February 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 37206] LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39197 SUBJECT: LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm DATE: 25/02/07 09:41:10 GMT FROM: kendall.ackley(a)warwick.ac.uk K. Ackley, S. Belkin, D. Steeghs, B. P. Gompertz, Y. Julakanti, M. Kennedy, B. Godson, G. Ramsay, D. O'Neill, M. Dyer, F. Jiménez-Ibarra, J. Lyman, K. Ulaczyk, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, L. Nuttall, E. Pallé, D. Pollacco, T. Killestein, and A. Kumar report on behalf of the GOTO collaboration: We are in the process of observing the LIGO/Virgo gravitational wave event S250206dm (GCN 39175; GCN 39178) with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022). Targeted observations with GOTO-N were performed beginning at Feb. 6 2025 21:31:11 UT, (+0.09h post trigger) and continued through to Feb. 7 2025 04:07:48 UT (+6.71h post trigger). GOTO covered the field of AT 2025azn (Hosseinzadeh et al, GCN 39191) at 22:25:45UT on 2025-02-06 (~1 hour after trigger, and 6 hours prior to the reported detection by Hosseinzadeh et al, GCN 39191) as part of the follow-up campaign for S250206dm. The observation consisted of a 4x90s exposure set in the GOTO L-band (400-700 nm). Analysis at the location of the potential optical transient does not show evidence of the source to a 3-sigma limiting AB magnitude of L > 19.8. Our previous observation of the field of AT 2025azm (Hosseinzadeh et al, GCN 39191) occurred on 2025-01-27. We do not see any evidence of excess flux down to a 3-sigma limiting AB magnitude of L > 19.0. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. Further observations are scheduled during the coming nights. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37205] LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39196 SUBJECT: LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations DATE: 25/02/07 09:16:25 GMT FROM: Igor Andreoni at JSI/UMD/NASA <igor.andreoni(a)gmail.com> James Freeburn (Swinburne/OzGrav), Jonathan Carney (UNC), Igor Andreoni (UNC), David Cook (IPAC): We followed up the gravitational wave trigger S250206dm (GCN 39175, GCN 39178, GCN 39184) using the Goodman High Throughput Spectrograph mounted on the SOAR telescope in imaging mode via Target of Opportunity observations (PI Andreoni). We observed 33 galaxies in the highest probability region (Cook at al. GCN 39174, GCN 39177, GCN 39185) using the list produced by crossmatching the sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023). Specifically, we considered the galaxy list obtained using the LVK S250206dm-6-Update sky localization (Cook at al. GCN 39185), focusing on the Southern high probability area. Observations were acquired from 2025-02-07 06:18 UT until 08:48 UT. Each galaxy was observed with 60s exposures in g+i filters. A list of the observed galaxies is presented in the table below. The completed pointings were uploaded to TreasureMap: https://treasuremap.space/alerts?graceids=S250206dm Data analysis is ongoing. object_name coordinates WISEA J161708.84-674024.7 16:17:08.87 -67:40:22.49 WISEA J162759.57-693615.7 16:27:59.57 -69:36:15.71 WISEA J154439.56-665529.0 15:44:39.56 -66:55:29.08 WISEA J155633.83-693531.5 15:56:33.83 -69:35:31.55 WISEA J160843.41-685023.4 16:08:43.41 -68:50:23.44 WISEA J154441.36-665502.6 15:44:41.37 -66:55:02.61 WISEA J160915.94-690504.9 16:09:15.95 -69:05:04.94 WISEA J161332.77-674621.1 16:13:32.78 -67:46:21.13 WISEA J165614.58-695645.9 16:56:14.58 -69:56:46.00 WISEA J163330.53-670950.7 16:33:30.54 -67:09:50.72 WISEA J154538.24-703944.1 15:45:38.25 -70:39:44.12 WISEA J153057.77-694546.5 15:30:57.77 -69:45:46.58 WISEA J160838.27-700230.8 16:08:38.27 -70:02:30.85 WISEA J111435.41-485220.0 11:14:35.41 -48:52:20.02 WISEA J161213.79-710729.1 16:12:13.79 -71:07:29.14 ESO 069-IG 006N 16:38:11.94 -68:26:08.84 WISEA J165744.21-680430.9 16:57:44.21 -68:04:30.93 WISEA J165527.54-702337.9 16:55:27.54 -70:23:37.91 WISEA J110452.75-455440.5 11:04:52.76 -45:54:40.57 WISEA J163202.83-693109.0 16:32:02.84 -69:31:09.01 WISEA J164922.44-690054.7 16:49:22.44 -69:00:54.76 WISEA J161735.32-701416.0 16:17:35.32 -70:14:16.00 WISEA J163253.56-702946.2 16:32:53.57 -70:29:46.22 WISEA J164915.17-690004.8 16:49:15.17 -69:00:04.87 ESO 069- G 003 16:24:32.07 -68:49:12.91 WISEA J161946.23-690837.2 16:19:46.23 -69:08:37.26 WISEA J153854.81-680647.5 15:38:54.81 -68:06:47.55 WISEA J151821.27-691417.9 15:18:21.28 -69:14:17.93 WISEA J155653.84-695749.1 15:56:53.88 -69:57:49.18 WISEA J165438.30-670413.8 16:54:38.30 -67:04:13.82 WISEA J163224.97-700239.7 16:32:24.97 -70:02:39.78 WISEA J110509.11-450337.3 11:05:09.11 -45:03:37.38 WISEA J161822.73-683741.1 16:18:22.73 -68:37:41.20 We thank the NOIRLab and SOAR staff for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/39196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37204] LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39195 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn DATE: 25/02/07 08:43:10 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> M. E. Huber (IfA, Hawaii), J. H. Gillanders (Oxford), K. C. Chambers (IfA, Hawaii) S. J. Smartt, K. W. Smith (Oxford/QUB), F. Stoppa, S. Srivastav (Oxford), D. R. Young, M. Nicholl, M. D. Fulton, M. McCollum, T. Moore, S. Sim, J. Weston, A. Aamer, C. R. Angus, X. Sheng (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), H. Stevance, A. Andersson (Oxford), L. Rhodes (TSI/McGill), A. S. B. Schultz, T. de Boer, J. Fairlamb, H. Gao, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, G. Paek, A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii), T.-W. Chen (NCU), A. Rest (STScI), and C. Stubbs (Harvard) We are currently observing the skymap of the LIGO/Virgo/KAGRA GW event S250206dm (LVK Collaboration, GCN 39175) with the twin Pan-STARRS telescope system (Chambers et al., 2016, arXiv:1612.05560) and will report detections of candidate optical transients to the TNS, and through GCNs. We also carried out targeted observations of AT2025azm and AT2025azn, two optical counterpart candidates reported by Hosseinzadeh et al., (GCN 39191). The Pan-STARRS system comprises two 1.8-m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy, and a broad w-filter, which is a composite of the gri-filters. The last Pan-STARRS observations of these fields was 69 days ago for AT2025azm, and 87 days ago for AT2025azn. There are no reliable historical detections at these positions in our database (typical limits of i<21, w<22). There are a few excess flux detections, but these are likely subtraction residuals in the cores of the host galaxies. Our targeted observations consisted of a sequence of 60 second exposures in griz filters for AT2025azm, and grizy filters for AT2025azn. Our observations of AT2025azm commenced at MJD 60713.27593 (2025-02-07 06:37:20.352 UTC), 9.20 hours after the merger event (LVK Collaboration, GCN 39175). Our observations of AT2025azn commenced at MJD 60713.28086 (2025-02-07 06:44:26.477 UTC), 9.31 hours after the merger event. The resultant images were processed with the Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target stacked images (Magnier et al., 2020a, ApJS, 251, 3; Magnier et al., 2020b, ApJS, 251, 6; Waters et al., 2020, ApJS, 251, 4). We do not detect either transient in any filter. The data were collected in poor seeing conditions (2-3 arcsec), and the 3.5 sigma limits for our 60 second exposures are: AT2025azm: g<20.1, r<20.6, i<19.9, z<19.9 AT2025azn: z<20.2, r<20.7, i<20.3, g<20.7, y<20.4 As we detect no excess flux in any of the difference images, to limits similar to (or deeper than) those reported by Hosseinzadeh et al., (GCN 39191), it suggests to us that they are not real transients. Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and NNX14AM74G, issued through the SSO Near-Earth Object Observations Program. Data processing is enabled by Queen's University Belfast and the University of Oxford, enabled through STFC grants ST/Y001605/1, ST/T000198/1 and ST/X001253/1, the Royal Society, and the Hintze Centre for Astrophysical Surveys. View this GCN Circular online at https://gcn.nasa.gov/circulars/39195. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37203] LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39194 SUBJECT: LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation DATE: 25/02/07 08:42:39 GMT FROM: Volodymyr Savchenko at UNIGE, EPFL <volodymyr.savchenko(a)epfl.ch> V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed a search for a prompt gamma-ray counterpart of S250206dm (GCN 39175). At the time of the event (2025-02-06 21:25:30 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 66 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (14% of optimal) response of ISGRI, strongly suppressed (33% of optimal) response of IBIS/Veto, and near-optimal (79% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was rather stable (excess variance 1.2). We have performed a search for any impulsive events in INTEGRAL SPI-ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~1.6e-07 (4.2e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. We report for completeness and in order of FAP, all excesses identified in the search region. We find: 1 tentatively associated excess: |T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP | |---|---|---|---|---| |-1.41 | 0.45 | 4.6 | 0.808 +/- 0.229 +/- 0.713 | 0.00626| 5 likely background excesses: |T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP | |---|---|---|---|---| |37.7 | 0.05 | 11 | 6.29 +/- 0.761 +/- 5.55 | 0.0769 | |1.01 | 0.1 | 3 | 1.17 +/- 0.49 +/- 1.03 | 0.23 | |-41.4 | 1.95 | 3.1 | 0.259 +/- 0.109 +/- 0.229 | 0.363 | |-152 | 1.4 | 3.7 | 0.352 +/- 0.129 +/- 0.31 | 0.489 | |7.46 | 0.1 | 3.4 | 1.3 +/- 0.492 +/- 1.15 | 0.699 | Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. We note that no independent IBAS alerts happened in the viscinity. SPI-ACS data can be retrieved in MMODA with [this](https://www.astro.unige.ch/mmoda/?DEC=-29.74516667&RA=265.97845833&T1=2025-02-06T21%3A24%3A30.000&T2=2025-02-06T21%3A26%3A30.000&T_format=isot&data_level=ordinary&instrument=spi_acs&product_type=spi_acs_lc&query_status=new&query_type=Real&selected_catalog=&src_name=1E+1740.7-2942&time_bin=0.05&time_bin_format=sec) link. INTEGRAL follow-up alert was distributed to SCIMMA through HERMES. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. Note that we send GCNs Circulars only when one of the following conditions is met: merger contains at least one neutron star, a singificant counterpart is reported. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S View this GCN Circular online at https://gcn.nasa.gov/circulars/39194. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37202] LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39193 SUBJECT: LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate DATE: 25/02/07 08:33:03 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Jean-Grégoire Ducoin (CPPM), Sarah Antier (OCA), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of the AT 2025azn candidate reported by the SAGUARO team (GCN Circ. 39191) as a possible optical counterpart of the GW transient S250206dm (GCN Circ. 29175, GCN Circ. 39184) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-07 06:39 to 07:27 UTC (9.24 to 10.04 hours after the GW transient), with a midpoint of 9.64 hours after the event, and obtained 840 seconds of exposure in the g filter and 840 seconds of exposure in the r filter in good weather conditions, albeit at airmass 2.1 to 2.8. The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). The FWHM in both stacks is about 2.0 arcsec. At the position of AT 2025azn, and after template subtraction using Pan-STARRS DR2 reference images, we do not detect any source at a 3 sigma limiting magnitudes of: g > 21.9 r > 21.7 Our magnitude limits are not corrected for Galactic extinction. These limits are significantly fainter than the detection reported by the SAGUARO team from observation taken about 2 hours earlier. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39193. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37201] GRB 250129A: Continued AbAO and Mondy optical observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39192 SUBJECT: GRB 250129A: Continued AbAO and Mondy optical observations DATE: 25/02/07 06:03:52 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of the IKI-GRB-FuN collaboration: We continued optical observations of the field of GRB 250129A (Beardmore et. al, GCN 39066; Lipunov et. al, GCN 39070; Schneider et. al, GCN 39071; Belkin et. al, GCN 39072; Izzo et. al, GCN 39073; Izzo et. al, GCN 39074; Ghosh et. al, GCN 39077; Schneider et. al, GCN 39078; Brivio et. al, GCN 39079; Goad et. al, GCN 39082; Siegel, GCN 39085; Osborne et. al, GCN 39089; Zheng et. al, GCN 39090; Schlekat et. al, GCN 39091; Antier et. al, GCN 39096; Odeh et. al, GCN 39097; Ferro et. al, GCN 39098; Malesani et. al, GCN 39100; Romanov, GCN 39101; Zheng et. al, GCN 39102; Watson et. al, GCN 39104; Watson et. al, GCN 39105; Akl et. al, GCN 39106; Moskvitin et. al, GCN 39107; Calapai et. al, GCN 39109; Schlekat et. al, GCN 39110; Gompertz et. al, GCN 39114; Ror et. al, GCN 39115; Frederiks et. al, GCN 39116; Wu et. al, GCN 39124; Paek et. al, GCN 39129; Moskvitin et. al, GCN 39130; Bochenek et. al, GCN 39131; Watson et. al, GCN 39136; Pankov et. al, GCN 39139; Pérez-Fournon et. al, GCN 39140; Markwardt et. al, GCN 39147) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy) and the 0.7-meter AS-32 telescope of the Abastumani Observatory (AbAO). The observations began at Mondy on 2025-02-02 at 19:46:28 UT, i.e. ~4.65 days since trigger. Using optimal image subtraction against PS1 template with apex_subtract pipeline, we detect the optical counterpart in the stacked image from Mondy, while obtaining an upper limit at AbAO. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Telescope (mid, days) (s) 2025-02-02 19:46:28 4.65439 41*120 R 21.63 0.18 23.1 AZT-33IK 2025-02-02 22:26:20 4.76923 93*60 R n/d n/d 21.8 AS-32 The photometry is based on nearby stars of the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37200] LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39191 SUBJECT: LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts DATE: 25/02/07 05:55:46 GMT FROM: Griffin Hosseinzadeh at UC San Diego <ghosseinzadeh(a)ucsd.edu> G. Hosseinzadeh, M. Shrestha, D. J. Sand, K. A. Bostroem, J. E. Andrews, B. Subrayan, J. Pearson, J. C. Rastinejad, M. J. Lundquist, C. D. Kilpatrick, W. Fong, K. Alexander, P. N. Daly, N. Franz, K. Paterson, S. D. Wyatt, J. Hogan, A. Gibbs, C. Fuls report on behalf of the SAGUARO collaboration: We initiated observations of the localization region of the possible NSBH merger S250206dm (LVK Collaboration, GCN 39175) using the 5 square degree imager mounted on the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ (Christensen et al. 2018). We observed 180 sq. deg. within the 95% confidence localization region of the Bilby map (LVK Collaboration, GCN 39178) starting at 2025-02-07 02:10:58 UTC (~5 hours after the merger). We subtract these images relative to deep reference images of each field and measure photometry calibrated to the Gaia DR2 catalog (Gaia Collaboration 2018). We performed a real-time analysis of the observations. Following the methods outlined in Rastinejad et al. (2022), we crossmatch each candidate with the TNS (Gal-Yam 2021) and point source catalogs (Tachibana and Miller 2018; Jayasinghe et al. 2019; Flesch et al. 2021; Gaia Collaboration 2023), search public ZTF photometry (Bellm et al. 2019), and run ATLAS forced photometry (Shingles et al. 2021) at the position of the candidate to rule out transients unrelated to the GW event. We determine a most likely host galaxy using the probability of chance coincidence method (Bloom et al. 2002) and search for an associated spectroscopic or photometric redshift in public galaxy catalogs (White et al. 2011; Alam et al. 2015; Beck et al. 2016, 2021; Dalya et al. 2021; DESI Collaboration et al. 2023). We discovered two possible transients in our images and reported them to the Transient Name Server. AT 2025azm (00:08:07.507 +32:33:56.70; 20.1 +/- 0.3 mag) is 1” from the center of a galaxy with a photometric redshift of z=0.07, corresponding to a distance of around 300 Mpc, in the Legacy Survey (Dey et al. 2019), SDSS (Alam et al. 2015), and Pan-STARRS1 (Chambers et al. 2016) catalogs. AT 2025azn (02:39:17.418 +49:34:21.10; 20.0 +/- 0.3 mag) is 0.5” from the center of a galaxy with a distance of 377 Mpc (z=0.08) in the GLADE catalog (Dalya et al. 2018). Both are consistent with the gravitational-wave distance within the error range. We encourage follow-up photometry and spectroscopy of both these candidates. Our analysis is ongoing. SAGUARO stands for Searches After Gravitational-waves Using ARizona's Observatories (Lundquist et al. 2019; Paterson et al. 2021; Hosseinzadeh et al. 2024). It is a partnership between the University of Arizona, Northwestern University, and the University of California, San Diego. View this GCN Circular online at https://gcn.nasa.gov/circulars/39191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37199] GRB 250207B: MAXI/GSC detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39190 SUBJECT: GRB 250207B: MAXI/GSC detection DATE: 25/02/07 04:26:02 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Tatano, M. Nakajima, H. Negoro (Nihon U.), M. Serino, Y. Kawakubo (AGU), Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.),　 M. Sugizaki (Kanazawa U.),　W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 02:23:36 UT on February 07, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (54.362 deg, 5.325 deg) = (03 37 26, +05 19 30) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.27 deg and 0.24 deg, respectively. The roll angle of long axis from the north direction is 124.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 218 +- 41 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (53.893, 6.160) deg = (03 35 34, +06 09 36) (J2000) (R.A., Dec) = (53.522, 5.823) deg = (03 34 05, +05 49 22) (J2000) (R.A., Dec) = (54.372, 4.895) deg = (03 37 29, +04 53 41) (J2000) (R.A., Dec) = (54.743, 5.230) deg = (03 38 58, +05 13 48) (J2000) There was no significant excess flux in the previous transit at 00:50 UT and in the next transit at 03:56 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/39190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37198] The EP-WXT trigger 01709131347 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39189 SUBJECT: The EP-WXT trigger 01709131347 is likely a flaring star DATE: 25/02/07 03:52:30 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Shui (IHEP, CAS), D. Y. Li, M. J. Liu, M. H. Zhang, W. D. Zhang (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131347) on 2025-02-06 23:24:12 (UTC) is likely a stellar flare associated with a spectroscopic binary G 118-68. The estimated flux of the flare is around 1.0 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.5 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37197] The EP-WXT trigger 01709131332 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39188 SUBJECT: The EP-WXT trigger 01709131332 is likely a flaring star DATE: 25/02/07 03:50:53 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. H. Zhang, M. J. Liu, D. Y. Li (NAOC, CAS), Q. C. Shui (IHEP, CAS), W. D. Zhang (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131332) on 2025-02-06 20:25:17 (UTC) is likely a stellar flare associated with a high proper motion star UPM J1217-3644. The estimated flux of the flare is around 1.2 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.2 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39188. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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