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

[vsnet-grb-info 38340] GRB 250430A: SVOM/VT optical observations
by GCN Circulars 02 May '25

02 May '25

TITLE: GCN CIRCULAR NUMBER: 40311 SUBJECT: GRB 250430A: SVOM/VT optical observations DATE: 25/05/02 03:29:23 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. L. Li, , L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), L. Zhang(IHEP), W. K. Zheng (UCB) report on behalf of the SVOM/VT team: SVOM/VT conducted ToO follow-up observations for GRB 250430A. The observation started on 2025 Apr 24 04:54:31 UT in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. The optical counterpart (Parsotan et al., GCN 40292; Odeh et al., GCN 40295;Garnichey et al., GCN 40301; Komesh et al., GCN 40307; Zheng et al., GCN 40310) was clearly detected in our observations. The afterglow was fading during our observations and the brightness was estimated to be 21.69+/-0.05 mag in VT_R, and 22.96+/-0.10 mag in VT_B, at the mid time of 13.39 hours post the burst. The photometry was estimated in AB magnitude and not corrected for Galactic extinction. Considering the host galaxy's brightness and red color (Garnichey et al., GCN 40301)，the photometry might be contaminated by the host galaxy's light, particularly in the VT_R band. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/40311. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38339] GRB 250430A: KAIT optical observations
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40310 SUBJECT: GRB 250430A: KAIT optical observations DATE: 25/05/01 21:27:09 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250403A (Parsotan et al., GCN 40292; Wang et al., GCN 40299) with a set of 120x60s images in the clear (roughly R) filters, at a mid time of 13.9 hours after the trigger. We marginally detected the optical afterglow (Parsotan et al., GCN 40292; Odeh et al., GCN 40295; Garnichey et al., GCN 40301; Komesh et al., GCN 40307) in the coadd image with a brightness of 21.7 +/- 0.3 mag (Vega). View this GCN Circular online at https://gcn.nasa.gov/circulars/40310. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38338] EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40309 SUBJECT: EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy. DATE: 25/05/01 20:14:32 GMT FROM: Stephen Smartt at University of Oxford <s.smartt(a)qub.ac.uk> J. H. Gillanders (Oxford), M. Huber, K. C. Chambers (IfA, Univ. Hawaii), S. J. Smartt, K. W. Smith, S. Srivastav, F. Stoppa (Oxford), M. Nicholl, D. Young, M. Fulton (QUB), T.-W. Chen (NCU, Taiwan) A. S. B. Schultz, T. de Boer, J. Fairlamb, G. Paek, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii). We observed the optical counterpart of EP250428b (Liu et al., GCN 40277), using the Pan-STARRS telescope system (Chambers et al., 2016, arXiv e-prints, 1612.05560) on MJD 60795.48 (2025-04-30 11:31 UTC), 2.2 days after the EP-WXT detection (Liu et al., GCN 40277). The Pan-STARRS system consists of two 1.8m 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. We used PS1 with 6x150s exposures in both r and i. The PS reference frames were subtracted from the stacked 900s images, and no source was detected to r > 22.6 and i > 22.5. There is a red source in the Legacy Surveys (Dey et al. 2019) DR10 at i=22.07 (r-i=0.76) morphologically classified as a galaxy (source type E), at 0.4" separation from the nominal centre of the EP250428b error circle (220.4575, 2.0989) from Wu et al. GCN 40285. The source is also visible in the Pan-STARRS 3Pi survey data and our night stack i-band. The only other source visible within 10 arcsec radius is a fainter object at 8.8 arcsec offset i=23.9 in the Lgeacy Survey. It is classified with a PSF-like morphology, although the significance of the detection would preclude a definitive stellar classification. We suggest the brigher, i=22.07, source may be the host galaxy of EP250428b. There is also a spatially coincident source in the unWISE catalogue (at 220.4576984 +2.0988141) in the 3.4mu band at 128 +/- 7 nMgy (Vega nanomaggies), or AB mag = 19.9 +/- 0.1. The source is visible as excess flux in the legacysurvey.org browser. This could suggest a high redshift host galaxy, but we caution that there is no recorded flux in the 4.6mu band in the unWISE catalogue The non-detection is consistent with the deeper limits reported in Busman et al. (GCN 40290) and Xin et al. GCN 40283) and also other GCN optical searches (Lipunov et al., GCN 40278; Konno et al., GCN 40281; Moskvitin et al., GCN 40282; Salgundi et al., GCN 40284). View this GCN Circular online at https://gcn.nasa.gov/circulars/40309. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38337] GRB 250430A / EP250430a: J-band upper limits with WINTER
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40308 SUBJECT: GRB 250430A / EP250430a: J-band upper limits with WINTER DATE: 25/05/01 17:50:27 GMT FROM: Geoffrey Mo at MIT <gmo(a)mit.edu> Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (LAM), Viraj Karambelkar (Caltech), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 250430A / EP250430a (Parsotan et al., GCN 40292; Wang et al., GCN 40299) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2025-05-01T08:49:52 UTC (15.3 hours after the GRB), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565). We do not detect a source at the optical and X-ray counterpart position (Parsotan et al., GCN 40292; Kawabata et al., GCN 40294; Odeh et al., GCN 40295; Garnichey et al., GCN 40301; Hagio et al., GCN 40302; Quadri et al., GCN 40303; Moretti et al., GCN 40304; Atri et al., GCN 40305; Komesh et al., GCN 40307). We obtain the following 5-sigma upper limit: J ~ 19.7 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/40308. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38336] GRB 250430A: NUTTelA-TAO Early Measurements
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40307 SUBJECT: GRB 250430A: NUTTelA-TAO Early Measurements DATE: 25/05/01 17:08:43 GMT FROM: Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh(a)nu.edu.kz> T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), B. Grossan (UCB, NU), D. Berdikhan (NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 250430A on receipt of an automated GCN / BAT position alert, observing in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). We started observations at 17:31:53 UT on 2025-04-30, 32 s after the BAT trigger. Observations were made in clear conditions for the first ~1 hour, followed by cloudy weather. Note that these observations provide essentially full-time coverage, simultaneous in two bands. A new and changing source consistent with the XRT/EP position (T. M. Parsotan et al., GCN 40292; C. Y. Wang et al., GCN 40299) was detected. We report the results for the earliest co-added images, without color corrections or corrections for galactic reddening, as following: filter tc-t0(s) mag err exposure_time (s) ------------------------------------------------------------------------------- r' 59 18.44 0.13 54 g' 55 UL18.10 45 r’ 162 18.56 0.14 120 g’ 227 19.23 0.11 300 … … … … tc-t0 = image center time minus trigger time. Calibration was done with 4 bright Pan-STARRS catalog stars on our images. A light curve of the optical transient is presented in Figure 1: https://ecl.nu.edu.kz/research/observations/gamma-ray-bursts/grb250430a We welcome opportunities for collaboration and data-sharing. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/40307. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38335] EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40306 SUBJECT: EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit DATE: 25/05/01 16:12:13 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), S. Basa (Pytheas/OHP/LAM), N.A. Rakotondrainibe (LAM), S. Vergani (CNRS, Obs. de Paris, LUX), A. Saccardi (CEA/Irfu), B. Schneider (LAM), J. T. Palmerio (CEA/Irfu) report on behalf of the MISTRAL-GRB collaboration: We observed EP250427a / GRB 250427A (Wang et al. GCN 40257, Ravasio et al. GCN 40262) a third time using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager in blue setting. We obtained 1x72sec + 1x600sec + 1x900sec + 4x720sec in the r’ band starting at 01:34:13UT on 2025-05-01 (T0+93.9 h after the trigger). In the stacked image, we do not significantly detect the optical afterglow reported by Pérez-García et al. GCN 40259; Liu et al. GCN 40260; Becerra et al. GCN 40261; Brivio et al. GCN 40264; Chornock et al. GCN 40265; Saccardi et al. GCN 40266; Pérez-Fournon et al. GCN 40267; Xi et al. GCN 40269; Swain et al. GCN 40270; Magnani et al. GCN 40271; de Wet et al. GCN 40272; Busmann et al. GCN 40273, Wang et al. GCN40274, Amram et al. GCN 40275, Siegel et al. GCN 40279, Amram et al. GCN 40288, Eappachen et al. GCN 40289, and Ghosh et al. GCN 40293 down to the following 5-sigma upper limit: r > 22.8. If we force the detection at the EP250427a afterglow position, we get a very marginal detection just below the detection limit with a preliminary magnitude of r=23.1+/-0.35 The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen, and the SOPHIE observer Owin Scutt. View this GCN Circular online at https://gcn.nasa.gov/circulars/40306. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38334] GRB 250430A: DDOTI Optical Observations
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40305 SUBJECT: GRB 250430A: DDOTI Optical Observations DATE: 25/05/01 14:06:36 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), and Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of the Swift/BAT GRB 250430A (Parsotan et al., GCN Circ. 40292) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-05-01 UTC. DDOTI observed the Swift/UVOT error region (Parsotan et al., GCN Circ. 40292) from 05:23 UTC to 10:43 UTC (from T+11.9 h to T+17.4 h after the trigger) with a total exposure of 2.3 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no any uncatalogued source at the position reported by Parsotan et al., (GCN Circ. 40292); Odeh et al., (GCN Circ. 40295); Wang et al., (GCN Circ. 40299); Garnichey et al., (GCN Circ. 40301); Hagio et al., (GCN Circ. 40302); Quadri (GCN Circ. 40303) and Moretti (GCN Circ. 40304) down to a 3-sigma limiting AB magnitude of: w > 20.6 We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40305. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38333] GRB 250430A: Leavitt Observatory optical upper limit
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40304 SUBJECT: GRB 250430A: Leavitt Observatory optical upper limit DATE: 25/05/01 14:02:45 GMT FROM: leavittob(a)gmail.com L. Moretti, E. Pavoni (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We observed the field of the GRB 250430A / EP250430a (Parsotan et al., GCN 40292; Wang et al., GCN 40299) with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy. The observations started approximately 6 hours after the Swift/BAT trigger time, with good weather conditions. We utilized the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A) to align and stack 25 individual frames of 120 sec each, with a median time of 2025-04-30T23:29:41 (UTC). All images are unfiltered and were processed by a single data processing pipeline based on astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). In the stacked frame, we did not found any optical uncatalogued object within the Swift error circle. Mid-Time (UTC) Rc limit Error 2025-04-30T23:29:41 >20.32 +/- 0.01 This upper limit is consistent with other observations reported by K. S. Kawabata et al. (GCN Circular 40294), Mohammad Odeh et al. (GCN Circular 40295), Andrea Saccardi et al (GCN Circular 40301), H. Hagio et al. (GCN Circular 40302), Quadri et al. (GCN 40303). Our photometry is in the AB system and is not corrected for galactic dust extinction. Magnitudes were estimated with the Pan-STARRS cat. and converted using Lupton (2005) equations. The message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/40304. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38332] GRB 250430A: Bassano Bresciano Observatory upper limit
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40303 SUBJECT: GRB 250430A: Bassano Bresciano Observatory upper limit DATE: 25/05/01 13:33:33 GMT FROM: Ulisse Quadri at Bassano Bresciano Observatory <osservatoriobassano(a)gmail.com> U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory) Members of: GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani. AAVSO - American Association of Variable Star Observers. GAC - Gruppo Astrofili Cremonesi. In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), B. De Simone (Universita' degli Studi Di Salerno) report: We imaged the field of GRB 250430A detected by Swift with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. The observations started 5h 01m after the GRB trigger with our Newton telescope D=250 mm F/D=4.8. We co-added 2 series of 150 exposures of 30 sec each. Start T0+ End T0+ Rc lim. Err. 5h 01m 6h 30m 20.3 +/- 0.2 6h 31m 8h 01m 20.3 +/- 0.2 We did not found any optical uncatalogued object within the Swift error circle. Our upper limit is consistent with other observations reported by K. S. Kawabata et al. (GCN Circular 40294), Mohammad Odeh et al. (GCN Circular 40295), Andrea Saccardi et al (GCN Circular 40301), H. Hagio et al. (GCN Circular 40302). Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations. Not corrected for galactic dust extinction. Reference: http://www.osservatoriobassano.altervista.org The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40303. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38331] GRB 250430A : MITSuME Akeno optical upper limits
by GCN Circulars 01 May '25

01 May '25

TITLE: GCN CIRCULAR NUMBER: 40302 SUBJECT: GRB 250430A : MITSuME Akeno optical upper limits DATE: 25/05/01 11:06:05 GMT FROM: hagio.h.ffca(a)m.isct.ac.jp H. Hagio, I. Takahashi, M. Sasada, H. Seki, S. Joshima, Y. Kubo, A. Ochi, R. Kato, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 240430A detected by Swift/BAT (Parsotan et al. GCN 40292) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2025-04-30 17:31:53 UT (32 seconds after the Swift/BAT trigger). We stacked the images with good conditions. We did not detect any obvious point sources at the position reported by Parsotan et al., GCN 40292, Odeh et al., GCN 40295, Wang et al., GCN 40299, and Garnichey et al., GCN 40301. We obtained the 5-sigma limits of the stacked images as follows: T0+[min] | MID-UT | T-EXP[sec] | 5-sigma limits ------------------------------------------------------------------------------------------------ 15.1 | 2025-04-30 17:46:27 | 620 | g'>18.2, Rc>18.2, Ic>17.8 78.5 | 2025-04-30 18:29:51 | 2880 | g'>19.3, Rc>19.6, Ic>19.0 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the trigger T-EXP: Total Exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire). View this GCN Circular online at https://gcn.nasa.gov/circulars/40302. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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