Gamma-ray Burst 041006

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 06 Oct 04 12:18:50 UT
NOTICE_TYPE:    HETE S/C_Alert
TRIGGER_NUM:    3570,   Seq_Num: 1
GRB_DATE:       13284 TJD;   280 DOY;   04/10/06
GRB_TIME:       44288.63 SOD {12:18:08.63} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE:  1.0 sig/noise  on a 13.280 [sec] timescale
SC_-Z_RA:        13 [deg]
SC_-Z_DEC:        6 [deg]
SC_LONG:        152 [deg East]
WXM_CNTR_RA:     13.708d {+00h 54m 50s} (J2000),
                 13.769d {+00h 55m 05s} (current),
                 13.066d {+00h 52m 16s} (1950)
WXM_CNTR_DEC:    +1.311d {+01d 18' 39"} (J2000),
                 +1.336d {+01d 20' 11"} (current),
                 +1.040d {+01d 02' 23"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     35 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.5 Y= 21.0 [sig/noise]
WXM_LC_SN:      X= 25.5 Y= 25.5 [sig/noise]
SUN_POSTN:      192.50d {+12h 50m 00s}   -5.36d {-05d 21' 37"}
SUN_DIST:       175.78 [deg]
MOON_POSTN:     106.39d {+07h 05m 33s}  +27.65d {+27d 39' 00"}
MOON_DIST:       91.70 [deg]
MOON_ILLUM:     49 [%]
GAL_COORDS:     124.71,-61.55 [deg] galactic lon,lat of the burst
ECL_COORDS:     13.12,-4.20 [deg] ecliptic lon,lat of the burst
COMMENTS:       Possible GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 06 Oct 04 12:18:59 UT
NOTICE_TYPE:    HETE S/C_Update
TRIGGER_NUM:    3570,   Seq_Num: 2
GRB_DATE:       13284 TJD;   280 DOY;   04/10/06
GRB_TIME:       44288.63 SOD {12:18:08.63} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE:  1.2 sig/noise  on a 18.800 [sec] timescale  
SC_-Z_RA:        13 [deg]
SC_-Z_DEC:        6 [deg]
SC_LONG:        152 [deg East] 
WXM_CNTR_RA:     13.708d {+00h 54m 50s} (J2000),
                 13.769d {+00h 55m 05s} (current), 
                 13.066d {+00h 52m 16s} (1950)
WXM_CNTR_DEC:    +1.311d {+01d 18' 39"} (J2000),
                 +1.336d {+01d 20' 11"} (current),
                 +1.040d {+01d 02' 23"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     35 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.5 Y= 21.0 [sig/noise]
WXM_LC_SN:      X= 25.5 Y= 25.5 [sig/noise]
SUN_POSTN:      192.50d {+12h 50m 00s}   -5.36d {-05d 21' 37"}
SUN_DIST:       175.78 [deg]
MOON_POSTN:     106.39d {+07h 05m 33s}  +27.65d {+27d 39' 00"} 
MOON_DIST:       91.70 [deg]
MOON_ILLUM:     49 [%]
GAL_COORDS:     124.71,-61.55 [deg] galactic lon,lat of the burst
ECL_COORDS:     13.12,-4.20 [deg] ecliptic lon,lat of the burst
COMMENTS:       Possible GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 06 Oct 04 12:19:02 UT
NOTICE_TYPE:    HETE S/C_Update
TRIGGER_NUM:    3570,   Seq_Num: 3
GRB_DATE:       13284 TJD;   280 DOY;   04/10/06
GRB_TIME:       44288.63 SOD {12:18:08.63} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE:  1.2 sig/noise  on a 18.800 [sec] timescale  
SC_-Z_RA:        13 [deg]
SC_-Z_DEC:        6 [deg]
SC_LONG:        152 [deg East] 
WXM_CNTR_RA:     13.725d {+00h 54m 54s} (J2000),
                 13.786d {+00h 55m 09s} (current), 
                 13.083d {+00h 52m 20s} (1950)
WXM_CNTR_DEC:    +1.310d {+01d 18' 37"} (J2000),
                 +1.336d {+01d 20' 10"} (current),
                 +1.039d {+01d 02' 22"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     42 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.5 Y= 25.5 [sig/noise]
WXM_LC_SN:      X= 25.5 Y= 25.5 [sig/noise]
SUN_POSTN:      192.50d {+12h 50m 00s}   -5.36d {-05d 21' 37"}
SUN_DIST:       175.78 [deg]
MOON_POSTN:     106.39d {+07h 05m 33s}  +27.65d {+27d 39' 00"} 
MOON_DIST:       91.68 [deg]
MOON_ILLUM:     49 [%]
GAL_COORDS:     124.75,-61.55 [deg] galactic lon,lat of the burst
ECL_COORDS:     13.14,-4.21 [deg] ecliptic lon,lat of the burst
COMMENTS:       Possible GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 06 Oct 04 12:21:42 UT
NOTICE_TYPE:    HETE S/C_Last  
TRIGGER_NUM:    3570,   Seq_Num: 4
GRB_DATE:       13284 TJD;   280 DOY;   04/10/06
GRB_TIME:       44288.63 SOD {12:18:08.63} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE:  1.2 sig/noise  on a 18.800 [sec] timescale  
SC_-Z_RA:        13 [deg]
SC_-Z_DEC:        6 [deg]
SC_LONG:        152 [deg East] 
WXM_CNTR_RA:     13.725d {+00h 54m 54s} (J2000),
                 13.786d {+00h 55m 09s} (current), 
                 13.083d {+00h 52m 20s} (1950)
WXM_CNTR_DEC:    +1.310d {+01d 18' 37"} (J2000),
                 +1.336d {+01d 20' 10"} (current),
                 +1.039d {+01d 02' 22"} (1950)
WXM_MAX_SIZE:   28.00 [arcmin] diameter
WXM_LOC_SN:     42 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.5 Y= 25.5 [sig/noise]
WXM_LC_SN:      X= 25.5 Y= 25.5 [sig/noise]
SUN_POSTN:      192.50d {+12h 50m 00s}   -5.36d {-05d 21' 37"}
SUN_DIST:       175.78 [deg]
MOON_POSTN:     106.39d {+07h 05m 33s}  +27.65d {+27d 39' 00"} 
MOON_DIST:       91.68 [deg]
MOON_ILLUM:     49 [%]
GAL_COORDS:     124.75,-61.55 [deg] galactic lon,lat of the burst
ECL_COORDS:     13.14,-4.21 [deg] ecliptic lon,lat of the burst
COMMENTS:       Possible GRB.
COMMENTS:       WXM error box is circular; not rectangular.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Wed 06 Oct 04 13:24:14 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    3570,   Seq_Num: 5
GRB_DATE:       13284 TJD;   280 DOY;   04/10/06
GRB_TIME:       44288.62 SOD {12:18:08.62} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE:  1.2 sig/noise  on a 18.800 [sec] timescale  
SC_-Z_RA:        13 [deg]
SC_-Z_DEC:        6 [deg]
SC_LONG:        152 [deg East] 
WXM_CNTR_RA:     13.719d {+00h 54m 53s} (J2000),
                 13.780d {+00h 55m 07s} (current), 
                 13.077d {+00h 52m 19s} (1950)
WXM_CNTR_DEC:    +1.201d {+01d 12' 04"} (J2000),
                 +1.227d {+01d 13' 36"} (current),
                 +0.930d {+00d 55' 49"} (1950)
WXM_MAX_SIZE:   10.00 [arcmin] diameter
WXM_LOC_SN:     100 sig/noise (pt src in image)
WXM_IMAGE_SN:   X= 25.5 Y= 25.5 [sig/noise]
WXM_LC_SN:      X= 25.5 Y= 25.5 [sig/noise]
SUN_POSTN:      192.50d {+12h 50m 00s}   -5.36d {-05d 21' 37"}
SUN_DIST:       175.67 [deg]
MOON_POSTN:     106.39d {+07h 05m 33s}  +27.65d {+27d 39' 00"} 
MOON_DIST:       91.74 [deg]
MOON_ILLUM:     49 [%]
GAL_COORDS:     124.74,-61.66 [deg] galactic lon,lat of the burst
ECL_COORDS:     13.09,-4.31 [deg] ecliptic lon,lat of the burst
COMMENTS:       Definite GRB.
COMMENTS:       Possible GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       Burst_Validity flag is true.
COMMENTS:       WXM data refined since S/C_Last Notice.

red DSS finding chart (5 arcmin radius) ps-file
GCN notice #2765
G. da Costa (Mount Stromlo Observatory), N. Noel (IAC) and P.A. Price (IfA, UH) report:
We have observed the error circle of GRB 041006 (HETE #3570) with the Wide Field Imager on the SSO 40-inch telescope. Inspected exposures at this time consist of a single 300 sec integration in V-band at 2004 Oct 6.54 UT. Comparison with the DSS yields an optical afterglow candidate at the coordinates:
00:54:50.17 +01:14:07.0 J2000
Further results will follow.
This message may be cited.
GCN notice #2766
P.A. Price (IfA, UH), G. da Costa (MSO) and N. Noel (IAC) report:
We have produced a finding chart of the optical afterglow candidate reported in GCN #2765, which is available from http://www.ifa.hawaii.edu/~price/grb041006.ps
The offset from the star marked is 46.95" East and 15.02" North.
We estimate that the optical afterglow was 17th magnitude in our image. Observers with spectroscopy resources are encouraged to observe the source.
GCN notice #2767
H. Fukushi(Tokyo Univ.), M. Isogai(Tokyo Univ.), and Y. Urata(RIKEN)
" We have detected the candidate reported by G. da Costa et al. (GCN 2765) in R-band at Kiso observatory. The brightness at about 55 min after the burst is R~17 compared with USNO-A2.0 stars."
This message may be cited.
GCN notice #2768
D.B. Fox (Caltech) reports on behalf of a larger collaboration:
"We have imaged the optical afterglow candidate of Costa, Noel & Price (GCN 2765) with the Robotic P60 on two occasions in the I-band, at mean epochs 12:32:07 UT and 12:41:36 UT. We can confirm that the candidate is stationary, and faded by approximately 0.45 +/- 0.15 mag in I over this interval by comparison to several nearby stars in the field."
GCN notice #2770
M. Galassi, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley, on behalf of the HETE Science Team;
T. Donaghy, E. Fenimore, C. Graziani, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa, Y. Urata, T. Yamazaki, Y. Yamamoto, and A. Yoshida, on behalf of the HETE WXM Team;
N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE FREGATE Team;
report:
The HETE Fregate and WXM instruments detected GRB 041006 (=H3570) at 12:18:08 UT (44288 SOD) on 06 October 2004. The WXM flight software localized the burst in real time, resulting in a GCN Notice 42 seconds after the burst trigger. The flight error region was a circle of 14 arcminutes radius (90% confidence) centered at
RA = 00h 54m 54s, DEC = +01d 18' 37" (J2000).
Ground analyses of the burst data allow the error region to be refined to a circle of 5.0 arcminutes radius (90% confidence) centered at
RA = 00h 54m 53s, DEC = +01d 12' 04" (J2000).
Preliminary spectral analyses show the 2-30 keV fluence of GRB 041006 to be 5e-6 erg/cm2 and the 30-400 keV fluence to be 7e-6 erg/cm2: the classification for GRB 041006 is, therefore, "X-ray rich GRB".
GRB 041006 is very similar to GRB 030329 in its lightcurve shape and spectral characteristics, although it is 20x fainter than GRB 030329. GRB 041006 shows a soft precursor before the main gamma-ray pulse. The empirical redshift indicator for this burst is 0.4; for GRB 030329, it was 0.2.
This message may be cited.
GCN notice #2771
P.A. Price (IfA, UH), G. da Costa (MSO) and N. Noel (IAC) report:
Preliminary analysis of six V-band frames from the SSO 40-inch from Oct 6.54 UT (t_GRB + 35 min) to 6.59 UT (t_GRB + 120 min) reveal that the afterglow has a temporal decay index of alpha ~ 0.7 over these observations, with an estimated magnitude of R ~ 18.5 mag at Oct 6.59 UT.
Assuming this decay holds, this predicts the GRB should be roughly R ~ 20 mag at local midnight, US Eastern daylight savings time (UTC-4h).
The afterglow is also detected in the B band.
This message may be cited.
GCN notice #2772
S.Maeno,E.sonoda,Y.Matsuo,M.Yamauchi (University of Miyazaki)
"We have observed the field covering the error box of GRB041006(HETE trigger 3570 trigger time 12:18:08UT) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki.
The observation was started at 12:21:59 UT on Aug.6. Observed field of view is 43 arcmin centered on R.A.=00h 55m 35.23s Dec=+01d 13' 33.4".
The preliminary magnitude of new source is about 16.8mag. compared with the USNO-A2.0 catalog.
The new source locates in the same position reported by G.da Costa et al. (GCN2765)"
GCN notice #2773
V. Lipunov, A.Krylov, V.Kornilov, G.Borisov, D.Kuvshinov, A.Belinski, M.Kuznetsov, S.Potanin, G.Antipov, E.Gorbovskoy, N.Tyurina Sternberg Astronomical Institute, Alexandr Krylov Observatory, Moscow
At 4h 30m after HETE GRB trigger time (alert 3570) MASTER robotic telescope ( http://observ.pereplet.ru) had imaging the corresponding area of the sky under the large zenit distance and bad weather conditions. The first image was started at 16h53m UT.
We have 50 unfiltered images of the error box (45s exposition, 40 x 50 arcmin, 200 mm camera).
There is no optical transient up to 18.4 m at position da Costa et al. (GCN2765).
Sum FITS image are available at
http://observ.pereplet.ru/images/GRB041006/
This message may be cited.
PS. Our wide-field camera (355mm) with AP16e CCD-camera are upgrading. So last 5 circulars ( GCN >=2659) based on observations on small telescope.
GCN notice #2774
V. Barnard, G. Schieven, R. Tilanus, J. Cox (all Joint Astronomy Centre), J-F. Lestrade (Observatoire de Paris) report on behalf of the JCMT afterglow collaboration:
We observed the afterglow position of GRB 041006 reported in GCN 2765 with SCUBA on the James Clerk Maxwell Telescope on Mauna Kea, beginning at 14:29:50 UT on 06/10/04. In reasonable weather we obtained a flux density at 850 microns of (2.93 +- 5.76) mJy. We were unable to observe further as the source set.
Further observations are planned for 07/10/04 UT.
GCN notice #2775
B. Kahharov, I. Asfandiyarov, M. Ibrahimov, D. Sharapov (UBAI), A.Pozanenko (IKI), V.Rumyantsev (CrAO), G.Beskin (SAO) report:
We have observed the filed of error box of GRB041006 (HETE #3570, M. Galassi, et al. GCN 2770) starting Oct.6 15:49 (UT) with 1.5m telescope of Mt.Maidanak High-altitude Observatory. Several BVRI images were taken between 15:49 and 16:51. We confirm a fading source found by G. Da Costa et al. (GCN 2765). Preliminary reduction of the data against the USNO-A2.0 catalog yield the following OT magnitudes in R
```
UT      exposure mag   err
15:49   180 s    18.7 (0.09)
16:46   300 s    19.1 (0.10)
```
The magnitudes assume a temporal decay index about 1.5 which is stepper than found by P.A. Price, et al. (GCN 2771) and may indicate a brake of a light curve of the OT.
This message may be cited.
GCN notice #2776
Yost, S. A., Smith, D. A., Rykoff, E. S., and Swan, H. report on behalf of the ROTSE collaboration:
Although ROTSE-IIIa (Siding Spring Observatory, Australia) was temporarily off-line when the initial alert for GRB 041006 (HETE-2 3570, GCN Circ. #2770) was distributed, ROTSE collaboration members reactivated the system and manually initiated a standard ROTSE response sequence (10 5-s images, 10 20-s images, and then a large number of 60-s images) 16 minutes after the time of the burst. The field was observed from Oct 6.52387 to 6.57424 (UTC). The observing plan was complicated by the receipt of a HETE-2 ground alert at Oct 6.558, which reset the sequence. ROTSE-III images are unfiltered and calibrated against the USNO A2.0 catalog in R-band.
The optical counterpart discovered by Da Costa, Noel, and Price (GCN Circ. #2765) is clearly visible. A preliminary analysis gives a magnitude of 17.1+-0.4 in the first ROTSE-IIIa image. The magnitude of the source clearly decays over the interval of the ROTSE-IIIa observations, and we cannot detect it during the short-exposure images taken after the receipt of the HETE-2 ground alert. We last detect the source at a (preliminary) magnitude of 18.1+-0.4 in a 60-s image taken beginning Oct 6.57263 (UTC). Three subsequent 60-s exposures show no evidence for the source to upper limits around 18.1. The decay is consistent with the same power-law reported by Price, Da Costa, and Noel (GCN Circ. #2771).
This message may be cited.
GCN notice #2777
P. Ferrero (IASF/CNR, Bologna; Osservatorio e Universita' di Teramo), C. Bartolini, G. Greco, A. Guarnieri, A. Piccioni (Universita' di Bologna), E. Mazzotti Epifani (INAF, Oss. di Capodimonte - Napoli), R. Gualandi (INAF, Bologna Observatory) and G. Pizzichini (IASF/CNR, Bologna) report:
we observed the OT of GRB 041006 (=HETE3570) reported by Da Costa, Noel and Price (GCN 2765). By comparison with USNOA.2 star U0900_00213019, at R.A.= 00h 54m 43.41s DEC.= +01d 15' 45.73", R mag=19.3 and USNOB.1 star 0912-0009780, at R.A.= 00h 54m 43.38s DEC.= +01d 15' 45.38", I mag= 18.57 , we obtain:
```
mean UT             filter                 exposure            mag
Oct. 6.8393           Rc                      900s             19.7
Oct. 6.8506           Rc                      900s             19.7
Oct. 6.8637           Rc                      900s             19.8
Oct. 6.8751           Ic                      900s             19.35
Oct. 6.9627           Rc                     4x900s            19.95
```
Magnitude errors are dominated by those on the magnitude of the comparison star, probably ~ 0.3 mag in both filter (Monet et al. 2003, ApJ 125, 984). The seeing was ~ 3".
Our images shall be available as soon as possible on a public directory from where it will be possible to retrieve by sftp using the hostname: ermione.bo.astro.it, username: publicGRB, password: GRB_bo and directory: GRB041006.
This message may be cited.
GCN notice #2778
E. Hoversten, K. Chiu, E. Nissen, C. Kelleman, K. Glazebrook (Johns Hopkins University, Baltimore, Maryland, USA)
We have observed a 7x11 arcminute field centered on the afterglow of GRB041006 (GCN 2770) with the Morris Offit 20in Telescope of the Maryland Space Grant Consortium. The telescope is located in downtown Baltimore, Maryland and the observations were made with a student built CCD camera on the night of 7 October 2004. Images were obtained in I band at midpoint time 7 October 2004 UT 05:10:22, with a total exposure of 7200 seconds.
We do not detect an optical counterpart, and place an preliminary upper limit on its magnitude at I=19.1 based on the faintest objects detectable in the field. Aperture photometry was made with APPHOT in a 9 arcsecond aperture, with relative photometry assuming I=16.1 (USNO-A2.0 red magnitude 16.2) for the reference star at 00:54:38.09 +01:12:59.9.
Our image of the field may be viewed at http://www.pha.jhu.edu/~chiu/JHUgrb.ps
More detailed analysis of data will follow. This message may be cited.
The Maryland Space Grant Consortium Observatory is supported by NASA's National Space Grant College and Fellowship Program. Further information is available at http://henry.pha.jhu.edu/msgc/observatory.html
GCN notice #2779
K. Ayani (Bisei Astronomical Observatory (BAO)) and H. Yamaoka (Kyushu Univ.) report:
We obtained R-band images of the optical afterglow (da Costa, Noel and Price, GCN 2765) of GRB 041006 (Galassi et al., GCN 2770) with the BAO 1.01-m reflector. The observation started on 16:44 UT. The stacked image (mean epoch = Oct. 6.71 UT) shows the OT of which a preliminary R magnitude is about 19.2, compared with the USNO A2.0 red magnitudes.
This message may be cited.
GCN notice #2780
GRB041006 (= H3570): Chandra Observations In Progress
G. Ricker, N. Butler, P. Ford, H. Marshall, R. Vanderspek (MIT); G. Garmire (PSU); and D. Lamb (U. Chicago), on behalf of a Chandra GRB ToO Team,
write:
Chandra grating spectrometer observations of the afterglow counterpart (Da Costa, Noel, and Price; GCN2765) for GRB041006 -- a bright, X-ray rich gamma-ray burst discovered by HETE (= H3570: Galassi et al, GCN 2770) -- are in progress.
The Chandra LETG/ACIS observation commenced at approximately 5:30 UT on 7 October 2004, and will continue for approximately 26 hours. The scheduling of contemporaneous photometry and spectroscopy at other wavelengths is strongly encouraged.
We are grateful to Harvey Tananbaum and the Chandra X-ray Center observatory staff for scheduling this observation to commence only 17 hours after the GRB event.
This message may be cited.
GCN notice #2781
H. Yamaoka (Kyushu Univ.), K. Ayani (Bisei Astronomical Observatory) and K. Itagaki (Teppo-cho, Yamagata) report:
We performed astrometry with the R-band Bisei image (Ayani and Yamaoka, GCN 2779) and an unfiltered-CCD image taken by KI with 0.60-m reflector on Oct. 6.65 UT. The reference frame is the 2MASS catalog (7 stars) and the UCAC2 catalog (44 stars), respectingly. Fitting error for each coordinate is better than 0".1. The mean of the results is: R.A. = 0h54m50s.23, Decl. = +01:14:04.9 (J2000.0), which is slightly (about 2") different from the value by da Costa, Noel and Price (GCN 2765).
This message may be cited.
GCN notice #2782
D. Fugazza, F. Fiore, S. Covino, L.A. Antonelli, P. D'Avanzo, F. Cocchia, D. Malesani, E. Pian, L. Stella (on behalf of the Italian CIBO collaboration); V. Lorenzi and G. Tessicini (INAF-TNG), report:
"We observed the optical afterglow (Da Costa, Noel & Price, GCN 2765; Maeno et al. GCN 2772) of the X-ray rich GRB 041006 (Galassi et al., GCN 2770) with the Italian 3.6m telescope TNG at the Canary Islands. Both photometric and spectroscopic observations were carried out using DOLORES under good observing conditions (seeing of ~1").
From two R-band images (2x120 s), we obtain the following magnitude on Oct 7.07 UT (0.557 days after the GRB):
R = 20.76 +- 0.04.
This value is based on a calibration with Landolt standard stars. We list below magnitudes we obtain for the two stars close to the optical transient:
```
star            RA            Dec           R mag    err
- ---------------------------------------------------------
U0900_00213234  00:54:47.045  +01:14:05.60  17.75 +- 0.04
U0900_00213423  00:54:50.131  +01:12:10.33  18.90 +- 0.04
```
Note as the above magnitudes are fainter than those given by USNO, by about 0.4 mag. This may indicate a non photometric night, or that the USNO catalog is not particularly accurate in this region of the sky.
Starting on Oct 7.10 UT, a low resolution (R ~ 1000) spectrum of the transient was also obtained. Observations consisted of three exposures, for a total exposure time of 1 hour, and cover the full spectral range 3800-8000 A. The observed spectrum has a relatively low signal-to-noise and does not show any strong obvious emission line. The most prominent absorption feature is at 4800 A. If this feature is identified with the blend of the MgII lambda2803,2796 doublet, a redshift of z=0.712 is implied. If this is the case, the MgI lambda2852, FeII lambda2382,2374 and FeII lambda2344 transitions might coincide with other absorption features in the spectrum, although each single line is not statistically significant.
At the estimated redshift the isotropic-equivalent gamma-ray energy of the burst is E = 1.5x10^52 erg (2-400 keV), adopting the fluence reported by Galassi et al. (GCN 2770),
We are particularly grateful to the TNG staff for their remarkable support to these observations."
This message is citeable.
GCN notice #2784
Klotz, A., Boer M., G. Stratta, and Atteia J-L. report:
TAROT observed the HETE alert #3570 on 2004 Oct. 06, 19:55 UT (middle time). The telescope took a series of 12 x 100-s unfiltered images of the afterglow reported by G. Da Costa et al. (GCN 2765)
We co-added frames to obtain a single image. Comparing to the USNO-1B catalog and DSS image, we are able to detect all stars brighter than R=19.4 but the afterglow is not visible.
The candidate proposed by Da Costa et al. (GCN 2765) is not detected at the 3 sigma level. We conclude that the afterglow had a magnitude R > 19.4.
This message may be cited
GCN notice #2785
GRB 041006 : optical follow-up observation at Lulin Observatory
D. Kinoshita, Z.Y. Lin K.Y. Huang, Y. Urata, K. Onda, W.H. Ip, T. Tamagawa on behalf of Lulin GRB collaboration report:
" We have observed the optical afterglow reported by Costa et al. (GCN 2765) at 7.65 hr after the burst using Lulin 1-m telescope. The afterglow's magnitude compared with USNOB-1 catalogue are:
```
   Filter  Exopsure    UT        Mag.
      B      300s    19:57:08  20.1 
      R      300s    20:02:54  19.9 
```
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GCN notice #2786
V. Barnard, G. Schieven, R. Tilanus, J. Cox (all Joint Astronomy Centre), R. Plume (University of Calgary), J-F. Lestrade (Observatoire de Paris) report on behalf of the JCMT afterglow collaboration:
Further observations of GRB 041006 with SCUBA at the JCMT were made on 07/10/04 at mean epoch 13:00:00 UT. In good weather conditions, the source was not detected, with an 850 micron result of (1.1 +- 1.7) mJy.
GCN notice #2787
A. M. Soderberg (Caltech) and D. A. Frail (NRAO) report on behalf of a larger collaboration:
"On 2004 Oct. 7.25 UT (t ~ 18 hrs) we carried out follow-up observations with the VLA at 8.46 and 4.96 GHz centered on the optical afterglow (GCN 2765) of GRB 041006 (GCN 2770). Within a circle of 1-arcsec radius, there are no radio sources detected at either frequency. We place 2-sigma upper limits of 82 and 118 microJy at 8.46 and 4.96 GHz, respectively."
GCN notice #2788
P. D'Avanzo, S. Covino, L.A. Antonelli, D. Fugazza, D. Malesani, F. Fiore, F. Cocchia, N. Masetti, E. Pian, L. Stella (on behalf of the Italian CIBO collaboration); V. Lorenzi and R. Barrena (INAF-TNG), report:
We observed again the optical afterglow (Da Costa, Noel & Price, GCN 2765; Maeno et al. GCN 2772) of GRB 041006 (Galassi et al., GCN 2770) with TNG. Photometry was performed in the UBVRI bands under good observing conditions (seeing 1.2").
We measure the following magnitude for the afterglow on Oct 8.10 UT (1.59 days after the GRB):
R = 22.12 +/- 0.08
A comparison with our previous measurement (Fugazza et al., GCN 2782) implies a dimming of 1.36 +- 0.09 mag. The corresponding decay index is alpha = 1.20 +- 0.08 (F = K t^-alpha), significantly steeper than the early-time value (alpha ~ 0.7: Fox, GCN 2768; Price, Da Costa & Noel, GCN 2771; Yost et al., GCN 2776). A break in the light curve must therefore be present, consistent with the suggestion of Kahharov et al. (GCN 2775). The fading is confirmed in the other bands and is achromatic within the errors.
We also observed again Landolt standard stars, finding the same zeropoint than in our previous observation (Fugazza et al., GCN 2782) to within 0.03 mag. We conclude that our calibration is correct and both nights were photometric.
The light curve of this event, including all the published photometry, can be found at the following URL:
http://www.sissa.it/~malesani/GRB/041006
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The data are taken from the available literature (filled circles) and from our measurements (Fugazza et al., GCN 2782; D'Avanzo et al., GCN 2788). Measurements based on USNO stars were dimmed by 0.4 mag, in order to match our zeropoint (determined in two photometric nights; see also Garnavich, Zhao & Pimenova, GCN 2792). Where not provided in the source, errors were arbitrarily fixed to 0.1 mag. To fix a normalization in the I band (Fox, GCN 2768), we assumed a typical afterglow color. For the earliest B and V-band points, the spectral index (α = 0.45) corresponding to the color provided by Da Costa & Noel (GCN 2789) was adopted. ASCII tables with all data are available upon request.
References: Fukushi, Isogai & Urata (GCN 2767); Fox (GCN 2768); Price, Da Costa & Noel (GCN 2771); Maeno et al. (GCN 2772); Lipunov et al. (GCN 2773); Kahharov et al. (GCN 2775); Yost et al. (GCN 2776); Ferrero et al. (GCN 2777); Hoversten et al. (GCN 2778); Ayana & Yamaoka (GCN 2779); Klotz et al (GCN 2784); Kinoshita et al. (GCN 2785); Da Costa & Noel (GCN 2789); Monfardini et al. (GCN 2790); Garnavich, Zhao & Pimenova (GCN 2792); Misrai & Pandey, (GCN 2795).
GCN notice #2789
G. Da Costa (RSAA, ANU) and N. Noel (IAC) report:
We have reduced our observations of the afterglow of GRB 041006 (GCN #2765). From observations of several photometric standards taken the same night, we find that the star at coordinates 00:54:37.96, +01:13:00.7 J2000 (i.e. south west of the offset star in the finder from GCN #2766) has B = 18.28 mag and V = 17.35 mag. From these, we estimate that the afterglow had a B-V colour of approximately 0.28 +/- 0.03 mag around 2004 Oct 6.58 UT.
GCN notice #2790
A. Monfardini (Liverpool), C. Mottram (Liverpool J.M. Uni.), C. Guidorzi (Liverpool), N. Tanvir (U. of Hertfordshire), C. Mundell (Liverpool), I. Steele (Liverpool), R. Priddey (Hertfordshire), M. Hughes (Hertfordshire), R. Smith (Liverpool), A. Gomboc (Liverpool), S. Fraser (Liverpool), M. Bode (Liverpool), A. Newsam (Liverpool) report:
We observed the optical afterglow of GRB 041006 with the 2.0m Liverpool Telescope on La Palma. We obtained BVRI imaging commencing 8.2 hours after the burst. We report preliminary R-band estimates:
```
R = 20.4 +/- 0.1 mag at Oct 6.92 UT  (exposure time = 600s)
R = 20.6 +/- 0.1 mag at Oct 6.98 UT  (exposure time = 600s)
```
These values were derived applying zero points inferred from the Landolt standard stars as cited in Fugazza et al (GCN 2782), which result in measured magnitudes ~0.3 mag fainter than those given in the USNO catalogue.
```
star            RA            Dec           R mag    err
----------------------------------------------------------
U0900_00213234  00:54:47.045  +01:14:05.60  17.75 +- 0.04
U0900_00213423  00:54:50.131  +01:12:10.33  18.90 +- 0.04
```
In summary, we confirm the R-band magnitude measured by Fugazza et al (GCN 2782) at 7.07UT.
GCN notice #2791
P.A. Price (IfA, UH), K. Roth (Gemini), J. Rich, B.P. Schmidt, B.A. Peterson (RSAA, ANU), L. Cowie (IfA, UH), C. Smith and A. Rest (CTIO) report:
We have observed the optical afterglow of GRB 041006 (GCN #2765) with the Gemini North Telescope + GMOS at 2004 Oct 7.36 UT. Observations consisted of 4 integrations of 1800 sec with the R400 grating and a 1 arcsec slit. Inspection of a single frame reveals absorption lines at 6750A and 6810A, which we interpret as corresponding to the Ca II H and K lines at a mean redshift of z = 0.716, in broad agreement with the redshift of z = 0.712 proposed by Fugazza et al. (GCN #2782).
We thank the staff of Gemini North for performing these observations.
GCN notice #2792
P. Garnavich, X. Zhao, T. Pimenova (Notre Dame)
We observed the field of the afterglow of GRB 041006 reported by Noel & Price (GCN 2765) with the 1.8-m Vatican Advanced Technology Telescope (VATT) beginning on Oct. 8.251 (UT) (2.25 days after the burst). Exposures totaling 25 minutes in R and B were obtained in 1" seeing. Standard stars were also observed and color terms applied to two local standards:
```
          RA  (J2000)   Dec                R            B
Star A  00:54:47.044 +01:14:05.61     17.71 (04)    18.24 (04)
Star B  00:54:54.494 +01:15:47.81     16.28 (04)    17.95 (04)
```
showing that the USNO A2.0 red magnitudes are 0.4 mag too bright for this field as noted by Fugazza et al. (GCN 2782) and that the B-mags are way off.
The optical transient is measured to be R=22.31 (05) and B=23.09 (06) mag. The reddening in this direction (Schlegel et al. 1998) is E(B-V)=0.026 mag so the intrinsic color is B-R=0.737 mag. corresponding to a power-law spectral slope of -1.0.
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GCN notice #2794
Kuntal Misra and S. B. Pandey (ARIES NainiTal), on behalf of larger Indian GRB collaboration
We observed several R_c band frames of the GRB 041006 optical afterglow, determined the magnitudes in comparison with the stars A and B as reported in GCN 2792 using 1.04-m telescope of ARIES Nainital India. The OT decayed by ~ 0.5 mag from Oct 6.75 to Oct 6.91 UT.
Preliminary R_c - band magnitudes are:
```
Oct 6.776284   19.81  0.05
Oct 6.830509   20.00  0.05
Oct 6.862395   20.02  0.05
Oct 6.877175   20.18  0.06
```
The temporal flux decay index is ~ -1.0. We did not notice any considerable steepening in the light curve using our data set.
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GCN notice #2795
Kuntal Misra and S. B. Pandey (ARIES NainiTal), on behalf of larger Indian GRB collaboration
We observed several R_c band frames of the GRB 041006 optical afterglow, determined the magnitudes in comparison with the stars A and B as reported in GCN 2792 using 1.04-m telescope of ARIES Nainital India. The OT decayed by ~ 0.5 mag from Oct 6.75 to Oct 6.91 UT.
Preliminary R_c magnitudes are:
```
Oct 6.776284   19.81  0.05
Oct 6.830509   20.00  0.05
Oct 6.862395   20.02  0.05
Oct 6.877175   20.18  0.06
```
The temporal flux decay index is ~ -1.0. We did not notice any considerable steepening in the light curve using our data set.
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GCN notice #2798
V.Rumyantsev (CrAO), V.Biryukov (SAI, MSU), A.Pozanenko (IKI) report:
We have observed the OT found by G. Da Costa, N. Noel and P.A. Price (GCN2765) of GRB041006 (HETE #3570, M. Galassi, et al. GCN2770) with AT-64 telescope of Crimean Astrophysical Observatory. Several 120 s exposure images in R-band were taken between (UT) Oct.6 17:11 - 22:40 under moderate weather conditions and poor seeing. After inspection only 21 images between Oct.6 (UT)18:33-20:27 is used for further reduction. Additional observation on Oct. 7 reveals no OT. The data reduction against seven USNO A2.0 field stars results to following magnitude of the OT and limiting magnitude for October 7
Mean UT, exposure, mag, S/N
```
Oct 6.81 21x120s   19.35R  3.8
Oct 7.85 64x120s   >20.0R  3
```
We do not apply a possible correction to a brightness of the field stars suggested by D. Fugazza et al. (GCN 2782), A. Monfardini et al. (GCN 2790) and P. Garnavich, X. Zhao, T. Pimenova (GCN 2792).
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GCN notice #2799
Scott Shaw (UGA), Autumn Homewood, Dieter H. Hartmann (Clemson)
Report on behalf of the Follow-Up-Network (FUN) GRB collaboration:
We observed a 6x6 arcminute field centered on the optical afterglow (GCN 2765, 2766) of GRB 041006 (=H3570) discovered by HETE (GCN 2770) with the SARA 0.9 m Telescope at KPNO. Observations were carried out under good seeing conditions with the AP7 CCD. We obtained 25 minutes of exposure each in B and R, and 70 minutes in V. Observations started at UT Oct. 7.6216, and ended Oct 7.7065. We do not detect the afterglow in either the B-band or the R-band, but do detect it in V. Our B-band limit is estimated as B > 19.8, based on field star photometry described in GCN 2789. The estimated R-band limit is R > 19.5, based on photometry described in GCN 2782. The detection in the V-band yields a preliminary magnitude, based on photometry described in GCN 2789, of V = 20.9 +/- 0.2 (statistical error).
The SARA home page can be found at http://www.astro.fit.edu/sara/sara.html
This message may be cited, but we caution that the final photometry remains to be carried out with a larger set of calibration stars.
GCN notice #2801
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired BVRcIc all-sky photometry for a 11x11 arcmin field centered on the afterglow coordinates (da Costa et al., GCN 2765; Yamaoka et al., GCN 2781) for the HETE burst GRB041006 (trigget 3570; Galassi et al., GCN 2770) with the USNOFS 1.0-m telescope on one marginally photometric night. Stars brighter than V=13.5 are saturated and should be used with care. We have placed the photometric data on our anonymous ftp site: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb041006.dat The astrometry in this file is based on linear plate solutions with respect to UCAC2. The external errors are less than 100mas. The estimated external photometric error is about 0.03mag and will be improved with additional calibration nights later this week.
In particular, the stars calibrated by Fugazza et al. (GCN 2782) and da Costa and Noel (GCN 2789) are present in the file, with similar magnitudes within error.
As always, you should check the dates on the .dat file prior to final publication to get the latest photometry. There is a README file on the ftp directory to give you information about the procedures used to calibrate these fields.
GCN notice #2802
J. P. U. Fynbo, B. L. Jensen, K. Pedersen, D. Watson, P. Jakobsson,=20 G. Bjornsson, J. M. Castro Cer=F3n, H. Pedersen, J. Hjorth=20 (U. Copenhagen), D. Zucker (MPIA) and T. Pursimo (NOT) report:
"We have observed the field of GRB 041006 (Galassi et al., GCN #2770)=20 at two epochs with the 2.56m Nordic Optical Telescope using the=20 MOSCA instrument (R-band). At the position of the afterglow (Costa et=20 al., GCN #2735), we detect the following:
```
Date (UT 2004) | t_b+  | exptime     | Seeing |  mag.
------------------------------------------------------------
Oct. 06.96       10.8h   300s+3x600s   ~0.8"    R~20.5
Oct. 11.18      112.2h   5x600s        ~1.9"    R~23.6
```
The photometry is relative to the magnitude of a nearby star as measured by Henden (GCN #2801). The source is clearly extended in=20 the 2nd epoch image (although the seeing was poor), so the potential host galaxy is most likely contributing most of the flux.
A section of the 2nd epoch image can be seen at http://www.astro.ku.dk/~brian_j/grb/grb041006
GCN notice #2803
S. Covino, D. Malesani, G. Tagliaferri, P. D'Avanzo, L.A. Antonelli, G. Chincarini, M. Della Valle, F. Fiore, D. Fugazza, L. Stella, on behalf of the MISTICI collaboration, report:
We observed the optical afterglow (Da Costa, Noel & Price, GCN 2765; Maeno et al. GCN 2772) of GRB 041006 (Galassi et al., GCN 2770) with the 8.2m ESO-VLT-UT2 (Kueyen) at Cerro Paranal. Observations were carried out under good observing conditions (seeing 0.9") with the FORS1 instrument.
The afterglow is clearly detected in the B, R and I bands. We report the following magnitude for the object (calculate performing PSF photometry):
R = 23.59 +- 0.06 on 2004 Oct 11.121 UT
The decay seem therefore even steeper than that inferred from the previous TNG observations (Fugazza et al., GCN 2782; D'Avanzo et al., GCN 2788).
In our coadded images, we also detect an extended emission surrounding the afterglow, apparently 2.5" in size (18 kpc at z=0.712; Fugazza et al., GCN 2782; Price et al., GCN 2791). As suggested by Fynbo et al. (GCN 2802), this is likely the host galaxy of GRB 041006. Performing PSF photometry, we estimate that the contribution inside the afterglow PSF area is likely very small. The afterglow is located inside the galaxy, about 1" South West of its nucleus.
A snapshot centered about the GRB position is posted online at the following URL: http://www.sissa.it/~malesani/GRB/041006 together with an updated light curve with all public data.
We acknowledge the excellent support from the observing staff at Paranal.
This message may be cited.
GCN notice #2804
G. Greco, C. Bartolini, A. Guarnieri, A. Piccioni (Universita' di Bologna) P. Ferrero (IASF/CNR, Bologna; Osservatorio e Universita' di Teramo), G. Pizzichini (IASF/CNR, Bologna), E. Mazzotti Epifani (INAF, Oss. di Capodimonte - Napoli) and R. Gualandi (INAF, Bologna Observatory) report:
On October 7, 2004 in clear sky conditions (seeing 2") we obtained two R-band images (1200 sec X 2) of the OT of GRB 041006 (=HETE 3570) reported by Da Costa, Noel and Price (GCN 2765) with the 152 cm telescope in Loiano.We co-added the two exposures and used the following stars in Henden's photometric calibration (GCN 2801):
```
               RA                 Decl.                                   
             13.6373            1.221278
             13.708797          1.202692
             13.783485          1.302545 
```
We find the following magnitude for the OT: R = 22.22 +/- 0.13 at UT 22:40 (mean value).
Our images are available in a public directory from where it is possible to retrieve them by sftp using:
```
hostname: ermione.bo.astro.it
username: publicGRB
password: GRB_bo 
directory: GRB041006
```
GCN notice #2808
GRB041006: Fading X-ray Afterglow Observed with Chandra
N. Butler, R. Vanderspek, H. L. Marshall, P. G. Ford, G. R. Ricker (MIT), D. Q. Lamb (U.Chicago), and G. P. Garmire (PSU)
report:
Beginning at October 7.213 (t[burst] + 16.80 hr) and continuing until October 8.286 (t[burst] + 42.57 hr), Chandra Low Energy Transmission Grating Spectrometer (LETGS) observations were conducted of a field centered on the optical afterglow candidate (Da Costa et al, GCN2765) for GRB041006, which was localized by the HETE WXM instrument (Galassi et al, GCN2770). We have detected a moderately bright, fading X-ray afterglow consistent in position with the optical source. Over the 86.3 ksec of data accumulation (livetime) for the Chandra observations, the mean counting rate was 0.010 counts/s in the dispersed 1st order LETGS spectrum and 0.007 counts/s in the 0ther order. The source we detected faded in brightness according to a power law, with a decay time slope of -1.0 +/- 0.1. We fit the 0th order and 1st order data jointly, requiring 20 or more counts per spectral bin. An absorbed power-law model provides an acceptable fit (chi^2/nu = 66.2/63), with the following best-fit paramters over the 0.5-6 keV range:
dN/dE = A * exp[-nH*s(E)] * E^ (-gamma) ph cm^(-2) s^(-1) keV^(-1) , with:
```
A = (1.0+/-0.2) x 10^(-4) , 
gamma = 1.9+/-0.2 , and
nH = (1.1+/-0.5) x 10^21 cm^(-2). 
```
The measured value of nH exceeds the anticipated Galactic column density (nH = 2.9 x 10^20 cm^(-2)) in the source direction. We measure a mean flux in the 0.5 to 6 keV band over the duration of the Chandra observation of ~3.7 x 10^(-13) ergs cm^(-2) s^(-1).
Our analyses are continuing, and more detailed results will be posted at:
http://space.mit.edu/HETE/Bursts/GRB041006
We thank Harvey Tananbaum and the Chandra X-ray Observatory Operations personnel, particularly Jeremy Drake and Brad Wargelin, for the impressive promptness with which this observation was planned and carried out.
The preliminary results reported here may be cited.
GCN notice #2814
K. Kinugasa, and E. Nishihara (Gunma Astronomical Observatory) report;
The sky position of optical afterglow (Da Costa et al. GCN 2765) of GRB041006 (Galassi et al. GCN 2770) was observed in J-, H-, and Ks-band on the night of 2004 Oct. 6 at GAO, Gunma, Japan, using the 1.5-m telescope and the IR Camera. The observation started at 14:40 UT (142 min after the GRB trigger).
We find no transient brighter than J~16.5, H~16.0, and Ks~14.0 at the position of the optical afterglow (Da Costa et al. GCN2765) compared with 2MASS JHK magnitudes.
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GCN notice #2821
S. Balman (METU), I. Bikmaev (KSU), U. Kiziloglu, A. Baykal (METU), E. Gogus, M.A. Alpar, U. Ertan (Sabanci U.), Z. Aslan, I. Khamitov, K. Uluc (TUG), N. Sakhibullin (KSU), R. Burenin, M. Pavlinsky (IKI), R. Sunyaev (IKI, MPA) report :
We observed the field centered on the optical afterglow (GCN 2765, 2766) of GRB 041006 (=H3570) discovered by HETE (GCN 2770) with the TUG (TUBITAK National Observatory, Turkey) 1.5-m Russian-Turkish Telescope (RTT150).
We obtained 6x180 s R band images on 2004.10.10 (3.53 d after burst) starting at 01:01:48 UT, and 10x180 s R band images on 2004.10.11 (4.51 d after burst) starting at 00:32:34 UT, using the imaging Loral Lick3 CCD.
The seeing was 1.8" on 2004.10.10 and 1.6" on 2004.10.11.
Our 2 sigma upper limits are m_R > 22.64 (Oct 10.05) and m_R > 23.30 (Oct 11.03).
We further obtained 18X600 s R band images on 2004.10.14 between 21:32:32 UT (8.4 d after the burst) and 01:32:18, with RTT150 using the imaging ANDOR CCD. The seeing was 1.3-1.6".
We detected the source at m_R = 23.8+/-0.25 (corresponding to 2 sigma detection). For calibration of the R band images we used the reference stars reported in GCN (2801).
An image of the field and the source location is presented at (cf. GCN 2802, 2803) : http://astroa.physics.metu.edu.tr/grb/grb041006/grb041006_rtt150.jpg
Our results in comparison with the extrapolation of the earlier detections on the R band light curve are shown at : http://astroa.physics.metu.edu.tr/grb/grb041006/grb041006_plot.gif
This message can be cited.
GCN notice #2826
I. Bikmaev, N. Sakhibullin (Kazan State University), M.A. Alpar (Sabanci U.), U. Kiziloglu, S. Balman (METU), Z. Aslan, I. Khamitov (TUG), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
We observed the afterglow of GRB 041006 (G. Da Costa et al., GCN 2765, P.A. Price, GCN 2766), discovered by HETE (M. Galassi et al., GCN 2770), with Russian-Turkish 1.5-m telescope (Bakyrlytepe, TUBITAK National Observatory, Turkey).
We made 48 x 300 sec images in R between Oct. 18, 19:50 UT, and Oct. 19, 00:37 UT (12.4 d after the burst) using the imaging ANDOR CCD. The seeing was 1.3-1.6" and weather was clear.
We detected the source at combined image with m_R = 24.0+/-0.2. For calibration of the R band images we used the reference stars reported in (A. Henden, GCN 2801). Part of 8 x 8 arcmin combined RTT150 image of the field and the source location is presented at:
http://www.tug.tubitak.gov.tr/~irekk/grb/grb041006/GRB041006_Oct18.jpg
Our measurement of R magnitude shows clear deviation on the extrapolation of the early detections on R band light curve and confirms our previous OT detection above the extrapolation (S.Balman et al., GCN 2821).
We, probably, see the supernova re-brightening, or the host galaxy. Supernova bump is more probable since the OT is outside the center of the host galaxy (J.Fynbo et al., GCN 2802, S. Covino et al., GCN 2803) and its brightness is still higher than that of the host.
This message can be cited.
GCN notice #2829
A. Garg, C. Stubbs, P. Challis, K. Z. Stanek (CfA), and P. Garnavich (Notre Dame)
We imaged the field of the GRB 041006 afterglow (Da Costa, Noel, & Price, GCN 2765) with the 6.5m Clay telescope of the Magellan Observatory on Nov. 3.1 (UT). A total exposure of 900s in the R filter was obtained with the MagIC instant imager in 0.6 arcsec seeing. We compared the Magellan image to data taken with the Vatican Advanced Technology Telescope (VATT) less than 2 days after the burst (GCN 2792) and detect a source at the position of the afterglow. Assuming the star 9" west and 4" north of the afterglow has a brightness of R=21.9 mag (based on the VATT calibration), we estimate the source in the Magellan images to be R=24.4 +/- 0.2 mag.
This is approximately 2 mags brighter than the extrapolation of first 4 days of the afterglow light curve. It is also marginally fainter than the brightness estimate of Bikmaev et al. (GCN 2826) on Oct. 18, implying that the source is variable and is not a structure on the host galaxy. We conclude that the light is dominated by a supernova that reached its peak brightness in the past two weeks.
This message can be cited.
GCN notice #2830
G. Williams, X. Fan, A. Diamond-Stanic, M. Bayliss, D. Reichart, S. Shaw, A. Homewood, D. H. Hartmann, and M. Schwartz report on behalf of the MMTO, U. North Carolina, and SARA GRB teams of the FUN GRB collaboration:
We observed the afterglow location (Da Costa et al., GCN 2765) of GRB 041006 (Galassi et al., GCN 2770) in Bg'VRc beginning 14.9 hours after the burst. Using the field calibration of Henden (GCN 2801), we report the following magnitudes:
```
Start      Mean Time  Filter  Exposure     Magnitude     Telescope
Date       Since GRB          Time (sec)   (1)
           (hours)            x Exposures
Oct 7.134  15.127     Rc      300 x 5      >19.3         0.9m SARA
Oct 7.153  15.582     B       300 x 5      >18.2         0.9m SARA
Oct 7.110  16.250     Rc      180 x 36     >19.3         0.6m MO(2)
Oct 7.172  16.426     V       300 x 14     21.2+/-0.6    0.9m SARA
Oct 7.280  18.408     g'      300 x 2      21.75+/-0.08  2.3m Bok


(1) Limiting magnitudes are 2 sigma.


(2) Morehead Observatory
```
Previously reported in GCN 2799, the SARA observations are updated now that the field calibration is available.
A light curve is available at:
http://www.physics.unc.edu/~mbayliss/grbdata/grb041006lc.eps
GCN notice #2832
K. Kinugasa (Gunma Astronomical Observatory) and K. Torii (Osaka U.) report:
Starting at 12:50:19 UT on 2004 October 6 (32 minutes after the burst trigger), the sky area of GRB041006 (Galassi, et al. GCN 2770) was observed with the GETS (0.25-m robotic telescope equipped with unfiltered CCD in the Gunma Astronomical Observatory). The observation continued for 6.5 hours and 30-s exposure frames were obtained.
We stacked 20 original frames into a single frame and find that the optical afterglow (Da Costa, et al. GCN 2765) is detected in the stacked frames. Between 12:57 and 14:55 UT (mean epoch), we obtained 10 independent measurements and the afterglow faded from Rc=17.8 to Rc=18.7 by using a comparison star from Henden's calibration (GCN 2801).
After 15:02 UT, intermittent clouds came to cover the field of view and the afterglow was not detected.
astro-ph/0612623 from 21 Dec 2006
Urata: Very early multi-color observations of the plateau phase of GRB 041006 afterglow
Observations of the optical afterglow of GRB 041006 with the Kiso Observatory 1.05 m Schmidt telescope, the Lulin Observatory 1.0 m telescope and the Xinglong Observatory 0.6 m telescope. Three-bands (B, V and R) of photometric data points were obtained on 2004 October 6, 0.025-0.329 days after the burst. These very early multi band light curves imply the existence of a color dependent plateau phase. The B-band light curve shows a clear plateau at around 0.03 days after the burst. The R band light curve shows the hint of a plateau, or a possible slope change, at around 0.1 days after the burst. The overall behavior of these multi-band light curves may be interpreted in terms of the sum of two separate components, one showing a monotonic decay the other exhibiting a rising and a falling phase, as described by the standard afterglow model.
0802.1649from 12 Feb 2008
Shirasaki: Multiple Component Analysis of Time Resolved Spectra of GRB041006: A Clue to the Nature of Underlying Soft Component of GRBs
Abstract: GRB 041006 was detected by HETE-2 at 12:18:08 UT on 06 October 2004. This GRB displays a soft X-ray emission, a precursor before the onset of the main event, and also a soft X-ray tail after the end of the main peak. The light curves in four different energy bands display different features; At higher energy bands several peaks are seen in the light curve, while at lower energy bands a single broader bump dominates. It is expected that these different features are the result of a mixture of several components each of which has different energetics and variability. To reveal the nature of each component, we analysed the time resolved spectra and they are successfully resolved into several components. We also found that these components can be classified into two distinct classes; One is a component which has an exponential decay of $E_{p}$ with a characteristic timescale shorter than $\sim$ 30 sec, and its spectrum is well represented by a broken power law function, which is frequently observed in many prompt GRB emissions, so it should have an internal-shock origin. Another is a component whose $E_{p}$ is almost unchanged with characteristic timescale longer than $\sim$ 60 sec, and shows a very soft emission and slower variability. The spectrum of the soft component is characterized by either a broken power law or a black body spectrum. This component might originate from a relatively wider and lower velocity jet or a photosphere of the fireball. By assuming that the soft component is a thermal emission, the radiation radius is initially $4.4 \times 10^{6}$ km, which is a typical radius of a blue supergiant, and its expansion velocity is $2.4 \times 10^{5}$ km/s in the source frame.
1002.3849 from 23 Feb 10
M. Arimoto et al.: Spectral Lag Relations in GRB Pulses Detected with HETE-2
T. Tamagawa, Y. Shirasaki, S. Sugita, I. Takahashi, J.-L. Atteia, A. Pelangeon, R. Vanderspek, C. Graziani, G. Prigozhin, J. Villasenor, J. G. Jernigan, G. B. Crew, T. Sakamoto, G. R. Ricker, S. E. Woosley, N. Butler, A. Levine, J. P. Doty, T. Q. Donaghy, D. Q. Lamb, E. Fenimore, M. Galassi, M. Boer, J.-P. Dezalay, J.-F. Olive, J. Braga, R. Manchanda, G. Pizzichini Using a pulse-fit method, we investigate the spectral lags between the traditional gamma-ray band (50-400 keV) and the X-ray band (6-25 keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB 030528, GRB 040924, GRB 041006, GRB 050408) detected with the WXM and FREGATE instruments aboard the HETE-2 satellite. We find several relations for the individual GRB pulses between the spectral lag and other observables, such as the luminosity, pulse duration, and peak energy (Epeak). The obtained results are consistent with those for BATSE, indicating that the BATSE correlations are still valid at lower energies (6-25 keV). Furthermore, we find that the photon energy dependence for the spectral lags can reconcile the simple curvature effect model. We discuss the implication of these results from various points of view.

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Jochen Greiner, last update: 23-Feb-2010 [Disclaimer]