Gamma-ray Burst 170105A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #20382
J. Tonry, L. Denneau, A. Heinze, B. Stalder, H. Weiland (IfA), C. W. Stubbs (Harvard), K. W. Smith, S. J. Smartt, (QUB), D. R. Young (QUB), A. Rest (STScI), K. C. Chambers (IfA), M. Coughlin (Harvard), M. E. Huber (IfA), D. E. Wright (QUB), H. Flewelling, E. A. Magnier, A. S. B. Schultz, C. Waters, R. J. Wainscoat (IfA)
Following on from GCN 20377, we have processed the ATLAS data beginning at 57758.296 (2016-01-05.296 UT) which started at a pointing centre of RA=80, DEC=-30, and moved north and east across the northern sky lobe to RA=170,80.
We find one transient that appears to be new (and recovered old ones). This object has some unusual characteristics that warrant further attention
ATLAS17aeu 09:13:13.89 +61:05:33.6 (138.30789 +61.09267) J2000
The position is within the inner 16% probability contour. This object is not spatially coincident with any star or host galaxy.
The lightcurve faded by 0.85 mag over 1.176hrs
```
  MJD           c mag  err
 57758.4129676  18.05 0.09
 57758.4144595  18.18 0.1 
 57758.4267173  18.22 0.1 
 57758.4419066  18.58 0.13
 57758.4469072  18.45 0.11
 57758.4479226  18.34 0.11
 57758.454986   18.39 0.11
 57758.4619614  18.90 0.18
```
(the cyan mag is effectively an average of g and r).
The object has now fallen below the detection limit (orange filter; o ~ 19) on the night of 57759.
Such a fast fade is unusual if the object is extragalactic.
The obvious immediate explanations for this object are 1) It is not a real astrophysical transient. We consider this unlikely. 2) The photometric errors are under-estimated and it is flat. We consider this unlikely, and the errors to be reliable. 3) It is a Galactic CV. But the fading is too fast for typical CVs. 4) It is an M-dwarf flare. But the fading is slow for a typical M-dwarf (which are usually between 2 and >5 mags per hour)
We note that there is no faint point source in the Pan-STARRS 3Pi stacked sky (Chambers et al. 2017, arXiv:1612.05560, and http://panstarrs.stsci.edu). There is no counterpart in the MPC, Vizier, WISE, various CV and stellar catalogues.
The object is 23 arcsec from the galaxy SDSS J091312.36+610554.2 which has a spectroscopic redshift of z = 0.199 +/- 0.00004. This implies a luminosity distance of 990 Mpc (for Ho=69). If ATLAS17aeu is related, it would be at a projected distance of 75kpc from the Galaxy.
This luminosity distance is consistent with the BAYESTAR 3D volume rendering (Singer et al. 2016, ApJ 829, L1) of G268556 which suggests a 10-90 percentile probability of 520-1010 Mpc in this direction.
If it were associated with the z = 0.199 +/- 0.00004 galaxy, then it would be unusually luminous (M_g ~ -21.5).
While a Galactic origin is still the most probable, it remains to be confirmed. We encourage a search of any contemporaneous data taken at the same time we detected this object and deep imaging of the position to recover any host object (star or galaxy).
GCN Circular #20387
R. Marcinkowski (PSI), H. Xiao (PSI) and W. Hajdas (PSI) report on behalf of the POLAR collaboration:
At 2017-01-05T06:14:07.0 UT(T0), during a routine on-ground search of data, POLAR detected the GRB 170105A, which was also observed by SPIACS at 2017-01-05T06:14:06 and Konus-Wind at 22450.264s UT (06:14:10.264).
The POLAR light curve consists of 1 peak with duration (T90) of 2.0 +/- 0.5 s measured from T0. The 0.5 s peak flux at T0 + 0.8 s is equal to 2490 +/- 90 counts/sec. POLAR recorded 3600 +/- 160 events from the burst. Above measurements are in the energy range of about 80 - 500 keV.
LC_URL: http://polar.psi.ch/triggers/GRB_170105A_raw.png or http://polar.psi.ch/pub/lc.php?event=GRB+170105A
The analysis results presented above are preliminary. Calibration of the instrument is ongoing. POLAR is a dedicated Gamma-Ray Burst polarimeter which was launched on-board the Chinese space laboratory Tiangong-2 (TG-2) on Sep 15, 2016. The energy detection range of POLAR is ~ 50-500 keV. More information about POLAR can be found at http://polar.psi.ch/pub , http://polar.ihep.ac.cn/en/ and http://isdc.unige.ch/polar/ .
This message is quotable in publications.
GCN Circular #20392
P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia(ASDC), N. Gehrels (NASA/GSFC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:
Swift has performed a targetted observation of the interesting transient ATLAS17aeu (Tonry et al., LVC Circ. 20382). The observations ran from 00:00 UT to 01:37 UT on 2017 Jan 7, and contained 1.4 ks of cleaned PC mode data.
A faint, uncatalouged X-ray source is found at RA, Dec = 138.3059, +61.0919 degrees, which corresponds to:
```
RA (J2000):  09h 13m 13.42s
Dec (J2000): +61d 05' 30.8")
```
with an uncertainty of 6.3 arcsec (radius, 90% confidence). This is 4.1" from the position of ATLAS17aeu, consitent with that object.
This source ("source5" of the XRT follow up of G268556) has a 0.3-10 keV count rate of 7.2 (+/-2.9) �10^-3 ct s^-1, corresponding to a 0.3-10 keV flux of 3.1 (+/-1.2) �10^-13 erg cm^-2 s^-1, assuming a power-law spectrum with Gamma=1.7 and NH=3e20 cm^-2. This is below the upper limit derived from the RASS at the source location. This source has not been previously observed by public XMM data, or Swift observations.
At the present time we cannot ascertain whether the source is variable, but follow up in encouraged.
A second, catalogued ("rank 4") source is also detected in our observations. Details of both sources are below.
For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3e20 cm^2, and photon index (Gamma)=1.7 RANK 3 sources
==============
These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger.
```
  Source 5:
  =============
    RA:          138.3059 ( = 09h 13m 13.42s) J2000
    Dec:         +61.0919 ( = +61d 05' 30.8") J2000
    Error:       +6.3 (arcsec, radius, 90% confidence).
    Peak Rate:   7.2e-03 +/- 2.9e-03 ct/sec (0.3-10 keV)
    Peak Flux:   3.1e-13 +/- 1.2e-13 erg cm^-2 s^-1 (0.3-10 keV)
    RASS UL:     1.8e-02 ct/sec, 3-sigma, converted to XRT (0.3-10 keV)
    
       so the source is not above the RASS 3-sigma upper limit.
    There is no evidence for fading.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW object.
```
RANK 4 sources
==============
These are catalogued X-ray sources, showing no signs of outburst compared to previous observations, so they are not likely to be related to the GW trigger.
```
  Source 4:
  =============
    RA:          138.0838 ( = 09h 12m 20.11s) J2000
    Dec:         +60.9299 ( = +60d 55' 47.6") J2000
    Error:       +5.1 (arcsec, radius, 90% confidence).
    Peak Rate:   1.6e-02 +/- 4.4e-03 ct/sec (0.3-10 keV)
    Peak Flux:   6.7e-13 +/- 1.9e-13 erg cm^-2 s^-1 (0.3-10 keV)
    Cat Source:  1RXS J091222.2+605603 in the ROSAT/RASSFSC catalogue
    Separation:  22.1" from the XRT source
    Cat Rate:    2.5e-02 +/- 9.4e-03 ct/sec
    Cat Flux:    7.1e-13 +/- 2.6e-13 erg cm^-2 s^-1 (0.3-10 keV)
       so the source is not above the catalogued flux.
    There is no evidence for fading.
    NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy
      which is consistent (within 3-sigma) with the distance to the GW object.

    A SIMBAD object `2MASS J09122029+6055503' is 3.1" away.
    There is 1 2MASS object within the source's 3-sigma error radius.
```
This circular is an official product of the Swift team.
GCN Circular #20393
M. M. Kasliwal (Caltech), S. M. Adams (Caltech), H. Vedantham (Caltech), V. Bhalerao (IUCAA), S. B. Cenko (NASA/GSFC), R. Quimby (SDSU)
report on behalf of the GROWTH (Global Relay of Observatories Watching Transients Happen) and iPTF (intermediate Palomar Transient Factory) collaborations
We observed the position of the fast-fading ATLAS17aeu (Tonry et al. LVC GCN#20382) with the Large Format Camera on the Palomar 200-inch Hale Telescope. At 2017-01-07 08:05:33 UTC, we found that ATLAS17aeu had faded further to i=21.9 +/- 0.3 mag (AB mags, calibration wrt SDSS).
If we fit a power law to the decay, the best-fit slope is 1.1 +/- 0.2 and best-fit t_zero is 57758.322 +/- 0.043 (i.e. 21.5 hr after GW trigger, LVC GCN#20364). We caution that we have not corrected for the filter differences between ATLAS and LFC. Incidentally, this t_zero is consistent with GRB070105A reported by POLAR (GCN#20387) and detected by ASTROSAT (GCN#20389). The hypothesis that this is the afterglow of the GRB appears consistent with the X-ray detection reported by Swift (Evans et al. LVC GCN#20390).
GCN Circular #20396
A. Corsi (TTU), M.M. Kasliwal (CalTech), D.A. Frail (NRAO), and N.T. Palliyaguru (TTU) report:
We observed the position of the fast-fading ATLAS17aeu (Tonry et al. LVC GCN#20382) located in the error region of LIGO/Virgo G268556 (LVC GCN#20364) with the Karl G. Jansky Very Large Array (VLA) in its A configuration. The observations started on 2017-Jan-07 14:06:40 UT, ended on 2017-Jan-07 15:06:29 UT, and were carried out in C-band (central frequency of about 6 GHz).
A provisional reduction of our data shows a radio source located at the position of ATLAS17aeu. For this source, we measure a radio flux of (159.0+/-9.8) uJy at 6.2 GHz.We note that the broad-band detection (radio, optical, and X-rays) of ATLAS17aeu is consistent with a GRB afterglow hypothesis (see Evans et al. LVC GCN#20390 and Kasliwal et al. LVC GCN#20393).
Further observations are planned.
We thank the VLA staff for rapidly executing these observations.
GCN Circular #20397
S. B. Cenko and E. Troja (NASA Goddard Space Flight Center) report on behalf of a larger collaboration:
We imaged the location of ATLAS17aeu (Tonry et al., LVC Circ. 20382) with the Large Monolithic Imager (LMI) on the 4.3 m Discovery Channel Telescope in Happy Jack, AZ. Observations were obtained in the g, r, and i filters beginning at 10:56 UT on 2017 January 7 (dt ~ 3.0 d after the GW trigger time). The optical source is clearly detected in all three filters, with the following AB magnitudes (see also Kasliwal et al., LVC Circ. 20393)
```
g = 22.45 +/- 0.05
r = 22.08 +/- 0.05
i = 21.96 +/- 0.05
```
The resulting SED is reasonably well fit by a power-law (fnu ~ nu^-alpha) with alpha ~ 0.9.
GCN Circular #20400
S.R. Oates (Uni. of Warwick), A. A. Breeveld (MSSL-UCL), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia(ASDC), N. Gehrels (NASA/GSFC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J.A. Nousek (PSU), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:
The Swift/UVOT performed targetted observations of the field of ATLAS transient ATLAS17aeu (Tonry et al., LVC Circ. 20382) from 00:00 UT to 01:35 UT on 2017 Jan 7 and again between 16:01 UT on 2017 Jan 7 to 01:30 on 2017 Jan 08. No optical afterglow consistent with the ATLAS position or 'source5' of the XRT follow up of G268556 (Evans et al., GCN Circ. 20390) is detected in the UVOT exposures at more than 3 sigma. We do note however a source at 2.9 sigma in the w2 filter, which in comparison to the second observation appears to have faded.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are:
```
Filter    T_start(UT)  T_stop(UT)  Exp(s)    Mag/3sigUL
v          7.007           7.009          144       > 19.1
v          7.667           7.936          1009      > 20.3

u          7.018           7.019          106      > 18.6
u          7.881           8.016          311       > 19.2

w1         7.014           7.018          290       > 19.5
w1         7.876           7.947          801       > 20.2

m2         7.009           7.014          435       > 20.0
m2         7.670           7.943          2413      > 21.2

w2         7.000           7.067          690       > 20.7   (20.76 +/- 0.37 detection at 2.9 sigma)   
w2         7.658          8.069          5177      > 22.0   (22.41 +/- 0.53 detection at 2.1 sigma)
```
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 transient (Schlegel et al. 1998).
GCN Circular #20406
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Tsvetkova, A. Kozlova, and T. Cline on behalf of the Konus-Wind team,
K. Hurley, on behalf of the IPN, and
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, report:
The long-duration, soft-spectrum GRB 170105A was detected by POLAR (Marcinkowski et al., GCN Circ. 20387), AstroSat (CZTI; Sharma et al., GCN Circ. 20389), Konus-Wind, and INTEGRAL (SPI-ACS) at about 22447 s UT (06:14:07).
We have triangulated this GRB to a Konus-INTEGRAL annulus centered at RA(2000)=129.749 deg (08h 38m 60s) Dec(2000)=+27.904 deg (+27d 54' 14"), whose radius is 34.255(-14.832,+1.812) deg (3 sigma).
This localization may be improved.
The distance between the annulus center line and the ATLAS17aeu optical transient reported by Tonry et al. (LVC Circ. 20382) is 0.57 degrees, strengthening the association of the transient with the GRB initially suggested by Kasliwal et al. (LVC Circ. 20393).
A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB170105_T22450/IPN/.
As observed by Konus-Wind, the burst had a fluence of 2.56(-0.13,+0.18)x10^-6 erg/cm2, and a 64-ms peak energy flux, measured from T0-0.204 s, of 2.47(-0.30,+0.58)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170105_T22450/.
GCN Circular #20407
K. C. Chambers (IfA), S. Smartt (QUB), J. Tonry, L. Denneau, A. Heinze, B. Stalder, H. Weiland (IfA), C. W. Stubbs (Harvard), K. W. Smith (QUB), T.-W. Chen (MPE), T. Kruehler (MPE), D. R. Young (QUB), A. Rest (STScI), M. Coughlin (Harvard), M. E. Huber (IfA), D. E. Wright (QUB), H. Flewelling, E. A. Magnier, A. S. B. Schultz, C. Waters, R. J. Wainscoat (IfA)
Further to our discovery of ATLAS17aeu (Tonry et al. GCN 20382), we took a spectrum with Gemini-North + GMOS (R400 grating, 4491-8778 Angs) on MJD = 57761.595. We also took an r-band image on the same night.
The spectrum has a blue featureless continuum, with a signal-to-noise in the continuum S/N~10 at 7000Angs. There are no clear emission or absorption lines visible that can anchor a redshift estimate.
The spectrum is not unlike some GRB afterglows as shown in the compilation of Fynbo et al. 2009, ApJS 185, 526 e.g. GRB060512, at z~2.1, GRB061110A (z=0.7578), GRB070129 (no z estimate, but below z<3.4)
We report three more photometric points, two from Pan-STARRS1 and the other from Gemini+GMOS.
```
MJD           Mag           Telescope
57758.38159   18.18 0.04 i  Pan-STARRS1
57759.46468   20.90 0.12 i  Pan-STARRS1
57761.51968   22.77 0.17 r  Gemini+GMOS
```
These data further support the hypothesis of Kasliwal et al. GCN 20393 that this is most likely the afterglow of GRB170105A, supported by the x-ray and radio detections of Evans et al. GCN 20390 and Corsi et al. GCN 20396.
Using the POLAR detection time, a temporal index of F_nu \propto t**(-1.4) would be consistent with the photometry reported to date, typical of GRB afterglows.
We note there are several other faint galaxies closer to ATLAS17aeu than the brighter galaxy at z = 0.199 highlighted in Tonry et al. (GCN 20382). They have SDSS photometric redshifts of z ~ 0.35 - 0.38, but are marginal detections in more than one band and therefore the photometric redshifts are uncertain.
GCN Circular #20412
V. Bhalerao and D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Detailed analysis of AstroSat CZTI data for GRB170105A (POLAR Observation: R. Marcinkowski et al., GCN Circ. 20387; CZTI detection: Sharma et al., GCN Circ. 20389) was carried out for localising the GRB. We modelled the counts in various quadrants using a raytracing code based on the instrument geometry. The GRB is localised to a 550 sq. deg. area, centred roughly on RA, Dec = 60, +80. While spectral fits are not possible at the current stage, the data indicate a rather soft spectrum, with strongest detection around 60-80 keV and almost no counts above 100 keV. Along with the T90 measurement in Sharma et al., GCN Circ. 20389, this suggests that GRB170501A was a long GRB.
A pdf showing the localisation region is available at: http://www.iucaa.in/~astrosat/czti_grb/GRB170105A/heal/GRB170105A_localisation.pdf
A healpix map with the localisation region is available at: http://www.iucaa.in/~astrosat/czti_grb/GRB170105A/heal/GRB170105A_localisation.fits
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
GCN Circular #20413
Varun Bhalerao (IUCAA), Sujay Mate (IUCAA), Dipankar Bhattacharya (IUCAA), Sukanta Bose (IUCAA), Gulab Chand Dewangan (IUCAA), Ranjeev Misra (IUCAA), Sanjit Mitra (IUCAA), A R Rao (TIFR), Tarun Souradeep (IUCAA), Santosh Vadawale (PRL), on behalf of the Astrosat CZTI team report:
Bhalerao et al. (GCN Circ. 20412) have used AstroSat CZTI to infer that GRB170105A is a long GRB, and have localised it to a ~550 square degree region (1-sigma). This region includes 3.9% probability of containing the LIGO trigger G268556, based on the revised LALInference sky map (Greco et al, 20385). The overlap with the IPN triangulation (Svikin et al., GCN Circ. 20406) is about 50 square degrees.
The position of ATLAS17aeu (Tonry et al., GCN Circ. 20382) is marginally outside the AstroSat CZTI error region, consistent at better than 1.1 sigma. This further indicates that ATLAS17aeu is the afterglow of GRB170105A (Kasliwal et al., GCN Circ. 20393).
GCN Circular #20415
P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia (ASDC), N. Gehrels (NASA/GSFC), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:
Swift has continued to observed ATLAS17aeu (Tonry et al., LVC Circ. 20382), gathering a total of 21.3 ks of data, from T0+222 ks to T0+470 ks (where T0 is the GW trigger time). The X-ray counterpart (Evans et al., LVC Circ. 20390) is now confirmed to be fading.
Assuming the trigger time from the GW event (LVC Circ. 20364) the light curve is decaying with a power-law index of 2.2 (+1.1, -1.2). If instead we take T0 from GRB 170105A (Marcinkowski et al., GCN Circ. 20387), the decay index is 1.7 (+1.1, -0.9). At the mid-point of the latest observation, GW_T0+453 ks (=GRB_T0+381 ks) the 0.3-10 keV XRT count-rate was 0.0017 (+/- 0.0006) ct/sec.
A spectrum compiled from the data can be fitted with an absorbed power-law, with NH consistent with the Galactic value of 4.6e20 cm^-2 (Willingale et al. 2013) and photon index Gamma=1.60 (+0.4, -0.3).
Using this spectrum the count-rate above corresponds to an observed (unabsorbed) 0.3-10 keV flux of (6.7+/-2.4)e-14 ( [7.2+/-2.6]e-14) erg cm^-2 s^-1.
The spectral and temporal indices are consistent with the values typically seen for X-ray GRB afterglows (e.g. the Swift-XRT GRB catalogue: http://www.swift.ac.uk/xrt_live_cat/; Evans et al. 2009).
This circular is an official product of the Swift GW follow up team.
GCN Circular #20416
A. Melandri (INAF-OAB), S. Piranomonte (INAF-OAR), P. D'Avanzo (INAF-OAB), G. Greco (Urbino University/INFN Firenze), G. Stratta (Urbino University/INFN Firenze), S. Ascenzi (INAF-OAR), M.T. Botticella (INAF-OAC), E. Palazzi (INAF-IASF Bo), A. Rossi (INAF-IASF Bo), E. Cappellaro (INAF-OAPD), S. Covino (INAF-OAB), V. D'Elia (INAF-ASDC), L. Amati (INAF-IASF Bo), L. A. Antonelli, (INAF-OAR), M. Branchesi (Urbino University/INFN Firenze), S. Campana (INAF-OAB), F. Getman (INAF-OAC), A. Grado (INAF-OAC), L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), L. Nicastro (INAF-IASF Bo), E. Pian (SNS-Pisa), L. Pulone (INAF-OAR), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), L. Tomasella (INAF-OAPD), S. Yang (INAF-OAPD), E. Brocato (INAF-OAR), L. Di Fabrizio, G. Mainella (INAF/TNG) on behalf of GRavitational Wave Inaf TeAm report:
We observed the position of the transient ATLAS17aeu (Tonry et al., LVC Circ. 20382) with the TNG 3.6m telescope located in Canary Islands equipped with the DOLORES camera in imaging mode. Observations consisted in 8x120s exposures in the I-band.
The transient is clearly detected with a magnitude I = 22.5 +/- 0.3 (Vega) at a mid time of 14:12 UT on 2017 Jan 8.
GCN Circular #20417
D. Xu (NAOC/CAS), J.Z. Liu, H.B. Niu, Y. Zhang, X. Zhang, G.X. Pu, S.G. Ma, T.Z. Yang, F.F. Song (XAO), X. Zhou, T.M. Zhang (NAOC/CAS), H.B. Zhao, B. Li, G.T. Zhaori (PMO), J.M. Bai, J.R. Mao (YNAO) report on behalf of a Chinese Gravitational Wave collaboration:
We have performed tiled observations of LIGO/Virgo G268556 (LVC, GCN 20364) using the Nanshan One-meter Wide field Telescope (NOWT), Xinjiang, China, the 0.6/0.9-m Schmidt telescope at Xinglong, Hebei, China, and the 1-m telescope at Xuyi, Jiangsu, China.
The Nanshan 1-m has a FOV of 1.3x1.3 deg^2, and covered the position of ATLAS17aeu (Tonry et al. GCN 20382), the potential optical afterglow of GRB 170105A (e.g., Marcinkowski et al., GCN 20387; Sharma et al., GCN 20389; Kasliwal, et al., GCN 20393), in a single night. We obtained an upper limit of m(V)>20.0 mag (3 sigma) at 14:55 UT on 2017-01-07.
The 0.6/0.9-m Schmidt telescope has a FOV of 1.5x1.5 deg^2, and covered the position of ATLAS17aeu also in a single night. We obtained an upper limit of m(White)>18.8 mag (5 sigma) at 18:26 UT on 2017-01-08.
The Xuyi 1-m has a FOV of 3.0x3.0 deg^2, and covered the position of ATLAS17aeu in a single night. We obtained an upper limit of m(r)>14 mag (3 sigma) at 14:32 UT on 2017-01-09.
In addition, we note that the two sources, dubbed EWE001 and EWE002, in GCN 20394, are obviously known sources in several surveys such as DSS II and SDSS.
GCN Circular #20419
T. Kupfer (Caltech), R. Quimby (SDSU), S. M. Adams (Caltech), H. Vedantham (Caltech), M. M. Kasliwal (Caltech)
report on behalf of the GROWTH (Global Relay of Observatories Watching Transients Happen) and iPTF (intermediate Palomar Transient Factory) collaborations
We report the spectroscopic follow-up observations on ATLAS17aeu (Tonry et al. LVC GCN #20382) and iPTF17cw (Kasliwal et al. LVC GCN #20398) using the Double Beam spectrograph (DBSP) on the Palomar 200-inch telescope. The position of both targets are within the probability contour of LIGO/Virgo G268556 (LVC, GCN #20364). All observations were obtained on 2017 Jan 7 UT under poor weather conditions with a partly cloudy sky. Classifications were performed using Superfit (Howell et al. 2005, ApJ, 634, 1190).
ATLAS17aeu was observed on 2017-01-07.5 UT with a total exposure time of 60 min resulting in a signal to noise ratio ~1.5 in the continuum. No obvious emission or absorption lines are detected in the spectrum. To search for features from a Galactic source at z=0, we set a 3-sigma flux limit around 6563 Angstrom of 3.3e-17 ergs/s/cm^2/A. This result is consistent with Chambers et al. (LVC GCN #20407) who reported a featureless spectrum of ATLAS17aeu obtained with Gemini.
iPTF17cw was observed on 2017-01-07.55 with a total exposure time of 20 min which results in a signal to noise ratio ~11 in the continuum. The spectrum shows a blue continuum peaking around 3850 Angstroem (rest frame) with weak, broad features. We found a good match of the spectrum with the SNIc-BL SN1998bw pre-maximum at z=0.093. The redshift is consistent with the photoz=0.101�0.0279 derived by SDSS for the host Galaxy.
GCN Circular #20421
A.K.H. Kong (NTHU/Oxford), J. Mao, X. Hou, J. Wang, and J.-M. Bai (YNAO)
We observed the field of the optical transient ATLAS17aeu (Tonry et al., LVC GCN 20382; Kasliwal et al., GCN 20398) that is within the error region of LIGO/Virgo G268556 (LVC, GCN 20364) with the 2.4-m GMG telescope at the Lijiang Observatory in Yunnan, China. We obtained an R-band image with the Yunnan Faint Object Spectrograph and Camera (YFOSC) on 2017-01-07 14:55:35 UT. ATLAS17aeu was not detected with a 3-sigma limit of about R~23 mag.
ATLAS17aeu was detected with i=21.9 mag on 2017-01-07 08:05:33 UT (Kasliwal et al., GCN 20398) and was proposed to be the afterglow of GRB 170105A. Our observation indicates that the source is fainter than the suggested power-law decay. However, due to the use of different filters in ATLAS, Palomar, and Lijiang, the lightcurve should be treated with caution.
GCN Circular #20425
K. P. Mooley, R. P. Fender (Oxford), A. Horesh (HUJI) report on behalf of a larger collaboration
We observed the optical transient ATLAS17aeu (Tonry et al., LVC GCN 20382) located in the error region of LIGO/Virgo G268556 (LVC GCN 20364) with the AMI Large Array on 2017 Jan 07.04 UT. At 15.5 GHz, the flux density of the source is 336+/-20 uJy. We are currently monitoring this source.
We thank the AMI staff for scheduling this observation. Since this source is likely the afterglow of GRB 170105A (e.g. Kasliwal et al., LVC GCN 20393; Chambers et al., LVC GCN 20407), we will be updating the AMI-GRB database (http://4pisky.org/ami-grb/) with the measurements.
GCN Circular #20735
A. Melandri (INAF-OAB), S. Piranomonte (INAF-OAR), M. Branchesi (Urbino University/INFN Firenze), S. Covino (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-ASDC), A. Rossi, (INAF-IASF Bo), L. Amati (INAF-IASF Bo), L. A. Antonelli, S. Ascenzi (INAF-OAR), M.T. Botticella (INAF-OAC), S. Campana (INAF-OAB), E. Cappellaro (INAF OAPd), F. Getman, A. Grado (INAF-OAC), G. Greco (Urbino University/INFN Firenze) , L. Limatola (INAF-OAC), M. Lisi (INAF-OAR), L. Nicastro (INAF-IASF Bo), E. Palazzi (INAF-IASF Bo), E. Pian (SNS-Pisa), L. Pulone (INAF-OAR), G. Stratta (Urbino University/INFN Firenze), G. Tagliaferri (INAF-OAB), V. Testa (INAF-OAR), L. Tomasella, S. Yang (INAF-OAPD), E. Brocato (INAF-OAR) on behalf of GRavitational Wave Inaf TeAm (GRAWITA) report:
We observed the field of the transient ATLAS17aeu (Tonry et al., GCN Circ. 20382) recognized to be the possible afterglow of GRB170105A (Kasliwal et al., GCN 20393), previously reported by POLAR (Marcinkowski et al., GCN 20387) and detected by AstroSAT CZTI (Sharma et al., GCN 20389). ATLAS17aeu was proposed to be associated with the galaxy SDSS J091312.36+610554.2 z=0.199, at a projected distance of 75 kpc (Tonry et al., GCN Circ. 20382). We used the TNG telescope equipped with DoLoRES in imaging mode. A 70 min exposure (r`-sloan filter) was obtained starting on 24/02/2017 20:48:16 UT. At the position of the afterglow we identify an extended source, which we propose to be the GRB host galaxy. The aperture photometry of the object is r= 24.23 +/- 0.20, calibrated against nearby SDSS stars.
A preliminary analysis shows that this ATLAS17aeu measurement is 2 magnitudes or more brighter than the value expected by the afterglows decay fit obtained from previous observations.
We thank the TNG staff, in particular Gloria Andreuzzi and Gianni Mainella for conducting the observations and the visiting astronomer Matteo Pinomonti for devoting his observing time to this target.

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Jochen Greiner, last update: 11-Jan-2017 [Disclaimer]