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Title: Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883

Abstract

The observed TeV light curve from the γ -ray binary PSR B1259-63/LS 2883 shows a decrease in the flux at periastron that has not been fully explained by emission mechanisms alone. This observed decrease can, however, be explained by γγ absorption due to the stellar and disk photons. We calculate the γγ absorption in PSR B1259-63/LS 2883 taking into account photons from both the circumstellar disk and star, assuming that the γ -rays originate at the position of the pulsar. The γγ absorption due to the circumstellar disk photons produces a ≈14% decrease in the flux, and there is a total decrease of ≈52% (>1 TeV) within a few days before periastron, accompanied by a hardening of the γ -ray photon index. While the γγ absorption alone is not sufficient to explain the full complexity of the H.E.S.S. γ -ray light curve, it results in a significant decrease in the predicted flux, which is coincident with the observed decrease. In addition, we have calculated an upper limit on the γγ absorption, assuming that the emission is produced at the apex of the bow shock. Future observations with CTA during the 2021 periastron passage may be able to confine the locationmore » of the emission based on the degree of γγ absorption, as well as measure the hardening of the spectrum around periastron.« less

Authors:
 [1];  [2]
  1. Centre for Space Research, North-West University, 2520 Potcheftroom (South Africa)
  2. Department of Physics, University of the Free State, 9300 Bloemfontein (South Africa)
Publication Date:
OSTI Identifier:
22661271
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 837; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; BINARY STARS; COMPUTERIZED SIMULATION; COSMIC GAMMA SOURCES; EMISSION; GAMMA RADIATION; PHOTONS; PULSARS; SHOCK WAVES; SPECTRA; TEV RANGE; VISIBLE RADIATION

Citation Formats

Sushch, Iurii, and Van Soelen, Brian, E-mail: iurii.sushch@desy.de, E-mail: vansoelenb@ufs.ac.za. Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA62FF.
Sushch, Iurii, & Van Soelen, Brian, E-mail: iurii.sushch@desy.de, E-mail: vansoelenb@ufs.ac.za. Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883. United States. doi:10.3847/1538-4357/AA62FF.
Sushch, Iurii, and Van Soelen, Brian, E-mail: iurii.sushch@desy.de, E-mail: vansoelenb@ufs.ac.za. Fri . "Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883". United States. doi:10.3847/1538-4357/AA62FF.
@article{osti_22661271,
title = {Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883},
author = {Sushch, Iurii and Van Soelen, Brian, E-mail: iurii.sushch@desy.de, E-mail: vansoelenb@ufs.ac.za},
abstractNote = {The observed TeV light curve from the γ -ray binary PSR B1259-63/LS 2883 shows a decrease in the flux at periastron that has not been fully explained by emission mechanisms alone. This observed decrease can, however, be explained by γγ absorption due to the stellar and disk photons. We calculate the γγ absorption in PSR B1259-63/LS 2883 taking into account photons from both the circumstellar disk and star, assuming that the γ -rays originate at the position of the pulsar. The γγ absorption due to the circumstellar disk photons produces a ≈14% decrease in the flux, and there is a total decrease of ≈52% (>1 TeV) within a few days before periastron, accompanied by a hardening of the γ -ray photon index. While the γγ absorption alone is not sufficient to explain the full complexity of the H.E.S.S. γ -ray light curve, it results in a significant decrease in the predicted flux, which is coincident with the observed decrease. In addition, we have calculated an upper limit on the γγ absorption, assuming that the emission is produced at the apex of the bow shock. Future observations with CTA during the 2021 periastron passage may be able to confine the location of the emission based on the degree of γγ absorption, as well as measure the hardening of the spectrum around periastron.},
doi = {10.3847/1538-4357/AA62FF},
journal = {Astrophysical Journal},
number = 2,
volume = 837,
place = {United States},
year = {Fri Mar 10 00:00:00 EST 2017},
month = {Fri Mar 10 00:00:00 EST 2017}
}