Discovery of ASKAP J173608.2–321635 as a Highly Polarized Transient Point Source with the Australian SKA Pathfinder
- 1 October 2021
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 920 (1), 45
- https://doi.org/10.3847/1538-4357/ac2360
Abstract
We report the discovery of a highly polarized, highly variable, steep-spectrum radio source, ASKAP J173608.2-321635, located similar to 4 degrees from the Galactic Center in the Galactic plane. The source was detected six times between 2020 January and 2020 September as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients (ASKAP VAST) survey at 888 MHz. It exhibited a high degree (similar to 25%) of circular polarization when it was visible. We monitored the source with the MeerKAT telescope from 2020 November to 2021 February on a 2-4 week cadence. The source was not detected with MeerKAT before 2021 February 7 when it appeared and reached a peak flux density of 5.6 mJy. The source was still highly circularly polarized, but also showed up to 80% linear polarization, and then faded rapidly with a timescale of one day. The rotation measure of the source varied significantly, from -11.8 +/- 0.8 rad m(-2) to -64.0 +/- 1.5 rad m(-2) over three days. No X-ray counterpart was found in follow-up Swift or Chandra observations about a week after the first MeerKAT detection, with upper limits of similar to 5.0 x 10(31) erg s(-1) (0.3-8 keV, assuming a distance similar to 10 kpc). No counterpart is seen in new or archival near-infrared observations down to J = 20.8 mag. We discuss possible identifications for ASKAP J173608.2-321635 including a low-mass star/substellar object with extremely low infrared luminosity, a pulsar with scatter-broadened pulses, a transient magnetar, or a Galactic Center radio transient: none of these fully explains the observations, which suggests that ASKAP J173608.2-321635 may represent part of a new class of objects being discovered through radio imaging surveys.Funding Information
- Australian Research Council (DP190100561)
- National Science Foundation (AST-1816492)
- European Research Council Consolidator Grant (No. 817661)
- Catalan Grant (SGR2017-1383)
- Spanish Grant (PGC2018-095512-BI00)
- European Research Council under the European Union’s Horizon 2020 research and innovation programme (No. 694745)
- Australian Research Council (DE210101738)
- NSERC Discovery Grants (RGPIN-2016-06569)
- NSERC Discovery Grants (RGPIN-2021-04001)
This publication has 123 references indexed in Scilit:
- A STRONGLY MAGNETIZED PULSAR WITHIN THE GRASP OF THE MILKY WAY'S SUPERMASSIVE BLACK HOLEThe Astrophysical Journal Letters, 2013
- INTRINSIC COLORS, TEMPERATURES, AND BOLOMETRIC CORRECTIONS OF PRE-MAIN-SEQUENCE STARSThe Astrophysical Journal Supplement Series, 2013
- Rotation measure variations for 20 millisecond pulsarsAstrophysics and Space Science, 2011
- Outburst of the 2 s Anomalous X‐Ray Pulsar 1E 1547.0−5408The Astrophysical Journal, 2008
- The second epoch Molonglo Galactic Plane Survey: compact source catalogueMonthly Notices of the Royal Astronomical Society, 2007
- Dispersion measure variations and their effect on precision pulsar timingMonthly Notices of the Royal Astronomical Society, 2007
- A Long-Period, Violently Variable X-ray Source in a Young Supernova RemnantScience, 2006
- Intraday variability in compact extragalactic radio sourcesAstronomy & Astrophysics, 2003
- Detection of the old stellar component of the major Galactic barMonthly Notices of the Royal Astronomical Society, 2000
- Interstellar scattering effects on the detection of narrow-band signalsThe Astrophysical Journal, 1991