- GCN/BACODINE POSITION NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 06 Apr 05 15:59:25 UT
NOTICE_TYPE: Swift-BAT GRB Position
TRIGGER_NUM: 113872, Seg_Num: 0
GRB_RA: 34.428d {+02h 17m 43s} (J2000),
34.476d {+02h 17m 54s} (current),
33.976d {+02h 15m 54s} (1950)
GRB_DEC: -50.178d {-50d 10' 39"} (J2000),
-50.154d {-50d 09' 12"} (current),
-50.408d {-50d 24' 28"} (1950)
GRB_ERROR: 4.00 [arcmin radius, statistical only]
GRB_INTEN: 9686 [cnts] Peak=297 [cnts/sec]
TRIGGER_DUR: 2.048 [sec]
TRIGGER_INDEX: 443 E_range: 15-50 keV
BKG_INTEN: 102389 [cnts]
BKG_TIME: 57496.00 SOD {15:58:16.00} UT
BKG_DUR: 24 [sec]
GRB_DATE: 13466 TJD; 96 DOY; 05/04/06
GRB_TIME: 57528.40 SOD {15:58:48.40} UT
GRB_PHI: 33.86 [deg]
GRB_THETA: 15.06 [deg]
SOLN_STATUS: 0x3
RATE_SIGNIF: 9.48 [sigma]
IMAGE_SIGNIF: 8.00 [sigma]
MERIT_PARAMS: +1 +0 +0 +1 +1 +0 +0 +0 -51 +1
SUN_POSTN: 15.62d {+01h 02m 30s} +6.66d {+06d 39' 33"}
SUN_DIST: 59.12 [deg]
MOON_POSTN: 350.61d {+23h 22m 26s} -7.17d {-07d 09' 57"}
MOON_DIST: 56.35 [deg]
MOON_ILLUM: 6 [%]
GAL_COORDS: 273.19,-61.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS: 2.89,-58.07 [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: Wed 06 Apr 05 16:00:22 UT
NOTICE_TYPE: Swift-XRT Nack-Position
TRIGGER_NUM: 113872, Seg_Num: 0
POINT_RA: 34.417d {+02h 17m 40s} (J2000)
POINT_DEC: -50.164d {-50d 09' 51"} (J2000)
GRB_DATE: 13466 TJD; 96 DOY; 05/04/06
GRB_TIME: 57615.24 SOD {16:00:15.24} UT
COUNTS: 2 Min_needed= 20
STD_DEV: 0.00 Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER: 1 Max_iter_allowed= 4
ERROR_CODE: 1
COMMENTS: SWIFT-XRT Nack Position.
COMMENTS: No source found in the image.
- GCN/SWIFT NOTICE
TITLE: GCN/SWIFT NOTICE
NOTICE_DATE: Wed 06 Apr 05 16:02:21 UT
NOTICE_TYPE: Swift-BAT GRB Lightcurve
TRIGGER_NUM: 113872, Seg_Num: 0
GRB_RA: 34.428d {+02h 17m 43s} (J2000),
34.476d {+02h 17m 54s} (current),
33.976d {+02h 15m 54s} (1950)
GRB_DEC: -50.178d {-50d 10' 39"} (J2000),
-50.154d {-50d 09' 12"} (current),
-50.408d {-50d 24' 28"} (1950)
GRB_DATE: 13466 TJD; 96 DOY; 05/04/06
GRB_TIME: 57528.40 SOD {15:58:48.40} UT
TRIGGER_INDEX: 443
GRB_PHI: 33.86 [deg]
GRB_THETA: 15.06 [deg]
DELTA_TIME: 13.00 [sec]
LC_URL: sw00113872000msb.lc
SUN_POSTN: 15.62d {+01h 02m 30s} +6.66d {+06d 39' 33"}
SUN_DIST: 59.12 [deg]
MOON_POSTN: 350.61d {+23h 22m 26s} -7.17d {-07d 09' 57"}
MOON_DIST: 56.35 [deg]
MOON_ILLUM: 6 [%]
GAL_COORDS: 273.19,-61.67 [deg] galactic lon,lat of the pointing direction
ECL_COORDS: 2.89,-58.07 [deg] ecliptic lon,lat of the pointing direction
COMMENTS: SWIFT-BAT GRB Lightcurve.
COMMENTS: This does not match any source in the ground catalog.
- GCN notice #3180
A. Parsons (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), S.
Hunsberger (PSU),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama),
J. Tueller (GSFC) D. Burrows, J. Kennea, J. Nousek (PSU), G.
Chincarini,
P. Romano (INAF-OAB)
on behalf of the Swift team:
At 15:58:48.40 UT Swift-BAT triggered on burst GRB 050406 (trigger
113872).
The BAT-derived position is RA,Dec= 34.428, -50.178 (J2000).
Significant emission
has been detected for at least 3 sec with possible low significance
peaks over
an additional 30 sec. The peak count rate was 800 cnts/sec. The source was
detected at 15 degrees off the bore-site and thus is in the fully-coded
field-of-view.
Swift slewed promptly and the UVOT imaged the field at the end of the
slew and did
not find a bright optical source in the 8 arcmin square binned field of
view centered on the BAT position.
The XRT also imaged the field promptly and did not find a bright X-ray
source within
the field of view. Based on previous experience, this lack of prompt
x-ray afterglow
suggests either that this trigger is not a GRB, or that it is a very
interesting and
unusual GRB. The BAT rate trigger and image are significant enough to
lean
toward an interpretation of an unusual GRB.
- GCN notice #3181
G. Cusomano (IASF/Palermo), J. Kennea, D. N. Burrows, J. E. Hill, D. Grupe,
J. A. Nousek (PSU),
J. P. Osborne, K. Page, M. Goad, A. Beardmore, A. F. Abbey, A. A. Wells
(U. Leicester), S. Campana, A. Moretti, C. Pagani, P. Romano,
G. Tagliaferri, G. Chincarini (OAB), V. Mangano (IASF/Palermo),
P. Giommi, M. Capalbi, M. Perri (ASDC), L. Angelini, F. Marshall,
N. White, N. Gehrels (NASA/GSFC), P. Roming, P. Meszaros (PSU),
P. Schady (MSSL), report on behalf of the Swift XRT team:
The Swift BAT instrument detected a GRB at 15:58:48 UT on 6th April 2005
(GCN Circ 3161). The observatory executed an automated slew to the BAT
position and the XRT began taking data at 16:00:15 UT. The XRT was in
Auto state but was not able to centroid on the afterglow due to low
source brightness. From downlinked data we find a uncataloged, fading
X-ray source located at:
RA(J2000) = 2:17:52.4,
Dec(J2000) = -50:11:18.9.
We estimate an uncertainty of about 5 arcseconds.
- GCN notice #3182
W. Landsman (GSFC), S. Hunsberger (PSU), A. Breeveld (MSSL), P. Roming
(PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), T. Poole
(MSSL), C. Gronwall (PSU), A. Blustin (MSSL), P. Brown, S. Rosen, K.
McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC), S. T. Holland, M.
Still (GSFC/USRA), S. Koch (PSU), M. Carter, H. Huckle (MSSL), P. Broos
(PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), J. Nousek (PSU), N.
Gehrels (GSFC), on behalf of the Swift UVOT team.
The Swift Ultra-Violet/Optical Telescope (UVOT) began settled
observations of the field of GRB 050406 (Parsons et al; GCN 3180) at
16:00:16 UT, 88s after the BAT trigger. The first data taken after
spacecraft settling was a 100s V image with pixel size 0.5x0.5 arcsec
and a field of view of 17x17 arcmin. Mid-exposure time was 138s after
the trigger. A comparison against the Digitized Sky Survey reveals no
new sources in the field down to a 3-sigma background limit of V =
18.8. This limit is based upon preliminary flight calibrations.
- GCN notice #3183
H. Krimm (GSFC/USRA), L. Barbier, S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (UMD), D.Q. Lamb (U. Chicago), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), M. Suzuki (Saitama), M. Tashiro (Saitama U.),
J. Tueller (GSFC), on behalf of the Swift/BAT team:
At 15:58:48.40 UT Swift-BAT detected GRB 050406 (trigger=113872)
(GCN Circ 3180, Parsons et al.). The refined BAT ground position is
(RA,Dec) = 34.471 -50.181, [deg; J2000] +- 3 arcmin, (95%
containment). This is 28 arc seconds from the position determined
on-board and originally reported.
Examination of the mask weighted light curve confirms that only the initial
peak is associated with the burst. The other possible emission reported
in GCN Circ 3180 is attributed to background fluctuations.
The shape of the peak is fast-rise, exponential decay in the 15-25 keV
band. In the 25-50 keV band, the peak starts ~2 secs earlier and the
shape is more symmetric. We derive T90 (15-25 keV) = 3 seconds
+/- 1 s, and T90 (15-350 keV) = 5 seconds +/- 1 s. Errors on T90
include systematics.
Analysis of the event data shows that this is a very soft burst with
no significant flux above 50 keV. Plotting GRB 050406 on a color-color
diagram indicates that this burst may have the characteristics of an
X-ray Flash. The fluence derived from the event data is
9.0 X 10^-8 erg/cm^2 in the 15-350 keV band, and
4.8 X 10^-8 erg/cm^2 in the 15-50 keV band. The 1-s peak flux
(T+0.6 s) is 3.2 ph/cm^2/s (15-25 keV). The photon index of the
1-s peak spectrum (T+0 s) is 2.32 +/- 0.53 (90% confidence).
The time-averaged spectrum yields a photon index of 2.38 +/- 0.34
(90% confidence). Both the 1-s and time-averaged spectra are well
fit by a simple power-law.
- GCN notice #3184
M. Capalbi, M. Perri (ASDC), P. Romano, A. Moretti, C. Pagani, G.=20
Tagliaferri (INAF-OAB), D. Malesani (SISSA), D. N. Burrows, J. Kennea, D.=
Grupe (PSU), K. Page, M. Goad, A. Beardmore (U. Leicester), V. La Parola,=
T. Mineo (IASF/Palermo), N. Gehrels (NASA/GSFC), and S. Kobayashi (PSU)=20
report on behalf of the Swift XRT team:
We have analyzed the Swift XRT data from the first orbit observation=20
of GRB 050406 (Parsons et al., GCN3180; Cusumano et al., GCN 3186). The=
new refined coordinates are:
RA(J2000) =3D 2h 17m 52.64s
Dec(J2000) =3D -50:11:18.80
This position is 28 arcseconds from the refined BAT position given in GCN=
3183 (Krimm et al. 2005). We estimate an uncertainty of 5 arcseconds=20
radius (90% containment).
This is 30 arcsec from the refined BAT position (Krimm et al., GCN=20
3183) and 3.2 arcsec from the preliminary XRT position (GCN 3186).
The [0.2-10] keV light curve in Windowed Timing (WT) and Photon Counting=20
(PC) mode starts 106 seconds from the BAT trigger (T0). At the beginning,=
the count rate is rapidly rising, peaking at about 218 seconds from T0.=20
Then it decays very fast, possibly flattening at T-T0=3D300 seconds.
A preliminary spectral fit to the WT data gives a spectral power law phot=
on=20
index of 2.1 =B1 0.3 in the [0.5-10] keV band, assuming Galactic absorpt=
ion=20
(3.3E20cm^-2). The average (in the time range 100-700 seconds from=20
trigger) estimated unabsorbed 0.5-10 keV flux is then about 2.8E-11 erg=20
cm^-2 s^-1.
- GCN notice #3185
Edo Berger, Gus Oemler, and Mike Gladders (Carnegie Observatories) report:
"On 2005, April 6.99 UT we imaged the position of GRB 050406 (GCN 3180)
with LDSS-3 on the Magellan/Clay telescope in the r-band and i-band.
Within the 5" radius XRT error circle (GCN 3184) we find a single faint
source (r~22 mag) close to the detection threshold of both images. The
position of this object is (J2000):
RA = 02:17:52.3
DEC= -50:11:15
with an uncertainty of about 0.5" in each coordinate. At the present we
cannot confirm whether the object has faded."
- GCN notice #3186
E. Rol (University Leicester), P. Schady (MSSL/PSU), S. Hunsberger (PSU), A.
Breeveld (MSSL), P. Boyd (GSFC/UMBC), C. Kouveliotou (MSFC), P. Roming (PSU),
J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the Swift UVOT team.
Starting with data taken 88 s after the BAT trigger (Parsons et al; GCN 3180),
we have co-added the early time data of GRB 050406 in each of the Swift
Ultra-Violet/Optical Telescope (UVOT) U, B, and V bands. We detect a source
within the XRT error circle (M. Capalbi et al; GCN 3184) at the 4.3 (19.0
magnitude), 3.0, and 2.5-sigma detection levels in the U, B, and V
respectively. We do not detect a source in a second deeper U band observation
taken 1.3 hours after the burst. The source is located at RA = 02:17:52.2, DEC
= -50:11:15.8. The UVOT source location and fading is consistent with the
Magellan candidate by Berger et al (GCN 3185) strongly suggesting that this is
the optical counterpart of XRF 050406. More detailed analysis of the UVOT data
is underway.
- astro-ph/0601173 from
Romano: X-ray flare in XRF 050406: evidence for prolonged engine activity
We present observations of XRF 050406, the first burst detected by Swift
showing a flare in its X-ray light curve. During this flare, which peaks at
t_peak ~210s after the BAT trigger, a flux variation of (delta F)/F~6 in a very
short time (delta t)/t_peak<<1 was observed. Its measured fluence in the 0.2-10
keV band was ~1.4x10^-8 erg cm^-2, which corresponds to 1-15% of the prompt
fluence. We present indications of spectral variations during the flare. We
argue that the producing mechanism is late internal shocks, which implies that
the central engine is still active at 210s, though with a reduced power with
respect to the prompt emission. The X-ray light curve flattens to a very
shallow slope with decay index of ~0.5 after ~4400s, which also supports
continued central engine activity at late times. This burst is classified as an
X-ray flash, with a relatively low fluence (~10^-7 erg cm^-2 in the 15-350 keV
band, E_iso~10^51 erg), a soft spectrum (photon index 2.65), no significant
flux above ~50 keV and a peak energy E_p<15 keV. XRF 050406 is one of the first
examples of a well-studied X-ray light curve of an XRF. We show that the main
afterglow characteristics are qualitatively similar to those of normal GRBs. In
particular, X-ray flares superimposed on a power-law light curve have now been
seen in both XRFs and GRBs. This indicates that a similar mechanism may be at
work for both kinds of events.
- astro-ph/0604158 from 7 Apr 2006
Corsi: XRF 050406 late time flattening: appearance of an IC component?
We investigate on the possible evidence for Inverse Compton (IC) emission in
the X-ray afterglow of XRF 050406. In the framework of the standard fireball
model, we show how the late time flattening observed in the X-ray light curve
between ~10^{4} s and ~10^{6} s can be explained in a synchrotron plus IC
scenario, when the IC peak frequency crosses the X-ray band. We thus conclude
that the appearance of an IC component above the synchrotron one at late times
successfully accounts for the X-ray observations.
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