//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15883 SUBJECT: iPTF14yb: iPTF Discovery of an Optical Afterglow-like Transient DATE: 14/02/26 21:40:35 GMT FROM: S. Bradley Cenko at NASA/GSFC S. B. Cenko (NASA/GSFC), M. M. Kasliwal (OCIW/Princeton), D. A. Perley (Caltech), D. Jewitt (UCLA), M. Ishiguro (Seoul National University), A. V. Filippenko (UC Berkeley), A. Horesh (Weizmann Institute), A. De Cia (Weizmann Institute), A. Rubin (Weizmann Institute), A. Gal-Yam (Weizmann Institute), O. Yaron (Weizmann Institute), I. Arcavi (LCOGT/KITP), Y. Cao (Caltech), and P. E. Nugent (LBNL/UCB) report on behalf of a larger collaboration: As part of the ongoing Intermediate Palomar Transient Factory survey, we report the discovery of a new optical transient source, iPTF14yb, located at RA = 14:45:58.01, Dec: +14:59:35.4 (J2000.0). In an image obtained at the Palomar 48-inch Oschin Schmidt telescope beginning at 10:18 UT on 2014 February 26, we measure an r-band magnitude of r = 18.42 +/- 0.05 mag. In subsequent P48 imaging, the source faded rapidly, with a measured magnitude of r = 20.4 +/- 0.2 mag at 13:08 UT on 2014 February 26. Nothing was detected at this location (r > 20.5 mag) in an image obtained at 09:05 UT on 2014 February 26 (i.e., 1.2 hours prior to discovery). A coaddition of previous (i)PTF imaging of this location from 2009-2012 with P48 reveals no sources at this location to a limit of r > 22.7 mag. We obtained a target-of-opportunity spectrum with the Low Resolution Imaging Spectrometer (LRIS) mounted on the 10 m Keck 1 telescope beginning at 15:27 UT on 2014 February 26 (i.e., 5.2 hours after discovery). Our spectrum covers the wavelength range from the atmospheric cutoff at ~ 3200 A to 10000 A. Super-imposed on a relatively flat continuum, we detect a number of absorption features at a common redshift of z = 1.98 (preliminary wavelength calibration), including Mg II, Fe II, Mg I, and Ly-alpha. Given the rapid temporal evolution, the large distance and luminosity, and the observed spectrum, iPTF14yb resembles the optical afterglow of a gamma-ray burst. We have triggered radio and X-ray observations to confirm this hypothesis, and encourage additional follow-up at all wavelengths (including archival searches of this location). [GCN OPS NOTE(27feb14): Per author's request, MI was added to the author list.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15884 SUBJECT: iPTF14yb: Swift-XRT detection DATE: 14/02/27 09:26:21 GMT FROM: Andy Beardmore at U Leicester A.P. Beardmore, P.A. Evans and K.L. Page (U. Leicester) report on behalf of the Swift-XRT team: We have analysed 2.3 ks of XRT data for the PTF-detected transient / possible GRB iPTF14yb, from 24.8 ks to 42.8 ks after the time of the initial PTF observation. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the PTF error circle. The refined XRT position is RA, Dec = 221.49179, +14.99396 which is equivalent to: RA (J2000): 14 45 58.03 Dec(J2000): +14 59 38.3 with an uncertainty of 3.7 arcsec (radius, 90% confidence). This position is 2.9 arcsec from the PTF position. The source has a mean count rate of 4.7e-02 ct/sec and shows marginal evidence for fading at the 1.6-sigma level, with a decay slope of 1.14, however more data are required to confirm this. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.15 (+0.51, -0.30). The best-fitting absorption column is consistent with the Galactic value of 1.5 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.5 x 10^20 cm^-2 Intrinsic column: 0 (+6.2, -0) x 10^21 cm^-2 at z=1.98 Photon index: 2.15 (+0.51, -0.30) The ROSAT (PSPC) All Sky Survey 3-sigma upper limit at the position of this source is 0.056 ct/sec, which, given the spectrum above, corresponds to 0.03 ct/sec in the XRT; hence the source was not seen at the current flux level at the time of the RASS. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00033157. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15886 SUBJECT: iPTF14yb: RATIR Optical and NIR Observations of the optical transient DATE: 14/02/27 19:18:21 GMT FROM: Antonino Cucchiara at NASA/GSFC Antonino Cucchiara (ORAU/GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of the transient iPTF14yb (Cenko et al., GCN 15883, Beardmore et al., GCN 15884) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2014/02 27.28 to 2014/02 27.54 UTC (20.53 to 26.68 hours after the reported time of discovery), obtaining a total of 3.91 hours exposure in the r and i bands and 1.64 hours exposure in the Z, Y, J, and H bands. For the source reported by Cenko et al. (GCN 15883), in comparison with the SDSS DR9 and 2MASS, we obtain the following detections and upper limit (3-sigma): r 22.28 +/- 0.09 i 22.02 +/- 0.09 Z 21.98 +/- 0.24 Y 22.12 +/- 0.35 J 21.88 +/- 0.35 H > 21.59 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the transient. Our photometry indicates that the transient is fading in r band according to a single power law with temporal index alpha=1.04. This behavior is also typical of a long gamma-ray burst type transient as suggested by Cenko et al. (GCN 15883) We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15887 SUBJECT: PTF14yb: GROND Transient Detection DATE: 14/02/27 22:00:43 GMT FROM: John Graham at STScI K. Varela, J. F. Graham, J. Greiner, (all MPE Garching) and D. A. Kann (TLS Tautenburg) report on behalf of the GROND team: We observed the iPTF-detected GRB optical afterglow-like transient iPTF14yb (Cenko et al. GCN 15883) simultaneously in g'r'i'z'JHK with the GROND instrument (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at La Silla Observatory (Chile). Observations started at 08:09 UT on February 27th 2014 (approximately 22 hours after initial detection). We clearly detect the source in the g'r'i'z' bands at the following (AB) magnitudes and errors: g = 22.37 +/- 0.04 r = 22.11 +/- 0.03 i = 22.07 +/- 0.06 z = 22.11 +/- 0.03 We do not detect the source in the JHK bands above our 3-sigma AB limits given below: J > 21.6 H > 21.0 K > 19.7 The values we measure are comparable with the concurrent RATIR observations (Cucchiara et al., GCN 15886). Given magnitudes are calibrated against SDSS field stars (g'r'i'z') as well as 2MASS field stars (JHK) and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.03 mag in the direction of the burst (Schlegel et al. 1998). Given the unusually flat spectral slope of 0.25 +/- 0.07 (after correcting for Galactic extinction) apparent in our photometry and the flat spectra noted in Cenko et al. (GCN 15883) with the present data we cannot distinguish between a powerlaw or a thermal spectrum. Deep NIR imaging is encouraged to allow this distinction. John Graham //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15888 SUBJECT: IPN triangulation of GRB 140226A, a possible GRB counterpart to iPTF14yb DATE: 14/02/28 00:25:44 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the Interplanetary Network, S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, and V. Connaughton, M. S. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi GBM team, report: We have examined IPN data for the period 2014-02-26T09:05:00 to 2014-02-26T10:18:00, when the optical transient source iPTF14yb was discovered (Cenko et al. GCN 15883). During this time, Konus, Swift, INTEGRAL, RHESSI, Odyssey, and MESSENGER were operating and returning data, although in the presence of increased solar activity. Suzaku was off. We have identified one event, at 2014-02-26T10:02:57 (36177 s), observed by Odyssey, INTEGRAL (SPI-ACS) and Konus (in the waiting mode), whose duration is ~15 s, and whose localization is consistent with iPTF14yb. Specifically, the Odyssey-INTEGRAL triangulation annulus is centered at RA, Dec = 206.305 degrees (13 h 45 m 13.2 s), -7.925 degrees (-7 o 55 ' 29 "), with radius 27.577 +/- 0.607 degrees (3 sigma). iPTF14yb lies 0.157 degrees from the center line of the annulus. The probability that the transient lies within the annulus by chance is roughly 0.005. At the time of this event, the optical transient was below the horizon for Swift, and no emission consistent with a GRB was seen in the data. Fermi was in the SAA. The RHESSI and MESSENGER backgrounds were high and variable due to solar activity, making the identification of this burst uncertain in their data. If this is indeed the GRB counterpart to iPTF14yb, this would appear to be the first GRB to be discovered on the basis of its optical counterpart. This triangulation can be improved. Detailed spectral and temporal information on this burst will be presented in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15889 SUBJECT: Konus-Wind observation of GRB 140226A DATE: 14/02/28 08:16:29 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 140226A (IPN trangulation: Hurley et al., GCN 15888), which is a possible counterpart to the optical transient source iPTF14yb (Cenko et al. GCN 15883), was detected by Konus-Wind in the waiting mode against the high solar particle background. The light curve shows a single pulse, which peaked at T0=36177 s UT (10:02:57) and had a duration of ~15 s. As observed by Konus-Wind, the burst had a fluence of (5.6 ± 1.1)x10^-6 erg/cm2 and a 2.944-s peak energy flux, measured from T0 of (8.6 ± 1.7)x10^-7 erg/cm2 (both in the 20 - 10000 keV energy range). Modeling the KW 3-channel time-integrated spectrum (from T0-6.263 s to T0+5.513 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.1 ± 0.1, and Ep = 414 ± 79 keV. All the quoted errors are estimated at 1 sigma confidence level. All the presented results are preliminary. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB140226A/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15891 SUBJECT: GRB 140226A / iPTF14yb: Swift-XRT confirms a fading X-ray source DATE: 14/02/28 15:11:10 GMT FROM: Andy Beardmore at U Leicester A.P. Beardmore (U. Leicester) reports on behalf of the Swift-XRT team: The Swift-XRT has continued to observe the source GRB 140226A / iPTF14yb (Cenko et al., GCN Circ. 15883; Cucchiara et al., GCN Circ. 15886; Varela et al., GCN Circ. 15887; Hurley et al., GCN Circ. 15888) and has now accumulated 9.1ks of data in Photon Counting (PC) mode. The X-ray light curve shows that the source announced by Beardmore et al. (GCN Circ. 15884) has faded, with a powerlaw decay index of 1.47 +0.29 -0.25 (with respect to the Konus-Wind T0; Golenetskii et al., GCN Circ. 15889). Taken together with the fading optical source and IPN localisation, the decaying X-ray source confirms the GRB origin of the object. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00033157. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15892 SUBJECT: GRB 140226A/iPTF14yb: RATIR Optical and NIR Observations DATE: 14/02/28 15:47:46 GMT FROM: Antonino Cucchiara at NASA/GSFC Antonino Cucchiara (ORAU/GSFC),Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed again the field of the GRB-like transient iPTF14yb (Cenko et al., GCN 15883, Beardmore et al., GCN 15884, 15891) 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 2014/02 28.34 to 2014/02 28.53 UTC (roughly 46 to 50 hours after the reported time of discovery), obtaining a total of 2.63 hours exposure in the r and i bands and 1.12 hours exposure in the Z and J bands. For the source within the Cenko et al. (GCN 15883) error circle, in comparison with the SDSS DR9 and 2MASS, we obtain the following detections and upper limits: r 23.28 +/- 0.32 i 22.51 +/- 0.20 Z > 22.11 J > 21.73 The detections are at the 2-sigma level and the upper limits at the 3-sigma level. These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Our photometry indicates that the transient is still fading in r band with a similar decay index (within the systematic errors) as reported by Cucchiara et al. (GCN 15886). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. [GCN OPS NOTE(28feb14): Per author's reuqest, the Y & H bands were removed from the last sentence in the first paragraph.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15893 SUBJECT: GRB 140226A/iPTF14yb: Mondy optical observations DATE: 14/02/28 16:22:51 GMT FROM: Alexei Pozanenko at IKI, Moscow A.Volnova (IKI), A. Pozanenko (IKI), I. Korobtsev (ISTP), E. Klunko (ISTP), M. Eselevich (ISTP), report on behalf of larger GRB follow-up collaboration: We observed the field of transient iPTF14yb (Cenko et al., GCN 15883, Beardmore et al., GCN 15884, 15891) of possible GRB 140226A (Hurley et al., GCN 15888) with AZT-33IK telescope of Mondy observatory on Feb. 27 between (UT) 18:59:34 - 19:59:36. On a stacked R-filter image of 30 x 120 s we marginally detected iPTF14yb source with S/N ~2, and photometry of the source R = 23.0 at Feb. 27.81221 (mid). The photometry is based on SDSS J144600.66+145826.2 star assuming R(Lupton transformation)= 17.624 +/- 0.018 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15894 SUBJECT: GRB 140226A/iPTF14yb: Swift/UVOT Observations DATE: 14/02/28 16:39:17 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU), F. E. Marshall (NASA/GSFC) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: Swift/UVOT started observations of GRB140226A/iPTF14yb (Cenko et al., GCN Circ. 15833) 25718 s after the IPN trigger (Hurley et al., GCN Circ. 15888). No optical counterpart is detected at the position of the iPTF or XRT positions (Beardmore et al., GCN Circ 15884) in summed exposures. Preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al al. 2011, AIP Conf. Proc. 1358, 373) is: Filter T_start (s) T_stop (s) Exp(s) Mag uvm2 25718 43672 2180 >21.24 v 124093 136265 4877 >20.96 v 147705 154552 1822 >20.54 No correction has been made for the expected Galactic extinction corresponding to E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15895 SUBJECT: GRB 140226A/iPTF14yb: 1.23m CAHA observations DATE: 14/03/01 07:09:10 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel (IAA-CSIC/UPV-EHU), A. Sanchez-Lavega, I. Ordonez, S. Perez-Hoyos, R. Hueso (UPV/EHU), J.J. Salamero, D. Cebrian, P. Martorell, R. Pidal (Obs. Guirguillano), report on behalf of the BEGIRA project: "We carried out optical observations of the GRB140226A/iPTF14yb transient field (Cenko et al., GCN 15883, Beardmore et al., GCN 15884, 15891) with the 1.23m CAHA telescope. The observations were performed in the R-band on Feb 28.14668-28.19763 UT. The object is detected with a Vega magnitude of R~23 calibrated against the USNO-B1.0 catalog." [GCN OPS NOTE(04mar14): Per author's request, A.S-L was added to the author list.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 16037 SUBJECT: GRB 140226A/iPTF14yb: Mondy optical observations DATE: 14/03/25 15:11:32 GMT FROM: Alexei Pozanenko at IKI, Moscow A.Volnova (IKI), A. Pozanenko (IKI), I. Korobtsev (ISTP), E. Klunko (ISTP), M. Eselevich (ISTP), report on behalf of larger GRB follow-up collaboration: We observed the field of transient iPTF14yb (Cenko et al., GCN 15883, Beardmore et al., GCN 15884, 15891) a possible counterpart of GRB 140226A (Hurley et al., GCN 15888) with AZT-33IK telescope of Mondy observatory on Feb. 28 between (UT) 19:22:46 - 21:52:52 R-filter. On a stacked image of 75 x 120 s we clearly detected iPTF14yb source with a magnitude of R = 22.86 ± 0.17 at Feb. 28.85959 (mid) or 2.44087 days after GRB 140226A trigger (Hurley et al., GCN 15888). The photometry is based on SDSS J144600.66+145826.2 star assuming R(Lupton transformation)= 17.624 +/- 0.018.