SEARCH FOR GAMMA-RAY EMISSION FROM AE AQUARII WITH SEVEN YEARS OF FERMI LAT OBSERVATIONS

Abstract

ABSTRACT AE Aquarii (AE Aqr) is a cataclysmic binary hosting one of the fastest rotating (  = 33.08 s) white dwarfs (WDs) known. Based on seven years of Fermi Large Area Telescope (LAT) Pass 8 data, we report on a deep search for gamma-ray emission from AE Aqr. Using X-ray observations from ASCA, XMM-Newton, Chandra, Swift, Suzaku, and NuSTAR, spanning 20 years, we substantially extend and improve the spin ephemeris of AE Aqr. Using this ephemeris, we searched for gamma-ray pulsations at the spin period of the WD. No gamma-ray pulsations were detected above 3σ significance. Neither phase-averaged gamma-ray emission nor gamma-ray variability of AE Aqr is detected by Fermi LAT. We impose the most restrictive upper limit to the gamma-ray flux from AE Aqr to date: erg cm−2 s−1 in the 100 MeV–300 GeV energy range, providing constraints on models.