GRB 090404

D. A. Perley (UC Berkeley) reports:

In the third paragraph of the previous circular (GCN 9601
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 ), the 
reference to the extended emission possibly associated with G1 being 
spread over several "arcminutes" should instead read that the emission 
is spread over several arcseconds.

A g-band thumbnail image showing this emission (and the nearby "knot") 
more clearly is posted to: 
http://lyra.berkeley.edu/~dperley/090404/090404_g.png

D. A. Perley, S. B. Cenko, and J. S. Bloom (UC Berkeley) report:

We imaged the field of dark gamma-ray burst GRB 090404 (Ziaeepour et 
al., GCN 9086
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 ) using the Keck I telescope (+LRIS) on the night of 
2009-06-25 (UT) for 1670 seconds in g-band and 1560 seconds in I-band 
under excellent (0.5 arcsecond) seeing and photometric conditions.

The object outside the XRT error circle mentioned by Malesani et al. 
(GCN 9093
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 , GCN 9095
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 ) is clearly detected as an extended source, likely a 
moderate-redshift galaxy (hereafter "G1").  A second, slightly fainter 
extended source ("G2") is also detected 3.5 arcseconds to its northeast, 
and the two sources appear to be connected by faint emission, perhaps a 
tidal bridge.  Both sources are marginally detected in Sloan Digital Sky 
Survey archival images (see also GCN 9096
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 ).

Additional faint, extended emission is detected just west of the 
brighter galaxy G1.  The emission appears to be spread over several 
arcminutes in the g-band image, with an obvious "knot" located 1 
arcsecond northeast of the millimeter afterglow position reported by 
Catro-Tirado et al. (GCN 9100
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 ).  The extended region itself passes 
directly through the millimeter position.  A false-color image of the 
field, with the millimeter and enhanced XRT positions 
(http://www.swift.ac.uk/xrt_positions/00348428/image.php) superimposed, 
is posted to: http://lyra.berkeley.edu/~dperley/090404/090404_gI.png

We hypothesize that the extended emission may be a tidal tail extending 
from G1 as a result of interaction with its northeastern neighbor. 
Alternatively, the extended region may represent a very faint background 
host galaxy.  Aperture photometry at the location of the millimeter 
afterglow gives a magnitude of g = 27.3 +/- 0.2.

We encourage spectroscopy of the two bright galaxies G1 and G2 to 
determine their redshifts.

A. J. Castro-Tirado (IAA-CSIC Granada), M. Bremer and J.-M. Winters
(IRAM Grenoble), J. Gorosabel, S. Guziy, M. Jelínek, P. Kubánek
(IAA-CSIC), A. de Ugarte Postigo (ESO Santiago) and D. Pérez-Ramírez
(Univ. de Jaén), report:

"Following the detection by Swift of GRB 090404 (Ziaeepour et al. GCNC
9086), millimeter observations were conducted on Apr 5.9 UT at the Plateau
de Bure Interferometer. Consistent the Swift/XRT enhanced position
(Beardmore et al. GCNC 9088) we clearly detect a millimeter source with a
108 GHz flux density of 1.1 mJy at coordinates RA(2000) = 15:56:57.52,
Dec(2000) = +35:30:57.5 with (0.3",0.2") 1-sigma error in (RA,DEC).
Pending of confirming its variability we propose this as the likely
millimeter afterglow to GRB 090404. Together with the lack of optical and
near-IR afterglows (Xin et al. GCNC 9090, Yock et al. GCNC 9092, Malesani
et al. GCNC 9095, Afonso et al. GCNC 9096, Jelínek et al. GCNC 9099), this
event strongly resembles the dark burst GRB 051022 (Castro-Tirado et al.
2007, A&A 475, 101). Further millimeter observations are scheduled."

This message can be quoted.

M. Jelínek, A. J. Castro-Tirado (IAA-CSIC Granada) and G. Bergond (CAHA
Almería), on behalf of a larger collaboration, report:

"Following the detection by Swift of GRB 090404 (Ziaeepour et al. GCNC
9086), JHKs observations (900-s each) were conducted on Apr 5.025 UT (8.5
hr after the burst) with the 3.5-m telescope (+ OMEGA2000) at the
German-Spanish Calar Alto Observatory, under excellent conditions (0".9
seeing). At the Swift/XRT enhanced position (Beardmore et al. GCNC 9088)
no nIR source is detected down to a limiting magnitude H = 21.5, in
agreement with the limits reported by Afonso et al (GCNC 9096)."

This message can be quoted.

P. Afonso, T. Kruehler, J. Greiner (MPE Garching) and S. Klose 
(TLS Tautenburg), report on behalf of the GROND team:

GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile), observed the field of GRB 090404 
(H. Ziaeepour et al. 2009, GCN #9086
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 ) simultaneously in the g'r'i'z'JHK bands.
Observations started on April 5, at 06:19 UTC (14.4 h after the burst) and
were carried out at air mass higher than 2.2.

We obtained several short exposures with a total integration time of 80 min
in g'r'i'z' and 72 min in JHK.

We do not detect any new object in the stacked images inside the enhanced XRT 
error circle (Beardmore et al. 2009, GCN #9088
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 ), down  to the following 
limiting magnitudes (all in the AB system):
  
g' > 23.8
r' > 24.3
i' > 23.3
z' > 23.1
J  > 22.3 
H  > 21.6 
K  > 20.3 
  
The upper limits have been obtained using SDSS and 2MASS field stars as 
reference. No correction has been made for the expected extinction 
corresponding to E(B-V) of 0.02 mag.

We further note that the nearby object reported by D. Malesani et al. (2009, 
GCN #9093
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 ) is present in the SDSS catalog, and also detected with GROND at
very similar magnitudes.

D. Malesani (DARK/NBI), P. D'Avanzo (Univ. Bicocca/INAF-Brera), P.
Jakobsson (Univ. Iceland), J.P.U. Fynbo (DARK/NBI), T. Liimets (Tartu Obs.
and NOT), and Z. Banhidi (NOT), report on behalf of a larger
collaboration:

Further to what reported in GCN 9093
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  (Malesani et al.), we observed again
the field of GRB 090404 (Ziaeepour et al., GCN 9086
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 ) with the NOT. The
object just outside the error circle noted in GCN 9093
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  is still well
detected in the R band. Comparison of the two epochs, taken with mean
times Apr 5.043 and Apr 5.214 UT (9.09 and 13.19 hr after the GRB,
respectively), reveals no fading of the object by more than 0.1 mag. This
corresponda to a limit on the decay index alpha < 0.25 (assuming F propto
t^-alpha).

The lack of significant variability and the location of the object outside
the XRT error circle make this object unlikely related to GRB 090404.

We acknowledge the NOT staff for excellent support.

[GCN OPS NOTE(06may09): Per author's request, the institutional
affiliation of Banhidi was changed to NOT.]

S. R. Oates (MSSL-UCL) and H. Ziaeepour report on behalf of the Swift/UVOT 
team:

The Swift/UVOT began observing the field of GRB 090404 96 s after the BAT 
trigger (Ziaeepour et al., GCN Circ. 9086
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 ). No optical afterglow is 
detected in the initial UVOT exposures at the refined position of the 
X-ray afterglow (Beardmore et al., GCN Circ. 9088
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 ).

The 3 sigma upper limits for the finding chart (fc) and summed exposures 
are reported below.

Filter    T_start (s) T_stop  Exposure      Mag/3UL
---------------------------------------------------
white fc     96         246     147         < 20.92
white	     591        1189    206         < 20.82
white        5121       18611   1084        < 21.80

u fc	     310        559     246         < 20.17
u    	     715        1140    39          < 18.60
u            4710       35856 	3049	    < 21.56

v 	     641        1239    78          < 18.58
v            5531       11198 	1150	    < 20.37

b   	     565        1164    58          < 19.35
b            4915       35968 	2078	    < 21.50

uvw1         691        1116    39          < 18.45
uvw1         4504       45467 	3237	    < 21.47

uvm2 	     665        1091    58          < 18.54
uvm2         5736       41754 	2695	    < 21.42

uvw2 	     616        1214    78          < 19.09
uvw2         5326       6965  	393 	    < 20.28

The above magnitudes are not corrected for the Galactic extinction 
corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel et al., 1998, 
ApJS, 500, 525).  The photometry is on the UVOT flight system described in 
Poole et al. (2008, MNRAS, 383,627).

D. Malesani, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (Univ. Iceland), A.J. 
Levan (Univ. Warwick), T. Liimets (Tartu Obs. and NOT), and Z. Banhidi 
(NOT), report on behalf of a larger collaboration:

We observed the field of GRB 090404 (Ziaeepour et al., GCN 9086
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 ) with 
the NOT equipped with StanCam. Observations were carried out in the R 
and I bands, starting on 2009 Apr 5.035 UT (8.89 hr after the GRB). A 
total of 20 min exposure per filter were secured.

We do not detect any object inside the revised XRT error circle 
(Beardmore et al., GCN 9088
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 ), down to limiting magnitudes R > 23.5, I > 
22.3, assuming R = 19.19 and I = 18.84 for the USNO-B1 star 1255-0233978 
at RA = 15:57:00.24, Dec = +35:31:28.0.

We note the presence of a faint object (R = 22.8), possibly extended, 
just outside the XRT circle, at coordinates (J2000):

RA = 15:56:57.72
Dec = +35:30:58.2

This position is 2.4" away from the XRT error circle center, which has 
currently an error radius of 1.4" (from 
http://www.swift.ac.uk/xrt_positions/index.php). We cannot state whether 
this object is related to GRB 090404. Further observations are ongoing.

[GCN OPS NOTE(06may09): Per author's request, the institutional
affiliation of Banhidi was changed to NOT.]

P. Yock (Auckland Univ.), B. Allen (Vintage Lane Obs., Blenheim), , A. de
Ugarte Postigo (ESO Santiago), P. Kub�nek (GACE, Univ. of Valencia), A.
Sota and A. J. Castro-Tirado (IAA-CSIC Granada), on behalf of a larger
collaboration, report:

"Following the detection by Swift of GRB 090404 (Ziaeepour et al. GCNC
9086), the 0.6-m Yock-Allen robotic telescope at the BOOTES-3 astronomical
station in Blenheim (New Zealand) responded automatically, under
non-favourable conditions (very high airmass). The first i'-band images
taken 185s after the trigger time (15:59:35 UT) set a limiting magnitude
of i' = 15 at this time. Follow-up observations at the 1.5-m telescope at
Observatorio de Sierra Nevada in Granada have been obtained starting at
21:46 UT. No optical afterglow in the I-band is detected at the Swift/XRT
enhanced position (Beardmore et al. GCNC 9088) down to the DSS2-infrared
limit.  A more detailed analysis is in progress."

This message can be quoted.

K.L. Page (U. Leicester) & H. Ziaeepour (UCL-MSSL) report on behalf of the 
Swift-XRT team:

We have analysed the first 3 orbits of XRT data obtained for GRB 090404 
(Ziaeepour et al. 2009, GCN Circ. 9086
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 ), comprising 129 s in Windowed 
Timing mode and 5.4 ks in Photon Counting (PC) mode. The UVOT-enhanced 
position was given by Beardmore et al. (GCN Circ. 9088
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 ).

The X-ray afterglow was initially very bright, starting at a count rate of 
~1200 count s^-1. The light-curve can be approximately modelled with a 
doubley broken power-law: alpha1 = 3.2 +/- 0.3 until around 120 s after 
the burst, at which point the decay steepened to a slope of alpha2 = 9.3 
+/- 0.3. After 265 s, the decay is much more gradual, with alpha3 = 0.17 
+/- 0.06.

The data show significant softening until at least 150 s after the 
trigger. A spectrum extracted from the first orbit of PC data can be 
fitted with a power-law of Gamma = 3.0 +/- 0.5 and a total absorbing 
column of 5.1x10^21 cm^-2, which is in excess of the Galactic value of 
2.0x10^20 cm^-2 (Kalberla et al. 2005). The counts to observed 
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum 
is 3.1x10^-11 (1.4x10^-10) erg cm^-2 count^-1.

If the light-curve continues to decay with alpha ~ 0.17, the predicted 
count rate at 24 hours is 0.14 count s^-1, corresponding to an observed 
(unabsorbed) flux of 4.3x10^-12 (2.0x10^-11) erg cm^-2 s^-1. However, we 
note that it is unlikely that the light-curve decay will still be this 
flat at 24 hours.

The results of the XRT-team automatic analysis are available at 
http://www.swift.ac.uk/xrt_products/00348428.

This circular is an official product of the Swift-XRT team.

GRB 090404: Xinglong TNT optical Upper Limit

L.P. Xin, W.K. Zheng, Y.L. Qiu, J.Y. Wei,
j. Wang, J.S. Deng, Y. Urata and J.Y. Hu 
on behalf of EAFON report:

We have observed GRB090404 (Ziaeepour et al., 
GCN 9086
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 ; Beardmore et al., GCN 9088
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 )
with Xinglong TNT telescope from Apr.4,15:58:17 (UT),
107 sec after the burst. After combined 18*20s white
band images, no new source was found in our combined
image. The 3 sigma upper limits calibrated to USNO-B1.0 
R2 magnitude is R=20.37 mag at the mean time of 333 sec 
after the trigger.

This message may be cited.

For more information about Xinglong GRBs Follow-up
observations, please visit the website:
http://www.xinglong-naoc.org/grb/

J. Tueller (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
T. N. Ukwatta (GWU), H. Ziaeepour (UCL-MSSL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090404 (trigger #348428)
(Ziaeepour, et al., GCN Circ. 9086
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 ).  The BAT ground-calculated position is
RA, Dec = 239.233, 35.518 deg, which is 
   RA(J2000)  =  15h 56m 55.8s 
   Dec(J2000) = +35d 31' 03.4" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.
 
The mask-weighted light curve shows at least 7 overlapping peaks starting
at ~T-50 sec and ending at ~T+150 sec.  T90 (15-350 keV) is 84 +- 14 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-35.2 to T+94.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.32 +- 0.08.  The fluence in the 15-150 keV band is 3.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+17.32 sec in the 15-150 keV band
is 1.9 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/348428/BA/

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 989 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 090404, 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 = 239.23986, +35.51615 which is equivalent
to:

RA (J2000): 15h 56m 57.57s
Dec (J2000): +35d 30' 58.1"

with an uncertainty of 1.8 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, arXiv:0812.3662).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

H. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), S. R. Oates (UCL-MSSL),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
B. Sbarufatti (INAF-IASFPA) report on behalf of the Swift Team:

At 15:56:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090404 (trigger=348428).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 239.218, +35.500 which is 
   RA(J2000) = 15h 56m 52s
   Dec(J2000) = +35d 29' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiply-peaked
structure with a duration of about 80 sec and possible activity 
out to T+100 sec.  The peak count rate was ~3500 counts/sec 
(15-350 keV), at ~17 sec after the trigger. 

The XRT began observing the field at 15:57:57.8 UT, 87.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 239.2351, +35.5173 which is equivalent to:
   RA(J2000)  = 15h 56m 56.42s
   Dec(J2000) = +35d 31' 02.2"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 79 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 96 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.02. 

Burst Advocate for this burst is H. Ziaeepour (hz AT mssl.ucl.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)