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

[vsnet-grb-info 37476] EP250223a: Kinder optical follow-up observations
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39464 SUBJECT: EP250223a: Kinder optical follow-up observations DATE: 25/02/25 01:49:48 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan (NCU), A. K. H. Kong (NTHU), T.-W. Chen, W.-J. Hou, H.-Y. Hsiao (all NCU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, C.-S. Lin, J.-K. Guo (all NCU), S. Yang, L. L. Fan, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP250223a (Lian et al., GCN 39429) using the 40cm SLT telescope and Lulin One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first SLT epoch of observations in the i-band started at 12:00:02 UT on the 24th of February 2024 (MJD = 60730.500), 20.92 hrs after the EP trigger. The first LOT epoch of observations in the r-band started at 14:42:53 UT on the 24th of February 2024 (MJD = 60730.613), 23.64 hrs after the EP trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked images, we clearly detected the optical counterpart candidate proposed by Hauptmann et al. (GCN 39436) and confirmed by several other observations (e.g., Levan et al al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Ducoin et al., GCN 39453; and O’Neill et al., GCN39455). We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on our stacked frames. The details of the observations and measured photometry (in the AB system) are as follows: --------------------------------------------------------------------------------------------------------------------------- Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | i | 60730.500 | 20.92 | 300 * 24 | 19.23 +/- 0.03 | 2".06 | 1.51 LOT | r | 60730.613 | 23.64 | 300 * 6 | 19.79 +/- 0.01 | 1".43 | 2.10 The presented magnitudes were calibrated using the field stars from the Pan-STARRS1 catalog and were not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_i = 0.16 mag and A_r = 0.22 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39464. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37475] GRB 250207a: ATCA Radio Upper Limits
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39463 SUBJECT: GRB 250207a: ATCA Radio Upper Limits DATE: 25/02/25 01:32:43 GMT FROM: agul8829(a)uni.sydney.edu.au A. Gulati (USyd), G. E. Anderson (Curtin), S. Chastain (UNM), A. J. van der Horst (GWU), J. K. Leung (UofT/HUJI), and L. Rhodes (TSI/McGill) on behalf of the ATCA PanRadio GRB collaboration We observed Swift and Fermi-detected GRB 250207A (Ferro et al., GCN 39182; Fermi GBM Collaboration, GCN 39181) as part of The Australia Telescope Compact Array (ATCA) "PanRadio GRB" Large Project C3542 (PI: G. Anderson) at 5.5 and 9 GHz on 2025-02-12, 2025-02-14 and 2025-02-21. No radio sources were detected near the Swift/XRT enhanced position (Osborne et al., GCN 39217 )in any of the observation epochs. The 3-sigma upper limits for the 9 GHz observations are 174, 96, and 60 uJy respectively. We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO. View this GCN Circular online at https://gcn.nasa.gov/circulars/39463. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37474] LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39462 SUBJECT: LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates DATE: 25/02/24 22:36:16 GMT FROM: Isaac McMahon at University of Zürich <isaac.mcmahon(a)ligo.org> I. McMahon (UZH), S. MacBride (UZH), H. T. Diehl (FNAL), S. Kaur (UZH), L. Joseph (Benedictine U.), N. Sherman (Boston U.), K. Herner (Fermilab), M. Soares-Santos (UZH), reporting on behalf of the Dark Energy Survey Gravitational Wave (DESGW) Team: At 03:45:38 UTC, the Dark Energy Camera (DECam) began observing in response to the joint LVK/Swift-BAT RAVEN alert issued for the candidate gravitational-wave event S250223dk (GCN 39443). We observed two fields centered on the following ICRS coordinates (85.80,-47.60) (85.83,-47.63) Both fields were observed in DECam g, r, i, and z filters with 360 second exposures. The limiting magnitude achieved is 23.36 in r-band. Images were processed by our difference imaging pipeline (Herner et al. 2020) using DES and public DECam images as templates. We employ the autoscan machine learning code (Goldstein et al. 2015) to reject subtraction artifacts. Candidates were initially selected by requiring at least two high signal to noise detections, which were separated in time in order to reject moving objects. We also require an autoscan score of at least 0.7 on at least one of those detections. After candidate selection, we report five high confidence candidates (listed below). After vetting and identification, four candidates were classified as nuclear candidates (likely AGNs), one candidate (2017239) has been labeled as a possible supernova. All candidates have a host galaxy match within 1 arcsecond. None of the candidate hosts are included in the ALLWISE and MILLIQUAS AGN catalogs (Secrest et. al 2015, Flesch 2023). No other candidates were found in the area. We encourage followup of the five candidates identified herein. | id | AT name | ra | dec | discovery_date (UT) | mag_g | mag_g_err | mag_r | mag_r_err | mag_i | mag_i_err | mag_z | mag_z_err | | --------------- | ---------- | ---------- | ---------- | ----------------------- | ------ | ----- | ------ | ----- | ------ | ----- | ------ | ----- | | 2014974 | AT2025cpl | 86.327994 | -47.827215 | 2025-02-24 03:45:38.271 | 22.487 | 0.043 | 22.151 | 0.031 | 21.744 | 0.053 | 21.894 | 0.106 | | 2014991 | AT2025cpm | 86.516403 | -47.893872 | 2025-02-24 03:45:38.271 | 23.448 | 0.107 | 22.905 | 0.060 | 22.453 | 0.103 | 22.308 | 0.153 | | 2015571 | AT2025cpo | 86.105565 | -47.689987 | 2025-02-24 03:45:38.271 | 22.972 | 0.053 | N/A | N/A | 22.423 | 0.084 | 22.765 | 0.203 | | 2015600 | AT2025cpp | 86.176728 | -47.763957 | 2025-02-24 03:52:10.108 | 21.980 | 0.024 | N/A | N/A | 22.097 | 0.061 | 22.312 | 0.132 | | 2017239 | AT2025cpq | 85.552523 | -47.577823 | 2025-02-24 03:58:42.138 | 24.503 | 0.268 | 23.980 | 0.161 | 23.972 | 0.320 | 24.265 | 0.851 | The DECam Search & Discovery Program for Optical Signatures of Gravitational Wave Events (DESGW) is carried out by the Dark Energy Survey (DES) collaboration in partnership with wide ranging groups in the community. DESGW uses data obtained with the Dark Energy Camera (DECam), which was constructed by the DES collaboration with support from the Department of Energy and member institutions, and utilizes data as distributed by the Science Data Archive at NOIRLAB. NOIRLAB is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank the Cerro Tololo observatory staff for their support in acquiring these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39462. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37473] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39461 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations DATE: 25/02/24 19:45:19 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi-GBM Team: For S250223dk and the Swift/BAT-GUANO ID 762004910 (The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration along with the Swift/BAT-GUANO team, GCN 39443) and using the combined skymap combined-ext.multiorder.fits,3, Fermi-GBM was observing 100% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S250223dk, neither for the Swift/BAT-GUANO trigger ID 762004910. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. Part of the joint localization region is behind the Earth for Fermi, located at RA=267.1, Dec=-5.5 with a radius of 68.0 degrees. We therefore set upper limits on impulsive gamma-ray emission for the joint localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by the joint LVK-Swift/BAT localization probability (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 2.00 2.90 6.40 1.024 s: 0.69 0.95 1.90 8.192 s: 0.23 0.32 0.63 Assuming the median luminosity distance of 6033 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128s: 14.15 16.94 64.06 1.024s: 4.88 5.55 19.02 8.192s: 1.63 1.87 6.31 View this GCN Circular online at https://gcn.nasa.gov/circulars/39461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37472] GRB 250119B: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39460 SUBJECT: GRB 250119B: VZLUSAT-2 detection DATE: 25/02/24 18:21:07 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250119B (FERMI/GBM detection: GCN 38979; INTEGRAL/SPI-ACS detection: GCN Circular 38997; Swift/BAT-GUANO detection: GCN 39007; Konus/Wind detection: GCN 39016; NuSTAR detection at 2025-01-19 08:27:23 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2025-01-19 08:27:44 UTC. The T90 duration is 41 s and the significance during T90 reaches 66 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250119B_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39460. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37471] GRB 250223C: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39459 SUBJECT: GRB 250223C: Fermi GBM Final Real-time Localization DATE: 25/02/24 17:27:23 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 16:18:20 UT on 23 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250223C (trigger 762020305.175056 / 250223679). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 262.6, Dec = 41.0 (J2000 degrees, equivalent to J2000 17h 30m, 41d 00'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 41.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39459. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37470] GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39458 SUBJECT: GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert DATE: 25/02/24 16:54:52 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, B. P. Gompertz, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the joint LVK/Swift-BAT RAVEN alert (LIGO, Virgo, KAGRA and Swift/BAT-GUANO teams, GCN 39443). Targeted observations of the combined 90% credible region (using the combined-ext.multiorder.fits,2 skymap) were performed by GOTO-South between 2025-02-24 09:41:31 UT (+21.67h) and 2025-02-24 13:18:31 (+25.28h) UT. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. 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. In the 5 arcmin circle centred at RA = 85.341, Dec = -47.544, containing 52% of the integrated joint probability (LIGO, Virgo, KAGRA and Swift/BAT-GUANO teams, GCN 39443), no credible counterpart candidates are identified to a 3-sigma limiting magnitude of L > 21.1 mag. Furthermore, no candidate optical counterparts are identified within the <1 deg2 combined 90% LVK+Swift/BAT-GUANO credible region. In addition to the targeted response, serendipitous imaging from the all-sky survey was obtained for the 90% credible region defined by the NITRATES search, starting from 2025-02-23 12:03:34 UT (+0.04h). This resulted in a total coverage of 1621 deg^2 within the 90% localisation contour of Swift/BAT-GUANO, corresponding to ~41.6% of its total 2D localisation probability. No credible optical counterparts were identified within this region. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. 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/39458. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37469] GRB 250202B: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39457 SUBJECT: GRB 250202B: VZLUSAT-2 detection DATE: 25/02/24 15:10:59 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250202B (FERMI/GBM: GCN Circular 39120; AstroSat/CZTI: GCN Circular 39122; NuSTAR detection: GCN 39135; Konus/Wind detection: GCN 39149; CALET/CGBM detection: trigger no. 1422503847; INTEGRAL/SPI-ACS peak detection at 2025-02-02 ~03:57:20 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2025-02-02 03:57:18 UTC. The T90 duration is 87 s and the significance during T90 reaches 80 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250202B_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39457. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37468] GRB 250219A: EP-FXT afterglow detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39456 SUBJECT: GRB 250219A: EP-FXT afterglow detection DATE: 25/02/24 14:43:44 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA), P. Y. Han, C. X. Zhang (HUST), J. Yang (NJU), X. Tian (GXU), D. F. Hu (PMO, CAS), W. Chen (NAO, CAS), J. Guan, C. K. Li, Y . Chen, S. M. Jia, W. W. Cui, D. W. Han, W. Li, C. Z. Liu, F . J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F . Zhao (IHEP , CAS), Y . Liu, C. C. Jin, C. Zhang, Z. X. Ling (NAOC,CAS), B. Cordier (CEA) on behalf of the SVOM and Einstein Probe teams We performed a follow-up observation of GRB 250219A (Daigne et al., GCN 39376) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-02-21T07:04:16 (T-TGRB ~ 1.63 days) for about 3ks of exposure in total. An uncatalogued X-ray source is detected by both FXT-A and FXT-B at the position of the x-ray afterglow candidate reported by Swift/XRT (Kennea et al., GCN 39379). This position is also consistent with the optical afterglow detected by SVOM/VT (Xin et al., GCN 39380), COLIBRÍ (Magnani et al. GCN 39382) and the NOT (Fu et al., GCN 39383). A preliminary analysis shows that the spectrum can be fitted with an absorbed power law with nH=1.53*10^20 cm^-2 and a photon index of 1.53 (-0.68/+0.70) . The observed flux in the 0.3-10.0 keV is 4.4 (+2.2/-1.1)*10^-13 erg/s/cm^2. Compared to the Swift/XRT epoch Kennea et al., GCN 39379), the observed source flux has faded by almost one order of magnitude with a temporal slope alpha~-0.56. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/39456. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37467] EP250223a: GOTO optical afterglow detections
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39455 SUBJECT: EP250223a: GOTO optical afterglow detections DATE: 25/02/24 13:59:07 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, B. P. Gompertz, A. J. Levan, K. Ulaczyk, G. Ramsay, A. Kumar, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the EP/WXT alert WXT01709131863 (Lian et al. GCN 39429). Three epochs of targeted observations were performed: at 2025-02-24 09:56:36 UT (+18.9h post trigger), 2025-02-24 11:04:37 UT (+20.0h post trigger), and 2025-02-24 12:12:37 UT (+21.1h post trigger). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. We detect the optical afterglow (Hauptmann et al., GCN 39436; Levan et al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Brivio et al., GCN 39450; Ducoin et al., GCN 39453) with magnitudes of L (400-700 nm) = 20.04 ± 0.15 mag (+18.9h), L = 19.78 ± 0.11 mag (+20.0h) and L = 19.97 ± 0.14 mag (+21.1h). Our measurements indicate no fading of the afterglow between 18 and 21 hours after trigger, continuing the shallow evolution noted by Ducoin et al. during the first 6 - 15 hours (GCN 39453). 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/39455. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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