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GCN Circular 33812

GRB 230513A: Zwicky Transient Facility continuous observations of a Fermi Short GRB (Trigger 705709044)
2023-05-18T04:32:06Z (21 days ago)
Tomas Ahumada at U. of Maryland <>
Tomas Ahumada (CIT), Viraj Karambelkar (CIT), Robert Stein (CIT), Harsh Kumar (IITB), Vishwajeet Swain (IITB), Anirudh Salgundi (IITB), Aswin Suresh (IITB), Theophile du Laz (CIT), Igor Andreoni (UMD), Michael Coughlin (UMN), Mansi Kasliwal (CIT), Varun Bhalerao (IITB), Simeon Reusch (DESY), Jannis Necker (DESY), Shreya Anand (CIT), report on behalf of the ZTF collaboration: We re-observed the localization region of the short GRB 230513A (trigger 705709044, GCN 33793) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite with the Palomar 48 inch telescope equipped with the 47 square degree Zwicky Transient Facility (ZTF) camera. We obtained a series of g- and r-band images beginning at 29 and 77 hours after the burst trigger time. For the first epoch of observations we covered 619.3 square degrees corresponding to ~82% of the probability region and reaching a median depth of 21.85 mag in the 300 sec r-band exposures, 22.36 mag in the 450 sec r-band exposures, and 21.82 mag in the 300 sec g-band exposures. For the second epoch ZTF covered 671.9 square degrees, corresponding to ~85% of the region, and reaching a median depth of 21.71 mag in 300 sec r-band exposures. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019). We queried the ZTF alert stream using Kowalski (Duev et al. 2019) through Fritz (Coughlin et al. 2023) and AMPEL (Nordin et al. 2019). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-match our candidates with the Minor Planet Center to flag known asteroids, reject stellar sources (Tachibana and Miller 2018), and apply machine learning algorithms (Mahabal et al. 2019). We require that no spatially coincident ZTF alerts were issued before the detection time of the GBM trigger. Close to 200 sources were time and spatially coincident with the burst. No source showed a photometric evolution consistent with a GRB afterglow, including the ones circulated on GCN 33801. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski (Duev et al. 2019). GROWTH India telescope is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). GROWTH-India project is supported by SERB and administered by IUSSTF, under grant number IUSSTF/PIRE Program/GROWTH/2015-16 and IUCAA. -- Tomás Ahumada (he/him) Ph.D. Candidate Department of Astronomy University of Maryland, College Park NASA <> Goddard Space Flight Center, Code 661 B.Sc. Astronomy, Pontificia Universidad Católica de Chile
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