Gamma-ray Burst 020124

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Thu 24 Jan 02 10:41:26 UT
NOTICE_TYPE:    HETE S/C_Alert
TRIGGER_NUM:    1896,   Seq_Num: 1
GRB_DATE:       12298 TJD;    24 DOY;   02/01/24
GRB_TIME:       38475.15 SOD {10:41:15.15} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     187  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       125 [deg]
SC_-Z_DEC:       16 [deg]
SUN_POSTN:      306.60d {+20h 26m 25s}  -19.19d {-19d 11' 24"}
MOON_POSTN:      63.98d {+04h 15m 54s}  +19.43d {+19d 26' 01"}
MOON_ILLUM:     76 [%]
COMMENTS:       Probable GRB.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Thu 24 Jan 02 12:06:53 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    1896,   Seq_Num: 3
GRB_DATE:       12298 TJD;    24 DOY;   02/01/24
GRB_TIME:       38475.14 SOD {10:41:15.14} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     187  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       125 [deg]
SC_-Z_DEC:       16 [deg]
WXM_CNTR_RA:   143.283d {+09h 33m 08s} (J2000),
               143.308d {+09h 33m 14s} (current),
               142.677d {+09h 30m 42s} (1950)
WXM_CNTR_DEC:  -11.594d {-11d 35' 38"} (J2000),
               -11.603d {-11d 36' 11"} (current),
               -11.372d {-11d 22' 18"} (1950)
WXM_CORNER1:   143.4740 -11.3180 [deg]
WXM_CORNER2:   143.5230 -11.7680 [deg]
WXM_CORNER3:   143.0430 -11.4200 [deg]
WXM_CORNER4:   143.0930 -11.8710 [deg]
WXM_MAX_SIZE:    38.40 [arcmin] diameter
WXM_LOC_SN:      7 sig/noise (pt src in image)
SUN_POSTN:      306.60d {+20h 26m 25s}  -19.19d {-19d 11' 24"}
SUN_DIST:       145.08 [deg]
MOON_POSTN:      63.98d {+04h 15m 54s}  +19.43d {+19d 26' 01"}
MOON_DIST:       84.03 [deg]
MOON_ILLUM:     76 [%]
GAL_COORDS:     245.07,28.27 [deg] galactic lon,lat of the burst
COMMENTS:       Probable GRB.
COMMENTS:       Burst_Validity flag is true.

GCN notice #1219
P.A. Price, B.P. Schmidt and T.S. Axelrod (RSAA, ANU) report:
We have observed the error box of HETE trigger #1896 with the MSO 50-inch telescope and MACHO imager at 2002 Jan 24.53 UT. Our observations consist of 3x300s exposures which cover the entire error box. We estimate the limiting magnitude of the combined R_MACHO image to be approximately R ~ 19 mag, based on USNO-A2.0. From a visual comparison with the Digitised Sky Survey, we do not identify any obvious transient source within the large error box. Alard-subtraction of another 3x300s combined image taken 45 minutes later does not reveal any variable objects on visual inspection of the residual image.
This message may be cited.

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/HETE BURST POSITION NOTICE
NOTICE_DATE:    Thu 24 Jan 02 21:25:48 UT
NOTICE_TYPE:    HETE Ground Analysis
TRIGGER_NUM:    1896,   Seq_Num: 4
GRB_DATE:       12298 TJD;    24 DOY;   02/01/24
GRB_TIME:       38475.13 SOD {10:41:15.13} UT
TRIGGER_SOURCE: Trigger on the 25-400 keV band.
GAMMA_RATE:     187  [cnts/s]  on a 1.300 [sec] timescale
SC_-Z_RA:       125 [deg]
SC_-Z_DEC:       16 [deg]
WXM_CNTR_RA:   143.206d {+09h 32m 49s} (J2000),
               143.231d {+09h 32m 55s} (current),
               142.599d {+09h 30m 24s} (1950)
WXM_CNTR_DEC:  -11.460d {-11d 27' 35"} (J2000),
               -11.469d {-11d 28' 08"} (current),
               -11.238d {-11d 14' 16"} (1950)
WXM_MAX_SIZE:    24.00 [arcmin] diameter
WXM_LOC_SN:      9 sig/noise (pt src in image)
SUN_POSTN:      306.60d {+20h 26m 25s}  -19.19d {-19d 11' 24"}
SUN_DIST:       145.24 [deg]
MOON_POSTN:      63.98d {+04h 15m 54s}  +19.43d {+19d 26' 01"}
MOON_DIST:       83.91 [deg]
MOON_ILLUM:     76 [%]
GAL_COORDS:     244.90,28.30 [deg] galactic lon,lat of the burst
COMMENTS:       Definite GRB.
COMMENTS:       WXM error box is circular; not rectangular.
COMMENTS:       Burst_Validity flag is true.
COMMENTS:       WXM data refined since S/C_Last Notice.

GCN notice #1220
GRB020124(=H1896): Localization of a Long GRB by HETE
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
G. Crew, R. Vanderspek, J. Doty, G. Monnelly, J. Villasenor, N. Butler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
M. Matsuoka, Y. Shirasaki, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, T. Donaghy, and C. Graziani, on behalf of the HETE WXM Team;
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE FREGATE Team;
write:
At 10:41:15.15 UTC (38475.15 s UT) on 24 January, the HETE FREGATE and WXM instruments detected and localized a long GRB. The burst, H1896, was promptly reported as a GCN Alert Notice within 11 seconds of the detection time, but no flight localization was derived. In a followup GCN Notice issued 1.4 hours after the GRB, the results of an initial ground analysis localization were reported as an error box with dimensions of 26 arcmin x 27 arcmin.
Further ground analysis of the WXM data has produced a significantly improved location which can be expressed as a circle with a 90% confidence radius of 12 arc minutes centered at:
```
          RA = +09h 32m 49s, Dec = -11d 27' 35" (J2000)
```
The revised error circle reported here is displaced by 9.2 arc minutes from the best-fit location found in the initial HETE ground analysis and reported in a GCN Notice (at 24 Jan 2002 12:06:53 UT).
The burst duration in the FREGATE 8-85 keV band was ~70 s. A total of 12,870 counts were detected during that interval, corresponding to a fluence of ~3 x 10-6 ergs cm-2 . The peak flux over 0.164s was >1 x 10-7 ergs cm-2 s-1 (i.e., >3 x Crab flux). The statistical significance was 9 sigma in the WXM 2-25 keV band.
This message is quotable.
GCN notice #1221
P.A. Price (RSAA, ANU), D.W. Fox, S.A. Yost (Caltech) with S. Pravdo, E. Helin, K. Lawrence, and M. Hicks of the NEAT/Palomar team report on behalf of a larger collaboration:
We have observed the revised error box of GRB 020124 / HETE #1896 (GCN #1220) with the Palomar 48-inch telescope + unfiltered CCD at 2002 Jan 25.4 UT (t_GRB + 22 hr). PSF-matched image subtraction was performed against images from the MSO 50-inch telescope taken in MACHO R-band (GCN #1219). In order to weed out objects of extreme colour which appear in the subtracted image, we also compared with the Digitised Sky Survey (DSS). We identify one object present in the subtracted image which is not present on the DSS-2 red plate (blue plate is unavailable) at coordinates
```
		RA: 9:32:50.8 Dec: -11:31:11 (J2000)
```
This object was not detected in the Palomar 48-inch images, which have a limiting magnitude fainter than the DSS (R ~ 21 mag). We estimate that the object was R ~ 18.5 mag at the time of our MSO images, based on comparison with USNO-A2.0 star approximately 34" E and 35" S with assumed R = 16.5 mag. Quick-look photometry on the individual MSO images reveal that the source faded by approximately 1 magnitude over the course of an hour.
We have also observed this object with the Palomar 60-inch telescope in R-band (which is approximately equivalent to R_MACHO) subsequent to the 48-inch images and do not detect the object to approximately R ~ 20 mag. We therefore consider that this object may be the afterglow of GRB 020124 and we encourage deep observations to confirm this.
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GCN notice #1223
K. Hurley and T. Cline, on behalf of the Ulysses and HETE GRB teams;
G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;
R. Vanderspek, G. Crew, J. Doty, G. Monnelly, J. Villasenor, N. Butler, T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;
N. Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Donaghy, C. Graziani, and T. Tavenner, on behalf of the HETE WXM Team;
J-L Atteia, M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE FREGATE Team;
report:
Ulysses observed GRB020124 (=H1896, GCN 1220) as a rather weak event. Triangulation using the FREGATE data gives an annulus centered at RA(2000)= 82.122 deg., Decl.(2000)=-66.103 deg., with radius 67.978 +/- 0.205 deg. (3 sigma). This annulus intersects the HETE WXM error circle (GCN 1220) at just two points:
```
  RA(2000)             Dec(2000)
  143.401		-11.407
  143.103		-11.286
```
The combined annulus/error circle has an area approximately 10% smaller than the error circle alone, or approximately 400 square arcminutes.
The optical transient reported by Price et al. (GCN 1221) lies within the region common to the Ulysses/FREGATE annulus and the WXM error circle, about 0.03 degrees from the center line of the annulus, increasing the likelihood that this object is indeed the GRB counterpart. A map may be found at ssl.berkeley.edu/ipn3/020124.
GCN notice #1224
J. Gorosabel (DSRI, Copenhagen), J. Hjorth (U. Copenhagen), T. Pursimo, A. A. Kaas (NOT), J. Fynbo, P. Moller (ESO), B. L. Jensen, H. Pedersen (U. Copenhagen), and M. I. Andersen (U. Oulu) report:
6 x 600 sec R-band images of the possible optical afterglow (Price et al., GCN #1221) of GRB 020124 (Ricker et al., GCN #1220) were obtained with StanCam at the 2.5-m Nordic Optical Telescope between Jan 26.035 and Jan 26.076 2002 UT. A faint object located at RA(J2000) = 09:32:50.83, Dec(J2000)= -11:31:11.0 (+- 0.74", based on USNO-A2.0) is consistent with the position reported by Price et al. Based on the same reference star as that used by Price et al. we find a preliminary magnitude of R = 23.84 +/- 0.17 for the object. A finding chart is posted at http://www.dsri.dk/~jgu/grb020124/grb020124.stancam.R.6x100.ave.ww.gif
GCN notice #1225
J. S. Bloom, on behalf of the larger Caltech-NRAO-GRB collaboration, reports:
"Using the JCAM optical imaging instrument mounted at the Palomar 200" telescope, we observed the field of GRB 020124 (Ricker et al., GCN #1220; Hurley et al., GCN #1223) on Jan 26.33 UT centered on the position of the optical transient (Price et al., GCN #1221). In non-photometric conditions (moderate to thick cirrus) we detect a faint source in the Sloan r' filter (24 x 200 sec total exposure) which is coincident with the transient position. This is in agreement with the imaging results reported earlier from Gorosabel et al. (GCN #1224). The coincident source is not detected in Bessel I-band (8 x 140 sec total exposure).
An image of the field is posted at: http://www.astro.caltech.edu/~jsb/grb020124-jcam.gif
We wish to thank A. Barth, W. W. Sargent, R. Burruss, and J. Mueller for assistance with these (remote) observations."
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GCN notice #1226
E.Pavlenko and V.Rumyantsev (on behalf of Crimean Observatory and Space Research Institute (Moscow) GRB follow-up teams) report:
"We have imaged of the error box for GRB 020124 / HETE #1896(GCN #1220) with the 0.60-m Zeiss telescope of Crimean Laboratory of SAI (field 5x7 arcminutes).
We obtained several frames which include the center of error box and partially covered its arrea at 2002 Jan. 24 20h54m46s - 23h32m43s UT.
We have observed the field noted in GCN1221 on 2002 Jan. 24 22h05m02s UT (i.e. GRB time + 11.5h). No new objects are seen within this frame (as well as within the rest frames) when comparing to the DSS-2 (R-band), brighter a limiting R magnitude of 18.5mag.
GCN notice #1227
VLT observations of GRB 020124: The fading optical/near-infrared afterglow
J. Hjorth (U. Copenhagen), J. Gorosabel (DSRI, Copenhagen), and J. Fynbo (ESO) report on behalf of the Gamma-Ray Afterglow Collaboration at ESO (GRACE):
We have obtained optical and near-infrared images of the possible optical afterglow (Price et al., GCN #1221; Gorosabel et al., GCN #1224; Bloom, GCN #1225) of GRB 020124 (Ricker et al., GCN #1220) with ESO's VLT. 30-min Ks-band exposures were obtained with ISAAC/Antu on Jan 26.20 (seeing FWHM = 0.50") and Jan 27.20 (FWHM = 0.44") 2002 UT; a 15-min R-band image (FWHM = 0.66") was obtained with FORS1/Melipal on Jan 27.28 2002 UT. The source identified by Gorosabel et al. in NOT R-band images obtained on Jan 26.06 (cf. GCN #1224) has clearly faded in the FORS1 R-band image. The source is also detected in the ISAAC Ks data and is fading between the two epochs of observation. These findings strongly suggest that the source identified by Price et al. is indeed the optical/NIR afterglow of GRB 020124. A more detailed analysis of the data is in progress. Meanwhile, we have posted images showing the decaying Ks-band source at http://www.astro.ku.dk/~jens/GRB020124_ISAAC_Ks_GRACE.gif
We appreciate the kind and efficient assistance of the ESO staff at Paranal Observatory (Nancy Ageorges, Thomas Szeifert and Riccardo Scarpa) in conducting the reported service mode observations.
GCN notice #1228
S.Bondar' (Kosmoten), A.Pozanenko (IKI) and V.Rumyantsev (CrAO) report:
We have observed the entire error box of GRB 020124 / HETE #1896 (GCN #1220) with 600mm automated telescope (TT600) of Kosmoten observatory. 9 images taken at 2002 Jan 24.94 covered the entire error box.
No new objects were found in comparison with DSS-2 in the GRB error box. Based on USNO-A2.0 catalogue we estimate limiting magnitude of the frame covered optical transient (GCN 1221,1224 ) to be R=16.3.
GCN notice #1236
M. Jelinek, P. Kubanek, L. Sveda, R. Hudec, M. Nekola [& BART Team] Astronomical Institute, Academy of Sciences of the Czech Republic, Ondrejov, report:
We have observed the entire error box of GRB020124 (HETE trigger 1896) with the Wide Field Camera (f=109mm, 1:1.7) of the BART robotic telescope. 38 unfiltered optical CCD images with the FOV of 7.2 x 4.8 deg each have been obtained between January 24.91365 and 24.99903 UT (11.5 - 13.5 hours after trigger).
No new objects down to magnitude of 15.0 were found in the GRB error box in comparison with the GSC catalogue.
This is the first time when the BART robotic telescope has sussesfully responded to the HETE GRB trigger without any human intervention. The observation delay was caused by waiting for the night and for good weather conditions.
GCN notice #1251
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired BVRcIc all-sky photometry on two photometric nights with the NOFS 1.0m telescope for an 11x11 arcmin field that is approximately centered on the error box for GRB020124 (=H1896; Ricker et al. GCN 1220; IPN triangulation reported by Hurley et al. GCN 1223). The position of the optical transient reported by Price et al. (GCN 1221) is within this field. Stars brighter than V=13.0 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/grb020124.dat The current photometry has a potential external zero-point error of about two percent. The astrometry in this file is based on linear plate solutions with respect to USNO-A2.0. The internal errors are less than 100mas.
In particular, the comparison star 34"E and 35" S that was used to calibrate the Price et al. field can be found in the .dat file with the following coordinates and magnitudes:
```
  RA = 09:32:53.13  DEC = -11:31:46.0  J2000
  B = 17.467  V = 16.896  Rc = 16.537  Ic = 16.182
```
GCN notice #1343
N. Kawai, Y. Urata (Titech/RIKEN), M. Kohama, K. Torii (RIKEN), A. Yoshida (AGU/RIKEN), K. Ayani, T. Kawabata (Bisei Astronomical Observatory), M. Chaya, H. Shibata, K. Sakamoto, M. Yamauchi (Miyazaki Univ.) on behalf of the RIBOTS/RIMOTS team
We have observed covering the entire error circle of GRB020124 (Ricker et al. GCN 1220) field with the RIBOTS/RIMOTS 30-cm telescopes. The observations started at an early epoch (+1.3 hours after the burst). All the images were taken with 15 sec exposure and stacked for deeper inspection.
From a comparison with the DSS-2 images we did not identify any new point source for the GRB. We summarize the observing time and the R-band limiting magnitude (SN=3), which was estimated by the comparison of our non-filter data with the R band field photometry by Henden (GCN 1251).
```
 Summary of observations on 2002/01/24

  Time(UT)     Limiting R mag
  start end    (SN=3)
  12:00 12:57  17.8          15s x 61 frames combined (RIMOTS)
  16:19 16:59  18.6          15s x 59 frames combined (RIBOTS)
  17:00 17:59  18.8          15s x 87 frames combined (RIBOTS)
  18:00 18:59  19.1          15s x 87 frames combined (RIBOTS)
  19:00 19:59  19.1          15s x 87 frames combined (RIBOTS)
  20:00 20:59  17.7          15s x 87 frames combined (RIBOTS)
```
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GCN notice #1378
K. Torii (RIKEN), T. Kato (Kyoto U.), H. Yamaoka (Kyushu U.), and A. Yoshida (Aoyama Gakuin U., RIKEN) report:
Based on the GCN alert notice, the GRB 020124 (Ricker, et al. GCN 1220) was observed at RIKEN with the 0.25m f/3.4 hyperboloid astro-camera equipped with unfiltered cooled CCD AP7p. The field of view was 50'x50' which covered the HETE's entire error region of 12' radius (GCN 1220). The observation started at 2002/1/24 12:43 UT (122 minutes after the burst) and 126 frames of 20-s exposure were acquired by 13:47 UT. The central time of all the exposures were 2002/1/24 13:15 UT.
PSF photometry was applied to each frame and then stacked to yield 3.0-sigma detection of the optical afterglow at the position reported by Price et al. (GCN 1221). By using 21 nearby comparison stars from the Henden's field photometry (GCN 1251), we derive the afterglow's magnitude as R=18.5 mag. The 1-sigma error range is estimated to be between R=18.2 and R=18.9.
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GCN notice #1389
HST detection of the likely host galaxy of GRB 020124
J. S. Bloom, P. A. Price, D. Fox, S. R. Kulkarni (Caltech), on behalf of the larger HST Collaboration, report:
"As part of our large HST Cycle 10 program (#9180) we triggered a series of STIS/Clear imaging visits on GRB 020124 (Ricker et al., GCN #1220; Hurley et al.; GCN #1223). The imaging, spanning three epochs (epoch 1: 2002 Feb 11.09, epoch2: 2002 Feb 18.30, epoch 3: 2002 Feb 25.71), was centered at the position of the fading optical transient (OT) (Price et al.; GCN #1221). Differential astrometry from our earlier Palomar imaging (Bloom et al., GCN #1225) reveals a faint source, consistent with the position of the OT, near the detection limit of the images. A view of region near the OT, as well as the uncertainty position of the OT relative to the HST image (about 300 mas 1-sigma), may be found at:
http://www.astro.caltech.edu/~jsb/GRB/grb020124/Images/grb020124-host.gif
In that image, two sources ("A", near the center of the OT position and "B" a faint ~2-sigma source near the outskirts of the OT position) are consistent with the OT position. The majority of the mapping error was due to the poor detection of the OT in the JCAM image, therefore, we expect that the astrometry could be significantly improved using better detection imaging of the OT.
Imaging differencing between epochs 1 and 3 does not reveal evidence for fading; we therefore identify source "A" as the likely host of GRB 020124. The difference image may be viewed at:
http://www.astro.caltech.edu/~jsb/GRB/grb020124/Images/grb020124-diff.gif
Summing the epochs (total exposure time 6.8 hrs) we find that the source was V=29.3 +/- 0.3 mag at a weighted mean time of 2002 Feb 17.6; this includes the estimated uncertainty due to the unknown color. If the source is indeed the host, it is one of the faintest known, along with the host of GRB 980326 (V=29.25, Fruchter et al.; GCN #1029) and GRB 000301C (V=29.0 mag, Fruchter et al.; GCN #1063).
The first imaging epoch is now available in the HST archives and we will supply reduced images of all three epochs upon request (jsb@astro.caltech.edu). Additionally, we have made the summed image from JCAM (see GCN #1225) available at the website:
http://www.astro.caltech.edu/~jsb/GRB/grb020124/
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GCN notice #1452
J. S. Bloom, E. Berger, and S. R. Kulkarni (Caltech), on behalf of the larger HST Collaboration, report:
"After thorough analysis of the three epochs of HST STIS/Clear imaging observations of GRB 020124, we now find that the faint source reported in Bloom et al. (GCN #1389) has faded between epoch 1 (11 Feb 2002 UT) and epoch 3 (25 Feb 2002 UT). This source ("S1"), is astrometrically consistent with the rapidly fading optical transient reported from Palomar 200-inch imaging (Bloom, GCN #1225). We therefore conclude that S1 is the afterglow, rather than the host. The source was R=28.6+/-0.2 mag on Feb 11.09 UT, and fainter than R~29.2 mag on Feb 25.71 UT. See the associated figure at:
http://www.astro.caltech.edu/~jsb/GRB/grb020124/grb020124-hst.gif
This figure shows the first epoch (9972 sec) and the combined images from 18 Feb and 25 Feb (14836 sec) with the same flux scaling.
When combined with ground-based data, these observations reveal that the rate of decay of the afterglow has steepened from a value of -1.6 to <-1.9 approximately 15 days after the burst.
Furthermore, we do not detect a persistent source (i.e. a host galaxy) within 1.75 arcsec of the OT position down to R~29.5 mag. Thus, a positionally-coincident host galaxy of GRB 020124 is the faintest host to date."
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Berger et al: ApJ 581 (2002) 981
Redshift z = 3.20
in (Hjorth et al. 2003, ApJ 597, 699)
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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