Multi-wavelength observations of a new redback millisecond pulsar candidate: 3FGL J0954.8-3948

TL;DR

This study identifies 3FGL J0954.8-3948 as a redback millisecond pulsar through multi-wavelength observations, revealing its binary nature, spectral properties, and orbital characteristics, thus confirming its pulsar system status.

Contribution

First comprehensive multi-wavelength analysis confirming 3FGL J0954.8-3948 as a redback millisecond pulsar with detailed spectral and orbital characterization.

Findings

Gamma-ray source localized near the binary system.

Spectral analysis indicates a hard X-ray spectrum (~1.4).

Optical, UV, and X-ray modulations detected in the system.

Abstract

We present a multi-wavelength study of the unassociated Fermi-LAT source, 3FGL J0954.8-3948, which is likely the gamma-ray counterpart of a 9.3-hour binary in the field. With more than 9 years of Pass 8 LAT data, we updated the gamma-ray spectral properties and the LAT localization of the gamma-ray source. While the binary lies outside the cataloged 95% error ellipse, the optimized LAT ellipse is 0.1 degrees closer and encloses the binary. The system is likely spectrally hard in X-rays (photon index ~ 1.4) with orbital modulations detected in optical, UV, and possibly X-rays. A steep spectrum radio counterpart (spectral index ~ -1.6) is also found in the TIFR GMRT Sky Survey (TGSS), implying that it is a pulsar system. We obtained a series of SOAR and Gemini spectroscopic observations in 2017/2018, which show a low-mass secondary orbiting in a close circular orbit with K2 = 272 km/s under strong irradiation by the primary compact object. All the observations as well as the modelling of the X/gamma-ray high-energy emission suggest that 3FGL J0954.8-3948 is a redback millisecond pulsar in a rotation-powered state.