Optical Light Curve of 4FGL J0935.3+0901: A Flaring Black Widow Candidate

TL;DR

This study presents optical photometry of a candidate black widow pulsar, revealing orbital modulation, flaring activity, and pulsar heating effects, supporting its classification as a black widow system.

Contribution

First detailed optical light curve analysis of 4FGL J0935.3+0901, confirming its black widow nature through observed pulsar heating and flaring behavior.

Findings

Detected orbital period of approximately 0.10153 days.

Observed day-to-day variability and flaring activity.

Light curve indicates pulsar heating rather than accretion.

Abstract

I obtained time-series photometry of the compact binary candidate for the Fermi source 4FGL J0935.3+0901. Superposed on the 2.44 hr orbital modulation are day-to-day variations and frequent flaring as seen in several redback and black widow millisecond pulsars (MSPs). The short orbital period favors a black widow. While the modulation of $\leq 1$ mag is smaller than that of most black widows, it could indicate a low orbital inclination. Although a published optical spectrum shows strong emission lines, the light curve evinces pulsar heating of the companion star rather than accretion-disk emission of a transitional MSP. Emission lines and flaring occur in the same objects, probably powered by shocks between the relativistic pulsar wind and a wind driven off the companion star. I also recovered the period in photometry from the Zwicky Transient Facility. A phase-connected ephemeris derived from MDM Observatory and ZTF data spanning 4 years yields a period of 0.10153276(36) days and an epoch for the ascending node of the putative pulsar.