//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8825 SUBJECT: GRB 090118: Possible burst detection from Swift-BAT slew data DATE: 09/01/18 22:02:25 GMT FROM: Antonio Copete at Harvard U A. Copete, J. Grindlay (Harvard) S. Barthelmy, C. Markwardt, N. Gehrels (NASA/GSFC) We report the detection of a likely GRB candidate by the BAT Slew Survey (BATSS), pending confirmation by Swift XRT, in the slew that started at 13:54:02 UT and lasted 94 sec. The ground-calculated position is RA, Dec = 49.865, +18.478 deg, which is RA (J2000) = 03h 19m 28s Dec(J2000) = +18d 28' 40" with an uncertainty of 3.69 arcmin (90% confidence, including systematics). The detection was triggered by simultaneous detections of 6.9 sigma and 8.0 sigma from imaging in the overlapping energy bands of 15-50 keV and 15-150 keV, respectively. The burst mask-tagged lightcurve in the 15-150keV band shows a broad emission peak starting at T+66 sec, lasting 19 sec, and peaking 3 times at T+71, T+74 and t+ T +81 sec. T90 = 16sec and T50 = 8sec. The time-averaged spectrum over the exposure time of the source is best fit by a simple power law with photon index 1.35, and the fluence in the 15-150 keV band is 4.0 x 10^-7 erg/cm^2. A follow-up Swift ToO observation has been scheduled to begin at 20:52 UT, 6.97 hours after the burst. Optical/IR observers are encouraged to image this field as soon as possible as it is an early-evening object. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8826 SUBJECT: GRB 090118: GROND Upper Limits DATE: 09/01/19 02:23:14 GMT FROM: Andrea Rossi at TLS Tautenburg F. Olivares (MPE Garching), A. Rossi (Tautenburg Obs.), A. Kupcu Yoldas (ESO), J. Greiner, and A. Yoldas (both MPE Garching) report on behalf of the GROND team: We observed the field of the possible GRB 090118 (Swift BATSS trigger, Copete et al. GCN #8825) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPI/ESO telescope at La Silla (Chile). Observations started at 00:55 UT, about 11 hrs after the GRB. Comparison to the Digital Sky Survey reveals no new sources within the Swift/BAT error circle (Copete et al. GCN #8825). Co-added images of the first 8 minutes yield the following 5-sigma limits (in AB magnitudes): r' > 23.2 i' > 22.5 The magnitudes are calibrated against SDSS. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8827 SUBJECT: GRB090118 Swift/UVOT upper limits DATE: 09/01/19 11:47:20 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began white-band observations of the field of the likely GRB candidate detected in the BAT Slew Survey (BATSS), GRB 090118 (Copete et al., GCN 8825) at 2009-01-018 20:55:35 UT, 25.3 ks after the burst. We do not detect any new source within the Swift BAT error circle (Copete et al., GCN 8825) in a co-added white-band image down to the following 5-sigma upper limit: Filter T_start T_stop Exp Mag (ks) (ks) (s) (5-sigma upper limit) ------------------------------------------------------------- white 25.3 35.3 1292 > 21.1 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.13 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8828 SUBJECT: GRB 090118: Swift-XRT observations DATE: 09/01/19 17:41:00 GMT FROM: Antonia Rowlinson at U.of Leicester GRB 090118: Swift-XRT observations B.A. Rowlinson and K.L. Page (U. Leicester) report on behalf of the Swift-XRT team:   Swift-XRT began a 6 ks follow-up ToO observation of the likely BAT Slew Survey GRB 090118 (Copete et al., GCN Circ. 8825) 25.3 ks after the start of the slew during which the burst was detected. No X-ray source is detected within the 3.69 arcmin error circle, with a 3-sigma upper limit of 5.8x10^-3 count s^-1.   However, there is a source just outside the 90% error circle, at a position of RA, Dec = 49.8276, 18.4148, which is equivalent to:   RA (J2000) = 03 19 18.62 Dec (J2000) = +18 24 53.3   with an uncertainty of 7.1 arcsec (radius, 90% confidence). This is a distance of 260.9 arcsec from the BATSS position.This source has a count rate of (9.0 +/- 2.2)x10^-3 count s^-1 in the first 1.6 ks of data and appears to be fading to a count rate of (5.0 +/- 1.4)x10^-3 count s^-1 in the last 4.2 ks of data. A spectrum extracted for this source can be fitted with a power-law of spectral index Gamma = 5.9 (+1.8, -1.4) with an absorbing column density of 4.6 (+3.1, -2.2) x 10^21 cm^-2, in excess of/consistent with the Galactic column in this direction of 8.9x10^20 cm^-2. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8829 SUBJECT: GRB 090118: KPNO 4m Detection of Candidate Afterglow DATE: 09/01/19 21:29:12 GMT FROM: Adria C. Updike at Clemson U Adria C. Updike and Dieter H. Hartmann (Clemson University) report: Using the KPNO 4m telescope and the NEWFIRM instrument, we observed the field of GRB 090118 (GCN 8825, Copete et al.) beginning 11.6 hours after the burst in the J and H bands. Within the XRT error circle (Rowlinson & Page, GCN 8828) we detect a faint source at coordinates RA 03:19:18.6 Dec +18:24:54.3 Variability has not been confirmed. Further observations are planned. Time after burst Band Magnitude ------------------------------------------- 11.6 hours J 21.0 +/- 0.5 12.5 hours H 20.2 +/- 0.4 A total of 40 minutes of exposures were taken in each band and the results were stacked. Magnitudes are calibrated to the 2MASS point source catalog and against a nearby star (RA 03:19:16.7, Dec +18:25:14, J = 14.05). No correction has been made for galactic extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8830 SUBJECT: GRB 090118 (BATSS): GRT Optical Observation DATE: 09/01/19 21:50:01 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC), T. Okajima (JHU/GSFC), T. N. Ukwatta (GWU/GSFC), Y. Urata (Saitama U), C. Wallace (FGCU) We observed the field of the possible GRB 090118 detected by the BAT Slew Survey (Copete et al., GCN #8825) with the 14-inch Goddard Robotic Telescope (GRT) located at the Goddard Geophysical and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/). Thirteen set of 30 sec and 60 sec exposures were taken in the R filter starting from Jan. 19 00:38:11 (UT) about 10.5 hr after the trigger. We do not detect the optical afterglow both in the individual images and the combined image within the BATSS error circle and also the X-ray source found by the Swift/XRT (Rowlinson et al., GCN #8828). The estimated three sigma upper limit of the combined image (total exposure of 1170 sec) is ~17.6 mag using the USNO-B1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8831 SUBJECT: GRB 090118: KPNO 4m 2nd Epoch Observations DATE: 09/01/20 07:40:24 GMT FROM: Adria C. Updike at Clemson U Adria C. Updike and Dieter H. Hartmann (Clemson University) report: We observed the field of GRB 090118 (GCN 8825, Copete et al.) for a second epoch beginning 36.7 hours after the burst. Our observations consisted of 80 min of J band exposures. In the stacked image, we still detect the candidate (GCN 8829, Updike & Hartmann). We re-analyzed our first epoch image relative to 17 2MASS field stars, as well as our second epoch image. The brightness of the candidate source appears to be constant within photometric uncertainties. While slow fading can't be ruled out, the two-epoch results suggest that most likely the candidate source is not the afterglow of GRB 090118. Third epoch observations are planned. Time after burst Band Magnitude Exp time ------------------------------------------------------ 11.6 hours J 21.2 +/- 0.6 40 min 36.7 hours J 21.4 +/- 0.6 80 min The images have been placed on the following site. http://www.ces.clemson.edu/~aupdike/GRB090118/090118_J.jpg //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8832 SUBJECT: GRB 090118: Subaru NIR Observation DATE: 09/01/20 11:02:37 GMT FROM: Nobuyuki Kawai at Tokyo Tech Y. Minowa, T.-S. Pyo, H. Terada, K. Aoki (Subaru, NAOJ), and N. Kawai (Tokyo Tech) report on behalf of the Subaru GRB team: We observed the field of GRB 090118 (GCN 8825, Copete et al.) with IRCS on the 8.2 m Subaru Telescope in J band beginning 39.2 hours after the burst (18 min exposure, mid-time 05:10 UT, Jan. 20). The afterglow candidate reported by Updike et al. (GCN 8829, 8831) was detected with J=21.3 mag, where the magnitude is estimated using nearby 2MASS stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8840 SUBJECT: GRB 090118: Swift XRT Observations - Confirmation of an Afterglow DATE: 09/01/22 20:14:14 GMT FROM: Antonia Rowlinson at U.of Leicester B.A. Rowlinson and K.L. Page (U. Leicester) report of behalf of the Swift-XRT team: Swift-XRT completed a 10ks follow-up ToO obsevation of GRB 090118 (Copete et al. GCN Circ. 8825) approximately 250ks after the burst. These observations confirm the previous Swift-XRT observations (Rowlinson & Page GCN Circ. 8828) that a fading source has been detected with a decay slope of alpha=0.61 +/- 0.3. This source is confirmed as the afterglow. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8850 SUBJECT: GRB 090118: no afterglow candidate DATE: 09/01/24 19:23:07 GMT FROM: Jochen Greiner at MPI A. Rossi (Tautenburg Obs.), T. Kruehler, J. Greiner and F. Olivares (all MPE Garching), report on behalf of the GROND team: We report on further analysis and new observations of the optical afterglow candidate of GRB 090118 (Copete et al. 2009, GCN #8825). We re-analyzed our first epoch images (Olivares et al. 2009, GCN Circ. 8826), taken at about 11 hrs after the GRB. No source is seen in our NIR images at the position of the X-ray afterglow (Rowlinson et al. 2008, GCN Circ. 8828), giving upper limits (Vega system) of J > 20.6 H > 19.6 K > 18.7 calibrated against 2MASS field stars. The XRT position (Rowlinson et al. 2009, GCN Circ. 8828) is outside of the field-of-view of the g'r'i'z' detectors, so no statement can be made on the optical brightness during our first epoch. We observed the field of GRB 090118 again with GROND on 2009-01-22 at a mid-time of 01:30 UTC, about 100 hours after the burst. We clearly detect the candidate mentioned by Updike and Hartmann (2009, GCN Circ. 8829) in our optical filters, but not in the NIR: g'= 23.46 +- 0.11 (AB) r'= 23.27 +- 0.10 (AB) i'= 22.95 +- 0.12 (AB) z'= 22.25 +- 0.14 (AB) J > 21.5 (Vega) H > 20.5 (Vega) K > 19.6 (Vega) No correction for the foreground extinction of E(B-V)=0.135 mag has been applied. Comparing our g'r'i'z' values with the J and H detections of Updike & Hartmann (2009a; GCN Circ. 8829) and Minowa et al. (2009; GCN Circ. 8832) about two days earlier, we find that the spectral energy distribution is smooth, thus supporting the non-fading nature of this object as indicated already by the results of Updike & Hartmann (2009b; GCN Circ. 8831) and Minowa et al. (2009; GCN Circ. 8832). The detection in g'r'i'z' implies that the object, whatever its nature, is at a redshift smaller than 3.5. This excludes the possibility that this object is at high redshift and exhibited a long plateau phase. The plateau phase would have to last more than 3 days in the NIR range, while at X-rays a steady decline has been seen (Rowlinson & Page 2009, GCN Circ. 8840). We conclude that this object is very likely not the optical/NIR afterglow of GRB 090118. Instead, the object's SED is consistent with a low-redshift galaxy.