Gamma-ray Burst 970228: Score !
The BeppoSAX Gamma Ray Burst Monitor (GRBM) was triggered on Feb.
28.12362 UT. The moderate intense Gamma Ray Burst lasted about 80 sec.
While BATSE was behind the Earth, Ulysses and TGRS have also detected this GRB.
Quick follow-up pointings with the NFI on BeppoSAX (8 hours and 3 days
after the GRB) find for the first time a fading X-ray source within the
GRB error box! In addition, also a variable optical counterpart has
Here you find some information on the follow-up observations of the
BeppoSAX GRB 970228.
Previous IAU Circulars
Results of Observations
6572 Discovery with WFC onboard BeppoSAX
6574 Westerbork observations: 0.7 mJy upper limit at 5 GHz; V and I images
show no variable optical object brighter than V=19
6576 bright X-ray source SAX J0501.7+1146 near border of GRB error box
which declined by a factor of 20 within 2.5 days; radio source of 0.8 mJy
at 20 cm at X-ray position
6577 TGRS results; 1.2 mJy upper limit at 86.5 GHz; R=21 mag object
at radio position
6578 OSSE results; Ulysses/BeppoSAX triangulation ring
6580 ROSAT all-sky survey upper limit; R=21 mag object is galaxy
6581 te-1 decay follows prediction of saturated Comptonization model;
R=21 mag galaxy confirmed; spectrum implies z=0.5
6582 no optical variability by >0.2 mag of objects brighter than B=19
and R=20; 30 optical objects down to B = 24.5 or R = 24, several are galaxies;
z=0.498 for galaxy at radio position
6584 optical star-like object at R.A. = 5h01m46s.70, Decl. = +11o46'53".0
was fading from V=21.3 and I=20.6 on Mar. 1.0 to V>23.6 and I>22.2 on Mar. 8.9.
6588 quiescent object at optical transient position has R=24 and is
6593 improved Ulysses/Wind IPN triangulation ring; ASCA detection on Mar. 7
6594 refined Ulysses/SAX triangulation
6598 difference in optical/X-ray luminosity to GRB 970111
6606 HST F606W and F814W detection of the optical counterpart at 25.7+/-0.3
and 24.2+/-0.3 within an embedded extended source
6611 J band detection (J=21.0 mag) and H and K band upper limits
6618 optical detection on Mar 3.1, 1997: no fast fading
6619 J and K band detections (J=23.5+/-0.2, K=22.0+/-0.2) on Mar 30/31;
HST F606W and F814W detection on Apr. 7, 1997: point source has 26.0+/-0.3 and
24.6+/-0.3 in these bands
6620 optical spectra of transient on Mar. 31 - Apr. 2, 1997: no 'obvious'
6629 optical transient shows proper motion of 540 mas/yr corresponding
to a transverse velocity of 260 km/s at 100 pc
6631 detection of point source on Apr. 5/6 at R=24.9+-0.3 (faded by 1 mag),
and fading of extended object below detection limit (not specified)
6635 broadband imaging of Feb. 28.8 and Mar. 4.8 imply fading by
>2.7 mag between these 4 days
6637 ROSAT HRI detection of fading X-ray source 11 days after GRB
yields 10" accurate position; optical transient is within this new
6643 Analysis of HST images reveal no fading of extended emission
6732 no emission lines in Keck II LRIS spectrum of object at optical
transient position; nebulosity seen at R~25.5
6747 V = 28.0 +/- 0.25 for OT and V = 25.7 +/- 0.15 for the nebula from
HST STIS observation on Sep. 4, 1997.
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Jochen Greiner, last update: 10-Dec-2007