//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31619 SUBJECT: ZTF22aabjpxh/AT2022cva: ZTF Discovery of a Rapidly Fading Transient with a Likely Long-GRB Counterpart DATE: 22/02/21 04:13:18 GMT FROM: Anna Ho at UC Berkeley Anna Y. Q. Ho (UCB), Daniel Perley (LJMU), Igor Andreoni (JSI), Mansi Kasliwal (Caltech), Dmitry Svinkin (Ioffe Institute), Aaron Tohuvavohu (U. Toronto), Harsh Kumar (IITB) on behalf of the Zwicky Transient Facility (ZTF) collaboration: We report the discovery of ZTF22aabjpxh (AT2022cva), a rapidly fading red transient located at 16:03:39.35 +31:14:04.72 (J2000) 240.9139656, 31.2346451 (J2000) first detected as part of the ZTF partnership survey. The source was discovered on JD 2459630.0001 at r=16.59 ± 0.01 mag, which was 0.98 days after the last non-detection (r>19.34). The transient position is 2'' from a galaxy in SDSS with a photometric redshift of 0.25 ± 0.05. Due to the rapid rise of almost 3 magnitudes in one day, and the possible high luminosity, we triggered follow-up photometry with the Spectral Energy Distribution Machine (SEDM) on the 60-inch telescope at Palomar Observatory (P60). SEDM photometry obtained the night after discovery established a rapid fade rate of 2.25 magnitudes in 0.88 days as well as red colors (g-r=0.41 ± 0.08, corrected for Galactic extinction). The transient was also detected as part of the ZTF public survey that night, and the rapid fade triggered the ZTFReST pipeline (Andreoni & Coughlin et al. 2021). Konus-Wind detected a long-duration GRB at UT 2022-02-19 09:27:25.350 that is consistent with the position of AT2022cva. The GRB burst time is 2.5 hours before the first ZTF detection. The GRB was also weakly detected by BAT. The ZTF optical position was outside the coded BAT FoV at the time of the burst, and the observed counts are consistent with a relatively soft burst coming from outside the BAT field of view. The Konus-BAT IPN annulus is consistent with the position of the ZTF transient, and the association is highly likely. We conclude that AT2022cva is the likely afterglow to the Konus-Wind GRB. Given the possible low redshift (z~0.3) continued photometric and spectroscopic observations are encouraged. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, IN2P3, University of Warwick, Ruhr University Bochum and Northwestern University. Operations are conducted by COO, IPAC, and UW. -- Anna Ho //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31624 SUBJECT: IPN triangulation of GRB 220219B (consistent with ZTF22aabjpxh/AT2022cva) DATE: 22/02/21 18:38:56 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, and S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report: The long-duration GRB 220219B has been detected by Konus-Wind (KW) and Swift (BAT), so far, at about 34045 s UT (09:27:25). The burst was outside the coded field of view of the BAT. We have triangulated it to a Konus-BAT annulus centered at RA(2000)=314.433 deg (20h 57m 44s) Dec(2000)=-14.987 deg (-14d 59' 15"), whose radius is 83.789 +/- 1.439 deg (3 sigma). This localization may be improved. The position of the optical transient ZTF22aabjpxh/AT2022cva (Ho et al., GCN Circ. 31619) is inside the annulus at 0.46 deg from its center line. The OT position is consistent with the Swift-BAT detection, Fermi-GBM non-detection, and the KW ecliptic latitude response. The positional and temporal coincidence of this burst with the OT supports the conclusion that the OT is the GRB counterpart. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB220219_T34045/IPN The time history and spectrum will be given in forthcoming GCN Circulars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31628 SUBJECT: ZTF22aabjpxh/AT2022cva: Assy optical observations DATE: 22/02/22 00:16:49 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Kim (FAI, HSE), A. Pozanenko (IKI), M. Krugov (FAI), I. Reva (FAI), N. Pankov (HSE, IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN: We observed ZTF22aabjpxh/AT2022cva transient (Ho et al., GCN 31619) what is considered the likely afterglow of GRB 220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624) with AZT-20 telescope of Assy-Turgen observatory starting on 2022-02-21 (UT) 19:44:30. We clearly detect the SDSS galaxy at photo_z = 0.248 (Ho et al., GCN 31619). Due to non-optimal seeing (FWHM of about 2.4") we could not discriminate the afterglow source from the galaxy. We use aperture photometry and preliminary photometry (AB) of a source (afterglow+host galaxy) is following Date UT start JD Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2022-02-21 19:44:30 2459632.327 40*60 r' 19.20 0.03 22.1 2022-02-21 21:57:59 2459632.416 40*60 r' 19.45 0.02 22.7 The photometry is based on nearby PS1 stars id r J160337.10+311328.5 16.987 J160343.10+311452.9 18.700 The photometry of the the source is brighter than reported either in PS1 or SDSS DR12, and source is variable. We can conclude that the afterglow is detected and dominate over host galaxy brightness. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31629 SUBJECT: ZTF22aabjpxh/AT2022cva: GMOS-N spectroscopy DATE: 22/02/22 02:00:06 GMT FROM: Anna Ho at UC Berkeley C. Fremling (Caltech), D. Perley (LJMU), A.Y.Q. Ho (UCB), report on behalf of the ZTF collaboration We obtained spectroscopy of ZTF22aabjpxh/AT2022cva (A.Y.Q. Ho et al. AstroNote 2022-45) with the Gemini Multi-Object Spectrographs (GMOS-N) mounted on the Gemini-North 8-meter telescope on Mauna Kea, under our ToO program GN-2022A-Q-127 (PI: Ho). We obtained 2x450 second exposures using the B600 grating and 2x450 second exposures using the R400 grating, starting 2022-02-21 14:04 UTC. Data reduction was performed with the Gemini iraf package, and we report the detection of host-galaxy emission lines at z=0.293. We simultaneously detect narrow emission from H-alpha, H-beta, NII, SII, OII and [OIII]. We thank the observers and the Gemini staff for their rapid response in facilitating this Target of Opportunity observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31635 SUBJECT: ZTF22aabjpxh/AT2022cva: NICER X-ray detection is consistent with a GRB afterglow DATE: 22/02/22 17:27:01 GMT FROM: Dheeraj R. Pasham at Mass. Inst. of Technology Dheeraj Pasham (MIT), Keith Gendreau (NASA/GSFC), Elizabeth Ferrara (NASA/GSFC), Anna Ho (UC Berkeley) NICER observed the rapidly fading transient AT2022cva (Ho et al. GCN 31619) for 2.4 ks starting at 2022-02-21T22:56:03. X-rays are clearly detected above the background in the 0.3-5.0 keV band with a mean background-subtracted count rate of 0.92+-0.02 counts/seconds. We fit the 0.3-5 keV X-ray spectrum with a redshifted powerlaw modified by neutral absorption in Milkway and host galaxy (tbabs*ztbabs*zpow in XSPEC). Using a Galactic nH value for tbabs (0.023e22 cm^2; HI4PI Collaboration, Bekhti et al. 2016) and a redshift of 0.293 (Fremling et al., GCN 31619) gives a good fit with a c-stat/degrees of freedom of 57/57. The best-fit power law index and host column density values are 1.36(+0.14,-0.12) and <5e20 cm^-2, respectively. The 0.3-5 keV observed flux is (2.24+-0.07)e-12 erg/s/cm^2. This corresponds to an observed luminosity of 5.04(+0.03,-0.33)e44 erg/s at a redshift of 0.293, which is typical for a GRB afterglow at a similar phase. NICER can carry out prompt follow-up observations of transients and is planning to systematically follow up alerts from LIGO/Virgo and other X-ray bright extra-galactic transients in the future. NICER is a 0.2-12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31639 SUBJECT: ZTF22aabjpxh/AT2022cva: 1.5m OSN optical observation DATE: 22/02/22 20:58:41 GMT FROM: Youdong HU at IAA-CSIC Y.-D. Hu, A. Sota, T.-R. Sun, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado and E. Fernandez-Garcia (IAA-CSIC), on behalf of a larger collaboration, report: Following the detection of ZTF22aabjpxh/AT2022cva reported by ZTF (Ho et al., GCN 31619) and NICER (Pasham et al. GCNC 31635) which could be consistent with GRB220219B (Svinkin et al. GCNC 31624), images in BVRI bands were obtained at the 1.5m OSN telescope in Granada (Spain) starting on 22 Feb. 2022 at 01:49:51 UT. In single exposures (R-band, 90 s), we measure R = 19.80+-0.13 at 02:22 UT for the above-mentioned optical transient lying at the edge of the nearby galaxy at redshift z = 0.293 as reported by Gemini-North (Fremling et al. GCNC 31629). This detection is consistent with the report from Assy-Turgen (Kim et al. GCNC 31628). We thank the staff at OSN for their excellent support. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31643 SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): Mondy optical observations DATE: 22/02/23 22:36:04 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI, HSE), A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP) report on behalf of GRB IKI FuN: We observed ZTF22aabjpxh/AT2022cva discovered by ZTF (Ho et al., GCN 31619) with AZT-33IK telescope of Mondy observatory on 2022-02-21 and 2022-02-22. ZTF22aabjpxh/AT2022cva was observed also in optic (Kim et al., GCN 31628; Hu et al., GCN 31639) and in X-ray by NICER (Pasham et al., GCN 31635). ZTF22aabjpxh/AT2022cva is considered the likely afterglow of GRB 220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624). We clearly detect the SDSS galaxy at z=0.293 (Fremling et al., GCN 31629). Due to non-optimal seeing we could not discriminate the afterglow from the galaxy. We use aperture photometry and preliminary photometry of a source (afterglow+host galaxy) is following Date UT start JD Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2022-02-21 19:30:32 2.43966 30*120 R 19.19 0.03 22.8 2022-02-22 19:31:06 3.43936 29*120 R 19.34 0.03 22.8 The photometry is based on nearby SDSS DR12 stars id r R(Lupton) V(Lupton) J160337.10+311328.5 16.987 16.79 17.19 J160343.10+311452.9 18.700 18.51 18.90 Assuming the host galaxy has R = 19.7 we subtract a host galaxy flux from a flux of the source (afterglow+host galaxy) and estimated power law index of a light curve of the afterglow as -1.2, which is typical for a GRB afterglow. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31683 SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): continued optical observations, SN signature search DATE: 22/03/05 10:45:37 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI, HSE), A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP), I. Reva (FAI), V. Kim (FAI) report on behalf of GRB IKI FuN: We are continuing observations of ZTF22aabjpxh/AT2022cva discovered by ZTF (Ho et al., GCN 31619) with AZT-33IK telescope of Mondy observatory and Zeiss-1000 on 2022-02-21 between 2022-02-23 and 2022-03-04, i.e. upt 13.4 days after GRB 220219B trigger. ZTF22aabjpxh/AT2022cva was observed in optic (Kim et al., GCN 31628; Hu et al., GCN 31639) and in X-ray by NICER (Pasham et al., GCN 31635) and XRT/Swift (Beardmore et al., GCN 31644). ZTF22aabjpxh/AT2022cva is considered the likely afterglow of GRB 220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624; Tsvetkova et al., GCN 31646). We clearly detect the SDSS galaxy at z=0.293 (Fremling et al., GCN 31629). Due to non-optimal seeing we could not discriminate the afterglow from the galaxy. We use aperture photometry of a source (afterglow + host galaxy). Based on our preliminary photometry we plot a light curve of the source, see upper panel of the Figure in http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png To estimate power law index of the afterglow we fit our photometric data by a single power law + constant host galaxy flux. The host galaxy fit is R = 19.68+/-0.05 and PL index alpha = -1.75+/-0.4. The light curve of the afterglow after subtraction of a flux of the host is presented at bottom panel of the Figure in http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png Power Law index is broadly compatible with the index of -1.6 obtained in XRT observations up to ~8 days, see XRT light curve at https://www.swift.ac.uk/xrt_live_cat/00021481/ We may conclude the source ZTF22aabjpxh/AT2022cva is the optical afterglow of GRB 220219B. Since the redshift of GRB 220219B (ZTF22aabjpxh/AT2022cva) is z=0.293 (Fremling et al., GCN 31629) we are searching for a supernova signature. Based on the Figure referenced above we still don't see any conclusive evidence for the existence of SN. We urge further multicolour observations to confirm/search for SN associated with GRB 220219B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31720 SUBJECT: ZTF22aabjpxh/AT2022cva: AMI-LA radio observation DATE: 22/03/09 13:44:36 GMT FROM: Lauren Rhodes at Oxford L. Rhodes (Oxford/MPIfR), R. Fender (Oxford/UCT) and D.R.A. Williams (JBCA) report: We observed ZTF22aabjpxh/AT2022cva (Ho et al., GCN 31619) with the Arcminute Microkelvin Imager - Large Array at 15.5GHz. The observation was made on 27th February 2022 at 04:42UT and lasted 4 hours. We detect a point source at the position of ZTF22aabjpxh with a flux density of 490+/-30uJy. The noise in the field is 34uJy. Subsequent observations show that the source is fading. We thank the staff at the MRAO for scheduling these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31736 SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): continued optical observations, possible photometric evidence of SN DATE: 22/03/11 02:03:18 GMT FROM: Alexei Pozanenko at IKI, Moscow S. Belkin (IKI, HSE), A. Pozanenko (IKI), E. Klunko (ISTP), A. Moskvitin (SAO RAS), R. Ya. Inasaridze (AbAO), N. Pankov (HSE), V. Kim (HSE, FAI), I. Reva (FAI), on behalf of GRB IKI FuN, and A. Rossi (INAF-OAS) report: We are continuing observations of ZTF22aabjpxh/AT2022cva discovered by ZTF (Ho et al., GCN 31619) with AZT-33IK telescope of Mondy observatory, AS-32 telescope of Abastumani observatory, and Zeiss-1000 telescope of SAO RAS between 2022-02-24 and 2022-03-09. ZTF22aabjpxh/AT2022cva was observed in optic (Kim et al., GCN 31628; Hu et al., GCN 31639; Belkin et al., GCNs 31643, 31683) and in X-ray by NICER (Pasham et al., GCN 31635) and XRT/Swift (Beardmore et al., GCN 31644). ZTF22aabjpxh/AT2022cva is considered an afterglow of GRB 220219B (Ho et al., GCN 31619; Svinkin et al., GCN 31624; Tsvetkova et al., GCN 31646; Belkin et al., GCN 31683). We clearly detect the SDSS galaxy at z=0.293 (Fremling et al., GCN 31629). Due to non-optimal seeing we could not discriminate the afterglow from the galaxy. We use aperture photometry of a source (afterglow + host galaxy). Based on our preliminary photometry we plot a light curve of the source, see an upper panel of the Figure in http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png To estimate power law index of the afterglow we fit our photometric data by a single power law + constant host galaxy flux between start of our observations and up to 13.4 days after GRB 220219B trigger. The host galaxy fit is R = 19.68+/-0.05 and PL index alpha = -1.75+/-0.4 (Belkin et al., GCN 31683). The light curve of the afterglow after subtraction of a flux of the host is presented at the bottom panel of the Figure in http://grb.rssi.ru/GRB220219B/GRB220219B_AT2022cva_LC.png Starting on ~15.5 days the light curve is rising above afterglow approximation by the single power law and we consider it as a possible evidence of rising supernova. We urge further spectroscopic and multicolour observations to confirm for SN associated with GRB 220219B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31739 SUBJECT: ZTF22aabjpxh/AT2022cva (GRB 220219B): evidence of supernova in LBT spectra DATE: 22/03/11 14:41:55 GMT FROM: Andrea Rossi at INAF A. Rossi, E. Pian, F. Cusano, E. Maiorano, E. Palazzi (INAF-OAS) on behalf of the CIBO collaboration, and S. Belkin (IKI, HSE) report : We report the results of the spectroscopic follow-up observations of ZTF22aabjpxh/AT2022cva, the afterglow of GRB 220219B (Ho et al., GCN 31619; Kim  et al., GCN 31628; Hu et al., GCN 31639; Belkin et al., GCNs 31643, 31683; Pasham et al., GCN 31635; Beardmore et al., GCN 31644; Tsvetkova et al., GCN 31646) at z=0.293 (Fremling et al., GCN 31629). The optical spectra were obtained with the Multi-Object Double Spectrographs (MODS) instrument mounted on the 2x8.4-m LBT telescope (Mt. Graham, AZ, USA) at ~11 UT on 2021-03-07, ~16 days (i.e. ~12 rest-frame days) after the burst trigger. The spectra covers the wavelength range 3200-10000 AA, and we obtained a total of 6 exposures of 900s. The resulting spectrum has been corrected for Galactic extinction (A_V = 0.025 mag). The slit was place in order to cover both the host galaxy and the GRB position. In addition to the host spectra, a second trace is well visible in the 2D image of the spectrum although superimposed to the one of the host galaxy. Its low S/N extracted spectrum shows features similar to those exhibited by XRF-associated SN2006aj at a similar phase (Mazzali et al. 2006, Nature, 442, 1018). This confirms the bump observed by Belkin et al. (GCN 31736) as due to the emerging contribution of the SN. We acknowledge the excellent support from the LBTO, in particular B. Rothberg and J. Williams, and from the LBT-INAF, particularly E. Marini in obtaining these observations.