- GCN Notice
TITLE: GCN/MAXI NOTICE
NOTICE_DATE: Mon 18 May 15 22:35:20 UT
NOTICE_TYPE: MAXI Unknown Source Position
EVENT_ID_NUM: 160705527
EVENT_RA: 234.21d {+15h 36m 50s} (J2000),
234.38d {+15h 37m 32s} (current),
233.63d {+15h 34m 32s} (1950)
EVENT_DEC: +16.27d {+16d 16' 16"} (J2000),
+16.22d {+16d 13' 16"} (current),
+16.43d {+16d 26' 06"} (1950)
EVENT_ERROR: 1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX: 775.0 +- 0.0 [mCrab]
EVENT_DATE: 17160 TJD; 138 DOY; 15/05/18
EVENT_TIME: 78154.00 SOD {21:42:34.00} UT
EVENT_TSCALE: 30s
EVENT_EBAND: Low, 2-4 keV
SUN_POSTN: 55.40d {+03h 41m 36s} +19.64d {+19d 38' 17"}
SUN_DIST: 144.13 [deg]
MOON_POSTN: 66.69d {+04h 26m 45s} +17.25d {+17d 15' 06"}
MOON_DIST: 144.40 [deg]
MOON_ILLUM: 1 [%]
GAL_COORDS: 25.81, 50.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 227.04, 34.53 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: MAXI Unknown Source Position. GRB or unknown X-ray Transient.
- GCN Circular #17825
T. Kawamuro (Kyoto U.), S. Nakahira, S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech),
A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R.Imatani (Osaka U.),
H. Negoro, M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Hori (Kyoto U.),
Y. Tsuboi, S. Kanetou (Chuo U.),
M. Yamauchi, D. Itoh (Miyazaki U.),
K. Yamaoka (Nagoya U.), M. Morii (ISM)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray
transient source at 21:42:14 UT.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (234.342 deg, 16.307 deg) = (15 37 22, +16 18 25) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii
of 0.20 deg and 0.20 deg, respectively. The roll angle of long axis from
the north direction is 75.0 deg counterclockwise. There is an additional
systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 327 +- 49 mCrab
(4-10keV, 1 sigma error).
Without assumptions on the source constancy,we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (233.970 deg, 15.521 deg) = (15 35 52, +15 31 15) (J2000)
(R.A., Dec) = (233.627 deg, 15.744 deg) = (15 34 30, +15 44 38) (J2000)
(R.A., Dec) = (234.594 deg, 16.941 deg) = (15 38 22, +16 56 26) (J2000)
(R.A., Dec) = (234.939 deg, 16.717 deg) = (15 39 45, +16 43 01) (J2000)
There was no significant excess flux in the previous transit at 5/18 21:39 UT.
- GCN Circular #17826
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the
MAXI GRB 150518A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00044
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of
finding
serendipitous sources, unrelated to the MAXI event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN
Circular
after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
- GCN Circular #17827
B. Sbarufatti (INAF-OAB/PSU), C. Pagani (U. Leicester), A.P. Beardmore
(U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V.
D'Elia (ASDC), D.N. Burrows (PSU), J.A. Kennea (PSU) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the MAXI-detected
burst GRB 150518A (Kawamuro et al. GCN Circ. 17825) in a series of
observations tiled on the sky. The total exposure time is 2.4 ks,
distributed over 7 tiles; the maximum exposure at a single sky location
was 742 s. The data were collected between T0+10.4 ks and T0+20.2 ks,
and are entirely in Photon Counting (PC) mode.
An uncatalogued X-ray source is detected and is above the RASS limit,
and is therefore likely the GRB afterglow. The position of this source
is RA, Dec=234.2006, +16.3291 which is equivalent to:
RA (J2000): 15:36:48.14
Dec(J2000): +16:19:44.9
with an uncertainty of 3.8 arcsec (radius, 90% confidence). This
position is 8.2 arcmin from the MAXI position. The light curve is
consistent with a constant source of mean count rate 4.0e-01 ct/sec. A
power-law fit gives an index of 0.4 (+0.7, -0.9).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.6 (+1.0, -0.8). The
best-fitting absorption column is 8.2 (+4.0, -3.2) x 10^21 cm^-2, in
excess of the Galactic value of 3.4 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 2.2 x 10^-11 (2.1 x 10^-10) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 8.2 (+4.0, -3.2) x 10^21 cm^-2
Galactic foreground: 3.4 x 10^20 cm^-2
Excess significance: 4.1 sigma
Photon index: 3.6 (+1.0, -0.8)
The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/xrt_products/TILED_GRB00044/index_1.php.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00044.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17828
M. De Pasquale (MSSL-UCL) and B.Cenko (NASA-GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150518A
10383 s after the MAXI-GSC trigger (Kawamuro et al, GCN Circ. 17825).
No UVOT source is detected at the XRT position or within the XRT error
circle (Sbarufatti et al., GCN Circ. 17827) in the initial UVOT exposures.
Preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) is
Filter T_start(s) T_stop(s) Exp(s) Mag U.L.
u 10383 20164 364 >20.3
The magnitudes in the table are not corrected for the Galactic extinctiondue to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).
- GCN Circular #17829
Dong Xu (NAOC/CAS), Xue-Bing Wu, Qian Yang (PKU) report
We observed the field of the XRT transient (Sbarufatti et al., GCN
17827), which is very likely the X-ray counterpart of GRB 150518A
(Kawamuro et al., GCN 17825) , using the 2.16m telescope located at
Xinglong, Hebei, China. Observations started at 14:23:06 UT (i.e.,
16.68 hr after the burst) in a rather poor seeing of 3", and 4x300s
R-band frames were obtained.
At the XRT-UVOT enhanced position (R.A. = 15:36:48.25, Dec. =
+16:19:47.3 , Err. Rad: = 2.2�?��?�), an optical source is well detected
at m(R) = 20.3 +/- 0.2 mag, calibrated with nearby SDSS stars. The
source largely looks round in our stacked image.
We note that there exists a source at the XRT-UVOT position that is
already detected and classified as a galaxy by SDSS (u=22.88, g=22.14,
r=21.43, i=21.24, z=20.74), with a photometric redshift of z_ph=0.35
+/- 0.11. The Xinglong detection is brighter than the SDSS detection
by about 1 magnitude in the R/r filters, and we thus think that it is
the optical afterglow of the GRB. If the afterglow is indeed
associated with the galaxy at such a redshift, it would be doable to
search for a GRB-associated supernova.
We thank Junjun Jia for carrying out these observations.
- GCN Circular #17830
We observed the Swift-XRT field of GRB 150518A (Sbarufatti et al., GCN 17827)
with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan
Observatory. Observations began from 16:02:40 UT, May 19, 2015, about 18.3
hours after the trigger. At the position of RA=15:36:48.27 DEC=16:19:47.1, we
clearly detect one source with roughly estimated magnitude r'~21.2+/- 0.1. We
could not distinguish the SDSS galaxy noticed by Xu et al. (GCN 17829) and the
afterglow at this position. Detailed analysis is ongoing.
We thank D. Xu for his kind information.
- GCN Circular #17831
Owen Littlejohns (ASU), 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), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja
(GSFC), Enrico Ramirez-Ruiz (UCSC), Jos� A. de Diego (UNAM), Leonid
Georgiev (UNAM), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM),
Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report:
We observed the field of GRB 150518A (Kawamuro, et al., GCN 17825)
with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the
Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from
2015/05 20.15 to 2015/05 20.24 UTC (29.94 to 32.08 hours after the
BAT trigger), obtaining a total of 1.78 hours exposure in the r, i
and z bands.
For a source within the Swift-XRT error circle (Sbarufattim et al.,
GCN 17827), in comparison with the SDSS DR9, we obtain the
following detections and upper limit (3-sigma):
r 21.26 +/- 0.04
i 21.04 +/- 0.04
z > 20.08
These magnitudes are in the AB system and are not corrected for
Galactic extinction in the direction of the GRB. This source is
spatially consistent with the catalogued galaxy SDSS
J153648.25+161946.9, as previously reported by Xinglong Station
(Xu, et al., GCN 17829). We note that the RATIR detections in the
r and i bands are brighter than the SDSS catalogue values,
indicating that the GRB may indeed be within the galaxy, providing
an excess flux. We also note that our detections are consistent
with those from Xinglong Station.
We thank the staff of the Observatorio Astron�mico Nacional in San
Pedro M�rtir.
- GCN Circular #17832
D. Xu (NAOC/CAS), A. J. Levan (Univ. Warwick), A. de Ugarte Postigo
(IAA/CSIC), N. R. Tanvir (Univ. Leicester), D. Malesani (DARK/NBI), J.
P. U. Fynbo (DARK/NBI), report on behalf of the X-shooter GRB collaboration.
We observed the optical counterpart (Xu et al., GCN 17829; Mao et al.,
GCN 17830; Littlejohns et al., GCN 17831) of the MAXI GRB 150518A
(Kawamuro et al., GCN 17825; Sbarufatti et al., GCN 17827) using the
X-shooter spectrograph at the ESO Very Large Telescope (VLT).
A total of 40 min integration was secured starting on 2015 May 20.184 UT
(1.28 days after the GRB) covering the wavelength range 3000-18000 AA.
The counterpart, which may include light from both host galaxy and
afterglow, is clearly detected, and a number of prominent emission lines
are visible. Among others, we identify the Balmer lines, [O II] 3727, [O
III] 4957,5007, [N II], [S II], all at a common redshift of z = 0.256.
At this redshift, any supernova similar to other associated with GRBs
would peak at R ~ 21. Although extinction along the line of the sight to
the burst is unknown at present, the low redshift makes GRB 150518A an
ideal opportunity for supernova characterisation.
We acknowledge excellent support from the observing staff in Paranal, in
particular Dimitri Gadotti, Marcelo Lopez, and John Pritchard.
- GCN Circular #17833
H. Negoro (Nihon U.), T. Kawamuro (Kyoto U.), S. Nakahira (JAXA),
M. Serino (RIKEN) on hehalf of the MAXI team:
The previous scan transit time reported in GCN 17825 (GRB 150518A)
was incorrect. The correct time was 20:09 UT on May 18, and not 21:39.
We apologize fo the mistake.
- GCN Circular #17834
A. S. Moskvitin (SAO RAS) report on behalf of larger GRB follow-up
collaboration:
The field of GRB 150518A (Kawamuro et al., GCNC 17825; Sbarufatti et al.,
GCNC 17827) was observed with the Zeiss-1000, 1-m telescope of SAO RAS.
The observations were carried out on the May, 19, 20:10:25 -- 21:26:30 UT
(T - T0 ~ 23 hours). 12 x 300 sec frames in Rc filter were obtained.
We clearly detect the source mentioned by the other teams (Xu et al.,
GCNC 17829, 17832; Mao et al., GCNC 17830; Littlejohns et al., GCNC 17831).
The magnitude of the object is R = 21.2 +/- 0.1 is almost equal
to the magnitude of SDSS J153648.25+161946.9 (within the errors),
probable host galaxy of GRB, so we can not find a significant excess from
the
possible OT.
Photometry is based on the nearby stars, whose SDSS magnitudes were
transformed to UBVRI system. The magnitude of object is not corrected
for the Galactic extinction.
- GCN Circular #17835
L. P. Xin, X. F. Wang, J. Y. Wei, Y. L. Qiu, J. S. Deng,
J. Wang, X. H. Han and C. Wu on behalf of EAFON report:
We observed GRB 150518A (Kawamuro, et al., GCN 17825)
with Xinglong 0.8-m TNT telescope during 2015-05-20,
16:51:46 and 18:16:34 (UT), bout 43.2-44.7 hour after the trigger time.
No any source was detected in our 17*300sec R-band coadded image within
the Swift-XRT error circle (Sbarufattim et al., GCN 17827) and at the
location of the reported source (Xu et al., GCN 17829; Mao et al., GCN 17830)
down to the 3 sigma limit of 20.7 mag, calibrated by USNO B1.0 R2 mag.
- GCN Circular #17836
C. Pagani (U. Leicester) reports on behalf of the Swift team:
A second epoch of XRT data was collected on the field of the MAXI-detected burst: GRB 150518A (Kawamuro et al., GCN Circ. 17825) on 2015 May 20. The observations consist of 5 ks of PC mode data, from T0+146 ks to T0+154 ks.
The X-ray source reported in GCN Circ. 17827, Sbarufatti et al., measured at a mean count rate of 3.4 x 10^-1 count s^-1 (0.3-10 keV) in the first epoch of XRT observations has faded with a power law decay index of alpha=1.04 +/- 0.11 to a mean count rate of 3.1 x 10^-2 count s^-1 (0.3-10 keV) in the second epoch. We therefore confirm that this is the X-ray afterglow of GRB 150518A.
This circular is an official product of the Swift-XRT team.
- GCN Circular #17837
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:
At about 15 minutes before the MAXI/GSC trigger on GRB 150518A
(Kawamuro, et al., GCN Circ. 17825; T0(MAXI)=21:42:14 UT)
Konus-Wind detected in the waiting mode a burst of high X-ray/soft
gamma-ray emission which had a duration of ~250 s.
Taking in account the proximity of this burst to the MAXI/GSC trigger
and consistency of the KW ecliptic latitude response with the position
of GRB 150518A we suggest this burst is the main part of GRB 150518A.
There is a hint of emission in the KW softest energy band (20-80 keV)
around T0(MAXI).
Due to a gap in the data during the main episode we cannot accurately
estimate the burst energetics.
The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB150518A/
- GCN Circular #17838
E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa,
A.Kuznetsov,D.Kuvshinov,
Lomonosov Moscow State University, Sternberg Astronomical Institute
D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory
K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev,
V.A.Poleshchuk
Irkutsk State University
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk
V.Krushinski, I.Zalozhnih, A. Popov
Ural Federal University, Kourovka
Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)
MASTER-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru,
FOV = 2x2 square degrees in paralel mode ( Lipunov et al., 2010, MASTER
Robotic Net, Advances in Astronomy, vol. 2010, pp. 1-7)) located in
Kislovodsk was pointed to the MAXI/GSC GRB150518A
(Kawamuro et al., GCN 17825) 21 sec after notice time and 3189 sec after
trigger time at 2015-05-18 22:35:43 UT. On our first (180s exposure)
image we do not found OTs within Swift/XRT erro-box (Sbarufatti et al.,
GCN 17827) brighter then 18.5 .
But we see bright object at positon: 15h 36m 53.67s , +16d 19m 36s.5
with 17.5 unfiltered mag outside XRT and inside MAXI.
MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru,
FOV = 2x2 square degrees in paralel mode ( Lipunov et al., 2010, MASTER
Robotic Net, Advances in Astronomy, vol. 2010, pp. 1-7)) located in
Souht Africa Astronomical Observatory was pointed to the MAXI/GSC
GRB150518A
(Kawamuro et al., GCN 17825) 13 sec after notice time and 3189 sec after
trigger time at 2015-05-18 22:35:35 UT. On our first (180s exposure)
image we not found OTs within Swift/XRT error-box (Sbarufatti et al.,
GCN 17827) brighter then
17.1 .
But we see bright object at positon: 15h 36m 51.70s , +16d 19m 13s.6
with ~ 17.0 unfiltered mag outside Swift/XRT and inside MAXI.
There is one asteroid MPC 2010 KL61 with poorly
astrometrical efemerids (Leave for survey recovery) at MPC Data Base.
The offset both Russian and South Africa OT positiion 36 arc sec. This
corresponds to parallax effect for Solar System Body.
We do not see any OT at the aftergow canditate position (Xu et al.,
GCNC 17829, 17832; Mao et al., GCNC 17830; Littlejohns et al., GCNC 17831;
Moskvitin GCN 17834) with same limit (3 sigma).
We have only one alert image in each telescope because MASTER telescope
recieved new MAXI correction of the error box and X-ray Transient leave
the MASTER FOV during alert observations.
But we have observation this X-ray aftergrow position before last
trigger activated by previouse Fermi (trigger number 451674501, 25 apr
2015) and during regular synoptic survey (MASTER-Tunka, ~ 2 days after
trigger).
Preliminary results:
Id Pro.type Date time Exp.time Limit Filt. Site
Starting (3sigma)
759597 SumSurvey 2015-05-20 17:02:11 480 20.1 W Tunka
1458076 MaxiAlert 2015-05-18 22:35:35 180 17.1 P/ SAAO
1458345 MaxiAlert 2015-05-18 22:35:43 180 18.5 P| Kislovodsk
823020 FermiInsp 2015-04-25 20:11:41 180 19.9 W Kislovodsk
Where W - unfiltered, P - polarization unfiltered. All magnitude
calculated with respect to hundrends USNO B stars with calibration:
m = 0.2B + 0.8R .
At the Tunka Survey we see marginaly faint (~2 sigma) object on the X-ray
position (Sbarufatti et al., GCN 17827). But this is may be noice. We have
a lot of images in MASTER NET Data Base imaging last
several years with Swift XRT error box. No object we see on this place
with 20.5 mag limit on first overview (since 2010).
The message may be cited.
- GCN Circular #17839
G. E. Anderson, K. Mooley, R. P. Fender, T. D. Staley (University of Oxford),
A. J. van der Horst (George Washington University), A. Rowlinson (CASS)
We observed the XRT position of GRB 150518A discovered by MAXI
(Sbarufatti et al., GCN 17827, Kawamuro et al., GCN 17825) at 15 GHz
with the Arcminute Microkelvin Imager (AMI-LA) starting on
2015 May 20.962 to 21.128 UT, corresponding to 2.1 days post-burst
(Golenetskii et al., GCN 17837). On this date we detected a radio source
coincident with the position of the optical counterpart (Xu et al., GCN 17829)
with a preliminary flux of 0.19 +/- 0.04 mJy. There are no catalogued radio
sources at this position.
An earlier observation was conducted on 2015 May 19.975 to 20.142 UT,
corresponding to 1.1 days post-burst, yielding a 3 sigma flux upper limit
of 0.13 mJy.
Further AMI monitoring is planned. We thank the AMI staff for scheduling these observations.
- GCN Circular #17840
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We observed the field of the MAXI/GSC GRB 150518A (Kawamuro, et al., GCN
17825) with AZT-33IK telescope of Sayan observatory (Mondy) starting on
May, 20 (UT) 16:50:47. We obtained several images in R-filter of 120 s
exposure. The optical afterglow candidate (Xu et al., GCN 17829) which
coincides with SDSS J153648.25+161946.9 galaxy is clearly detected.
Photometry of the galaxy is following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-05-20 16:50:47 1.81150 R 20*120 21.22 0.1
Photometry is based on SDSS DR9 stars:
SDSS9_id R(Lupton)
J153646.11+161904.1 17.65
J153638.21+162002.8 18.41
J153637.55+162040.3 17.10
J153645.59+162055.5 16.35
- GCN Circular #17841
S.Harita, T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano,
S. Kurita, Y.Ono, Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the XRT-UVOT enhanced position of GRB150518A (T.Kawamuro et al., GCN Circular #17825) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-05-19 11:08:33 UT (~13.5 h after the burst).
We detected the previously reported optical afterglow of GRB150518A (B.Sbarufatti et al., GCN Circular #17827) in the Rc and Ic band.
Although estimated magnitude of Ic band has large error, we could find a faint point source.
We obtained following limits for the magnitudes.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------------------------------------------------
48379 13:43:24 4380 >20.7 20.4+/-0.3 19.7+/-0.43
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration
- GCN Circular #17859
We observed the position of the soft-long GRB 150518A (Kawamuro et al., GCN
17825) with the Karl G. Jansky Very Large Array (VLA) beginning on 2015 May
21.12 UT (2.23 days after the burst) at the mean frequency of 6.0 GHz. In
this hour long observation, we detect a faint radio source at the position:
RA: 15 36 48.25
DEC: 16 19 46.82
with an average positional uncertainty of 0.01 arcsec. The VLA is currently
operating in BnA configuration. The radio afterglow position is consistent
with that reported by the Swift-XRT (Sbarufatti et al. GCN 17827).
We measure a 6.0 GHz flux density of the afterglow to be ~222 +/- 7
microJy. This flux density is comparable to that reported by the Arcminute
Microkelvin Imager (Anderson et al. GCN 17839).
Further multiband observations are planned.
We thank the VLA staff for quickly executing these observations.
- GCN Circular #17860
T. Sakamoto (AGU), M. Serino (RIKEN), S. Nakahira (JAXA), H. Negoro (Nihon U.),
S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech),
A. Yoshida, Y. Kawakubo, H. Ohtsuki (AGU),
H. Tsunemi, R.Imatani (Osaka U.),
M. Nakajima, K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Hori, T. Kawamuro (Kyoto U.),
Y. Tsuboi, S. Kanetou (Chuo U.),
M. Yamauchi, D. Itoh (Miyazaki U.),
K. Yamaoka (Nagoya U.), M. Morii (ISM)
We report further analysis using the MAXI/GSC data of MAXI GRB 150518A
(Kawamuro et al. GCN Circ. 17825). The MAXI GSC light curve shows a constant
flux during the scan. Due to a poor statistics, it is hard to claim a
variability in the light curve. The MAXI light curve plot is available from
the following URL.
http://maxi.riken.jp/grbs/150518a/
The GSC spectrum (2-20 keV) using the data from 21:42:00 UT to 21:42:49 UT
is best fit by a simple power-law model. The best fit power-law photon index
is 1.3 +- 0.4. The column density is not well constrained from the GSC spectrum.
The unabsorbed flux in the 2-20 keV band is (1.0 +- 0.3) x 10^-8 erg/cm2/s.
From this best fit model, the unabsorbed X-ray flux in the 0.3-10 keV band
(Swift/XRT energy band) is (7.9 +- 2.4) x 10^-9 erg/cm2/s. No emission was
detected from the GRB position during the next scan starting from 23:11 UT at
the 1 sigma upper limit of ~9 mCrab.
Using the possible host galaxy redshift of 0.256 (Xu et al. GCN Circ. 17832),
the X-ray luminosity at the time of the MAXI detection is 1.7 x 10^48 erg/s (2-20 keV)
and 1.3 x 10^48 erg/s (0.3-10 keV). Assuming the onset of this GRB is the
detection by Konus-Wind (Golenetskii et al. GCN Circ. 17837), we found that
the MAXI luminosity around ~1000 sec after this onset is consistent with a typical
early afterglow emission seen by Swift/XRT (e.g., Racusin et al. 2011, ApJ, 738, 138).
On the other hand, if the possible emission seen by the Konus-Wind data around
the MAXI detection is real, the duration of GRB 150518A can be >1000 s. As we
reported above, the MAXI GSC spectrum is rather hard for an afterglow. In this
case, this GRB can be classified as an ultra-long GRB.
All the quoted errors are at the 90% confidence level. The assumed cosmological
parameters are H0 = 71 km s^-1 Mpc^-1, Omega_m = 0.27 and Omega_lamda = 0.73.
- GCN Circular #17861
Owen Littlejohns (ASU), 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), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja
(GSFC), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid
Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM),
Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report:
We continued to observe the field of GRB 150518A (Kawamuro, et al., GCN
17825) with the Reionization and Transients Infrared Camera (RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron=F3mico Nacional on Sierra San Pedro M=E1rtir for two further epochs.
Our first full epoch now extends from 2015/05 20.15 to 2015/05 20.47 UTC
(29.94 to 37.69 hours after the BAT trigger), obtaining a total of 6.04
hours exposure in the r, i and z bands.
For the previously reported SDSS galaxy (Xu, et al., GCN 17829; Mao,
et al., GCN 17830; Littlejohns, et al., GCN 17831), in comparison with
the SDSS DR9, we obtain the following detections:
r 21.27 +/- 0.04
i 21.02 +/- 0.04
z 20.53 +/- 0.24
The second epoch of RATIR observations ranged from 2015/05 21.21 to
2015/05 21.45 UTC (55.33 to 61.20 hours after the BAT trigger),
obtaining a total of 3.59 hours exposure in the r and i bands, and
1.07 hours in the z band. For the same SDSS galaxy, again in
comparison with the SDSS DR9, we obtain the following detections
and upper limit (3-sigma):
r 21.40 +/- 0.08
i 21.08 +/- 0.08
z > 17.70
The third epoch of RATIR observations was from 2015/05 22.15 to
2015/05 22.47 UTC (77.99 to 85.61 hours after the BAT trigger),
obtaining a total of 6.04 hours exposure in the r, i and z bands.
In this epoch, we obtain the following detections of the SDSS galaxy:
r 21.34 +/- 0.04
i 21.08 +/- 0.04
z 20.80 +/- 0.35
These magnitudes are in the AB system and are not corrected for
Galactic extinction in the direction of the GRB.
Combining the r and i band observations from the second and third
epochs, we find marginal evidence that the source has faded, changing
by 0.07 +/-0.04 magnitudes when compared to the first epoch of RATIR
observations (Littlejohns, et al., GCN 17831). During the full first
epoch of observations, we also observed marginal (1-sigma) evidence
for fading by 0.05 magnitudes in the r and i bands. Finally, we note
that image subtraction between the third and first epochs, in both r
and i band, yield positive residuals in the Swift-XRT error circle at
the 1-sigma level.
We thank the staff of the Observatorio Astron=F3mico Nacional in San
Pedro M=E1rtir.
- GCN Circular #17903
A. Pozanenko (IKI), E. Mazaeva (IKI), A. Sergeev (IRA NASU, IAKhNU), I.
Reva (Fesenkov Astrophysical Institute), A. Volnova (IKI), E. Klunko
(ISTP), I. Korobtsev (ISTP), report on behalf of larger GRB follow-up
collaboration:
We observed the field of the MAXI/GSC GRB 150518A (Kawamuro, et al., GCN
17825) with AZT-33IK telescope of Sayan observatory (Mondy), Zeiss-1000
(East) 1-m telescope of Tien Shan Astronomical
Observatory and AZT-22 telescope of Maidanak observatory.
Observations are continuing in R-filter. The SDSS J153648.25+161946.9
galaxy which coincides with the optical afterglow (Xu et al., GCN 17829)
is detected in all observations. The light curve of the host
galaxy+afterglow are suggesting re-brightening with a possible maximum
brightness on June 2-5. We suggest that this re-brightening can be
attributed to Supernova associated with GRB 150518A. Preliminary light
curve of the possible SN+host can be found in
http://grb.rssi.ru/GRB150518A/GRB150518A_lc.png
Photometry of the host galaxy+SN at the possible maximum brightness are
following
Date UT start t-T0 Filter OT Err. Observatory
(mid, days)
2015-06-02 17:43:30 14.8605 R 20.89 0.13 TSHAO
2015-06-03 20:33:20 15.8862 R 20.82 0.10 Maidanak
2015-06-05 18:11:19 17.8535 R 20.90 0.07 Maidanak
Photometry is based on SDSS DR9 stars:
SDSS9_id R(Lupton)
J153646.11+161904.1 17.65
J153638.21+162002.8 18.41
J153637.55+162040.3 17.10
J153645.59+162055.5 16.35
The maximum brightness of a the possible Supernova is an agreement with
the brightness predicted for the SN at redshift z = 0.256 (Xu et al.,
GCN 17832).
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