J/ApJ/702/489 ROTSE observations of gamma-ray burst afterglows (Rykoff+, 2009)
Looking into the fireball: ROTSE-III and Swift observations of early gamma-ray
burst afterglows.
Rykoff E.S., Aharonian F., Akerlof C.W., Ashley M.C.B., Barthelmy S.D.,
Flewelling H.A., Gehrels N., Gogus E., Guver T., Kiziloglu U., Krimm H.A.,
McKay T.A., Ozel M., Phillips A., Quimby R.M., Rowell G., Rujopakarn W.,
Schaefer B.E., Smith D.A., Vestrand W.T., Wheeler J.C., Wren J., Yuan F.,
Yost S.A.
<Astrophys. J., 702, 489-505 (2009)>
=2009ApJ...702..489R 2009ApJ...702..489R
ADC_Keywords: Gamma rays ; Magnitudes
Keywords: gamma rays: bursts
Abstract:
We report on a complete set of early optical afterglows of gamma-ray
bursts (GRBs) obtained with the Robotic Optical Transient Search
Experiment (ROTSE-III) telescope network from 2005 March through 2007
June. This set is comprised of 12 afterglows with early optical and
Swift/X-Ray Telescope observations, with a median ROTSE-III response
time of 45s after the start of γ-ray emission (8s after the GCN
notice time). These afterglows span 4 orders of magnitude in optical
luminosity, and the contemporaneous X-ray detections allow
multi-wavelength spectral analysis. Excluding X-ray flares, the
broadband synchrotron spectra show that the optical and X-ray emission
originate in a common region, consistent with predictions of the
external forward shock in the fireball model. However, the fireball
model is inadequate to predict the temporal decay indices of the early
afterglows, even after accounting for possible long-duration
continuous energy injection. We find that the optical afterglow is a
clean tracer of the forward shock, and we use the peak time of the
forward shock to estimate the initial bulk Lorentz factor of the GRB
outflow, and find 100≲Γ0≲1000, consistent with expectations.
Description:
In this paper, we present new ROTSE-III photometry that has not
previously been published for eight bursts (GRB 050525a, GRB 050922c,
GRB 060111b, GRB 060605, GRB 060729, GRB 060904b, GRB 061007, GRB
070611). The remaining four bursts (GRB 050319, GRB 050401, GRB
050801, GRB 051109a) have ROTSE-III data that have been previously
published (Quimby et al. 2006ApJ...640..402Q 2006ApJ...640..402Q; Rykoff et al.
2005ApJ...631L.121R 2005ApJ...631L.121R, 2006ApJ...638L...5R 2006ApJ...638L...5R; Yost et al.
2007ApJ...657..925Y 2007ApJ...657..925Y), and is re-analyzed here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 108 13 Summary of GRBs and ROTSE-III responses
table2.dat 79 444 ROTSE-III CR optical photometry
refs.dat 42 37 References
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See also:
J/ApJ/693/1484 : Early optical afterglow catalog (Cenko+, 2009)
J/ApJ/690/163 : The first Swift UV-Opt GRB afterglow catalog (Roming+, 2009)
J/ApJ/701/824 : Afterglows of short and long-duration GRBs (Nysewander+, 2009)
J/ApJS/175/179 : The BAT1 gamma-ray burst catalog (Sakamoto+, 2008)
J/ApJ/686/1209 : Optical properties of GRB afterglows (Melandri+, 2008)
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- 7 A7 --- GRB GRB identification
9- 14 I6 --- Trig The Swift trigger number
16- 26 A11 --- T0 t0 (UT): the onset of γ-ray emission (1)
27 A1 --- f_T0 [a] adjusted T0 (1)
29- 30 I2 --- r_T0 ? GRB reference (see refs.dat file)
32- 33 I2 h RAh Optical afterglow hour of right ascension (J2000)
35- 36 I2 min RAm Minute of right ascension (J2000)
38- 42 F5.2 s RAs Second of right ascension (J2000)
44 A1 --- DE- Sign of declination (J2000)
45- 46 I2 deg DEd Optical afterglow degree of declination (J2000)
48- 49 I2 arcmin DEm Arcminute of declination (J2000)
51- 54 F4.1 arcsec DEs Arcsecond of declination (J2000)
56- 62 A7 --- r_pos Reference(s) for position (see refs.dat file)
64- 68 F5.1 s T90 ? The burst BAT T90 duration in 15-350keV band
from Sakamoto et al. (2008, Cat. J/ApJS/175/179)
70- 75 F6.1 s XRT ? XRT response: delay from trigger time to
first XRT observation
77- 80 A4 --- Tel ROTSE telescope with the response
82- 87 F6.1 s ROTSE Delay from trigger time to first ROTSE observation
89- 92 F4.1 mag mag ? Peak optical magnitude
94- 98 F5.3 --- z ? Burst redshift
99 A1 --- u_z [?e] Uncertainty flag on z (2)
101-108 A8 --- r_z Reference(s) of z (see refs.dat file)
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Note (1):
a = For most of the bursts, we use the Swift/BAT trigger time as the start
time t0. For three bursts (GRB 050319, GRB 050401, and GRB 060111b), we
detect significant γ-ray emission prior to the trigger time, and we
have adjusted the start time (T0) accordingly. We have performed
systematic checks on the determination of t0, which are described in
Section 3.2.
Note (2): Flag as follows:
? = For GRB 060111b, the detection in the UV constrains the redshift to be
≲1.5. We have therefore assumed a fiducial redshift of 1.0 for this
burst.
e = For GRB 050801, multi-wavelength optical and NUV observations with
UVOT have been used to estimate a photometric redshift of z∼1.6
(de Pasquale et al. 2007MNRAS.377.1638D 2007MNRAS.377.1638D).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- GRB The Γ-ray Burst identification
9- 12 A4 --- Tel Telescope used in observation
14- 20 F7.1 s Tst Start of the observation (1)
22- 28 F7.1 s Tend End of the observation (1)
30 A1 --- l_CRmag Limit flag on CRmag
31- 37 F7.2 mag CRmag The CR magnitude (2)
39- 42 F4.2 mag e_CRmag ? Uncertainty in CRmag
44 A1 --- l_FOpt Limit flag on FOpt
45- 52 F8.4 mJy FOpt Optical flux density at 1.93eV (3)
54- 59 F6.4 mJy e_FOpt ? Uncertainty in FOpt
61- 69 F9.7 mJy FXray ? X-ray flux density at 2.77keV (4)
71- 79 F9.7 mJy e_FXray ? Uncertainty in FXray
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Note (1): Relative to the Swift/BAT trigger time. See t0 in Table 1.
Note (2): The unfiltered thinned ROTSE-III CCDs have a peak response
similar to an R-band filter. The magnitude zero point was calculated
from the median offset of the fiducial reference stars to the USNO-B1.0
R-band measurements to produce CR magnitudes.
Note (3): Corrected for Galactic extinction and Lyα absorption in the IGM.
Note (4): Corrected for Galactic and host absorption.
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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 I2 --- Ref Reference number
4- 22 A19 --- BibCode Bibcode
24- 42 A19 --- Aut Author(s) name(s)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Sep-2011