GRB180626A

This page lists all entries on GRB180626A in GRBweb

Summary IPN Swift GCN 22850 GCN 22851 GCN 22852 GCN 22853 GCN 22854 GCN 22855 GCN 22857 GCN 22859 GCN 22860 GCN 22861 GCN 22862 GCN 22865 GCN 22869 GCN 22870

Summary table
Variable Value Source
T0 8:21:04 UTC GCN_circulars,INTEGRAL
ra 243.5755° Swift
decl 14.7571° Swift
pos_error 1.05e-04° Swift
T90 30.07 s Swift
T90_start 8:21:16 UTC Swift
fluence 4.80e-06 erg/cm² Swift
T100 42.07 s
GBM_located False
mjd 58295.347962962966 GCN_circulars,INTEGRAL
IPN table
GRB_name GRB180626A
ra 243.5667°
decl 14.7500°
pos_error 5.00e-02°
Swift table
GRB_name GRB180626A
t_trigger 8:21:16 UTC
ra 243.5755°
decl 14.7571°
pos_error 1.05e-04°
T90 30.07 s
fluence 4.80e-06 erg/cm²
GCN 22850 table
GRB_name GRB180626A
GCN_number 22850
Detection_method Swift Det
t_trigger 8:21:16 UTC
ra 243.5670°
decl 14.7640°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22850 SUBJECT: GRB 180626A: Swift detection of a burst with an optical counterpart DATE: 18/06/26 08:34:26 GMT FROM: Kim Page at U.of Leicester P. A. Evans (U Leicester), A. P. Beardmore (U Leicester), J.D. Gropp (PSU), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team: At 08:21:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180626A (trigger=844615). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 243.567, +14.764 which is RA(J2000) = 16h 14m 16s Dec(J2000) = +14d 45' 52" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 50 sec. The peak count rate was ~3400 counts/sec (15-350 keV), at ~-2 sec after the trigger. The XRT began observing the field at 08:23:16.9 UT, 120.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 243.57544, 14.75598 which is equivalent to: RA(J2000) = 16h 14m 18.11s Dec(J2000) = +14d 45' 21.5" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 41 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.47 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.28/-2.05) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 123 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 16:14:18.12 = 243.57551 DEC(J2000) = +14:45:25.5 = 14.75707 with a 90%-confidence error radius of about 0.81 arc sec. This position is 5.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 20.71 with a 1-sigma error of about 0.23. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN 22851 table
GRB_name GRB180626A
GCN_number 22851
Detection_method INTEGRAL
t_trigger 8:21:04 UTC
ra 243.5715°
decl 14.7486°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22851 SUBJECT: GRB 180626A: A long GRB detected by INTEGRAL DATE: 18/06/26 09:34:14 GMT FROM: Diego Gotz at CEA D.Gotz (CEA, Saclay), S.Mereghetti (IASF-Milano), C.Ferrigno, E. Bozzo, V.Savchenko (ISDC, Versoix), L. Ducci (IAAT/ISDC) and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: a gamma ray burst lasting about 40 s has been detected by IBAS in the IBIS/ISGRI data at 08:21:04 UT of June 26, 2018 The refined coordinates (J2000) are: R.A.= 243.5715 deg DEC.= 14.7486 deg with an uncertainty of 1.1 arcmin (90% c.l.). The burst had a measured peak flux of about 2.7 counts/cm2/s (20-200 keV, 1-s integration time) and a fluence in the same energy range of about 2e-6 erg/cm2. We note that both those values are lower limits, due to telemetry saturation at satellite level. This burst was also detected by the Swift/BAT, XRT and UVOT (Evans et al., GCN 22850), and the IBIS position is at 33 arc seconds from the UVOT one. A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html
GCN 22852 table
GRB_name GRB180626A
GCN_number 22852
Detection_method Swift-XRT Det
ra 243.5760°
decl 14.7569°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22852 SUBJECT: GRB 180626A: Enhanced Swift-XRT position DATE: 18/06/26 10:07:10 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 804 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180626A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 243.57603, +14.75692 which is equivalent to: RA (J2000): 16h 14m 18.25s Dec (J2000): +14d 45' 24.9" with an uncertainty of 1.8 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN 22853 table
GRB_name GRB180626A
GCN_number 22853
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22853 SUBJECT: GRB 180626A: ISON-MN optical observations DATE: 18/06/26 11:25:47 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), E. Mazaeva (IKI), A. Pozanenko (IKI), A. Volnova (IKI), I. Molotov (KIAM) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 180626A (Evans et al., GCN 22850) with ISON-NM observatory. Observation started 51 s after burst trigger. We do not find optical afterglow (Evans et al., GCN 22850) in a combined image of first 5 frames. Preliminary photometry of the filed is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-06-26 08:22:07 0.00146 CR 5* 20 n/d n/d 17.3 The photometry is based on several nearby USNO-B1.0 stars.
GCN 22854 table
GRB_name GRB180626A
GCN_number 22854
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22854 SUBJECT: GRB 180626A: LCO Haleakala observations DATE: 18/06/26 12:13:43 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy R. Martone, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara (U. of Virgin Islands) on behalf of a large collaboration report: The LCO 2-m unit at Haleakala Observatory (Hawaii), former FTN, began observing Swift and INTEGRAL GRB 180626A (Evans et al. GCN 22850; Gotz et al. GCN 22851) on June 26, 08:41:11 UT (20 min after the GRB trigger time) with the SDSS ri filters. The optical counterpart (Evans et al.) is clearly detected with the following magnitudes: Mid Time since GRB Exposure Filter Magnitude (hrs) (s) ------------------------------------------------------------------ 0.424 5x120 SDSS-R 20.96 +- 0.12 0.617 5x120 SDSS-I 20.53 +- 0.12 ------------------------------------------------------------------ as calibrated against nearby SDSS objects.
GCN 22855 table
GRB_name GRB180626A
GCN_number 22855
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22855 SUBJECT: GRB 180626A: RATIR Optical Detection DATE: 18/06/26 12:36:12 GMT FROM: Eleonora Troja at GSFC Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesus Gonzalez (UNAM), Carlos Roman-Zuniga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 180626A (Evans, et al., GCN 22850) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronomico Nacional on Sierra San Pedro Martir from 2018/06 26.42 to 2018/06 26.43 UTC (1.61 to 2.06 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r and i bands. For a source at the position of the UVOT counterpart, in comparison with the SDSS DR9 catalog, we obtain the following detections: r = 21.57 +/- 0.22 i = 20.91 +/- 0.13 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. These magnitudes are fainter than the values reported by Martone et al. (GCN 22854) suggesting that the source is indeed the fading GRB afterglow. We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.
GCN 22857 table
GRB_name GRB180626A
GCN_number 22857
Detection_method Swift-UVOT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22857 SUBJECT: GRB 180626A: Swift/UVOT Detection DATE: 18/06/26 15:22:56 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180626A 123 s after the BAT trigger (Evans et al., GCN Circ. 22850). A fading source consistent with the XRT position (Osborne et al. GCN Circ. 22852) and also seen by Martone et al. (GCN Circ. 22854) and Troja et al. (GCN Circ. 22855) is detected in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the finding chart (FC) and early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 123 273 147 20.57 ± 0.22 white 633 1033 190 >21.4 v 665 6473 452 >20.2 b 591 5858 246 >20.4 u 336 6936 529 >20.7 w1 714 6882 432 >21.0 m2 5043 6677 393 >20.1 w2 641 6268 432 >21.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).
GCN 22859 table
GRB_name GRB180626A
GCN_number 22859
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22859 SUBJECT: GRB 180626A: COATLI Optical Detection DATE: 18/06/26 17:10:10 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William H. Lee (UNAM), Carlos Román-Zúñiga (UNAM), Alexander Kutyrev (GSFC), and Eleonora Troja (GSFC) report: We observed the field of GRB 180626A (Evans et al., GCN 22850) with the COATLI 50-cm telescope and interim imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) from 2018-06-20 08:21:50.6 to 11:18:41.7 UTC (from 33.7 seconds after the trigger or 17.9 seconds after the alert to 2.95 hours after the trigger), obtaining a total of 7020 seconds of exposure in the w filter. Within the enhanced XRT error region (Osborne et al., GCN Circ. 22852), we detect the afterglow previously reported by Evans et al. (GCN Circ. 22850), Martone et al. (GCN Circ. 22854), and Breeveld et al. (GCN Circ. 22857) with w = 21.4 +/- 0.9 In our first set of 30 images each of 5 seconds of exposure, from 08:21:50.6 to 08:27:10.1 UTC, we do not detect the afterglow with a 10-sigma limiting magnitude of w > 19.2 These magnitudes are calibrated against the Pan-STARRS1 catalog and the USNO-B1 catalog (adjusted to an approximate AB system) and are not corrected for Galactic extinction in the direction of the GRB. We thank the COATLI technical team (Fernando Ángeles, Oscar Chapa, Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica, Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio Astronómico Nacional.
GCN 22860 table
GRB_name GRB180626A
GCN_number 22860
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 22860 SUBJECT: GRB 180626A: Swift-XRT refined Analysis DATE: 18/06/26 18:28:59 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), A.P. Beardmore (U. Leicester), S.L. Gibson (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (PSU), S. J. LaPorte (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 180626A (Evans et al. GCN Circ. 22850), from 129 s to 22.4 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 22852). The light curve can be modelled with an initial power-law decay with an index of alpha=0.21 (+0.14, -0.15), followed by a break at T+2992 s to an alpha of 0.90 (+0.11, -0.10). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.01 (+/-0.11). The best-fitting absorption column is 2.2 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+/-0.4) x 10^21 cm^-2 Galactic foreground: 3.5 x 10^20 cm^-2 Excess significance: 8.0 sigma Photon index: 2.01 (+/-0.11) If the light curve continues to decay with a power-law decay index of 0.90, the count rate at T+24 hours will be 0.028 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-12 (1.4 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00844615. This circular is an official product of the Swift-XRT team.
GCN 22861 table
GRB_name GRB180626A
GCN_number 22861
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22861 SUBJECT: GRB 180626A: KAIT Optical Upper Limit DATE: 18/06/26 19:58:36 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to GRB 180626A (Evans et al., GCN 22850; Gotz et al., GCN 22851) starting at 08:23:31 UT, 135 s after the Swift/BAT trigger. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. Since the INTEGRAL trigger was received earlier than the Swift trigger, KAIT responed to the INTEGRAL trigger first. Unfortunately the UVOT afterglow location (Evans et al., GCN 22850) is outside our field of view for the first few images. We later manually re-pointed to the UVOT afterglow location starting at 08:52:10 UT about 30 minutes after the Swift/BAT trigger, with the updated exposure time of 60 s per image. We do not detect the afterglow at the reported UVOT location (Evans et al., GCN 22850) in our single image, nor in the co-added images. The typical limiting magnitude of our single clear image is about 19.5 mag calibrated to the PS1 catalog.
GCN 22862 table
GRB_name GRB180626A
GCN_number 22862
Detection_method Swift-BAT Det
ra 243.5690°
decl 14.7590°
Circular_text TITLE: GCN CIRCULAR NUMBER: 22862 SUBJECT: GRB 180626A: Swift-BAT refined analysis DATE: 18/06/26 20:41:06 GMT FROM: Hans Krimm at NSF/NASA-GSFC H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. A. Evans (U Leicester), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+526 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180626A (trigger #844615) (Evans, et al., GCN Circ. 22850). The BAT ground-calculated position is RA, Dec = 243.569, 14.759 deg which is RA(J2000) = 16h 14m 16.6s Dec(J2000) = +14d 45' 32.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%. The mask-weighted light curve shows a multi-peaked structure. The first peak is from approximately T-10 to T+5 sec, with a second overlapping peak from T+5 to T+20 sec, followed by a weaker peak from T+20 to T+30 sec. T90 (15-350 keV) is 30.07 +- 1.42 sec (estimated error including systematics). The time-averaged spectrum from T-10.01 to T+25.59 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.64 +- 0.27, and Epeak of 47.7 +- 12.2 keV (chi squared 40.18 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.8 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T-3.69 sec in the 15-150 keV band is 4.1 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.01 +- 0.06 (chi squared 46.26 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/844615/BA/
GCN 22865 table
GRB_name GRB180626A
GCN_number 22865
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22865 SUBJECT: GRB 180626A: RATIR Optical Observations DATE: 18/06/27 05:11:57 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 180626A (Evans, et al., GCN Circ. 22850) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2018/06 27.16 to 2018/06 27.20 UTC (19.60 to 20.46 hours after the BAT trigger), obtaining a total of 0.71 hours exposure in the r and i bands. For a source at the position of the UVOT counterpart, in comparison with the SDSS DR9 catalog, we obtain the following detections: r = 22.39 +/- 0.20 i = 21.92 +/- 0.15 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source flux has faded approximately as t^-0.35 since our previous observations (Troja et al., GCN Circ. 22855). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.
GCN 22869 table
GRB_name GRB180626A
GCN_number 22869
Detection_method Konus-Wind Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 22869 SUBJECT: Konus-Wind observation of GRB 180626A DATE: 18/06/29 10:49:02 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long GRB 180626A (Swift-BAT trigger #844615: Evans et al., GCN 22850; Krimm et al., GCN 22862; INTEGRAL detection: Gotz et al., GCN 22851) was detected by Konus-Wind (KW) in the waiting mode. The burst light curve shows a single emission episode with a duration of ~ 36 s. As observed by KW, the burst had a fluence of 7.21(-0.79,+0.97)x10^-6 erg/cm2 and a 2.944-s peak flux, measured from ~T0(BAT)-3.841 s, of 3.92(-0.49,+0.58)x10^-7 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Modeling the KW 3-channel time-integrated spectrum (from ~T0(BAT)-9.7 s to ~T0(BAT)+25.6 s) by a simple power-law model yields a power law index of -2.19(-0.04,+0.05), chi2 = 2.5/1 dof. The KW light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB180626A/ All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary.
GCN 22870 table
GRB_name GRB180626A
GCN_number 22870
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 22870 SUBJECT: GRB 180626A: TSHAO optical upper limit DATE: 18/06/29 16:09:33 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), A. Kusakin (FAPHI), I. Reva (FAPHI), A. Volnova (IKI), M. Krugov (FAPHI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 180626A (Evans et al., GCN 22850; Gotz et al., GCN 22851) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on June 26 (UT) 16:26:21. We obtained several images in R-filter. The optical afterglow (Evans et al., GCN 22850; Martone et al. GCN 22854; Troja et al. GCN 22855; Watson et al. GCN 22859) is not detected in a stacked image. Preliminary photometry of the field is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-06-26 16:26:21 0.41918 R 99*120 n/d n/d 21.5 The photometry is based on several nearby SDSS-DR10 stars. Ref.stars SDSS-DR9_id R(Lupton) J161422.32+144433.2 15.113 J161357.84+144752.0 13.989 J161440.94+144745.0 13.136