September 2, 4, 5, and 6, at the observatory, observations were made of yet another interesting gamma ray burster – GRB 100901A. Notice about it arrived when it was already morning at the observatory, and we were able to begin observing it just over 20 hours after the recording of the burst.The optical afterglow was easily visible on the images, with a brightness of mag. 17.82. This is the brightest of such objects observed at our observatory. Its uniqueness is that GRB 100901A has preserved its brightness at such a high level longer than all the other known gamma ray bursters. In the picture at left, you can see how the brightness of the afterglow faded over the next three days. The last estimate of the brightness was received at the Maidanak Observatory (Volnova et al., GCN 11266). After 6.2977 days, the brightness of the object had faded to mag. 22.05.

As with the previous unusual gamma ray burster GRB 100814A, a sufficiently rare occurrence was recorded – radio afterglow. The EVLA radio telescope (Expanded Very Large Array) recorded an afterglow at frequencies of 4.5 and 7.9 gHz.


NUMBER:  11234

SUBJECT: GRB 100901A: ISON-NM optical observations

DATE:    10/09/06 17:30:05 GMT

FROM:    Leonid Elenin at ISON

L. Elenin, I. Molotov (ISON) and A. Pozanenko (IKI) report on behalf of

larger GRB  follow-up collaboration:

We continue observation of the Swift GRB 100901A (Immler et al. GCN Circ.

11159) with 0.45-m telescope of ISON-NM observatory on Sep. 04 (UT) 09:04:35 –

10:06:19, Sep. 05 (UT) 08:45:52 – 09:50:20 and Sep. 06 (UT) 09:36:57 – 11:14:22.

The afterglow (Immler et al., GCN 11159; Guidorzi et al., GCN 11160; Ivanov

et al., GCN 11161; Klunko et al., GCN 11162) is well detected on stacked images

for three epochs.

Preliminary photometry of unfiltered image against USNO-B1.0 1127-0027229,

assuming R=16.16  is following:

T-T0      filter   exposure   mag.  mag. error


2.8336    W      12×300   19.78    +/- 0.25

3.8206    W      12×300   20.38    +/- 0.20

4.8700    W      20×300   20.97    +/- 0.22


The images of GRB100901A is available at:

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