//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23309 SUBJECT: GRB 181010A: Swift detection of a burst with an optical counterpart DATE: 18/10/10 06:07:32 GMT FROM: Scott Barthelmy at NASA/GSFC A. Melandri (INAF-OAB), S. D. Barthelmy (GSFC), M. J. Moss (George Washington University), K. L. Page (U Leicester) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 05:55:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 181010A (trigger=866434). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 52.557, -23.035, which is RA(J2000) = 03h 30m 14s Dec(J2000) = -23d 02' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks with a total duration of about 25 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~8 sec after the trigger. The XRT began observing the field at 05:57:24.7 UT, 93.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 52.56984, -23.03721 which is equivalent to: RA(J2000) = 03h 30m 16.76s Dec(J2000) = -23d 02' 14.0" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 43 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 (1.89 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.9 (+2.46/-2.18) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 96 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 03:30:16.89 = 52.57036 DEC(J2000) = -23:02:15.4 = -23.03760 with a 90%-confidence error radius of about 0.78 arc sec. This position is 3.0 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.37 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 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.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23310 SUBJECT: GRB 181010A: MASTER-Argentina OT detection DATE: 18/10/10 06:54:35 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa,A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, South African Astronomical Observatory A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory O. Gres, N.M. Budnev, Yu.Ishmuhametova Applied Physics Institute of Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the GRB181010.25 19 sec after notice time and 42 sec after trigger time at 2018-10-10 05:56:33 UT. On our first (60s coadd exposure) coadd set we found 1 optical transient within SWIFT error-box (ra=52.55 dec=-23.0344 r=0.05) brighter than 18.24. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 72 2018-10-10 05:56:33 60 ( 3h 30m 16.8s , -23d 2m 14.9s) 18.05 The 5-sigma upper limit has been about 18.7 mag The message may be cited. ==================================================================== The galactic latitude b = -53 deg., longitude l = 215 deg. The observations made on zenit distance = 15 deg.The moon ( 2 % bright part) below the horizon (The altitude of the Moon is -50 deg. ). The sun altitude is -45.7 deg. The object can be observed till sunrise at 2018-10-10 10:03:45 . THIS BLOCK FOR MASTER-Team USERS ONLY. Link to GRB181010.25 page: https://200.123.254.238:49004//master2/grb.php?not=2018-10-10+05%3A56%3A14&sat=SWIFT&gcrd=%2852.55d%2C-23.0344d%29&eb=0.05&trig=2018-10-10+05%3A55%3A51&n=GRB181010.25 Long transients in E.B. https://200.123.254.238:49004//master2/trans.php?wh=transients.coord2000@%27%3C%2852.55d%2C-23.0344d%29%2C0.1d%3E%27%3A%3Ascircle+and+transients.datetime%3E%3D%272018-10-10+05%3A55%3A51%27&class=9&t2=SWIFT+GRB181010.25+optical+counterpart+candidate Short transients in E.B. https://200.123.254.238:49004//master2/trans3.php?wh=transients3.coord2000@%27%3C%2852.55d%2C-23.0344d%29%2C0.1d%3E%27%3A%3Ascircle+and+transients3.datetime%3E%3D%272018-10-10+05%3A55%3A51%27&class=-1&t2=SWIFT+GRB181010.25+optical+counterpart+candidate Two tube transients in E.B. https://200.123.254.238:49004//master2/trans2.php?wh=transients2.coord2000@%27%3C%2852.55d%2C-23.0344d%29%2C0.1d%3E%27%3A%3Ascircle+and+transients2.datetime%3E%3D%272018-10-10+05%3A55%3A51%27&class=0&t2=SWIFT+GRB181010.25+optical+counterpart+candidate Undef. objects 1 image https://200.123.254.238:49004//master2/aobj.php?wh=stars.coord2000@%27%3C%2852.55d%2C-23.0344d%29%2C0.1d%3E%27%3A%3Ascircle+and+stars.class=0+and+stars.status+and+stars.proc_id=626837&t2=SWIFT+GRB181010.25+1+image+optical+counterpart+candidate The observation and reduction will continue. This circular was generated automatically. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23311 SUBJECT: GRB 181010A: LCO Cerro Tololo observations DATE: 18/10/10 07:35:32 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, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report: We automatically began observing Swift GRB 181010A (Melandri et al. GCN 23309) with one LCO 1-m unit at Cerro Tololo from October 10, 06:02:54 UT (corresponding to 7.1 minutes from the GRB trigger time) with the SDSS r' filter. We clearly detect the optical counterpart reported by Swift-UVOT with r'=19.98 +- 0.12 mag from a 3x120s exposure at a mid time of 10.7 minutes post GRB, as calibrated against nearby Pan-STARRS objects. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23312 SUBJECT: GRB 181010A: RATIR Optical and NIR Afterglow Detection DATE: 18/10/10 08:02:49 GMT FROM: Eleonora Troja at GSFC Eleonora Troja (GSFC), 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), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesus Gonzalez (UNAM), Carlos Román-Zuniga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 181010A (Melandri, et al., GCN 23309) 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 2018/10 10.25 to 2018/10 10.29 UTC (4.2 min to 1.10 hours after the BAT trigger), obtaining a total of 0.50 hours exposure in the r and i bands and 0.24 hours exposure in the Z, Y, J, and H bands. At the position of the optical afterglow (Melandri, et al., GCN 23309; Gorbovskoy, et al., GCN 23310), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections: r 20.30 +/- 0.20 i 21.03 +/- 0.10 Z 20.67 +/- 0.24 Y 20.24 +/- 0.21 J 19.87 +/- 0.24 H 19.16 +/- 0.17 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir. Further observations are on-going. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23313 SUBJECT: GRB 181010A: Enhanced Swift-XRT position DATE: 18/10/10 10:29:09 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 441 s of XRT Photon Counting mode data and 1 UVOT images for GRB 181010A, 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 = 52.57030, -23.03844 which is equivalent to: RA (J2000): 03h 30m 16.87s Dec (J2000): -23d 02' 18.4" 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23315 SUBJECT: GRB 181010A: VLT/X-shooter redshift DATE: 18/10/10 11:49:03 GMT FROM: Jean Baptiste at Paris Observatory J-B. Vielfaure (CNRS - GEPI/Observatorie de Paris), J. Japelj (API, U. Amsterdam), D. B. Malesani (DAWN/NBI and DARK/NBI), V. D'Elia (SSDC), J. P. U. Fynbo (DAWN/NBI), N. R. Tanvir (Univ. Leicester), S. D. Vergani (CNRS - GEPI/Observatorie de Paris), A. Rossi (INAF-OAS), P. Vreeswijk (Radboud Univ. Nijmegen), L. Izzo (HETH/IAA-CSIC), D. A. Kann (HETH/IAA-CSIC), B. Milvang-Jensen (DAWN/NBI), D. Xu (NAOC) and K. E. Heintz (Univ. of Iceland), report on behalf of the Stargate collaboration: We observed the optical counterpart of GRB 181010A (Melandri et al. GCN 23309; E. Gorbovskoy et al. 23310; R. Martone et al. 23311; E. Troja et al. 23312) with the ESO-VLT UT2 equipped with the X-shooter spectrograph. From the acquisition image we measure a preliminary magnitude of 20.4 +/- 0.1 mag in the r-band, calibrated against local Pan-STARRS sources. Several spectra with increasing exposure time were collected; in this analysis we consider only one with 600s exposure obtained in a Rapid Response Mode at 06:18:24.9 UT (at the start of observation, 0.37 hr after the GRB). A bright continuum is observed across the entire wavelength range covered by X-shooter. Several absorption and emission features are detected, which can be identified as due to H-alpha and [OIII]5007/4959 in emission at z = 1.39. At this same redshift we also detect AlII1854/1862, SiII1808, the MgII doublet, and MgI in absorption. Fine-structure lines from FeII and NiII are also detected at z = 1.39, which makes the redshift association with the GRB secure. An intervening system at z = 0.67 with absorption features due to the MgII doublet and MgI is also identified in the spectrum. We acknowledge the ESO observing staff at Paranal, in particular Jorge Lillo-Box. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23316 SUBJECT: GRB 181010A: Swift-XRT refined Analysis DATE: 18/10/10 12:30:27 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), S. J. LaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and A. Melandri report on behalf of the Swift-XRT team: We have analysed 7.3 ks of XRT data for GRB 181010A (Melandri et al. GCN Circ. 23309), from 96 s to 17.1 ks after the BAT trigger. The data comprise 77 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 23313). The light curve can be modelled with an initial power-law decay with an index of alpha=0.741 (+/-0.021), followed by a break at T+11.9 ks to an alpha of 3.6 (+4.4, -0.7). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.88 (+0.11, -0.10). The best-fitting absorption column is 3.1 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 1.9 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 4.0 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.1 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 1.9 x 10^20 cm^-2 Excess significance: 10.7 sigma Photon index: 1.88 (+0.11, -0.10) If the light curve continues to decay with a power-law decay index of 3.6, the count rate at T+24 hours will be 1.8 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.4 x 10^-15 (1.0 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00866434. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23317 SUBJECT: GRB 181010A: Swift/UVOT Detection DATE: 18/10/10 12:55:25 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181010A 96 s after the BAT trigger (Melandri et al., GCN Circ. 23309). A source consistent with the XRT position (Evans et al. GCN Circ. 23313) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:30:16.89 = 52.57038 (deg.) Dec (J2000) = -23:02:15.4 = -23.03761 (deg.) with an estimated uncertainty of 0.49 arc sec. (radius, 90% confidence), consistent with (MASTER-OAFA, Gorbovskoy et al., GCN Circ. 23310; LCO Cerro Tololo, Martone et al., GCN Circ. 23311; RATIR, Troja et al., GCN Circ. 23312; VLT/X-shooter, Vielfaure et al., GCN Circ. 23315) Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 96 246 147 19.42 +/- 0.09 white 589 6359 247 >21.0 v 3867 5503 393 >19.4 b 564 6323 413 >20.9 u 309 6117 639 >20.6 uvw1 4277 5912 393 >20.1 uvm2 4072 5707 393 >20.7 uvw2 5098 5298 197 >20.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23319 SUBJECT: GRB 181010A: ePESSTO NTT optical observations DATE: 18/10/10 18:48:11 GMT FROM: Paolo D'Avanzo at INAF-OAB T. Reynolds (Turku), S. Moran (Turku/NOT), P. D'Avanzo (INAF-OAB), D. B. Malesani (DAWN/NBI and DARK/NBI), M. De Pasquale (Istanbul Univ.), S. Campana, A. Melandri (INAF-OAB), J. Harmanen, H. Kuncarayakti (Turku), R. Cartier (CTIO), M. Dennefeld (IAP), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), I. Manulis (Weizmann) report: We observed the optical counterpart of GRB 181010A (Melandri et al. GCN 23309; Gorbovskoy et al. GCN 23310; Martone et al. GCN 23311; Troja et al. GCN 23312; Vielfaure et al. GCN 23315; Emery et al. GCN 23317) under the extended Public ESO Spectroscopic Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40; http://www.pessto.org ). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument in imaging mode starting from 2018-10-10 at 08:37:50 UT (i.e. 2.7 hours from the burst). The observations ended at 08:53:03 UT and were carried out with the R and i filters. The optical afterglow is clearly detected in the R-band image. From preliminary photometry, we find a magnitude of R ~ 22.9 +/- 0.1 (Vega, calibrated against the USNOB1 catalogue). The afterglow is marginally detected in the i-band. From preliminary forced photometry at the afterglow position, we derive a magnitude of i ~ 21.4 +/- 0.4 (AB, calibrated against the Pan-STARRS catalogue). These results, compared to previous reports (e.g. Martone et al. GCN 23311; Troja et al. GCN 23312; Vielfaure et al. GCN 23315), suggest for a significant fading of the optical afterglow flux. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23320 SUBJECT: GRB 181010A: Fermi GBM observation DATE: 18/10/10 19:34:51 GMT FROM: Peter Veres at UAH A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 05:55:59.39 UT on 10 October 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 181010A (trigger 560843764 / 181010247), which was also detected by the Swift/BAT (Melandri et al. 2018, GCN 23309). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 48.1 degrees. The GBM light curve shows two structured pulses followed a weak tail with an overall duration (T90) of about 60 s (50-300 keV). The time-averaged spectrum from T0-0.256s to T0+1.280s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.8 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 280 +/- 80 keV. The event fluence (10-1000 keV) in this time interval is (6.13 +/- 0.98)E-07 erg/cm^2. The 1.024 sec peak photon flux measured starting from T0-0.128 s in the 10-1000 keV band is 3.35 +/- 0.29 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23321 SUBJECT: GRB 181010A: Swift-BAT refined analysis DATE: 18/10/10 21:12:55 GMT FROM: Scott Barthelmy at NASA/GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), 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+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 181010A (trigger #866434) (Melandri, et al., GCN Circ. 23309). The BAT ground-calculated position is RA, Dec = 52.574, -23.023 deg, which is RA(J2000) = 03h 30m 17.7s Dec(J2000) = -23d 01' 22.7" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%. The mask-weighted light curve shows several overlapping peaks starting at ~T-5sec, peaking at ~T+8 sec, and returning to baseline at ~T+15 sec. T90 (15-350 keV) is 16.4 +- 2.2 sec (estimated error including systematics). The time-averaged spectrum from T-4.04 to T+15.21 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.52 +- 0.15. The fluence in the 15-150 keV band is 6.9 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+7.43 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. 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/866434/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23323 SUBJECT: GRB 181010A: REM optical and NIR afterglow detection DATE: 18/10/11 11:06:56 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S.Covino, D. Fugazza, A. Melandri (INAF-OAB), on behalf of the REM team, report: We observed the optical counterpart of GRB 181010A (Melandri et al. GCN 23309; Gorbovskoy et al. GCN 23310; Martone et al. GCN 23311; Troja et al. GCN 23312; Vielfaure et al. GCN 23315; Emery et al. GCN 23317; D'Avanzo et al. GCN 23319) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile). The observations were performed starting on 2018 October 10 at 05:56:52 UT (i.e. 61 seconds after the burst) and were carried simultaneously in the g, r, i, z, and H bands. The GRB afterglow is detected in the first set of optical and NIR images. From preliminary photometry we estimate the following magnitudes: r = 18.2 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue) H = 14.4 +/- 0.2 (Vega; calibrated against the 2MASS catalogue) at a mean time of 4.1 minutes from the GRB time (Melandri et al. GCN 23309). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23326 SUBJECT: GROND afterglow detection of GRB 181010A DATE: 18/10/11 16:01:19 GMT FROM: Patricia Schady at Swift P. Schady (Uni. of Bath, UK) and J. Bolmer (MPE, Garching) report: We observed the field of GRB 181010A (Swift trigger 866434; Melandri et al., GCN #23309) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations were performed in rapid response mode, and started at 05:59 UT, 3 mins after the GRB trigger. They were performed at an average seeing of 1.4" and at an average airmass of 1.0. We detect a new source at a position consistent with the X-ray and optical afterglow (Gorbovskoy et al., GCN #23310; Evans et al., GCN #23313; Emery, GCN #23317). Based on the first 3.3 min of total exposures in g'r'i'z' and 3 min in JHK, we measure the following preliminary AB magnitudes: g' = 20.02 +/- 0.02 mag r' = 19.33 +/- 0.01 mag i' = 19.13 +/- 0.02 mag z' = 18.56 +/- 0.01 mag J = 17.78 +/- 0.03 mag H = 17.02 +/- 0.03 mag Given magnitudes are calibrated against PanSTARRS and 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.03 in the direction of the burst (Schlafly & Finkbeiner 2011). We thank Markus Rabus for the excellend support from La Silla.