J/ApJ/772/73 GRB with early-time optical emission (Kopac+, 2013)
GRB 090727 and gamma-ray bursts with early-time optical emission.
Kopac D., Kobayashi S., Gomboc A., Japelj J., Mundell C.G., Guidorzi C.,
Melandri A., Bersier D., Cano Z., Smith R.J., Steele I.A., Virgili F.J.
<Astrophys. J., 772, 73 (2013)>
=2013ApJ...772...73K 2013ApJ...772...73K
ADC_Keywords: Gamma rays ; Photometry, SDSS ; Redshifts
Keywords: gamma-ray burst: general; gamma-ray burst: individual: GRB 090727
Abstract:
We present a multi-wavelength analysis of Swift gamma-ray burst
GRB 090727, for which optical emission was detected during the prompt
γ-ray emission by the 2m autonomous robotic Liverpool Telescope
and subsequently monitored for a further two days with the Liverpool
and Faulkes Telescopes. Within the context of the standard fireball
model, we rule out a reverse shock origin for the early-time optical
emission in GRB 090727 and instead conclude that the early-time
optical flash likely corresponds to emission from an internal
dissipation process. Putting GRB 090727 into a broader observational
and theoretical context, we build a sample of 36 γ-ray bursts
(GRBs) with contemporaneous early-time optical and γ-ray
detections. From these GRBs, we extract a sub-sample of 18 GRBs, which
show optical peaks during prompt γ-ray emission, and perform
detailed temporal and spectral analysis in γ-ray, X-ray, and
optical bands. We find that in most cases early-time optical emission
shows sharp and steep behavior, and notice a rich diversity of
spectral properties. Using a simple internal shock dissipation model,
we show that the emission during prompt GRB phase can occur at very
different frequencies via synchrotron radiation. Based on the results
obtained from observations and simulation, we conclude that the
standard external shock interpretation for early-time optical emission
is disfavored in most cases due to sharp peaks (Δt/t<1) and
steep rise/decay indices, and that internal dissipation can explain
the properties of GRBs with optical peaks during γ-ray emission.
Description:
In this paper, we present a detailed multi-wavelength analysis of
GRB 090727, which was detected by the Swift satellite and promptly
observed automatically by the LT through the prompt and afterglow
phases. We then compile a sample of GRBs observed to date with
contemporaneous γ-ray and optical detection. From this master
sample, we select a sub-sample of 18 GRBs suitable for detailed
temporal analysis.
On 2009 July 27, at t0=22:42:18 UT, the BAT on board Swift was
triggered by the long GRB 090727. Soon after the trigger, Swift slewed
to the position of the burst and the XRT started collecting data at
t=131s, while γ-ray emission was still ongoing. The LT responded
automatically to the Swift BAT trigger, slewing to the GRB position at
RAJ2000=21:03:50.6, DEJ2000=+64:55:30 to begin automatic optical
follow-up observations at t=166s in r', i', and z' Sloan Digital Sky
Survey filter. Later we manually triggered the Faulkes Telescope North
(FTN) to obtain additional data at t∼14hr and t∼34hr in the R and i'
filters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 49 34 GRB 090727 optical photometry
table5.dat 54 36 *General properties of GRBs in the master sample
table8.dat 85 63 Early time optical and γ-ray flux densities
and spectral indices for 18 GRBs in the sub-sample
refs.dat 61 32 References
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Note on table5.dat: Master sample, i.e., GRBs with optical detection during
prompt γ-ray emission.
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See also:
IX/20 : The Fourth BATSE Burst Revised Catalog (Paciesas+ 1999)
J/A+A/557/A12 : Optical light curves of γ-ray bursts (Zaninoni+, 2013)
J/ApJS/209/20 : Swift GRB catalog with X-ray data (Grupe+, 2013)
J/MNRAS/428/729 : GRB Swift X-ray light curves analysis (Margutti+, 2013)
J/MNRAS/421/2692 : Optical/NIR observations of GRB 080310 (Littlejohns+, 2012)
J/MNRAS/421/1874 : GRB 100901A and GRB 100906A light curves (Gorbovskoy+, 2012)
J/ApJ/746/170 : Follow-up resources for high-redshift GRBs (Morgan+, 2012)
J/A+A/530/A21 : Spectral properties of 438 GRBs (Nava+, 2011)
J/ApJS/195/2 : The second Swift BAT GRB catalog (BAT2) (Sakamoto+, 2011)
J/AJ/141/36 : GRB 080607 multi-band light curves (Perley+, 2011)
J/ApJ/743/154 : Multi-band phot. of GRB 110205A + 110213A (Cucchiara+, 2011)
J/ApJ/720/1513 : The afterglows of Swift-era GRBs. I. (Kann+, 2010)
J/ApJ/711/495 : Durations of Swift/BAT GRBs (Butler+, 2010)
J/ApJ/702/489 : ROTSE observations of GRB afterglows (Rykoff+, 2009)
J/ApJ/701/824 : Afterglows of short and long-duration GRBs (Nysewander+, 2009)
J/ApJ/691/723 : BVIJHKs observations of GRB 080319B (Bloom+, 2009)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJS/180/192 : BeppoSAX/GRBM γ-ray Burst Catalog (Frontera+, 2009)
J/PAZh/35/10 : Gamma-ray bursts with known redshifts (Badjin+, 2009)
J/ApJ/672/449 : GRB 061126 light curves (Perley+, 2008)
J/A+A/473/347 : BeppoSAX complete catalogue of GRBs (Vetere+, 2007)
J/A+A/455/813 : BeppoSAX catalog of GRB X-ray afterglows (De Pasquale+, 2006)
J/A+A/427/87 : List of GRBs (Gorosabel+, 2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 F8.1 s Tmid Time of mid-exposure since GRB trigger time
10- 13 I4 s Exp [10/1800] Exposure time
15- 17 A3 --- Tel Telescope: FTN=Faulkes Telescope North, or
LT=2-m Liverpool Telescope
19- 20 A2 --- Filt Filter (r',i', z' or R)
22 A1 --- l_mag Limit flag on mag
24- 28 F5.2 mag mag [18.3/23.4] Magnitude in Filt; corrected for
the Galactic extinction
30- 33 F4.2 mag e_mag [0.1/0.5]? mag uncertainty
35 A1 --- l_FOpt Limit flag on FOpt
37- 42 F6.4 mJy FOpt [0.001/0.2] Optical flux density (1)
44- 49 F6.4 mJy e_FOpt [0.0007/0.02]? FOpt uncertainty
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Note (1): The calibrated magnitudes were converted to flux densities using
Fukugita et al. (1996AJ....111.1748F 1996AJ....111.1748F).
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GRB GRB name
9 A1 --- n_GRB [abcl] Individual notes (1)
11- 15 F5.1 s T90 [15/600] Burst duration with 5-95% of fluence (2)
16 A1 --- r_T90 Flag on T90 (2)
18- 21 F4.2 --- z [0.3/6.3]? Redshift
22 A1 --- f_z [*] *: not a spectroscopic redshift
24- 29 F6.3 10+46J E [0.02/28]? Isotropic γ-ray energy release
(Eγiso) in 1053erg
31 A1 --- LC Light Curve morphology (3)
33- 34 I2 --- r_LC ? Optical Light Curve morphology reference
(see refs.dat file)
36- 38 A3 --- T8 Included in the sub-sample? (Yes ot No)
40- 49 A10 --- Ref Reference for z and E (see refs.dat file)
51- 54 A4 --- Notes Notes in the corresponding Appendix number;
also given the optical emission references
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Note (1): Flag as follows:
a = The optical flare at ∼500s after the trigger (Boer et al.
2006ApJ...638L..71B 2006ApJ...638L..71B) occurs after the end of the prompt γ-ray
emission, but it is coincident with the X-ray flare, suggesting a common
origin via the late internal shock model (Wei et al. 2006ApJ...636L..69W 2006ApJ...636L..69W).
b = The optical bump at ∼250s after the trigger is perhaps coincident with the
late-time γ-ray activity (late internal shocks), but it is
non-prominent when compared with the background afterglow component
(Perley et al. 2008ApJ...688..470P 2008ApJ...688..470P).
c = early-time optical peak is probably associated with the prompt emission
(Guidorzi et al. 2011MNRAS.417.2124G 2011MNRAS.417.2124G), but this GRB was not included in
the sub-sample due to sparsity of the data and too few optical data points
during the peak to allow detailed temporal analysis.
l = For GRB 050820A the total duration is given instead of T90
(Cenko et al. 2006ApJ...652..490C 2006ApJ...652..490C).
Note (2): T90 was obtained from Sakamoto et al. (2011, J/ApJS/195/2), except
flagged d-k (see refs.dat file).
Note (3): Light curve morphologies (references are given in the
column "Ref" and "Notes" except otherwise noted):
a = optical peak/peaks during γ-ray emission,
b = optical decay during γ-ray emission,
c = optical rise during γ-ray emission.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GRB GRB name (1)
9 A1 --- f_GRB [*] Flag on GRB (2)
11- 15 F5.1 s Tmid Time of mid-exposure since GRB trigger time
17- 21 F5.1 s Exp Exposure time
23- 25 F3.1 10+14Hz nuOpt [4.8/8.6] Optical frequency νopt
27- 34 F8.2 mJy FOpt Optical flux density (3)
36- 42 F7.2 mJy e_FOpt Uncertainty in FOpt
44- 47 F4.1 10+18Hz nuGR [4.6/27] γ-ray frequency
49- 54 F6.1 uJy FGR γ-ray flux density
56- 60 F5.1 uJy e_FGR Uncertainty in FGR
62- 66 F5.2 --- betaG Power-law slope βγ of γ-ray
spectrum (βγ=Γ-1)
68- 71 F4.2 --- e_betaG The 90% confidence interval in betaG
73- 78 F6.3 --- betaG-O Power-law slope of optical-to-γ index
81- 85 F5.3 --- e_betaG-O The 90% confidence interval in betaG-O
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Note (1): Optical emission references are given in Appendices A.1-A.17.
γ-ray flux densities and spectral indices were extracted from the
analysis of the Swift BAT data (Section 6.2), except for GRB 990123,
GRB 041219A and GRB 050820A, for which FGR and betaG were taken from
Yost et al. (2007ApJ...669.1107Y 2007ApJ...669.1107Y) and Yost et al. (2007ApJ...657..925Y 2007ApJ...657..925Y).
Note (2):
* : Indicates optical flux densities are also corrected for the host
galaxy extinction (references are given in Appendices A.1 - A.17).
Note (3): Corrected for the Galactic extinction using
Schlegel, Finkbeiner & Davis (1998ApJ...500..525S 1998ApJ...500..525S).
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode
24- 42 A19 --- Aut Author's name
44- 61 A18 --- Comm Comment (catalog's reference in VizieR)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-Feb-2015