. These systems can be easily missed in radio pulsar surveys owing to the eclipse of the radio signal by the intra-binary plasma from the ablated companion star photosphere, making them better targets for multi-wavelength observations. We used optical and X-ray data from public databases to carry out a systematic investigation of all the unidentified $gamma$-ray sources from the Fermi Large Area Telescope (LAT) Third Source Catalog (3FGL), which have been pre-selected as likely MSP candidates according to a machine-learning technique analysis. We tested our procedure by recovering known binary BW/RB identifications and searched for new ones, finding possible candidates. At the same time, we investigated previously proposed BW/RB identifications and we ruled out one of them based upon the updated $gamma$-ray source coordinates.
Redbacks (RBs) and black widows (BWs) are two peculiar classes of eclipsing millisecond pulsars (MSPs). The accretion-induced collapse (AIC) of an oxygen/neon/magnesium composition white dwarf to a neutron star has been suggested as one possible form
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