Exploring possible gamma-ray emission in polar magnetic CVs using Fermi-LAT data

Abstract

Polar (AM Herculis) systems, a subclass of Magnetic Cataclysmic Variables (MCVs), exhibit unique characteristics such as strong magnetic fields ranging from 10 to 230 MG, phase-locked rotation, and orbital periods devoid of accretion disks. These systems are known for emitting strong X-rays, UV radiation, infrared radiation, and polarized light. The potential candidacy of polar systems for gamma-ray emissions have been explored. In this study, we present preliminary analysis of Fermi LAT data in the energy range of 0.1-500 GeV, focusing on the detection of gamma-ray emissions and pulsed signals associated with the orbital periods of specific sources. Using a binned likelihood analysis technique, we initially observed soft count spectra, hinting a potential emissions at a lower energy levels. Further narrowing our focus to the energy range of 50 MeV-20 GeV, we identified sources with test statistics (TS) exceeding the Fermi detection threshold. Subsequently, we explored the possibility of pulsed emissions modulated to the orbital period of these systems. We present pulsed emission results for sources WW Hor ($P_{orb}$ = 115.5 mins; - log Prob = 5,397, EXO 023432-5237.3), EF Eridani ($P_{orb}$ = 81 mins; - log Prob = 5.842), EU UMa ($P_{orb}$ = 90 mins; - log Prob = 4.133), AR UMa ($P_{orb}$ = 115.6 mins; - log Prob = 4.557), and V834 Cen ($P_{orb}$ = 101.5 mins; - log Prob = 4.450, E1405-451). The search for periodic emission revealed evidence of pulsed emission at the orbital period within a 0.6$^{\circ}$ region of interest. We detected gamma-ray pulsations with significance above 4 $\sigma$ in all sources. Since we used ephemerides derived from optical or X-rays, continuous monitoring of these sources to improve their ephemerides may improve our results.