Tighter upper limits to radio emission from GAIA BH3 with the VLA

ATel #16832; LO Sjouwerman (NRAO/UNM) & JM Blanchard (NRAO)
on 27 Sep 2024; 19:48 UT
Credential Certification: Lorant Sjouwerman (lsjouwer@nrao.edu)

Tweet

Following up on our preliminary upper limits for GAIA BH3 in ATel 16677 (2024-06-28) and a prediction of possible few micro-Jy level radio continuum emission by Cappelluti et al. (https://arxiv.org/pdf/2406.07602), we were motivated to request filler time at the NSF's Karl G. Jansky Very Large Array (VLA) to significantly improve upon our earlier findings. GAIA BH3 is suggested to be a 33 Msun black hole in a low-metallicity binary stellar system (see e.g., Gaia Collaboration/Panuzzo et al. 2024, A&A 686, L2 and [*]; Gilfanov et al. 2024 ATel 16591; Balbinot et al. 2024, A&A 687, L3; Marin Pina et al. 2024, A&A 688, L2; El-Badry https://arxiv.org/pdf/2404.13047v2; Iorio et al. https://arxiv.org/pdf/2404.17568). We now report an upper limit of ~2.3 uJy/beam at 15 GHz (12-18 GHz, Ku-band continuum) radio emission from GAIA BH3 or its companion, at (proper motion corrected J2000) R.A. 19:39:18.6700 Dec. +14:55:50.191, determined in the VLA B-array configuration. Our 41h of filler observations in B-array during 2024-08-23 to 2024-09-16 resulted in about 26h05m on-source time, achieving a noise level of about 0.64 uJy/beam. We do not detect any significant radio emission, i.e., more than 3.5 sigma, in the direct vicinity of GAIA BH3, either in the combined data nor during each of the 18 (higher noise) individual 1-4 hour wideband continuum observations. Future observations, presumably when the companion is near its periapsis/peribothron in 2030 or with more sensitive new instruments like the ngVLA, would yield the best opportunity to determine the existence of radio emission of GAIA BH3 and/or its binary companion. We thank the NRAO Exploratory DDT reviewers and VLA schedulers for supporting this endeavor with a generous allocation of filler time. -- [*] https://great.ast.cam.ac.uk/Greatwiki/GreatMeet-PM17?action=AttachFile&do=view&target=EAS2024-S4-Panuzzo.pdf