GRB 050219B

E. Berger (Carnegie Observatories) and D.B. Fox (Caltech) report on behalf
of the Carnegie-Caltech-NRAO collaboration:
 
"On 2005, February 24.09 UT we obtained near-infrared spectra with GNIRS
on the Gemini-south telescope of the NIR afterglow of GRB 050219b,
identified in images from the Las Campanas 100-inch telescope (see also
GCN 3064
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 ). As reported in GCN 3064
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  (also GCN 3052
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 : UVOT limits), the NIR
afterglow is significantly brighter than optical limits obtained
contemporaneously, suggesting a large dust extinction or a high redshift
(z>5) origin.
 
Using Director's Discretionary time we obtained a total of 4800 sec on
source in the cross-dispersed mode which covers the range of 1-2.5 microns
in six echelle orders (R~1700).  No continuum or emission lines were
detected in the combined 2-d spectrum.
 
We thank Phil Puxley, Gemini South Associate Director, for the allocation
of DD time, and Claudia Winge for extensive help with the Phase I/II setup
and the observations."

P. D'Avanzo, D. Fugazza, S. Covino, G. Tagliaferri, D. Malesani, L.A. 
Antonelli, S. Campana, G. Chincarini, M. Della Valle, F. Fiore, L. 
Stella, F.M. Zerbi, on behalf of the MISTICI collaboration report :


Optical and near-infrared monitoring of the field of GRB050219b 
(Cummings et al., GCN 3044
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 ) was performed at the ESO-VLT, with the FORS2 
and ISAAC instruments respectively. Observations were carried out under 
a clear sky, starting 0.18 days after the GRB. The log is reported below.

Mean date (UT) t-t0 (days)  filter  seeing (")
----------------------------------------------
Feb 20.062     0.18         R       1.0
Feb 21.062     1.18         R       1.0
Feb 21.088     1.21         Ks      0.5
Feb 24.024     4.14         Ks      0.5
----------------------------------------------
t0 = Feb 19.879 UT (GRB trigger).

In the refined XRT position and error circle (Burrows et al., GCNs 3043
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 ; 
Racusin et al., GCN 3049
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 ) we detect three sources in the Ks images:


1. RA: 05:25:15.99  Dec: -57:45:28.7
2. RA: 05:25:16.13  Dec: -57:45:30.5
3. RA: 05:25:15.59  Dec: -57:45:25.4

Source #2 and #3 do not exhibit significant variations (the latter being 
also present in the 2MASS catalogue).
Source #1 is pointlike and is fading by 1.09 +- 0.19 mag in the Ks band 
between 1.21 and 4.15 days after the burst. We therefore identify this 
is the NIR afterglow of GRB050219b. The flux decay index (F = 
K*t^-delta) is delta = 0.81 +- 0.14.

The candidate afterglow has a magnitude Ks = 21.47 +- 0.18 on Feb 24.02, 
based upon field calibration with standard stars. We caution that we get 
Ks = 16.45 +- 0.04 for the 2MASS star quoted above (source #3), which 
has a tabulated magnitude K=15.345 in the 2MASS catalog.

In the R band, no source is detected at the position of the candidate 
afterglow, down to a limiting magnitude R~23, based on calibration 
against the USNO catalog.

Further observations are planned at the VLT.

This message can be cited.

T. Poole (MSSL), C. Gronwall (PSU), A. Blustin (MSSL), P. Brown (PSU), S.
Rosen, K. McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC), S. Holland,
M. Still (GSFC/USRA), W. Landsman (GSFC), S. Hunsberger (PSU), A. Breeveld
(MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU),
T. Kennedy, P. Smith, B. Hancock (MSSL), S. Koch (PSU), M. Carter, H.
Huckle (MSSL),  P. Broos, J. Racusin (PSU), E. Fenimore (LANL),
B. Zhang (UNLV), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the
Swift UVOT team.

CORRECTION: The time at which the UVOT began observations of GRB050219b 
should read as 21:57:51 in GCN 3046
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  and GCN 3050
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 . This was 52 minutes 
after the initial Swift BAT trigger (Cummings et al, GCN 3044
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 ), the delay 
being caused by the Earth-limb constraint.

No new source was detected at the corrected XRT position (Racusin et al, 
GCN 3049
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 ), and the 3-sigma limiting magnitudes given in GCN 3050
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  still 
apply:

Filter	Lim_Mag  Tot_Exposure(s)   T_start (s)
  UVW2	~ 22.16		1154	     T+3120
  UVM2	~ 22.24		1435	     T+3243
  UVW1	~ 22.23   	940	     T+3349
  U	~ 20.74   	100	     T+3455
  B	~ 20.9    	100	     T+3561
  V	~ 19.41   	100	     T+3136

We caution that the instrument is not yet fully calibrated and that the
magnitude limits presented here may need to be refined.

T. Poole (MSSL), C. Gronwall (PSU), A. Blustin (MSSL), P. Brown (PSU), S. 
Rosen, K. McGowan, M. De Pasquale (MSSL), P. Boyd (GSFC/UMBC), S. Holland, 
M. Still (GSFC/USRA), W. Landsman (GSFC), S. Hunsberger (PSU), A. Breeveld 
(MSSL), P. Roming (PSU), K. Mason, P. Schady (MSSL), M. Ivanushkina (PSU), 
T. Kennedy, P. Smith, B. Hancock (MSSL), S. Koch (PSU), M. Carter, H. 
Huckle (MSSL),  P. Broos, J. Racusin (PSU), E. Fenimore (LANL),
B. Zhang (UNLV), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the 
Swift UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of
GRB050219b on February 19, 2005, at 12:57:51 UT, 52 minutes after the
initial Swift BAT trigger (Cummings et al, GCN 3044
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 ). The delay in
observations was due to the Earth-limb constraint, which prevented an
immediate slew.  We detect no source at the Swift XRT position (Burrows et
al, GCN 3043
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 ).  The limiting magnitudes (3-sigma) in each of the UVOT
filters are as follows:

A re-examination of the UVOT data at the new XRT position (Racusin et al, 
GCN 3049
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 ) revealed no new source detection down to the following 3-sigma 
limiting magnitudes

Filter	Lim_Mag  Duration   T_start
   UVW2	~ 22.16	  1154	     T+3120
   UVM2	~ 22.24   1435	     T+3243
   UVW1	~ 22.23   940	     T+3349
   U	~ 20.74   100	     T+3455
   B	~ 20.9    100	     T+3561
   V	~ 19.41   100	     T+3136

Several exposures were taken in the UV filters, and these were co-added in 
order to derive the limiting magnitudes. This is the cause of the apparent 
overlap between the duration of these exposure and the start time of the 
exposures in the optical filters.

We caution that the instrument is not yet fully calibrated and that the
magnitude limits presented here may need to be refined.

J. L. Racusin (PSU), C. Pagani, S. Campana (INAF-OAB), V. La Parola
(INAF-IASF/Palermo), D. C. Morris, D. N. Burrows, J. A. Nousek (PSU), O.
Godet, A. F. Abbey (U. Leicester),  F. Tamburelli (ASDC), K. Hurley 
(UC-Berkeley),
B. Zhang (U. Nevada), D. Hinshaw, L. Angelini, N. White, N. Gehrels (GSFC),
report on behalf of the Swift XRT team:

We have found an error in the processing that produced the refined Swift 
XRT position reported in GCN 3045
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 .  We have now corrected that error and 
have a new, corrected position for the X-ray afterglow of GRB 050219b:

CORRECTED COORDINATES:

RA(J2000) = 05:25:16.31
Dec(J2000) = -57:45:27.31

The estimated uncertainty in this position is 6.3 arcseconds.

Please refer to this GCN instead of GCN 3045
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 .

E. Berger, D. Kelson (Carnegie Observatories) and S. Gonzalez (Las
Campanas Observatory) report:

"We imaged a field centered on the XRT error circle (GCN 3045
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 ) of GRB
050219b (GCN 3044
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 ) with the Las Campanas Observatory's du Pont 2.5-m
telescope in the Ks-band and the Swope 40-in telescope in the R-band
(2005, Feb 20.095, 5.2 hours after the burst).  We do not detect any
bright sources within the 6.3 arcsec radius XRT error circle in either
band.  However, a faint source close to the detection limit of the Ks-band
image is located at (J2000):
        RA  = 05:25:15.21
        DEC = -57:45:10.4
about 1.3" from the nominal XRT position."

M. Ivanushkina (PSU), T. Poole (MSSL), C. Gronwall (PSU), A. Blustin 
(MSSL), P. Brown (PSU), S. Rosen, K. McGowan, M. De Pasquale (MSSL), P. 
Boyd (GSFC/UMBC), S. Holland, M. Still (GSFC/USRA), W. Landsman (GSFC), S. 
Hunsberger (PSU), A. Breeveld (MSSL), P. Roming (PSU), K. Mason, P. Schady 
(MSSL) P. Broos (PSU), T. Kennedy, P. Smith, B. Hancock (MSSL), S. Koch 
(PSU), M. Carter, H. Huckle (MSSL),  J. Racusin (PSU), E. Fenimore (LANL), 
B. Zhang (UNLV), J. Nousek (PSU), N. Gehrels (GSFC), on behalf of the 
Swift UVOT team.

The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of
GRB050219b on February 19, 2005, at 12:57:51 UT, 52 minutes after the
initial Swift BAT trigger (Cummings et al, GCN 3044
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 ). The delay in 
observations was due to the Earth-limb constraint, which prevented an 
immediate slew.  We detect no source at the Swift XRT position (Burrows et 
al, GCN 3043
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 ).  The limiting magnitudes (3-sigma) in each of the UVOT 
filters are as follows:

Filter	Lim_Mag  Duration   T_start
  UVW2	~ 22.04	  1154	     T+3120
  UVM2	~ 20.95   100	     T+3243
  UVW1	~ 20.65   100	     T+3349
  U	~ 20.92   100	     T+3455
  B	~ 20.85   100	     T+3561
  V	~ 19.38   100	     T+3136

The limiting magnitude for the UVW2 filter was calculated from a summation 
of four separate exposures taken at different times between observations 
made in other filters. This is the cause of the overlap between the 
duration of the UVW2 exposure and the start of some of the other 
exposures.

We caution that the instrument is not yet fully calibrated and that the
magnitude limits presented here may need to be refined.

J. L. Racusin (PSU), C. Pagani, S. Campana (INAF-OAB), V. La Parola 
(INAF-IASF/Palermo), D. C. Morris, D. N. Burrows, J. A. Nousek (PSU), O. 
Godet, A. F. Abbey (U. Leicester),  F. Tamburelli (ASDC), K. Hurley 
(UC-Berkeley),
B. Zhang (U. Nevada), D. Hinshaw, L. Angelini, N. White, N. Gehrels (GSFC),
report on behalf of the Swift XRT team:

Ground processing of Photon Counting mode data from 3 epochs (roughly 3600 
- 10,000 s post-burst) gives the following refined Swift XRT afterglow 
position for GRB 050219b:

RA(J2000) = 05:25:15.3
Dec(J2000) = -57:45:09.2

The estimated uncertainty in this position is 6.3 arcseconds.

J. Cummings, S. Barthelmy, L. Barbier, J. Cannizzo (GSFC), M. Chester (PSU),
E. Fenimore, M. Galassi (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC), G. Sato (ISAS), M. Suzuki (Saitama),
T. Takahashi (ISAS), J. Tueller (GSFC), B. Zhang (UNLV)
on behalf of the Swift-BAT team:

At 21:05:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on-board GRB050219b.  Because of the Earth-limb constraint,
the spacecraft could not immediately slew to the burst location.
The location became unconstrained at T+50 min, and the spacecraft slewed.
The XRT and UVOT instruments then began their standard set of pre-programmed
observing sequences.

Using the time interval of the burst, the ground-calculated location
is RA,Dec 81.287,-57.770 (J2000) with an uncertainty of 4 arcmin
(radius, including a systematic uncertainty, 90% containment).
The burst was 54 degrees off the BAT boresight (10% encoding).

The burst lightcurve has five overlapping peaks preceeded by a slow rise,
with a T90 duration of ~27 sec (and T50 is 6.8 sec).  The peak flux
is 26 ph/cm2/sec for a 1-sec interval (15-350 keV).  Using a simple power law
model, the fluence is ~2.3 (+/-30%) e-5 erg/cm^2 (15-350 keV).

D. N. Burrows, J. E. Hill, J. A. Kennea, J. L. Racusin (PSU), C. 
Pagani,  A. Moretti (INAF-OAB), O. Godet, A. F. Abbey (U. Leicester), V. La 
Parola (INAF-IASF/Palermo), F. Tamburelli (ASDC), K. Hurley (UC-Berkeley), 
B. Zhang (U. Nevada), D. Hinshaw, L. Angelini, N. White, N. Gehrels (GSFC), 
report on behalf of the Swift XRT team:

CORRECTION: shortly after submitting this information to the GCN, we 
discovered an error in the XRT position.  The original rectangular error 
box based on WT mode data was correct, but the error circle based on image 
mode data was incorrect.  That position is corrected below.

The Swift BAT instrument detected GRB 050219b at 21:05:51 UT on 19 February 
2005.  The burst was too close to the Earth limb to allow immediate 
observation by the XRT and UVOT.  The observatory executed an automated 
slew to the BAT position at 21:56:25 UT and the XRT began taking data at 
about 21:58 UT.  The XRT was in Auto state and attempted to obtain a GRB 
position, but the source was too faint to obtain a reliable on-board 
centroid.  The ground-processed centroid of this image gives an approximate 
source position of:

CORRECTION:

RA(J2000) = 05:25:15.2
Dec(J2000) = -57:45:25.2

We estimate an uncertainty of 15 arcseconds in this position.

XRT then began observations in Windowed Timing mode, which provides 1-D 
position information.  There appears to be a fairly bright X-ray source at 
a position bounded by the following error box:

RA, Dec (J2000):
Corner #1: 05:25:44.9, -57:55:55.3
Corner #2: 05:25:44.2, -57:55:57.4
Corner #3: 05:24:41.7, -57:33:54.5
Corner #4: 05:24:41.0, -57:33:56.6

Photon-counting mode frames taken in the following orbit are expected to 
produce a more accurate position, and will be reported when they become 
available on the ground.

D. N. Burrows, J. E. Hill, J. A. Kennea, J. L. Racusin (PSU), C. 
Pagani,  A. Moretti (INAF-OAB), O. Godet, A. F. Abbey (U. Leicester), V. La 
Parola (INAF-IASF/Palermo), F. Tamburelli (ASDC), K. Hurley (UC-Berkeley), 
B. Zhang (U. Nevada), D. Hinshaw, L. Angelini, N. White, N. Gehrels (GSFC), 
report on behalf of the Swift XRT team:

The Swift BAT instrument detected GRB 050219b at 21:05:51 UT on 19 February 
2005.  The burst was too close to the Earth limb to allow immediate 
observation by the XRT and UVOT.  The observatory executed an automated 
slew to the BAT position at 21:56:25 UT and the XRT began taking data at 
about 21:58 UT.  The XRT was in Auto state and attempted to obtain a GRB 
position, but the source was too faint to obtain a reliable on-board 
centroid.  The ground-processed centroid of this image gives an approximate 
source position of:

RA(J2000) = 05:24:26.5
Dec(J2000) = -57:47:51.3

We estimate an uncertainty of 15 arcseconds in this position.

XRT then began observations in Windowed Timing mode, which provides 1-D 
position information.  There appears to be a fairly bright X-ray source at 
a position bounded by the following error box:

RA, Dec (J2000):
Corner #1: 05:25:44.9, -57:55:55.3
Corner #2: 05:25:44.2, -57:55:57.4
Corner #3: 05:24:41.7, -57:33:54.5
Corner #4: 05:24:41.0, -57:33:56.6

Photon-counting mode frames taken in the following orbit are expected to 
produce a more accurate position, and will be reported when they become 
available on the ground.