We present the study of multiwavelength observations of an unidentified Fermi Large Area Telescope (LAT) source, 4FGL J1910.7−5320, a new candidate redback millisecond pulsar binary. In the 4FGL 95% error region of 4FGL J1910.7−5320, we find a possible binary with a 8.36 hr orbital period from the Catalina Real-Time Transient Survey, confirmed by optical spectroscopy using the SOAR telescope. This optical source was recently independently discovered as a redback pulsar by the TRAPUM project, confirming our prediction. We fit the optical spectral energy distributions of 4FGL J1910.7−5320 with a blackbody model, inferring a maximum distance of 4.1 kpc by assuming that the companion fills its Roche lobe with a radius of
Large widefield surveys make possible the serendipitous discovery of rare subclasses of pulsars. One such class are ‘spider’-type pulsar binaries, comprised of a pulsar in a compact orbit with a low-mass (sub)stellar companion. In a search for circularly polarized radio sources in Australian Square Kilometre Array Pathfinder (ASKAP) Pilot Survey observations, we discovered highly variable and circularly polarized emission from a radio source within the error region of the γ-ray source 4FGL J1646.5−4406. The variability is consistent with the eclipse of a compact, steep-spectrum source behind ablated material from a companion in an ∼5.3 h binary orbit. Based on the eclipse properties and spatial coincidence with 4FGL J1646.5−4406, we argue that the source is likely a recycled pulsar in a ‘redback’ binary system. Using properties of the eclipses from ASKAP and Murchison Widefield Array observations, we provide broad constraints on the properties of the eclipse medium. We identified a potential optical/infrared counterpart in archival data consistent with a variable low-mass star. Using the Parkes radio telescope ‘Murriyang’ and the Meer Karoo Array Telescope (MeerKAT) , we searched extensively for radio pulsations but yielded no viable detections of pulsed emission. We suggest that the non-detection of pulses is due to scattering in the intra-binary material, but scattering from the interstellar medium can also plausibly explain the pulse non-detections if the interstellar dispersion measure exceeds ∼600 pc cm−3. Orbital constraints derived from optical observations of the counterpart would be highly valuable for future γ-ray pulsation searches, which may confirm the source nature as a pulsar.
more » « less- NSF-PAR ID:
- 10491233
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 528
- Issue:
- 4
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 5730-5741
- Size(s):
- ["p. 5730-5741"]
- Sponsoring Org:
- National Science Foundation
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