TY - JOUR
T1 - A long-term study of high-energy gamma-ray emission from the Vela, Geminga, and Crab pulsars
AU - Ramanamurthy, P. V.
AU - Bertsch, D. L.
AU - Fichtel, C. E.
AU - Kanbach, G.
AU - Kniffen, D. A.
AU - Mayer-Hasselwander, H. A.
AU - Nolan, P. L.
AU - Sreekumar, P.
AU - Thompson, D. J.
PY - 1995/9/10
Y1 - 1995/9/10
N2 - We have analyzed ∼3 yr of data on the Vela, Geminga, and Crab pulsars in the energy range 30 MeV to 30 GeV, gathered by the EGRET detector aboard the Compton Gamma Ray Observatory, to study long-term variability in the various characteristics of high-energy gamma-ray emission by these objects. The light curves at energies ≥ 100 MeV are generally constant in time. However, it is noticed that occasionally the emission of high-energy gamma rays under one of the two peaks of the Vela and Crab pulsars is significantly less than the long-term average. The ratio of background-subtracted pulsed intensities under the two peaks, P2/P1, in the Crab pulsar is consistent with both the hypotheses of a 13.5 yr sinusoidal variation and a constant (no variation) ratio. While the integral flux at E ≥ 100 MeV is nearly constant in the case of the Crab pulsar, it appears to be variable in the cases of the Vela and Geminga pulsars. The slopes of the energy spectra show evidence of variability particularly for the Vela and Geminga pulsars.
AB - We have analyzed ∼3 yr of data on the Vela, Geminga, and Crab pulsars in the energy range 30 MeV to 30 GeV, gathered by the EGRET detector aboard the Compton Gamma Ray Observatory, to study long-term variability in the various characteristics of high-energy gamma-ray emission by these objects. The light curves at energies ≥ 100 MeV are generally constant in time. However, it is noticed that occasionally the emission of high-energy gamma rays under one of the two peaks of the Vela and Crab pulsars is significantly less than the long-term average. The ratio of background-subtracted pulsed intensities under the two peaks, P2/P1, in the Crab pulsar is consistent with both the hypotheses of a 13.5 yr sinusoidal variation and a constant (no variation) ratio. While the integral flux at E ≥ 100 MeV is nearly constant in the case of the Crab pulsar, it appears to be variable in the cases of the Vela and Geminga pulsars. The slopes of the energy spectra show evidence of variability particularly for the Vela and Geminga pulsars.
UR - https://www.scopus.com/pages/publications/0000686759
UR - https://www.scopus.com/pages/publications/0000686759#tab=citedBy
U2 - 10.1086/176184
DO - 10.1086/176184
M3 - Article
AN - SCOPUS:0000686759
SN - 0004-637X
VL - 450
SP - 791
EP - 804
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
ER -