GRB 090902B
GCN Circular 9866
Subject
GRB 090902B: Fermi GBM detection of a bright burst
Date
2009-09-02T21:19:03Z (16 years ago)
From
Elisabetta Bissaldi at MPE <ebs@mpe.mpg.de>
Elisabetta Bissaldi (MPE) and Valerie Connaughton (UAH)
report on behalf of the Fermi GBM Team:
"At 11:05:08.31 UT on 2 September 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090202B (trigger 273582310 / 090902462).
The on-ground calculated location, using the GBM trigger
data, is RA = 264.5, DEC = 26.5 (J2000 degrees,
equivalent to 17h 38m, 26d 30'), with an uncertainty
of 1.0 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
The angle from the Fermi LAT boresight is 52 degrees.
Moreover, this burst was bright enough to result in
a Fermi spacecraft repointing maneuver.
The burst was also independently detected by INTEGRAL SPI-ACS.
The GBM light curve consists of a bright pulse
with a duration of about 21 s.
The time-averaged spectrum between 50 keV and 40 MeV
from T0 to T0+22 s is well fit by a Band function
with Epeak = 775 +/- 11 keV, alpha = -0.696 +/- 0.012
and beta = -3.85 (+0.21/-0.31).
The event fluence (50 keV - 10 MeV) in this time interval is
(3.74 +/- 0.03)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+14 s in the 50 keV - 10 MeV band
is 46.1 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 9867
Subject
GRB 090902B: Fermi LAT detection
Date
2009-09-02T22:48:18Z (16 years ago)
From
Hiroyasu Tajima at SLAC <htajima@slac.stanford.edu>
Francesco de Palma (Universit� e INFN Bari), Johan Bregeon (INFN,
Pisa) and Hiro Tajima (SLAC) report on behalf of the Fermi LAT team:
At 11:05:15 UT on 2 Sep 2009, the Fermi Large Area Telescope (LAT)
detected gamma rays from the long GRB 090902B, which was triggered and
located by the Fermi Gamma-ray Burst Monitor (GBM) (trigger
273582310/090902462, GCN9866). The angle of the GBM best position (RA,
Dec= 264.5, 26.5) with respect to the LAT boresight was 51 degrees at
the time of the trigger, which is close the edge of our field of view.
The data from the Fermi LAT show a significant increase in the event
rate within 1 degree of the GBM location after the GBM trigger that is
spatially and temporally correlated with the GBM emission with high
significance. More than 200 photons above 100 MeV and more than 30
photons above 1 GeV are observed within 100 seconds. The highest
energy photon is a 33.4 GeV event which is observed 82 seconds after
the GBM trigger.
The best LAT on-ground localization is found to be (RA,Dec=265.00,
27.33) with a 90% containment radius of 0.06 deg (statistical; 68%
containment radius: 0.04 deg, preliminary systematic error is less
than 0.1 deg) which is consistent with the GBM localization. A Swift
TOO request has been issued.
Further analysis is ongoing.
The point of contact for this burst is
Francesco de Palma (francesco.depalma@ba.infn.it)
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 9868
Subject
GRB 090902B: Swift/XRT Afterglow Candidate
Date
2009-09-03T03:00:57Z (16 years ago)
From
Jamie A. Kennea at PSU/Swift-XRT <kennea@astro.psu.edu>
J. A. Kennea (PSU) and G. Stratta (ASDC) report on behalf of the Swift/XRT
team:
At 23:36 UT, September 2nd, 2009, Swift began a Target of Opportunity
observation of the Fermi GBM/LAT discovered burst GRB 090902B (de Palma et
al., GCN #9867, Bissaldi et al., GCN #9866), approximately 12.5 hours
after the Fermi detection. In early data we detect an uncatalogued point
source at the following location, RA, Dec = 264.93984, 27.32405, which is
equivalent to:
RA (J2000) = 17h 39m 45.6s
Dec (J2000) = +27d 19' 26.6''
with an estimated uncertainty of 4.2 arcseconds radius (90% confidence).
This position is 3.2 arcmin from the reported LAT position, inside the LAT
error radius.
At this time we cannot confirm if the point source is fading. Observations
of this field are on-going.
GCN Circular 9869
Subject
GRB090902B: Swift/UVOT observations
Date
2009-09-03T04:57:44Z (16 years ago)
From
Craig Swenson at PSU/Swift <cswenson@astro.psu.edu>
C. A. Swenson (PSU) and M. H. Siegel (PSU) report on behalf of the Swift
UVOT team:
The Swift/UVOT began observations of the field of GRB090902B
approximately 12.5 hours after the Fermi GBM/LAT trigger (de Palma et
al., GCN #9867, Bissaldi et al., GCN #9866). Within the initial 4.2"
XRT error circle (Kennea et al., GCN #9868) we find a very faint source:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 273627410 273634846 2691 20.41 +- 0.20 (5.5-sigma)
This source does not seem to appear in the DSS; however, its proximity
to another DSS source, also within the XRT error circle, makes
identifying this source as the afterglow difficult. We await an
enhanced XRT position and/or ground-based detection to confirm the
nature of this potential afterglow candidate.
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 9870
Subject
GRB 090902B: Optical afterglow candidate
Date
2009-09-03T05:30:08Z (16 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley, I. K. W. Kleiser, and J. M. Rex (UC Berkeley) report:
We imaged the location of the Swift-XRT candidate afterglow (GCN 9868,
Kennea et al.) of extremely bright Fermi GRB 090902B (GCN 9866, Bissaldi
et al.) with the Nickel 1-meter telescope at Lick Observatory. We
marginally detect a faint source in individual 600-second exposures at
the western edge of the XRT error circle with a magnitude comparable to
the Digitized Sky Survey limit. This is likely the same source observed
by the UVOT (GCN 9868, Swenson et al.).
We cannot confirm fading behavior at this time, and further observations
are encouraged. A finding chart showing the XRT error circle and the
putative afterglow is available at the following URL:
http://lyra.berkeley.edu/~dperley/090902b/090902b_lick.jpg
GCN Circular 9871
Subject
GRB 090902B: Enhanced Swift-XRT position
Date
2009-09-03T06:25:14Z (16 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team.
Using 2.7 ks of XRT Photon Counting mode data and 2 UVOT images for GRB
090902B, 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 = 264.93859, 27.32448 which is equivalent to:
RA (J2000): 17h 39m 45.26s
Dec (J2000): +27d 19' 28.1"
with an uncertainty of 2.1 arcsec (radius, 90% confidence).
Position enhancement is described by Goad et al. (2007, A&A, 476, 1401)
and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular 9872
Subject
GRB 090902B: Fermi LAT and GBM refined analysis.
Date
2009-09-03T07:36:42Z (16 years ago)
From
Valerie Connaughton at MSFC <valerie@nasa.gov>
F. de Palma (Universit� e INFN Bari), E. Bissaldi (MPE), H. Tajima (SLAC),
S. Guiriec (UAH), N. Omodei (INFN Pisa), V. Vasileiou (NASA GSFC/UMBC)
and V. Connaughton (UAH) report for the Fermi LAT and GBM teams:
Further analysis of GRB 090902B (Bissaldi et al. GCN 9866, de Palma et al.
GCN 9867, Kennea et al. GCN 9868) reveals it is detected in the Fermi
Large Area Telescope (LAT) at least until 300 s after the Fermi
Gamma-Ray Burst Monitor (GBM) trigger time, T0=11:05:08.31 UT.
Spectral analysis of the main emission episode, from T0 to T0+25 s, shows a
deviation from the Band function obtained from fitting GBM data between
50 keV and 40 MeV (GCN 9866). This deviation is apparent both below 50
keV in the GBM and above 100 MeV in the LAT. It is well-fit by a single
power-law, with a well-constrained index that is retrieved from a fit of
the
GBM data alone, the LAT data alone, and when jointly fitting the entire
data set.
The parameters for this multi-component fit are Band_alpha =
0.61 � 0.01, Band_beta = 3.87 � 0.16, Band_EPeak = 798 � 7 keV,
and a power-law index of 1.94 � 0.01 that shows no evidence for a
spectral cut-off below 100 GeV. The fluence between 8 keV and 30
GeV is 4.86 � 0.06 x 10-4 ergs/cm2.
The points of contact for this burst are:
Francesco de Palma (francesco.depalma@ba.infn.it) and
Elisabetta Bissaldi (ebs@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.
This message can be cited.
GCN Circular 9873
Subject
GRB 090902B: Gemini-N absorption redshift
Date
2009-09-03T08:23:17Z (16 years ago)
From
Antonino Cucchiara at PSU <cucchiara@astro.psu.edu>
A. Cucchiara, D. B. Fox (PSU), N. Tanvir (U. Leicester),
E. Berger (Harvard U.) report on behalf of a large collaboration.
"On 2009 September 3.27 UT we observed the Fermi/LAT GRB 090902B
(Bissaldi et al., GCN 9866, de Palma 9867) with the Gemini-N
telescope equipped with the GMOS spectrograph.
A single object has been found at the position of the Swift/XRT
afterglow (Kennea et al. GCN 9868, Perley et al., GCN 9870) in
our acquisition image.
A pair of 900 sec exposures spectra were obtained with a wavelength
coverage of 4500-7500A under good conditions.
The spectrum reveals a series of metal absorption features,
MgII[2796,2803], MgI[2853],MnII[2606], FeII[2600], MnII[2594],
FeII[2586], FeII[2260], SiII[1808], SiII*[1816].
All these features are consistent with a redshift of z = 1.822,
which, therefore, we conclude is the redshift of GRB 090902B.
We thank the Gemini-N staff for performing this observation,
in particular Ricardo Schiavon."
GCN Circular 9874
Subject
GRB 090902B: GROND NIR Afterglow Observations
Date
2009-09-03T09:14:50Z (16 years ago)
From
Thomas Kruehler at MPE/MPI <kruehler@mpe.mpg.de>
F. Olivares, P. Afonso, J. Greiner (all MPE Garching), S. McBreen (MPE +
UCD), T. Kruehler, A. Rau, A. Yoldas, G. Kanbach (all MPE), and S. Klose
(TLS Tautenburg) report on behalf of the GROND team:
The field of GRB 090902B, (Fermi GBM trigger 273582310/090902462, Bissaldi
et al., GCN #9866) which was detected by the LAT (de Palma et al., GCN
#9867), was observed 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 LaSilla
Observatory (Chile).
Observations started at 00:21 UT on September 3, 2009, 13.25 hours after
the GRB trigger. They were performed at a seeing of around 2", at an
average air mass larger than 2.0 and under variable sky conditions. We
detect a NIR source within the Swift/XRT error circle reported by Kennea et
al. (GCN #9868) and on the edge of the Swift/XRT enhanced position (Evans
et al. GCN #9871), at:
RA (J2000.0) = 17h 39m 45.41s
DEC (J2000.0) = +27d 19' 27.1"
with an uncertainty of 0.5" in each coordinate.
This position seems consistent with the object reported by Perley et al.
(GCN #9870) and is very likely the source reported by Swenson & Siegel (GCN
#9869).
The source is not in the field of view of the griz channels, so no
statement can be made about the optical bands.
The afterglow (Cucchiara et al. GCN #9873) has the following preliminary AB
magnitude and shows tentative evidence of fading within the observations.
midtime J_AB mag
-----------------------------------------------
01:09:31 UT 20.26 +/- 0.07
Calibrations was done against 2MASS catalog stars. No Galactic extinction
correction was applied.
GCN Circular 9875
Subject
GRB 090902B: Faulkes Telescope North observations
Date
2009-09-03T10:09:22Z (16 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), N.R. Tanvir (U. Leicester),
Z. Cano, I. A. Steele, A. Melandri, D. Bersier,
S. Kobayashi, C.J. Mottram, C.G. Mundell,
R.J. Smith (Liverpool JMU), A. Gomboc (U. Ljubljana),
P. O'Brien (U. Leicester) on behalf of a large
collaboration report:
On 2009 September 03 at 07:50:02 UT we began observing
the Fermi GRB 090902B (Bissaldi et al., GCN 9866; de Palma
et al. GCN 9867, 9872) with the Faulkes Telescope North
using the R filter.
Within the Swift UVOT-enhanced XRT error circle (Evans et al.
GCN 9871) we clearly detect the afterglow candidate (Swenson et
al. GCN 9869, Perley et al. GCN 9870, Cucchiara et al. GCN 9873,
Olivares et al. GCN 9874) at the following position (J2000):
RA: 17:39:45.35
Dec: +27:19:27.1
with an uncertainty of 0.7". At the mid epoch of 21.01 hours
post burst we measure R=21.03 +- 0.11 mag.
Calibration was performed with the USNOB-1 star RA=17:39:42.74
Dec=+27:19:13.76 assuming R2=17.46.
GCN Circular 9876
Subject
GRB090902B: Swift XRT refined analysis
Date
2009-09-03T15:30:29Z (16 years ago)
From
Giulia Stratta at ASDC <stratta@asdc.asi.it>
G. Stratta, V. D'Elia, M. Perri (ASDC) report on behalf of the
Swift XRT team:
At 23:36 UT, September 2nd, 2009, Swift began a Target of Opportunity
observation of the Fermi GBM/LAT discovered burst GRB 090902B (de
Palma et al., GCN 9867, Bissaldi et al., GCN 9866) about 12.5 hours
after the trigger.
We confirm that the X-ray source reported by Kennea et al. (GCN
Circ. 9868) shows a decaying behavior and is likely the afterglow of
GRB 090902B.
The enhanced XRT position for this burst was given by Evans
(GCN. Circ 9871).
The X-ray light curve from T+12.53 hr to T+17.38 hr can be fit with
a single power-law model with a decay index of -1.3+/-0.9 (90% confidence
level).
With 4.8 ks of integration time, the X-ray spectrum from T+12.53 hr to T+17.38 hr
after the Fermi/GBM trigger can be fit by an absorbed power-law model
with a photon index of 2.1 (+0.3,-0.3) and a rest frame column density of
(3.4+/-0.9) x 10^22 cm^-2 at z=1.822 (Cucchiara et al., GCN 9873)
in addition to the Galactic column density
in the direction of the burst (3.88 x 10^20 cm^-2, Kalberla et al. 2005).
Errors are at 90% confidence level.
The observed 0.3-10.0 keV flux is 3.2 x 10^-12 erg cm^-2 s^-1 which
corresponds to an unabsorbed flux of 4.1 x 10^-12 erg cm^-2 s^-1.
Providing the source continues to decay at the same rate, we predict an
observed flux of about 8.7 x 10^-13 erg cm^-2 s^-1 at T+2 days.
This circular is an official product of the Swift-XRT team.
[GCN OPS NOTE(03sep09): Per author's request, the missing Cucchiara
reference was added.]
GCN Circular 9877
Subject
GRB 090902B: Swift/UVOT refined analysis
Date
2009-09-03T19:55:45Z (16 years ago)
From
Craig Swenson at PSU/Swift <cswenson@astro.psu.edu>
C. A. Swenson (PSU) and G. Stratta (ASDC) report on behalf of the
Swift/UVOT team:
The Swift/UVOT began observations of the field of GRB 090902B
approximately 12.5 hours after the Fermi GBM/LAT trigger (de Palma
et al., GCN Circ. 9867; Bissaldi et al., GCN Circ. 9866). We can
now confirm the detection of the optical afterglow (Swenson et al.,
GCN Circ. 9869; Perley et al., GCN Circ. 9870; Cucchiara et al.,
GCN Circ. 9873; Olivares et al., GCN Circ. 9874; Guidorzi et al.,
GCN Circ. 9875) coincident with the enhanced Swift-XRT position (Evans,
GCN Circ. 9871). We also observe a decay in the optical afterglow.
The observed magnitudes using the UVOT photometric system (Poole et
al. 2008, MNRAS, 383, 627) are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 45096 46188 1075 20.26 � 0.19
u 50891 58703 3613 20.50 � 0.11
u 62457 81106 8756 20.85 � 0.10
The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 9878
Subject
GRB 090902B: ROTSE-III Detection of Optical Afterglow
Date
2009-09-03T20:40:17Z (16 years ago)
From
Shashi Bhushan Pandey at ROTSE <shaship@umich.edu>
S. B. Pandey, W. Zheng, F. Yuan and C. Akerlof (U Mich), report on behalf
of the
ROTSE collaboration:
ROTSE-IIIa, located at the Siding Spring Observatory Australia, responded ~
283 sec after the GBM trigger 273582310 (Bissaldi E. & Connaughton V. GCNC
9866). The Set of images starting ~ 1.4 hours after the trigger covered the
GRB 090902B location. The OT (Perley et al. GCNC 9870, Kennea & Stratta
GCNC 9868) was detected at 15.9+-0.2 mag in the sum of 30x60 sec exposures.
The images taken by ROTSE-IIIc (located naer the H.E.S.S. site at Mt.
Gamsberg, Namibia) around 6.6 hours after the burst marginally detect the
OT, indicating a decay of ~ 2 magnitudes. The unfiltered images were
calibrated relative to USNO B1.0. Further analysis is in progress.
GCN Circular 9883
Subject
GRB 090902B: WSRT Radio Observation
Date
2009-09-04T07:17:14Z (16 years ago)
From
Alexander van der Horst at NASA/MSFC <Alexander.J.VanDerHorst@nasa.gov>
A.J. van der Horst (NASA/MSFC/ORAU) A.P. Kamble, R.A.M.J. Wijers
(U of Amsterdam) and C. Kouveliotou (NASA/MSFC) report on behalf of
a large collaboration:
"We observed the position of the GRB 090902B afterglow with the
Westerbork Synthesis Radio Telescope at 4.8 GHz at September 3 12.72 UT
to September 4 0.35 UT, i.e. 1.07 - 1.55 days after the burst (GCN 9866).
We detect a radio source at the 4-sigma level with a flux density
of 111 +/- 28 microJy at the position of the optical counterpart
(GCN 9869, GCN 9874).
We would like to thank the WSRT staff for scheduling and obtaining these
observations."
GCN Circular 9889
Subject
GRB 090902B: VLA radio detection
Date
2009-09-04T13:23:07Z (16 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
Poonam Chandra (RMC) and Dale A. Frail (NRAO) report on behalf of a
larger collaboration:
"We used the Very Large Array (VLA) to observe the field of view towards
the GRB 090902B (GCN 9866) at a frequency of 8.46 GHz on 2009 Sep.
03.94 UT. We clearly detect the GRB afterglow at the GROND NIR afterglow
position (GCN 9874) at a flux density of 141+/-39 uJy.
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 9897
Subject
GRB 090902B: Suzaku WAM observation of the prompt emission
Date
2009-09-05T04:36:48Z (16 years ago)
From
Kazutaka Yamaoka at Aoyama Gakuin U <yamaoka@phys.aoyama.ac.jp>
Y. Terada, M. Tashiro, A. Endo, K. Onda, T. Sugasahara,
W. Iwakiri (Saitama U.), K. Yamaoka, S. Sugita (Aoyama Gakuin U.),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji,
E. Sonoda, K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi
(Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata (NCU),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong
(Nihon U.), on behalf of the Suzaku WAM team, report
The Fermi detected long GRB 090902B (Bissaldi et al., GCN 9866,
de Palma et al. GCN 9867) triggered the Suzaku Wide-band All-sky
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at
11:05:08.446 UT (=T0). The observed light curve shows a multi-peaked
structure lasting from T0-0.5 s to T0+24.5 s with a duration (T90) of about
19 seconds. The fluence in 100 - 1000 keV was 1.45 (-0.04, +0.03)x10^-4 erg/cm^2.
The 1-s peak flux measured from T0+14.5 s was 21.3 (-1.3, +0.9) photons/cm^2/s
in the same energy range.
Preliminary result shows that the time-averaged spectrum from
T0-0.5 s to T0+24.5 s is well fitted by a power-law with exponential
cutoff model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha: 0.91 +/- 0.10, and
Epeak: 885 (-38, +39) keV (chi^2/d.o.f. = 25.5/24).
Due to this GRB brightness, a 3% systematcic error was
added for low energy channels. In addition, there might be
some calibration uncertainties in fluence because the GRB
photons came into the WAM through the base plate of the satellite.
All the quoted errors are at 90% confidence level.
The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html
GCN Circular 9916
Subject
GRB 090902B: Skynet/PROMPT Observations
Date
2009-09-16T20:05:51Z (16 years ago)
From
Josh Haislip at U.North Carolina <haislip@physics.unc.edu>
J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, A. Foster, J. Moore, A.
Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander
report:
Skynet observed the Fermi/LAT localization of GRB 090902B (de Palma et al.,
GCN 9867) with four of the 16" PROMPT telescopes at CTIO beginning 13.3
hours after the trigger in BVRI through variable cloud cover.
We do not detect the afterglow (Kennea et al., GCN 9868; Swenson & Siegel,
GCN 9869). Stacking only images that increase the limiting magnitude
yields:
mean 1-sig. 1-sig.
time 3-sig. sys. stat.
since lim. cal. cal. cal.
trig. tel. exp. fil. mag. stars unc. unc.
(h) (# x s) (mag) (mag)
14.4 PROMPT-4 18 x 80 R 19.8 240 USNO B1 0.185 0.001
14.4 PROMPT-3 18 x 80 B 19.0 100 USNO B1 0.296 0.002
14.4 PROMPT-5 18 x 80 I 19.0 278 USNO B1 0.234 0.001
14.4 PROMPT-2 17 x 80 V 19.0 217 NOMAD 0.255 0.001