- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sun 24 Jul 05 12:39:19 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 147478, Seg_Num: 0
GRB_RA: 246.214d {+16h 24m 51s} (J2000),
246.300d {+16h 25m 12s} (current),
245.442d {+16h 21m 46s} (1950)
GRB_DEC: -27.524d {-27d 31' 25"} (J2000),
-27.536d {-27d 32' 10"} (current),
-27.410d {-27d 24' 35"} (1950)
GRB_ERROR: 4.00 [arcmin radius, statistical only]
GRB_INTEN: 830 [cnts] Image_Peak=108 [image_cnts]
TRIGGER_DUR: 0.064 [sec]
TRIGGER_INDEX: 10419 E_range: 25-100 keV
BKG_INTEN: 37390 [cnts]
BKG_TIME: 45240.00 SOD {12:34:00.00} UT
BKG_DUR: 8 [sec]
GRB_DATE: 13575 TJD; 205 DOY; 05/07/24
GRB_TIME: 45249.32 SOD {12:34:09.32} UT
GRB_PHI: 45.65 [deg]
GRB_THETA: 33.32 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 32.83 [sigma]
IMAGE_SIGNIF: 10.77 [sigma]
MERIT_PARAMS: +1 +0 +0 -2 +2 +15 +0 +1 +59 +1
SUN_POSTN: 123.96d {+08h 15m 50s} +19.78d {+19d 46' 40"}
SUN_DIST: 127.07 [deg]
MOON_POSTN: 347.21d {+23h 08m 50s} -8.46d {-08d 27' 51"}
MOON_DIST: 95.62 [deg]
MOON_ILLUM: 87 [%]
GAL_COORDS: 350.40, 15.09 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 248.93, -5.81 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS: SWIFT-BAT GRB Coordinates.
COMMENTS: This is a rate trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
- red DSS finding chart
ps-file
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sun 24 Jul 05 12:41:16 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 147478, Seg_Num: 0
GRB_RA: 246.214d {+16h 24m 51s} (J2000),
246.300d {+16h 25m 12s} (current),
245.442d {+16h 21m 46s} (1950)
GRB_DEC: -27.524d {-27d 31' 25"} (J2000),
-27.536d {-27d 32' 10"} (current),
-27.410d {-27d 24' 35"} (1950)
GRB_DATE: 13575 TJD; 205 DOY; 05/07/24
GRB_TIME: 45249.36 SOD {12:34:09.36} UT
TRIGGER_INDEX: 10419
GRB_PHI: 45.65 [deg]
GRB_THETA: 33.32 [deg]
DELTA_TIME: 60.00 [sec]
LC_URL: sw00147478000msb.lc
SUN_POSTN: 123.96d {+08h 15m 50s} +19.78d {+19d 46' 40"}
SUN_DIST: 127.07 [deg]
MOON_POSTN: 347.21d {+23h 08m 50s} -8.46d {-08d 27' 51"}
MOON_DIST: 95.62 [deg]
MOON_ILLUM: 87 [%]
GAL_COORDS: 350.40, 15.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 248.93, -5.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-BAT GRB Lightcurve.
COMMENTS:
COMMENTS: The next comments were copied from the BAT_POS Notice:
COMMENTS: This is a rate trigger.
COMMENTS: A point_source was found.
COMMENTS: This does not match any source in the on-board catalog.
COMMENTS: This does not match any source in the ground catalog.
COMMENTS: This is a GRB.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sun 24 Jul 05 12:42:33 UT
NOTICE_TYPE: Swift-UVOT Dark Burst Image
TRIGGER_NUM: 147478, Seg_Num: 0
POINT_RA: 246.232d {+16h 24m 56s} (J2000)
POINT_DEC: -27.520d {-27d 31' 12"} (J2000)
ROLL: 274.881d
GRB_DATE: 13575 TJD; 205 DOY; 05/07/24
GRB_TIME: 45325.62 SOD {12:35:25.62} UT
FILTER: 3, V
EXPOSURE_ID: 2195
X_OFFSET: 1632 [pixels]
Y_OFFSET: 666 [pixels]
WIDTH: 0 [pixels]
HEIGHT: 0 [pixels]
X_GRB_POS: 0
Y_GRB_POS: 0
BINNING_INDEX: 0
DB_URL: sw00147478000msuni.fits
SUN_POSTN: 123.96d {+08h 15m 51s} +19.78d {+19d 46' 39"}
SUN_DIST: 127.09 [deg]
MOON_POSTN: 347.22d {+23h 08m 53s} -8.46d {-08d 27' 30"}
MOON_DIST: 95.62 [deg]
MOON_ILLUM: 87 [%]
GAL_COORDS: 350.42, 15.08 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 248.94, -5.80 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-UVOT Dark Burst Image.
COMMENTS: The GRB Position came from the Window Position in the Mode Command.
COMMENTS: The image has 1x1 binning (ie no compression).
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Sun 24 Jul 05 12:39:59 UT
NOTICE_TYPE: Swift-XRT Position
TRIGGER_NUM: 147478, Seg_Num: 0
GRB_RA: 246.1871d {+16h 24m 44.9s} (J2000),
246.2731d {+16h 25m 05.5s} (current),
245.4145d {+16h 21m 39.4s} (1950)
GRB_DEC: -27.5428d {-27d 32' 34.0"} (J2000),
-27.5553d {-27d 33' 19.0"} (current),
-27.4287d {-27d 25' 43.2"} (1950)
GRB_ERROR: 5.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN: 8720.00 [arb]
GRB_SIGNIF: 6.16 [sigma]
GRB_DATE: 13575 TJD; 205 DOY; 05/07/24
GRB_TIME: 45322.86 SOD {12:35:22.86} UT [Start of CCD integration]
TAM[0-3]: 327.64 237.20 261.34 242.91
AMPLIFIER: 2
WAVEFORM: 134
SUN_POSTN: 123.96d {+08h 15m 51s} +19.78d {+19d 46' 39"}
SUN_DIST: 127.05 [deg]
MOON_POSTN: 347.22d {+23h 08m 53s} -8.46d {-08d 27' 31"}
MOON_DIST: 95.65 [deg]
MOON_ILLUM: 87 [%]
GAL_COORDS: 350.37, 15.10 [deg] galactic lon,lat of the burst
ECL_COORDS: 248.91, -5.83 [deg] ecliptic lon,lat of the burst
COMMENTS: SWIFT-XRT Coordinates.
COMMENTS: WARNING: XRT alignment calibration is on-going, and there may be
COMMENTS: residual systematic offsets of several arcseconds not accounted for yet
COMMENTS: by our on-board position determination algorithm. We have increased
COMMENTS: the estimated error circle radius to take this into account.
- GCN notice #3665
S. Covino (INAF/OAB), L.A. Antonelli (INAF/OAR), P. Romano (INAF/OAB),
D. Palmer (LANL), C. Markwardt(GSFC, UMd), D. Burrows (PSU), N. Gehrels
(GSFC), S. Barthelmy (GSFC), M. Chester (PSU), S. Hunsberger (PSU), J.
Cummings (GSFC/NRC) on behalf of the Swift team
At 12:34:09 UT, Swift-BAT triggered and located GRB050724
(trigger=147478). The spacecraft slewed immediately. The BAT on-board
calculated location is RA,Dec 246.214, -27.524 {+16h 24m 51s, -27d 31'
25"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment,
stat+sys). The light curve appears to be short, with full-width half
maximum of less than 0.25 sec, and a peak rate of 10,000 ct/s in that
interval.
The XRT started the observation at 12:35:22.9 UT with XRT in automatic
state, 74 sec after the BAT Trigger. A rapidly fading, uncatalogued, X-
ray source was detected at the following position RA, Dec 16h 24m 44.9s,
-27d 32' 34.0" with an uncertainty of about 6 arcsec (90% containment).
This is 1.78 arcmin from the BAT position reported above.
This message can be cited.
- GCN notice #3666
L.A. Antonelli (INAF/OAR), S. Covino (INAF/OAB), D. Malesani (SISSA),
P. Romano, A. Moretti (INAF/OAB) on behalf of the MISTICI collaboration
report:
We looked at the DSS image of the field of the short GRB 050724 (Covino
et al., GCN 3665). We note the presence of a faint object located at
RA: 16h 24m 44.9s DEC -27d 32' 33.3" (J2000) and centered on XRT
position (Covino et al., GCN 3665) which is under the threshold of both
USNO and 2MASS catalogues. We estimated a R mag for this object of 19.1
calibrating with the nearby USNO star (U600_20428424 RA: 16:24:47.92,
DEC: -27:32:21.05 R=16.5 mag).
This message can be cited
- GCN notice #3667
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hinshaw (GSFC-SPSYS), D. Hullinger (GSFC/UMD), C. Markwardt (GSFC/UMD),
K. McLean (LANL) D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the full data set from the recent telemetry downlink, we report
further analysis of Swift-BAT Trigger #147478 (Covino, et al., GCN 3665).
The ground-analysis position is RA,Dec 246.177,-27.525 (J2000) with an
uncertainty of 3 arcmin (radius, 90%, stat+sys). T90 is 3 +- 1 sec.
The lightcurve has an initial hard FRED peak at T+0.00 sec (FWHM of 0.256 sec)
and there is a smaller much softer peak at T+1.00 sec. Fitting a simple
power law over the full interval from T-1.0 to T+3.0 seconds, the photon index
is 1.71 +/- 0.16 with a fluence of 6.3 +/- 1.0 X 10^-7 erg/cm^2.
The peak flux in a 1-sec wide window starting at T+0.04 seconds
is 3.9 +/- 0.3 ph/cm^2/sec. All values are in the 15-350 keV band
at the 90% confidence level.
Given the second emission peak at T+1, the T90 of 3 sec, and
the power law index value of 1.71, we can not confirm, nor rule out,
that this burst falls into the short-burst category. However, in the
energy range above 25 keV, the second, softer peak and subsequent emission
is much less prominent, and so it is likely that BATSE would have
classified this as a short GRB.
- GCN notice #3668
I.C. Yen (NTNU), H.C. Lin, K.Y. Huang, W.H. Ip (NCU),
Y. Urata (RIKEN), Y. Qiu (BAO), Y.Q. Lou (THCA)
on behalf of EAFON report:
" We started to image the GRB 050724 error region (Covino et al GCN
3665) at 14.26 UT (~1.69 hours after the burst) using 1.0-m telescope
at Lulin Observatory, Taiwan. The source reported by Antonelli et
al. (GCN 3666) was detected in a series of R-band 300 sec
exposure. Our preliminary analysis shows the brightness of the source
do not have significant variability during our monitoring observations
(1.69-3.59 hours after the burst).
This message may be cited."
- GCN notice #3669
P. Romano, A. Moretti, S. Covino (INAF-OAB), L.A. Antonelli(IANF-OAR),
D.N. Burrows, D. Grupe (PSU), M. Chester (PSU), G. Chincarini, G.
Tagliaferri (INAF-OAB), P. Boyd (GSFC-UMBC) on behalf of the Swift-XRT
Team report.
We have analyzed the Swift XRT data from the first orbit observation of
GRB 050724 (Covino et al., GCN 3665). The new refined coordinates are:
RA(J2000) = 16h 24m 45s Dec(J2000) = -27 32 25.2. This position is 65
arcseconds from the refined BAT position given in GCN 3667 (H. Krimm et
al), and 9 arcseconds from the XRT position given in GCN 3665. We
estimate an uncertainty of 6.3 arcseconds radius (90% containment).
However, we note that there is accumulating evidence of a time-dependent
systematic shift in XRT positions derived from ground-processed data
towards lower declinations than the optical counterparts. This effect is
being investigated but is not yet understood. Extrapolation of earlier
positional errors suggests that the correct position could be
approximately 7 arcseconds north of the position given above, which
would be close to the on-board position given in GCN 3665.
A preliminary spectral fit (simple absorbed power-law) to the WT data
yields a photon index of 1.93-/+0.05 in the [0.5-10] keV band. The
derived NH is (5.7)E21 cm^-2, which is higher than the Galactic value
(1.46E+21 cm-2; Dickey & Lockman 1990). The average (79-342 seconds from
trigger) estimated unabsorbed 0.5-10 keV flux is 5.3E-9 ergs/s/cm2.
The light curves in Windowed Timing (WT) and Photon Counting (PC) mode
start 79 and 343 seconds from the BAT trigger (T0), and they show a
fading afterglow which can be fitted with a broken power law of slopes
-3.2+/-0.1 and -0.8+/-0.2. The unabsorbed 0.5-10.0 keV flux at 24 hours
after the burst is then estimated to 9E-14 ergs/s/cm2.
- GCN notice #3670
M. Chester (PSU), S. Covino (OAB), P. Schady (MSSL), P. Roming (PSU) N.
Gehrels (GSFC), on behalf of the Swift UVOT team.
Using summed images from Swift/UVOT of the field of GRB 050724 (Covino
et al., GCN 3665), accumulated during the first forty minutes after the
BAT trigger, no new source is detected within the XRT error circle in
the V filter down to a 3-sigma limit of V=18.84.
The magnitudes are based on preliminary zero-points, measured in orbit,
and will require refinement with further calibration.
- GCN notice #3671
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), A. Alpar (SabUni),
I. Bikmaev, N. Sakhibullin (KSU/AST)
report:
We observed the error box of GRB 050724 (Covino et al., GCN 3665) with
Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe, TUBITAK National
Observatory, Turkey). We made a set of 600s exposures in R, starting at
18:11 UT, July 24, i.e. approximately 5.6 hours after the burst.
Observations were made at very high zenith distance (65-75 degrees) and
in poor seeing conditions (~2 arcsec).
We found no variable sources brighter than our limiting magnitude, which
is only slightly deeper than DSS.
This message may be cited.
- GCN notice #3672
J. S. Bloom (UC Berkeley), A. Dupree (Smithsonian Astrophysical
Observatory), H-W. Chen (MIT), & J. X. Prochaska (UC Santa Cruz) report:
"Comparison of the 2MASS catalog with a short exposure with the
unfiltered MIKE (Magellan II/Clay) guider CCD camera beginning on
2005-07-24 23:25:25 UTC shows faint sources near the XRT localizations
(GCNs #3665 & #3669). We find the following positions (systematic
error relative to the ICRS is 0.2" in both RA and DEC):
A 16:24:44.964 -27:32:23.21 J2000 Source 1 in #3669 error circle
B 16:24:44.912 -27:32:32.73 J2000 Source 1 in #3665 error circle,
noted by Antonelli et al. #3666
C 16:24:45.303 -27:32:34.67 J2000 Source 2 in #3665 error circle
D 16:24:44.398 -27:32:26.85 J2000 Bright galaxy to the West of
XRT error circles
Source D appears to be an extended galaxy and, while formally excluded
by the 90% confidence regions of the various positions reported for
the X-ray afterglow, is of interest nonetheless (especially given what
appears to be an emerging trend of low-redshift galaxies associated
with short bursts)."
A finding chart may be found at:
http://astro.berkeley.edu/~jbloom/grb050724.png
Please email JSB if you would like to make use of the guider FITS image.
This message may be cited.
- GCN notice #3673
A.J. Castro-Tirado, J. Gorosabel, A. de Ugarte Postigo,
S. Guziy and M. Jel=EDnek (IAA-CSIC), M. Karrer (Obs.=20
de Geneve), H.-J. Roeser (MPI Heidelberg), N. El=EDas-Rosa=20
(Obs. Astr. di Padova), O. Bogdanov (Nikolaev State Univ.)
and A. Aguirre (CAHA Almer=EDa)=20
report:
"We have imaged a 6' x 6' region centred on the SWIFT/BAT=20
error box for the short/hard GRB 050724 (Covino et al.=20
GCNC 3665) with the 1.2-m Mercator telescope (+ Merope) at=20
the Observatorio del Roque de los Muchachos on La Palma=20
starting on July 24.890 UT (i.e. 8.8 hours after the
GRB) under good meteorological conditions. Within=20
the refined SWIFT/XRT position (Romano et al. GCNC 3669),=20
the co-added R-band image (5400 s exposure time) shows a=20
source close to the center of the 6.3 arcsec radius error=20
box, labelled as A by Bloom et al. (GCN Circ. 3672).=20
Coordinates yield: RA(2000) =3D 16 24 44.96, Dec(2000)=20
=3D -27 32 23.6 (+/- 0.5"). We measure R =3D 22.40 +/- 0.13
using the USNO-A2.0 star at RA(2000) =3D 16 24 44.55, Dec(2000)
=3D -27 32 59.9. This source is blue, since it is barely=20
detected in contemporaneous J- and K-band images obtained=20
at the 3.5-m telescope (+ Omega2000) at the German-Spanish=20
Calar Alto Observatory and in H-band frames obtained at the=20
3.5-m Telescope Nazionale Galileo (+ NICS) on La Palma. The=20
colours of objects B and C are also consistent with being=20
blue, in contrast to the redder galaxy labelled D. Further=20
observations are needed to confirm whether any of these=20
objects has any relationship to GRB 050724." =20
This message can be quoted.
- GCN notice #3674
K. Torii (Osaka U.) reports on behalf of the ART collaboration:
The error region of the possible short GRB 050724 (Covino et
al. 3665, Krimm et al. GCN 3667) was observed by the 14 inch Automated
Response Telescope in Osaka. The imaging started at 2005 July 24
12:40:35 UT (75 s after the alert reception; 386 s after the
trigger) and RcIcBV frames of 60s integration were obtained.
We find no optical counterpart for the X-ray afterglow (GCN 3665,
Romano et al. GCN 3669) and derive its 3-sigma upper limit
relative to USNO-B1.0 magnitude as follows.
================================
Start(UT) Filter Mag Exposure
--------------------------------
12:41:43 Ic >14.5 60s
--------------------------------
- GCN notice #3675
S. Piranomonte (INAF/OAR), D. Fugazza (INAF/OABr), F. Fiore (INAF/OAR), S.
+Covino (INAF/OABr), P. D'Avanzo (INAF/OABr), D. Malesani (SISSA), G.
+Tagliaferri (INAF/OABr), G. Chincarini (Univ.
Milano-Bicocca) and L. Stella (INAF/OAR), on behalf of the MISTICI
+collaboration, report:
Using the FORS1 instrument at the ESO VLT, we obtained a spectrum of the
object indicated by Antonelli et al. (GCN 3666), also named as object B
by Bloom et al. (GCN 3672). This object is liying close to the XRT
errorbox center (Covino et al., GCN 3665; Romano et al., GCN 3669).
Observations were obtained on 2005, July 24, starting at 23:16:00
UT, under good seeing conditions. We used the grism 300V with a slit of
1.0 arcsec. The integration time was 900 s.
The object is identified with a star trough Ca, CN, G-band, Hbeta, Na
and Halpha faint absorption lines. It has therefore no likely
association with GRB 050724.
We thank the excellent work by the ESO staff in performing these
observations.
This message may be cited.
- GCN notice #3676
P. B. Cameron (Caltech) and D. A. Frail (NRAO) report on behalf
of the Caltech-NRAO-Carnegie collaboration:
"We observed the field of GRB050724 (GCN 3665) with the Very Large
Array at 8.5 GHz on July 25.09. We identify one radio source that is
~9" west from the center of the XRT error circle (GCN#3669). Its
position is (J2000): RA= 16:24:44.35, Dec= -27:32:26.9.
We note that, within our current astrometric errors this source is
positionally coincident with with the bright galaxy identified as
Source D by Bloom et al. (GCN#3672). Based on background source
counts, we expect 0.02 sources per square arcminute above this
brightness (~170 uJy). Further observations are planned to determine
the nature of this radio source.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
- GCN notice #3677
Ron Remillard (MIT), Jean Swank (GSFC), and Alan Levine (MIT)
report for the RXTE/ASM team at MIT and NASA/GSFC
The RXTE All-Sky Monitor detected GRB050724 in a single camera (SSC 2)
with a significance of 9.5 sigma. The event duration is 2.0 (0.5) s,
and the burst (integrated) is detected in each of the 3
standard ASM energy bands: 1.5-3, 3-5, and 5-12 keV. When plotted at
32 ms time resolution, the instantaneous maximum is 10.8 (3.0) Crab.
Despite weak statistics, the burst profile appears to show
two peaks, as reported in GCN Circular 3667, and both peaks are
stronger at 5-12 keV, compared to 2-5 keV
(see http://xte.mit.edu/~rr/grb050724_32ms.ps)
- GCN notice #3678
L.A. Antonelli (INAF/OAR), P. Romano, A. Moretti, S. Covino (INAF/OAB),
D. Burrows (PSU) on behalf of the SWIFT XRT Team report:
We have analyzed the first 20 ksec of the Swift XRT observation of GRB
050724 (GCN 3665, Covino et al.). We derived a refined position of the
X-ray afterglow
by performing a boresight correction based on the USNO catalog. The new
coordinates of the X-ray afterglow are: RA(J2000) = 16h 24m 44.8s,
Dec (J2000) = -27d 32' 31.8" with an uncertainty of 5.4 arcseconds
radius (3 sigma). This position is 69 arcseconds from the refined BAT
position given in GCN 3667 (H. Krimm et al), 2.6 arcseconds from the
XRT position given in GCN 3665 and 7.1 arcseconds from the XRT position
given in GCN 3669 (Romano et al.).
This message can be cited.
- GCN notice #3679
J.X. Prochaska (UCO/Lick), H.-W. Chen (MIT), J.S. Bloom (UCB),
and A. Stephens (Gemini) report on behalf of the GRAASP
collaboration:
We have obtained GMOS/R400 spectroscopy (2400s) of the Sources
identified as A, B and D in GCN #3672. We confirm
the identification of Source B as a Galactic star
(GCN #3675). We tentatively identify Source A as a
Galactic star based on its PSF and featureless spectrum.
Our acquisition image of the field clearly demonstrates
that Source D is extended and therefore a galaxy. Our
spectrum of the galaxy is nearly featureless
(lambda=5000-9000A), indicating the galaxy is an early
type consistent with its red color (GCN #3673).
We assign a possible redshift of z=0.257 based on
absorption features at ~6510A and ~7415A which we
associate with MgI and NaI. The galaxy is located
7.2" from the refined XRT position (GCN #3678) which
would correspond to 27kpc at z=0.257.
Further observations are encouraged.
We thank the Gemini staff for their help in acquiring
this dataset.
Plots of the data can be found here:
http://www.graasp.org/Data/050724
Jason X. Prochaska
UCO/Lick Observatory
UC Santa Cruz
Santa Cruz, CA 95064
xavier@ucolick.org
http://www.ucolick.org/~xavier/
831-459-2135 (Direct)
831-459-2991 (UCO/Lick Main)
831-459-5244 (Fax)
- GCN notice #3680
A. de Ugarte Postigo, J. Gorosabel, A.J. Castro-Tirado,
M. Jelinek, S. Guziy (IAA-CSIC), H.-J. Roeser (MPI Heidelberg),
A. Aguirre, S. Pedraz (CAHA), O. Bogdanov (Nikolaev State Univ.),
report:
"We have observed the field of GRB 050724 (GCN Circ. 3665) in the
J-band with the 3.5m Calar Alto telescope (mean observing epoch July
25.86 UT, Texp=45 min). A comparison with the images taken yesterday
with the same telescope (mean observing epoch July 24.87 UT, Texp=15
min) did not reveal any variable source in the reported XRT error
boxes (GCN Circ. 3678, 3665, 3669) down to J~20. At first epoch we
note the presence of a possible object on our detection limit (J~20.5)
located at RA(J2000)=16:24:45.02, DEC(J2000)=-27:32:29.1. However, the
worse seeing on July 25.86 UT prevented us from confirming its
potential variability."
This message can be cited.
- GCN notice #3681
A. Gal-Yam, S. B. Cenko (Caltech), E. Berger (Carnegie), W. Krzeminski
(LCO) and B. Lee (Toronto) report on behalf of the Caltech-NRAO-Carnegie
collaboration:
We have obtained three epochs of optical imaging of the field of GRB
050724 (Covino et al., GCN 3665) with the RetroCam CCD Camera on the
1.0-m Swope telescope at Las Campanas Observatory. Each epoch consisted
of 2 x 15 min exposures in I-band, with the last epoch also containing one
additional ten minute exposure.
We subtracted the coadded sum image obtained during the second night of
observations (epoch 3; July 26.05 UT) from the coadded sum images taken
during the first night (epoch 1, July 25.02 UT; epoch 2, July 25.11 UT ) using
the CPM (Gal-Yam et al. 2004) and ISIS (Alard et al. 1999) codes. We
clearly detect a variable point source superposed on galaxy "D" of
Bloom et al. (GCN 3672).
The variable source is offset from the galaxy core (see figure at
http://www.its.caltech.edu/~cenko/grb050724/grb050724.jpg the green
circle is centered on the galaxy core from epoch 3, the red is centered
on the OT). Furthermore, the light distribution in epoch 1 is markedly
different from that in epoch 3, due to the effect of the OT light,
disfavoring the possibility that the optical variability results from
Galaxy D being an AGN.
Calibrating the OT magnitudes against "I2" magnitudes of four nearby stars
from the USNO B1 catalog, we find that the OT brightened by 0.6
magnitudes between epochs 1 and 2 (I=21.25 at epoch 1, 12 hours after
the burst; I=20.65 at epoch 2, 14.3 hours after the GRB). We note that
such behavior is rare among optical afterglows.
- GCN notice #3684
A. M. Soderberg, P. B. Cameron (Caltech) and D. A. Frail
(NRAO) report on behalf of the Caltech-NRAO-Carnegie collaboration:
"We have undertaken additional VLA observations of GRB050724 (GCN 3665) on
2005 July 26.21 UT. The flux density of the radio source, identified in
GCN 3676, has varied significantly between these two epochs.
This radio variability, together with the close proximity of the radio
source with the XRT position (GCN 3676; chance coincidence<0.15%), and
the optical variations noted in GCN 3681, argue that this is the afterglow
of GRB050724. 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 notice #3685
P. Romano, A. Moretti (OAB), S. Vaughan (U. Leicester), L. A. Antonelli (OAR), S. Campana, G. Chincarini, S. Covino,D. Malesani, G. Tagliaferri (OAB), J. Osborne, R. Willingale, P.T. O'Brien, A. Levan, K. L. Page, M. R. Goad (U. Leicester), D. N. Burrows (PSU), report:
Analysis of the SWIFT XRT observation of GRB050724 in Photon Counting (PC) mode has revealed in the first orbit a diffuse X-ray halo centered around the afterglow location. The halo has the form of complete ring which increases in radius through the observation and reached the distance of ~100 arcsec during the first ~2000 sec after the trigger (T0). We can exclude it is due to instrumental effects. During the observation, which started ~343 seconds after the burst trigger time (PC mode), the observed halo follows the expected behaviour of a "light-echo" as X-rays are scattered by dust in our Galaxy. From the radial expansion of the halo we estimate a distance of 175 -/+ 50 pc to the dust (from the observer, 90% confidence interval).
GRB 050724 is in the direction (Galactic) l = 350.37, b = 15.10 degrees, in which the density of interstellar medium is quite high as testified by both the neutral Hydrogen column density nH=1.5E21 cm-2 and the optical extiction E(B-V)=0.61 (A_V=2.029, A_K=0.225). This line of sight includes the Scorpius Centaurus OB association at ~150-200 pc, consistent with the derived distance to the scattering medium.
The X-ray WT spectrum of GRB050724 is represented by a powerlaw with Photon index 1.93-/+0.05 in the [0.5-10] keV band (as reported in GCN 3669; Romano et al.). The scattered X-ray light has, as expected, a softer spectrum with Photon index 3.2-0.8+1.0 (first orbit).
More information is posted at:
http://www.merate.mi.astro.it/~romano/grb050724/index.html
- GCN notice #3690
P. D'Avanzo, S. Covino (INAF/OABr), L.A. Antonelli, A. Melandri
(INAF/OAR), D. Malesani (SISSA), A. Moretti, P. Romano, G. Tagliaferri
(INAF/OAB), S. Piranomonte (INAF/OAR), G. Chincarini (Univ. Milano-
Bicocca), and L. Stella (INAF/OAR) report on behalf of the MISTICI
collaboration
We observed the afterglow of GRB050724 (Covino et al., GCN 3665) with
the ESO-VLT equipped with the FORS1 camera, starting on 2005 Jul 25.01
and Jul 25.98 (12 and 35 hours after the burst respectively). The seeing
was 1.0" and 0.8" in the two epochs respectively. Observations were
carried out in the R and I filters.
We clearly detect all the sources listed by Bloom et al. (GCN 3672) and
Castro-Tirado et al. (GCN 3673).
PSF-matched image subtraction was performed with the ISIS package (Alard
& Lupton, 1998). A highly significant variable source is detected
superimposed to the galaxy named as source "D" in GCN 3672 (for a figure
see http://www.merate.mi.astro.it/~covino/GRB050724). The source is
slightly offset with respect to the galaxy center. We give below the
0.2" uncertainty position of the galaxy and the OT:
Galaxy centroid: 16:24:44.405 -27:32:26.95
OT centroid: 16:24:44.400 -27:32:27.90
Assuming the object has completely disappeared in our second epoch, the
magnitude of the variable source was I = 20.85 +/- 0.05 at our first
epoch. This value was derived by adding artificial stars of known
brightness to the reference frame, calibrated with Landolt standard
stars. This source faded between the two epochs in both the R and I
bands.
Therefore, we confirm the variability reported by Gal-Yam et al. (GCN
3681). However, our source appears (in both the R and I bands) 1" South
with respect to the core of the host galaxy. This is at variance with
the picture posted by Gal-Yam et al. (GCN 3681), where the variable
object appears North of the host galaxy centroid. After the
rebrightening episode reported by them, the source has therefore clearly
faded.
This message may be cited.
- GCN notice #3694
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS
consortium, report:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 050724
(GCN 3665, Covino et al.) at two separate epochs.
The two epochs had mid-exposure times of 2005-07-25 01:58 UT
(13.4 hours post-burst) and 2005-07-27 03:21 UT (62.8 hours
post-burst). Total summed exposure times at each epoch
amounted to 36 minutes in I and 30 minutes in J, resulting in
approximate limiting magnitudes of I>22 and J>20.
In order to search for variability in the host galaxy of GRB 050724
("source D" from Bloom et al. GCN 3672), the ISIS image subtraction
routine was used (Alard et al. 1999). When the second epoch
images are subtracted from the first epoch images, the residual light
of the afterglow is clearly detected in both the I and J
subtracted frames (in agreement with both GCN 3681, Gal-Yam
et al. GCN 3690, D'Avanzo et al.). The centroid of this residual is ~0.2"
west and ~0.5" south of the centroid of the host galaxy.
Preliminary differential photometry of the host galaxy yields a decay
of 0.19 +/- 0.03 magnitudes in I and 0.17 +/- 0.05 magnitudes in J
between the two imaging epochs.
Assuming the afterglow no longer contributes significantly to the
brightness of the host galaxy at the second epoch, then the magnitude
of the host galaxy is I = 18.78 +/- 0.27 and J = 16.94 +/- 0.09.
Unfortunately, imaging was done under non-photometric conditions so
no Landolt or Persson standard stars are available with which
to determine the offset between instrumental and apparent
magnitude. Therefore, the above values are determined using "on-chip"
standards (USNO-B1 stars in the optical and 2MASS stars in the IR) and the
error is strongly dominated by the uncertainty in the offset derived from
these stars.
Given the above values for the magnitude of the host and its
dimming, the afterglow of GRB 050724 is determined to have a magnitude of
I = 20.58 +/- 0.32 and J = 18.87 +/- 0.32 at 13.4 hours post-burst.
- GCN notice #3696
A. M. Soderberg (Caltech) reports on behalf of the
Caltech-NRAO-Carnegie collaboration:
"Further observations of the radio afterglow (GCN 3676, 3684)
of GRB050724 (GCN 3665) have allowed for a position to be derived
with increased astrometric accuracy:
RA (J2000) 16 24 44.369 =B1 0.007s
DEC (J2000) -27 32 27.5 =B1 0.2"
which is consistent with the position of the optical transient
(GCN 3681, 3690)."
- GCN notice #3697
D. N. Burrows, D. Grupe (PSU), C. Kouveliotou, S. Patel (MSFC), P. Meszaros
(PSU), B. Zhang (UNLV), and R. A. M. J. Wijers (U. Amsterdam) report:
We observed the X-ray afterglow of the short GRB 050724 (Covino et al., GCN
3665) with the Chandra X-ray observatory from 20:09 UT on 26 July 2005 to
10:45 UT on 27 July 2005. The total exposure time was 50 ks. We find an
uncataloged X-ray source coincident with the VLT source reported by
D'Avanzo et al. (GCN 3690) and the VLA source reported by Cameron and Frail
(GRB 3676) as updated by Soderberg (GCN 3696). The Chandra position is:
RA (J2000) = 16 24 44.36
Dec (J2000) = -27 32 27.5.
The astrometry has been verified by comparisons with one 2MASS star with an
X-ray counterpart on the ACIS S-3 chip. We estimate an uncertainty of 0.2
arcseconds radius.
The X-ray source flux appears to decrease during the Chandra observation,
although with marginal statistical significance.
- GCN notice #3699
K. Wiersema (U. of Amsterdam), E. Rol (U. of Leicester),
R. Starling (U. of Amsterdam), N. Tanvir (U. of Hertfordshire),
D. S. Bloomfield, H. Thompson (Queen's University Belfast)
report:
We have observed the position of the short burst
GRB 050724 (Covino et al. GCN 3665) with the William Herschel
Telescope at the Observatorio del Roque de los Muchachos on
La Palma, using the Aux port Imager.
We observed two epochs, with midpoints 0.424 days and 3.405
after burst. The epoch 1 observations consisted of
4 x 15 + 5 minutes exposure time in R band. Epoch 2
consisted of 4 x 15 minutes in R band.
At the first epoch the weather conditions were good with an
average seeing of 0.8 arcsec. During the second epoch the seeing
was considerably worse, with an average seeing ~1.3 arcsec.
PSF-matched image subtraction of the two epochs using the
ISIS code (Alard et al. 1999) reveals a clearly fading source.
This behaviour is confirmed in a subtraction of the first and
last image from the first epoch. The position of the fading
source matches that described in e.g. GCNs 3690 and 3694,
as well as the radio (GCN 3684) and X-ray afterglow position
(GCN 3683, 3697).
We performed aperture photometry of the host galaxy plus the OT
with respect to two unsaturated USNO stars: 0624-0502999 and
0624-0503050, whose values we take from the USNO-B catalogue.
We find a magnitude difference of approximately 0.2 magnitudes
between the two epochs.
Assuming the contribution of the afterglow to the total flux
at the second epoch to be negligible, we estimate the afterglow to
be approximately R ~22.1 at our first epoch.
A jpg image showing the position of the afterglow and the host
can be found on:
http://remote.science.uva.nl/~kwrsema/grb050724/
We thank the staff of the WHT for outstanding support for these
observations.
- GCN notice #3700
J. X. Prochaska (UCO/Lick), J. S. Bloom (UCB), H.-W. Chen (MIT),
B. Hansen (UCLA), J. Kalirai (UCSC), M. Rich (UCLA) and H. Richer (UBC)
report on behalf of the GRAASP collaboration:
"We have obtained LRISb spectroscopy (900s; 2005-07-29 06:31 UT)
of the putative host galaxy of GRB 050724 (Object D in GCN #3672).
We confirm our previously reported redshift (GCN #3679)
based on the identification of Ca H+K, G-band absorption features,
and the 4000Ang break. We report a redshift z=0.258 +/- 0.002.
The velocity dispersion based on CaK appears to exceed 200km/s.
The galaxy shows no [OII] emission in our spectrum suggesting minimal
current star formation.
PAIRITEL imaging of the galaxy from July 29 UT yields a K-band magnitude
of 15.3 +/- 0.2 in a 3" radius aperture. At this redshift,
and including the effects of Galactic extinction, the galaxy
is 1.7 L* based off the 2MASS luminosity function.
The properties of this galaxy -- a massive early-type at
moderate redshift -- are strikingly similar to the probable host
galaxy of GRB 050509b (GCN #3399).
Based on this redshift and the reported fluence in GCN #3667,
the isotropic -equivalent energy release is
E_gamma(iso) = 9.9e49 erg [19-440 keV, comoving], more than 1
order of magnitude brighter than 050509b
(Bloom et al. astro-ph/0505480)."
Figures and imaging can be found at this following site:
http://www.graasp.org/Data/050724
- GCN notice #3892
A. Pastorello (MPA), K. Kawabata (Hiroshima Univ.), E. Pian, (INAF-OATs),
K. Nomoto (Tokyo Univ.), P. Mazzali (INAF,MPA,Tokyo), T. Hattori, M. Iye,
T. Sasaki (Subaru,NAOJ), on behalf of a larger collaboration, report:
On August 10, 2005, at 07.7 UT we observed the field of GRB050724 with
Subaru+FOCAS and I filter. The exposure time was 2 minutes. The seeing
was 0.4". No object is detected at the position of the optical transient
reported by Berger et al. (submitted to Nature, astro-ph/0508115). The
3-sigma upper limit is I = 23 (this is not corrected for the Galactic
reddening).
This message may be cited.
- astro-ph/0511351 from 11 Nov 2005
Vaughan: The dust-scattered X-ray halo around Swift GRB 050724
This paper discusses the X-ray halo around the Swift gamma-ray burst GRB
050724 (z=0.258), detected by the Swift X-Ray Telescope. The halo, which forms
a ring around the fading X-ray source, expands to a radius of 200" within 8 ks
of the burst exactly as expected for small-angle X-ray scattering by Galactic
dust along the line of sight to a cosmologically distant GRB. The expansion
curve and radial profile of the halo constrain the scattering dust to be
concentrated at a distance of D = 139 +/- 9 pc (from Earth) in a cloud/sheet of
thickness delta-D < 22 pc. The halo was observed only out to scattering angles
of 200", for which the scattering is dominated by the largest grains, with a
maximum size estimated to be a_max ~ 0.4-0.5 um. The scattering-to-extinction
ratio was estimated to be tau_scat/A_V > 0.022; this is a lower limit to the
true value because contribution from smaller grains, which scatter to larger
angles, was not directly observed. The line-of-sight to the GRB passes close to
the Ophiuchus molecular cloud complex, which provides a plausible site for the
scattering dust.
- astro-ph/0603475 from 17 Mar 2006
Campana: The X-ray afterglow of the short gamma ray burst 050724
Short duration (<2 s) Gamma-ray bursts (GRBs) have been a mystery since their
discovery. Until May 2005 very little was known about short GRBs, but this
situation has changed rapidly in the last few months since the Swift and HETE-2
satellites have made it possible to discover X-ray and optical counterparts to
these sources. Positional associations indicate that short GRBs arise in
close-by galaxies (z<0.7). Here we report on a detailed study of the short GRB
050724 X-ray afterglow. This burst shows strong flaring variability in the
X-ray band. It clearly confirms early suggestions of X-ray activity in the
50-100 s time interval following the GRB onset seen with BATSE. Late flare
activity is also observed. These observations support the idea that flares are
related to the inner engine for short GRBs, as well as long GRBs.
- astro-ph/0603773 from 28 Mar 2006
Grupe: Jet Breaks in Short Gamma-Ray Bursts. I: The Uncollimated Afterglow of GRB 050724
We report the results of the Chandra observations of the Swift-discovered
short Gamma-Ray Burst GRB 050724. Chandra observed this burst twice, about two
days after the burst and a second time three weeks later. The first Chandra
pointing occurred at the end of a strong late-time flare. About 150 photons
were detected during this 49.3 ks observation in the 0.4-10.0 keV range. The
spectral fit is in good agreement with spectral analysis of earlier Swift XRT
data. In the second Chandra pointing the afterglow was clearly detected with 8
photons in 44.6 ks. From the combined Swift XRT and Chandra-ACIS-S light curve
we find significant flaring superposed on an underlying power-law decay slope
of $\alpha$=0.90\plm0.02. There is no evidence for a break between about 1 ks
after the burst and the last Chandra pointing about three weeks after the
burst. The non-detection of a jet break places a lower limit of 25$^{\circ}$ on
the jet opening angle, indicating that the outflow is less strongly collimated
than most previously-reported long GRBs. This implies that the beaming
corrected energy of GRB 050724 is at least $4\times 10^{49}$ ergs.
- 0706.1273 from 8 Jun 2007
Malesani: Multicolor observations of the afterglow of the short/hard GRB 050724
Abstract: New information on short/hard gamma-ray bursts (GRBs) is being gathered
thanks to the discovery of their optical and X-ray afterglows. However, some
key aspects are still poorly understood, including the collimation level of the
outflow, the duration of the central engine activity, and the properties of the
progenitor systems. We want to constrain the physical properties of the short
GRB 050724 and of its host galaxy, in turn drawing some inferences on the
global short GRB population. We present optical observations of the afterglow
of GRB 050724 and of its host galaxy, significantly expanding the existing
dataset for this event. We compare our results with models, complementing them
with available measurements in the literature. Including X-ray data, we study
the afterglow light curve and spectrum. We also present observations of the
host galaxy. The observed optical emission was likely related to the large
flare observed in the X-ray light curve. The apparent steep decay was therefore
not due to the jet effect. Available data are indeed consistent with low
collimation, in turn implying a large energy release, comparable to that of
long GRBs. The flare properties also constrain the internal shock mechanism,
requiring a large Lorentz factor contrast between the colliding shells. This
implies that the central engine was active at late times, rather than ejecting
all shells simultaneously. The host galaxy has red colors and no ongoing star
formation, consistent with previous findings on this GRB. However, it is not a
pure elliptical, and has some faint spiral structure. GRB 050724 provides the
most compelling case for association between a short burst and a galaxy with
old stellar population. It thus plays a pivotal role in constraining
progenitors models, which must allow long delays between birth and explosion.
- 1104.5552 from 2 May 11
D.M. Coward et al.: Toward an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence
Quantum Cosmology (gr-qc)
Observations of an optical source coincident with gravitational wave emission detected from a binary neutron star coalescence will improve the
confidence of detection, provide host galaxy localisation, and test models for the progenitors of short gamma ray bursts. We employ optical
observations of three short gamma ray bursts, 050724, 050709, 051221, to estimate the detection rate of a coordinated optical and gravitational
wave search of neutron star mergers. Model R-band optical afterglow light curves of these bursts that include a jet-break are extrapolated for
these sources at the sensitivity horizon of an Advanced LIGO/Virgo network. Using optical sensitivity limits of three telescopes, namely TAROT
(m=18), Zadko (m=21) and an (8-10) meter class telescope (m=26), we approximate detection rates and cadence times for imaging. We find a median
coincident detection rate of 4 yr^{-1} for the three bursts. GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic
rate of 13 coincident detections yr^{-1}, and would be detectable by Zadko up to five days after the trigger. Late time imaging to m=26 could
detect off-axis afterglows for GRB 051221 like bursts several months after the trigger. For a broad distribution of beaming angles, the optimal
strategy for identifying the optical emissions triggered by gravitational wave detectors is rapid response searches with robotic telescopes
followed by deeper imaging at later times if an afterglow is not detected within several days of the trigger.
- 1310.4506 from 18 Oct 13
Brian D. Metzger et al.: Constraints on long-lived remnants of neutron star binary mergers from late-time radio observations of short duration gamma-ray bursts
The coalescence of a binary neutron star (NS) system may in some cases produce a massive NS remnant that is long-lived and, potentially,
indefinitely stable to gravitational collapse. Such a remnant has been proposed as an explanation for the late X-ray emission observed
following some short duration gamma-ray bursts (GRBs) and as possible electromagnetic counterparts to the gravitational wave chirp. A stable NS
merger remnant necessarily possesses a large rotational energy > 1e52 erg, the majority of which is ultimately deposited into the surrounding
circumburst medium (CBM) at mildly relativistic velocities. We present Very Large Array radio observations of 7 short GRBs, some of which
possessed temporally extended X-ray emission, on timescales of ~1-3 years following the initial burst. No radio sources were detected, with
typical upper limits ~0.3 mJy at 1.4 GHz. A basic model for the synchrotron emission from the blast wave is used to constrain the presence of a
long-lived NS merger remnant in each system. Depending on the GRB, our non-detections translate into upper limits on the CBM density n < 3e-2 -
3e-3 particles/cm^3 required for consistency with the remnant hypothesis. Our upper limits rule out a long-lived remnant in GRB 050724 and
060505, but cannot rule out such a remnant in other systems due to their lower inferred CBM densities based on afterglow modeling or the lack
of such constraints. Additional VLA observations in the near future could place tighter limits on the presence of merger remnants in these
system. The population of long-lived NS merger remnants will also be constrained by their (non-)detection with upcoming radio transient
surveys.
- 1607.00416 from 5 Jul 16
Wen-fai Fong et al.: Radio Constraints on Long-Lived Magnetar Remnants in Short Gamma-Ray Bursts
The merger of a neutron star binary may result in the formation of a rapidly-spinning magnetar. The magnetar can potentially survive for
seconds or longer as a supramassive neutron star before collapsing to a black hole if, indeed, it collapses at all. During this process, a
fraction of the magnetar's rotational energy of ~10^53 erg is transferred via magnetic spin-down to the surrounding ejecta. The resulting
interaction between the ejecta and the surrounding circumburst medium powers a >year-long synchrotron radio transient. We present a search for
radio emission with the Very Large Array following nine short-duration gamma-ray bursts (GRBs) at rest-frame times of ~1.3-7.6 years after the
bursts, focusing on those events which exhibit early-time excess X-ray emission that may signify the presence of magnetars. We place upper
limits of <18-32 microJy on the 6.0 GHz radio emission, corresponding to spectral luminosities of <(0.05-8.3)x10^39 erg s^-1. Comparing these
limits to the predicted radio emission from a long-lived remnant and incorporating measurements of the circumburst densities from broad-band
modeling of short GRB afterglows, we rule out a stable magnetar with an energy of 10^53 erg for half of the events in our sample. A
supramassive remnant that injects a lower rotational energy of 10^52 erg is ruled out for a single event, GRB 050724A. This study represents
the deepest and most extensive search for long-term radio emission following short GRBs to date, and thus the most stringent limits placed on
the physical properties of magnetars associated with short GRBs from radio observations.
- 1608.03375 from 12 Aug 16
He Gao et al.: Searching for magnetar powered merger-novae from short GRBs
The merger of a double neutron star (NS-NS) binary may result in a rapidly rotating massive NS with an extremely strong magnetic field (i.e., a
millisecond magnetar). In this case, the magnetic spin-down of the NS remnant provides an additional source of sustained energy injection,
which would continuously power the merger ejecta. The thermal emission from the merger ejecta would give rise to a bright optical
"magnetar-powered merger-nova". In this work, we carry out a complete search for magnetar-powered merger-nova from \emph{Swift} short gamma-ray
burst (SGRB) sample. We focus on short GRBs with extended emission or internal plateau, which may signify the presence of magnetars as the
central engine. We eventually find three candidates of "magnetar-powered merger-nova" from the late observations of GRB 050724, GRB 070714B and
GRB 061006. With standard parameter values, the magentar remnant scenario could well interpret the multi-band data of all three bursts,
including the extended emission and their late chromatic features in the optical and X-ray data. The peak luminosities of these merger-novae
reach several times $10^{42}~{\rm erg~s^{-1}}$, more than one order of magnitude brighter than traditional "kilo-novae" with peak luminosity of
$\sim 10^{41}~{\rm erg~s^{-1}}$. Intense, multi-color late time observations of short GRBs are encouraged to identify more merger-novae in the
future.
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