- GCN Circular #9044
Julie McEnery (NASA/GSFC), Sara Cutini (ASDC), Masanori Ohno (ISAS/JAXA) and Elmar Koerding (AIM/Saclay) report on behalf of the Fermi LAT collaboration and Valerie Connaughton (UAH) reports on behalf of the
Fermi GBM collaboration
At 09:36.46 UT on 28 March 2009, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 090328 (trigger 259925808 / GRB090328401). The GBM lightcurve shows a multi-peaked event, with the brightest set of peaks occurring within 50 sec and a further peak at 60 sec tailing off beyond 100 sec post-trigger. The burst is detected at least to 1 MeV.
The Fermi Large Area Telescope (LAT) has significantly detected this GRB. Emission was observed in the LAT up to a few GeV with a detection significance of more than 5 sigma.
The current best LAT on-ground localization is found to be (RA,Dec=90.87, -41.95) with a 68% containment radius of 0.11 deg, and a systematic error less than 0.1 deg. The GBM on-ground localization is consistent with this LAT localization within statistical and systematic uncertainties.
We further report that the Fermi Observatory executed a maneuver following this trigger and tracked the burst location for the next 5 hours, subject to Earth-angle constraints.
Swift TOO observations have been requested at the LAT measured position.
Further analysis is ongoing.
The points of contact for this burst are Julie McEnery (LAT, julie.mcenery@nasa.gov) and Valerie Connaughton (GBM, valerie@nasa.gov).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
This message can be cited.
- GCN Circular #9045
J. Kennea (PSU) reports on behalf of the Swift/XRT Team:
Swift began a TOO observation observation of the LAT error circle of GRB
090328 (McEnery et al, GCN #9044) at 01:26UT March 29th, 2009. Preliminary
analysis of the downlinked XRT data finds an uncatalogued X-ray source
approximately 10 arcminutes from the centre of the LAT error circle, at
the following location: RA, Dec = 90.66485, -41.88421 which is equivalent
to:
RA(J2000) = 06h 02m 39.6s
Dec(J2000)= -41d 53m 03.2s
with an estimated uncertainty of 6 arcseconds radius (90% confidence). We
cannot confirm at this time if the afterglow candidate is fading.
- GCN Circular #9046
J. Kennea (PSU), P. Evans and M. Goad (U Leicester) report on behalf of
the Swift/XRT Team:
Further analysis of the candidate afterglow of GRB 090328 has been
performed utilizing downlinked Swift XRT and UVOT data. Using 1329 s of
XRT Photon Counting mode data and 2 UVOT images, 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 = 90.66494,
-41.88265 which is equivalent to:
RA (J2000): 06 02 39.58
Dec (J2000): -41 52 57.5
with an uncertainty of 2.0 arcsec (radius, 90% confidence). Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is
an extension of this method.
Swift/UVOT detects a point source at a location consistant with the
XRT error circle, detected in the U and White filters. A catalogue search
does not reveal any known source at the location of this source. We
tentatively suggest that this UVOT source may be the optical afterglow of
GRB 090328, although this cannot be confirmed until either the optical or
X-ray afterglow candidates are seen to fade.
- GCN Circular #9048
S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began observing the field of GRB 090328 16 hrs
after the Fermi LAT trigger (McEnery et al., GCN 9044). We detect
a candidate optical afterglow in the u and white filters at:
RA(J2000.0) = 06:02:39.67
DEC(J2000.0) = -41:52:54.5
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
At the moment we are unable to tell if the source is fading, further
observations have been performed, but due to a data gap, the data
is currently unavaliable.
Preliminary magnitudes for the white and u filters are:
Filter T_mid (hrs) Exposure(s) Mag Err
------------------------------------------------------------
u 16.0 793 19.04 +/- 0.13
white 16.1 173 19.56 +/- 0.14
The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0.06 mag (Schlegel et al.,
1998, ApJS, 500, 525). The photometry is on the UVOT flight system
described in Poole et al. (2008, MNRAS, 383,627).
- GCN Circular #9049
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T.Cline on behalf of the Konus-Wind team,
A. von Kienlin, G. Lichti, A. Rau, and K. Hurley on behalf of the
INTEGRAL SPI-ACS GRB team, and
V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM
team, report:
Konus-Wind and INTEGRAL (SPI-ACS) have so far observed the long bright
GRB 090328 (McEnery et al. GCN 9044). We have triangulated this
burst to a Konus-SPI-ACS annulus centered at RA(2000),
Dec(2000) =26.911, +1.465, whose radius is 72.339 +/- 0.671 degrees (3
sigma).
This annulus intersects the GBM localization, and the LAT localization
lies 0.357 degrees from the center line of this annulus. A map is
posted at http://www.ioffe.ru/LEA/GRBs/GRB090328_T34609/IPN/
showing the GBM contours (statistical) and best-fit position (diamond),
the IPN annulus (solid line), and the LAT best-fit position (diamond)
and error circle (68% CL, statistical).
This map will also be posted at http://ssl.berkeley.edu/ipn3/090328 .
The IPN localization may be improved.
- GCN Circular #9050
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P.
Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind
team, report:
The long bright GRB 090328 (Fermi-GBM trigger trigger 259925808 /
GRB090328401) localized by Fermi-LAT (McEnery et al., GCN 9044; the LAT
localization was confirmed by the IPN triangulation: Golenetskii et al.,
GCN 9049) triggered Konus-Wind at T0=34609.486 s UT (09:36:49.486).
The burst light curve shows a multipeaked structure with a duration of
~80 s. There is a hint of an extended soft emission.
As observed by Konus-Wind the burst
had a fluence of 9.25(-1.98, +1.63)x10^-5 erg/cm2,
and a 64-ms peak flux measured from T0+20.064 s
of 1.22(-0.26, +0.25)x10^-5 erg/cm2/s
(both in the 20 keV - 8 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+72.960 s) is well fitted (in the 20 keV - 8 MeV
range) by GRB (Band) model for which:
the low-energy photon index alpha = -1.04(-0.10, +0.11),
the high energy photon index beta = -2.05(-0.90, +0.22),
the peak energy Ep = 592(-141, +237) keV (chi2 = 78.4/81 dof).
The spectrum of the most intense part
(from T0 to T0+23.808 s) is well fitted (in the 20 keV - 8 MeV
range) by GRB (Band) model for which:
the low-energy photon index alpha = -0.94 +/- 0.08,
the high energy photon index beta = -2.07(-0.36, +0.16),
the peak energy Ep = 600(-100, +147) keV (chi2 = 81.1/81 dof).
The fluence of this part is 7.48(-0.93, +0.83)x10^-5 erg/cm2 (in the 20
keV - 8 MeV energy range).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090328_T34609/
- GCN Circular #9052
A. Rowlinson and K. Page (U. Leicester) report on behalf of the
Swift/XRT Team:
We have analysed 3.4 ks of XRT data for the Fermi GBM and LAT detected
GRB 090328 (McEnery et al. GCN Circ. 9044, Kennea et al. GCN Circ.
9045), from 57.1 ks to 94.3 ks after the BAT trigger. The data are
entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay
index of alpha=2.60 (+/-0.28).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.9 (+0.3, -0.4). The
best-fitting absorption column is 1.9 (+1.4, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 5.0 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 4.9 x 10^-11 (6.6 x 10^-11) erg
cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of
2.60, the count rate at T+48 hours will be 0.004 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.96 x
10^-13(2.64 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00031387.
This circular is an official product of the Swift-XRT team
- GCN Circular #9053
S. B. Cenko, J. S. Bloom, A. N. Morgan, and D. A. Perley (UC Berkeley)
report on behalf of a larger collaboration:
We have obtained optical spectra of the candidate UVOT afterglow (GCN
9046, 9048) of the Fermi GRB090328 (GCN 9044) with the Gemini Multi-Object
Spectrograph mounted on the Gemini South Telescope. Observations began at
00:05 UT on 2009 March 29.
Our first 1500 second spectrum uses the R400 grating and covers the
approximate wavelength range from 4000-8000 A. We find a single bright
emission line at observed wavelength ~ 6470 A that we identify as
[OII] 3727 at z = 0.736, along with an absorption doublet consistent with
Mg II 2796/2803 at the same redshift. We therefore suggest that
this is the redshift of GRB090328. Further observations are in progress.
We wish to thank the entire staff at Gemini observatory, in particular M.
Edwards and J. Blakeslee, for the prompt execution of our observations.
- GCN Circular #9054
Adria Updike (Clemson University), Sylvio Klose (Tautenburg Obs.),
Christian Clemens and Jochen Greiner (MPE Garching) report on behalf of
the GROND team:
We observed the field of GRB 090328 (Fermi trigger 259925808; McEnergy et
al., GCN 9044) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla
Observatory (Chile).
Observations started at 23:24 UT on date, about 1.6 days after the GRB
trigger, and are continuing. They were performed at an average seeing of
1.8" and at an average airmass of 1.06.
We detect the afterglow reported by Kennea et al. (GCN 9045) in all bands.
Based on the first 8 min of total exposures in g'r'i'z' JHK, we estimate
preliminary magnitudes (all in AB system) of
g' = 20.97 +/- 0.05 mag,
r' = 20.23 +/- 0.03 mag,
i' = 19.89 +/- 0.04 mag,
z' = 19.54 +/- 0.03 mag,
J = 19.54 +/- 0.06 mag,
H = 19.02 +/- 0.06 mag and
K = 18.52 +/- 0.08 mag
Given magnitudes are calibrated against USNO as well as 2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V) = 0.06 mag in the direction of the
burst (Schlegel et al. 1998).
- GCN Circular #9057
Arne Rau (MPE), Valerie Connaughton (UAH) and Michael Briggs (UAH)
report on behalf of the Fermi GBM team:
"We have performed spectral analysis of the GBM data for GRB 090328 (GCN
9044).
The spectrum from T0+3.1s to T0+29.7s is best fit by a Band function
with indices alpha=-0.93 +/- 0.02 and beta=-2.2 +/- 0.1, and peak energy
of Epeak=653 +/- 45 keV (chi squared 365 for 311 d.o.f.). At a redshift
of 0.736 (GCN 9053), the Epeak in the GRB rest frame, Epeak_rest, is
1133 +/- 0.078 MeV.
The event fluence in this time interval is (8.09 +/- 0.10)E-5 erg/cm^2
in the 8-1000 keV band and (9.5 +/- 1.0)E-5 erg/cm^2 in the 8keV-40MeV
band. Using standard cosmology (Omega_matter = 0.27, Omega_lambda =
0.73, H0=71) the isotropic equivalent energy in the 8keV-40MeV band is
E_iso = (2.3 +/- 0.2)E+53 ergs. The 1-sec peak photon flux measured
starting from T0+23.5 s in the 8-1000 keV band is 18.5 +/- 0.5 ph/s/cm^2.
This time interval consists of three main emission peaks, from T0+3.1s
to T0+8.2s, from T0+13.3s to T0+19.5s, and from T0+23.6 to T0+25.6s. All
of these shorter intervals are also best fit by a Band function. For the
first interval the power-law indices are alpha=-0.79 +/- 0.04 and
beta=-2.3 +/- 0.2, Epeak is 648 +/- 68 keV, Epeak_rest is 1125 +/- 118
keV, and the fluence (8-1000 keV) is (3.80 +/- 0.08)E-06. For the second
interval the power-law indices are alpha=-0.86 +/- 0.03, beta=-2.3 +/-
0.2, Epeak is 676 +/- 62 keV, Epeak_rest is 1174 +/- 108 keV, and the
fluence (8-1000 keV) is (4.35 +/- 0.07)E-6. For the third interval the
power-law indices are alpha=-0.94 +/- 0.05, beta=-2.4 +/- 0.3, Epeak is
481 +/- 60 keV, Epeak_rest is 835 +/- 104 keV, and the fluence (8-1000
keV) is (4.3 +/- 0.1)E-6.
The spectral analysis results presented above are preliminary; final
results will be published in the GBM GRB Catalog."
- GCN Circular #9058
Bill Allen (Vintage Lane Obs., Blenheim, New Zealand), Phil Yock (Aucklan=
d
Univ., NZ), A. de Ugarte Postigo (ESO Santiago), Ian Bond (Massey Univ.,=20
NZ),
John Hearnshaw (Univ. of Canterbury, NZ), Grant Christie (Stardome Obs.,=20
NZ),
Petr Kub=E1nek (GACE, Univ. of Valencia), S. Castillo (Univ. de M=E1laga)=
,
J. M. Castro Cer=F3n (ESAC Madrid), T. Mateo Sanguino (Univ. de Huelva),
D. P=E9rez-Ram=EDrez (Univ. de Ja=E9n), A. Claret, J. M. Garc=EDa Pelayo,=
J.=20
Gorosabel,
S. Guziy, M. Jel=EDnek, S. Mart=EDn Ruiz and A. J. Castro-Tirado (IAA-CSI=
C=20
Granada), report:
"Following the detection by Fermi LAT and GBM of GRB 090328 (McEnery
et al. GCNC 9044), follow-up observations were performed by the 0.6-m
Yock-Allen robotic telescope at the new BOOTES-3 astronomical station in
Blenheim (New Zealand). A co-added 1500s unfiltered image, obtained on
29 Mar (22:12-22:41 UT, i.e. 36.8 hr after the onset of the event) shows=20
a rather
bright optical afterglow at the UVOT position reported by Kennea et al.=20
(GCNC
9046). We measure R~19.7+/-0.3 (clear filter), calibrated against USNO-B1=
.0
stars. Additional observations are encouraged."
This message can be quoted.
- GCN Circular #9060
D. A. Frail (NRAO), P. Chandra (RMC), and B. Cenko (UC Berkeley)
report on behalf of a larger collaboration:
"We observed a field toward the optical afterglow (GCN Circ. 9046, GCN
Circ. 9048) of the Fermi GBM/LAT GRB 090328 (GCN Circ. 9044, GCN
Circ. 9057) on March 30.99 UT using the Very Large Array (VLA) at a
frequency of 8.46 GHz. We detect an unresolved radio source at the GRB
afterglow position with a flux density of 337+/-60 uJy at a (J2000)
position of:
RA = 06h 02m 39.67s
DEC = -41d 52' 53.8"
with a conservative error of 0.25" The source was not detected (<180
uJy) in observations taken 24 hours earlier. Further observations are
planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
- GCN Circular #9077
Sara Cutini (ASDC), V. Vasileiou (NASA/GSFC, UMBC) and Jim Chiang
(SLAC/KIPAC) report on behalf of the Fermi LAT team.
We report further analysis with the LAT data on GRB 090328 (McEnery
et al. GCN Circ. 9044, Kennea et al. GCN Circ. 9045).
The emission in the LAT lasts up around 900s after the trigger, we
did not find evidence for further high-energy delayed emission beyond
900s.
Considering the rate of events passing the on board event filters for
gamma-rays, the light curve shows a single pulse peaking at 25s which
corresponds to the third spike of GBM light curve (A. Rau at al. GCN
Circ. 9057).
The highest energy events detected by the LAT which are spatially
coincident with the burst position arrived hundreds of seconds after
the GRB trigger time.
In a preliminary time resolved spectral analysis we find no evidence
of a change in spectral index during the whole duration of the burst.
The points of contact for this burst are Julie McEnery (LAT,
julie.mcenery@nasa.gov) and Arne Rau (GBM, arau@mpe.mpg.de).
The Fermi LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV. It is the product of
an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.
- GCN Report 207.1
GCN_Report 207.1 has been posted:
http://gcn.gsfc.nasa.gov/reports/report_207_1.pdf
by F.E. Marshall
at NASA/GSFC
titled: "Final Results on Swift GRB 090328A"
- 1003.3885 from 23 Mar 10
S. McBreen et al.: Optical and near-infrared follow-up observations of four Fermi/LAT GRBs : Redshifts, afterglows, energetics and host galaxies
Fermi can measure the spectral properties of gamma-ray bursts over a very large energy range and is opening a new window on the prompt emission
of these energetic events. Localizations by the instruments on Fermi in combination with follow-up by Swift provide accurate positions for
observations at longer wavelengths leading to the determination of redshifts, the true energy budget, host galaxy properties and facilitate
comparison with pre-Fermi bursts. Multi-wavelength follow-up observations were performed on the afterglows of four bursts with high energy
emission detected by Fermi/LAT : GRB090323, GRB090328, GRB090510 and GRB090902B. They were obtained in the optical/near-infrared bands with
GROND mounted at the MPG/ESO 2.2m telescope and additionally of GRB090323 in the optical with the 2 m telescope in Tautenburg, Germany. Three
of the events are classified as long bursts while GRB090510 is a well localized short GRB with GeV emission. In addition, host galaxies were
detected for three of the four bursts. Spectroscopic follow-up was initiated with the VLT for GRB090328 and GRB090510. The afterglow
observations in 7 bands are presented for all bursts and their host galaxies are investigated. Knowledge of the distance and the local dust
extinction enables comparison of the afterglows of LAT-detected GRBs with the general sample. The spectroscopic redshifts of GRB090328 and
GRB090510 were determined to be z=0.7354+/-0.0003 and z=0.903 +/- 0.001 and dust corrected star-formation rates of 4.8 Mdot yr^-1 and 0.60
M_dot yr^-1 were derived for their host galaxies, respectively. The afterglows of long bursts exhibit power-law decay indices alpha from less
than 1 to ~2.3 and spectral indices (beta) values from 0.65 to ~1.2 which are fairly standard for GRB afterglows. Constraints are placed on the
jet half opening angles of less than 2.1 deg to greater than 6.4 deg which allows limits to be placed on the beaming corrected energies. These
range from less than 5x10^50 erg to the one of the highest values ever recorded, greater than 2.2x10^52 erg for GRB090902B, and are not
consistent with a standard candle. The extremely energetic long Fermi bursts have optical afterglows which lie in the top half of the
brightness distribution of all optical afterglows detected in the Swift era or even in the top 5% if incompleteness is considered. The
properties of the host galaxies of these LAT detected bursts in terms of extinction, star formation rates and masses do not appear to differ
from previous samples.
- 1305.1620 from 9 May 13
E. S. Gorbovskoy et al.: The MASTER-II Network of Robotic Optical Telescopes. First Results
The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for
studies of the prompt optical emission of gamma- ray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of
the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network,
during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most
cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first
place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground
telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB
110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was ob- served for GRB 100901A and GRB
100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras
carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424.
Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all,
photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half
of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery
of 38 variable stars.
- 1305.3689 from 17 May 13
Martin Lemoine et al.: On the magnetisation of gamma-ray burst blast waves
The origin of magnetic fields that permeate the blast waves of gamma-ray bursts is a long-standing problem. The present paper argues that in
four GRBs revealing extended emission at >100 MeV, with follow-up in the radio, optical and X-ray domains at later times, this magnetisation
can be described as the partial decay of the microturbulence that is generated in the shock precursor. Assuming that the extended high energy
emission can be interpreted as synchrotron emission of shock accelerated electrons, we model the multi-wavelength light curves of GRB 090902B,
GRB 090323, GRB 090328 and GRB 110731A, using a simplified then a full synchrotron calculation with power law decaying microturbulence
\epsilon_B \propto t^{\alpha_t} (t denotes the time since injection through the shock, in the comoving blast frame). We find that these models
point to a consistent value of the decay exponent -0.5 < \alpha_t < -0.4.
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