ASKAP radio detections following the recent brightening of the Nova V1716 Sco

ATel #16155; Akash Anumarlapudi (UWM), David Kaplan (UWM), Gregory Sivakoff (U. Alberta), Tara Murphy (U. Sydney), Ashna Gulati (U. Sydney) and Dougal Dobie (Swinburne/OzGrav) on behalf of the VAST collaboration.
on 26 Jul 2023; 16:39 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Akash Anumarlapudi (aakash@uwm.edu)

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V1716 Sco was discovered on 2023-04-20T16:29:16 and classified as a classical nova by A. Pearce (ATel #16003, #16004). However, analysis of pre-discovery ASAS-SN images showed a bright source on 2023-04-20T09:50:24 which possibly points to an earlier eruption time (ATel #16018). Soon after this, between 2023-04-21 and 2023-04-22, Fermi detected hard X-ray photons from this source, with photon energies as high as 23.5 GeV (ATel #16002). NuSTAR follow-up of this source roughly 1.5 days later showed an X-ray detection best described by a hard X-ray component, consistent with a heavily absorbed thermal plasma (#ATel 16018). Swift first reported the X-ray detection of this source, on 2023-05-01 (ATel #16069) with properties similar to NuSTAR observations. However, it is only after 2023-05-31 that the X-ray detection showed the appearance of an additional soft component (ATel #16069). Continued monitoring of this source by Swift out to 2023-07-24 revealed that this soft component brightened (ATel #16150).

We report Australian SKA Pathfinder (ASKAP) observations of V1716 Sco taken as part of the Variable And Slow Transients Survey (VAST; Murphy et al. 2021) at 887.5 MHz. The field of V1716 Sco was observed with a cadence of roughly every two weeks. The source was not detected in the early ASKAP data, with a typical 3-sigma upper limit of 0.75 mJy, until its first detection on 2023-06-12, and has continued to brighten since then. The details of the last non-detection and all of the detections are given below.

| Start time of observation (UTC) | Peak flux density (mJy) | Error (mJy) |
| 2023-06-05T15:05:40 | <0.75 | --- |
| 2023-06-12T15:20:31 | 1.81 | 0.22 |
| 2023-06-21T14:04:07 | 1.53 | 0.23 |
| 2023-06-22T16:05:48 | 2.00 | 0.22 |
| 2023-07-02T16:14:52 | 6.83 | 0.98 |
| 2023-07-04T13:33:30 | 7.70 | 0.24 |
| 2023-07-18T14:46:55 | 7.78 | 0.24 |
Note: Observations have a typical integration time of 12 min.

This seems to follow the appearance of the soft X-ray component observed by Swift. We encourage follow-up of this source at other frequencies to understand its evolution.

This work uses data obtained from Inyarrimanha Ilgari Bundara / the Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamaji People as the Traditional Owners and native title holders of the Observatory site. CSIRO’s ASKAP radio telescope is part of the Australia Telescope National Facility (https://ror.org/05qajvd42). The operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Research Centre. The establishment of ASKAP, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory, and the Pawsey Supercomputing Research Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund.

ASKAP light curve for this event can be obtained here.