J/ApJ/654/L21 R-band light curves of GRB 060206 and GRB 060210 (Stanek+, 2007)
"Anomalous" optical gamma-ray burst afterglows are common:
two z∼4 bursts, GRB 060206 and GRB 060210.
Stanek K.Z., Dai X., Prieto J.L., An D., Garnavich P.M., Calkins M.L.,
Serven J., Worthey G., Hao H., Dobrzycki A., Howk C., Matheson T.
<Astrophys. J., 654, L21-L24 (2007)>
=2007ApJ...654L..21S 2007ApJ...654L..21S
ADC_Keywords: Gamma rays ; Photometry
Keywords: gamma rays: bursts
Abstract:
We report on two z∼4 gamma-ray bursts, GRB 060206 and GRB 060210, for
which we have obtained well-sampled optical light curves. Both light
curves show unusual behavior. GRB 060206 experienced a slow early
decay, followed by a rapid increase in brightness by factor 2.5 about
1hr after the burst. Its afterglow then faded in a broken power-law
fashion, with a smooth break at tb=0.6 days, but with additional,
less dramatic bumps and wiggles. The afterglow of GRB 060210 is also
unusual: the light curve was more or less flat between 60 and 300s
after the burst, followed by a 70% increase at 600s after the burst,
after which the light curve declined as a ∼t-1.3 power law. We argue
that anomalous optical afterglows are likely to be the norm and that
such rapid optical variations should be seen in many bursts, given
good enough sampling. Given that, some of the usual procedures, such
as deriving the jet opening angle from fitting a smooth function to
the optical light curve, might often have a poor statistical
significance. We propose that the rapid rise at ∼3000s in the optical
for GRB 060206 and the optical bump at ∼700s in GRB 060210 might be
due to the turn-on of the external shock. The existence and timing of
such features could provide us with valuable additional information
about the bursts.
Description:
The majority of our data were obtained with the MDM 2.4m telescope,
with additional data obtained using the MDM 1.3m telescope. For the
bright afterglow of GRB 060206, we have obtained 83 high
signal-to-noise ratio R-band images between 1.7 and 8.7hr after the
burst, followed by an additional 16 R-band images during the next two
nights. For the much fainter afterglow of GRB 060210, we have obtained
12 R-band images between 0.48 and 2.0hr after the burst.
Objects:
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RA (2000) DE Designation(s) (files)
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13 31 47 +35 04 30 GRB 060206 = XRR 060206 (table1a.dat)
03 50 57.4 +27 01 34 GRB 060210 = GRB 060210 (table1b.dat)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1a.dat 30 99 R-band light curves for GRB 060206
table1b.dat 30 12 R-band light curves for GRB 060210
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See also:
J/ApJ/641/L13 : Light-curve data for GRB 030329 (Gorosabel+, 2006)
J/ApJ/642/L99 : R-band photometry of GRB 060206 (Wozniak+, 2006)
J/ApJ/654/L25 : Light-curve data for GRB 050319 (Huang+, 2007)
Byte-by-byte Description of file: table1?.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- GRB GRB identification
12- 17 F6.4 d Time Time since discovery (1)
19- 24 F6.3 mag Rmag The R band magnitude
26- 30 F5.3 mag e_Rmag The 1σ error in Rmag
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Note (1):
* For GRB 060206, 2006 February 6, 04:46:53 UT (Morris et al.,
2006GCN..4682....1M 2006GCN..4682....1M, http://gcn.gsfc.nasa.gov/gcn/gcn3/4682.gcn3).
* For GRB 060210, 2006 February 10, 04:58:50 UT (Beardmore et al.,
2006GCN..4724....1B 2006GCN..4724....1B, http://gcn.gsfc.nasa.gov/gcn/gcn3/4724.gcn3).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 15-Nov-2008