J/ApJ/865/153 Analysis of Fermi GRB data. IV. Spectral lags (Lu+, 2018)
A comprehensive analysis of Fermi gamma-ray burst data.
IV. Spectral lag and its relation to Ep evolution.
Lu R.-J., Liang Y.-F., Lin D.-B., Lu J., Wang X.-G., Lu H.-J., Liu H.-B.,
Liang E.-W., Zhang B.
<Astrophys. J., 865, 153 (2018)>
=2018ApJ...865..153L 2018ApJ...865..153L
ADC_Keywords: GRB; Models
Keywords: gamma-ray burst: general ; methods: statistical
Abstract:
The spectral evolution and spectral lag behavior of 92 bright pulses
from 84 gamma-ray bursts observed by the Fermi Gamma-ray Burst Monitor
(GBM) telescope are studied. These pulses can be classified into
hard-to-soft pulses (H2S; 64/92), H2S-dominated-tracking pulses
(21/92), and other tracking pulses (7/92). We focus on the
relationship between spectral evolution and spectral lags of H2S and
H2S-dominated-tracking pulses. The main trend of spectral evolution
(lag behavior) is estimated with logEp∝kElog(t+t0)
(τ∝k^τlogE), where Ep is the peak photon energy in
the radiation spectrum, t+t0 is the observer time relative to the
beginning of pulse -t0, and ^τ is the spectral lag of photons with
energy E with respect to the energy band 8-25keV. For H2S and
H2S-dominated-tracking pulses, a weak correlation between k_^τ/W
and kE is found, where W is the pulse width. We also study the
spectral lag behavior with peak time tpE of pulses for 30
well-shaped pulses and estimate the main trend of the spectral lag
behavior with logtpE∝ktplogE. It is found that ktp is
correlated with kE. We perform simulations under a phenomenological
model of spectral evolution, and find that these correlations are
reproduced. We then conclude that spectral lags are closely related to
spectral evolution within the pulse. The most natural explanation of
these observations is that the emission is from the electrons in the
same fluid unit at an emission site moving away from the central
engine, as expected in the models invoking magnetic dissipation in a
moderately high-σ outflow.
Description:
We download the Gamma-ray Burst Monitor (GBM) telescope data of GRBs
by 2015 August from Fermi Archive FTP websites.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pulses.dat 18 92 List of the 92 pulses; table added by CDS
table1.dat 89 211 *Results of light curve fitting with Equation (1)
for 92 pulses
table2.dat 129 699 *Results of the time-resolved RMFIT spectral
analysis for 92 pulses
table3.dat 40 357 Results of the spectral lag analysis for 92 pulses
table4.dat 54 92 Values of τ31, W, kτ, kE for 92 pulses
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Note on table1.dat: The empirical pulse model (Kocevski+ 2003ApJ...596..389K 2003ApJ...596..389K),
i.e., Equation (1):
I(t)=Im((t+t0)/(tm+t0))r
[d/(d+r)+r/(d+r)((t+t0)/(tm+t0))r+1]-(r+d)/(r+I)
to fit the bright pulses, where t0 measures the offset of the pulse
zero time relative to the GRB trigger time, tm is the time of the peak
flux (Im), and r and d are the power-law rising and decaying indices,
respectively.
See section 2 for further details.
Note on table2.dat: The Gamma-Ray Spectral Fitting Package (RMFIT,
Version 4.3.2: http://fermi.gsfc.nasa.gov/ssc/data/analysis/rmfit/) is
used to extract the time-dependent spectra with a signal-to-noise
(S/N) ratio of S/N>40 and perform joint spectral fitting with the Band
function (Band & Trzhaskovskaya 1993ADNDT..55...43B 1993ADNDT..55...43B).
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See also:
J/ApJS/126/19 : BATSE gamma-ray burst spectral catalog. I. (Preece+, 2000)
J/ApJ/720/1146 : Spectral analysis of GRBs (Lu+, 2010)
J/ApJ/740/104 : BATSE GRB pulse catalog - preliminary data (Hakkila+, 2011)
J/A+A/525/A53 : GBM parameters for detected FERMI bursts (Guetta+, 2011)
J/ApJS/199/18 : The Fermi GBM catalog (Paciesas+, 2012)
J/ApJ/754/121 : GRBs from Fermi/GBM and LAT (The Fermi Team, 2012)
J/ApJ/756/112 : Fermi/GBM GRB time-resolved spectral analysis (Lu+, 2012)
J/ApJ/763/15 : Fermi GRB analysis. III. T90 distributions (Qin+, 2013)
J/MNRAS/431/3608 : BeppoSAX/GRBM and Fermi/GBM long GRBs (Dichiara+, 2013)
J/ApJS/207/39 : IPN supplement to the Fermi GBM (Hurley+, 2013)
J/ApJS/211/13 : The second Fermi/GBM GRB catalog (4yr) (von Kienlin+, 2014)
J/ApJS/216/32 : Localizations of GRBs with Fermi GBM (Connaughton+, 2015)
J/ApJS/218/11 : The 5yr Fermi/GBM magnetar burst catalog (Collazzi+, 2015)
J/ApJ/811/93 : Fermi/GBM GRB minimum timescales (Golkhou+, 2015)
J/ApJ/818/110 : Short GRBs with Fermi GBM and Swift BAT (Burns+, 2016)
J/ApJ/826/228 : The Fermi-GBM three-year X-ray burst catalog (Jenke+, 2016)
J/A+A/588/A135 : Fermi/GBM GRB time-resolved spectral catalog (Yu+, 2016)
J/ApJS/223/28 : The third Fermi/GBM GRB catalog (6yr) (Bhat+, 2016)
J/ApJS/229/31 : IPN supplement to the 2nd Fermi GBM catalog (Hurley+, 2017)
J/ApJ/844/126 : New spectral lag measurements of Fermi/GBM GRBs (Shao+, 2017)
J/ApJ/855/101 : BATSE TTE GRB pulse catalog (Hakkila+, 2018)
ftp://legacy.gsfc.nasa.gov/fermi/data/ : Fermi FTP data
http://fermi.gsfc.nasa.gov/ssc/data/ : Fermi data on NASA website
Byte-by-byte Description of file: pulses.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- --- [Fermi]
7- 17 A11 --- GRB GRB trigger name (bnYYMMDDddd)
18 I1 --- m_GRB ? GRB pulse segment fit
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- GRB GRB trigger name (bnYYMMDDddd)
12 I1 --- m_GRB ? GRB pulse segment fit
14- 16 A3 --- Bin Energy Bin (1)
18- 23 F6.2 --- Im [7.2/676.6] model peak flux
25- 28 F4.2 --- e_Im [0.3/7.6] Uncertainty in Im
30- 35 F6.2 --- tm [0.08/113.5] Model time of peak flux
37- 44 F8.2 --- e_tm [0/27493] Uncertainty in tm
46- 50 F5.2 --- r [0.2/46.7] Model power-law rising index
52- 56 F5.2 --- e_r [0.01/19] Uncertainty in r
58- 65 F8.2 --- d [0/51523.6] Model power-law decaying index
67- 76 F10.2 --- e_d [0/7402830] Uncertainty in d
78- 84 F7.2 --- t0 [-103/8] Offset of the pulse zero time
86- 89 F4.2 --- chi2 [0.3/2] Reduced χ2
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Note (1): Energy Bin(s) as follows:
NaI = 8-1000keV;
N1 = 8-25keV;
N2 = 25-50keV;
N3 = 50-100keV;
N4 = 100-300keV;
N5 = 300-1000keV;
N6 = 300-1000keV (BGO);
N7 = 1000-5000keV (BGO).
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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- 17 A17 --- Name GRB Common Name
19- 27 A9 --- Pulse Pulse segment fit
29- 39 A11 --- GRB GRB trigger name (bnYYMMDDddd)
40 I1 --- m_GRB ? GRB pulse segment fit
42- 47 F6.2 s Tmin [-4.5/135.7] Time bin, minimum
49- 54 F6.2 s Tmax [-2/157] Time bin, maximum
56- 60 F5.2 --- Amp [0/43.5] Amplitude from RMFIT
62- 67 F6.2 --- e_Amp [0/107] Uncertainty in Amp
69- 75 F7.2 keV Ep [7.7/3973] peak photon energy from RMFIT
77- 83 F7.2 keV e_Ep [0/1174] Uncertainty in Ep
85- 89 F5.2 --- alpha [-2/1] RMFIT, α parameter
91- 94 F4.2 --- e_alpha [0/1.5] Uncertainty in α
96-101 F6.2 --- beta [-6/100] RMFIT, β parameter
103-106 F4.2 --- e_beta [0/1.4] Uncertainty in β
108-115 E8.2 mW/m2 Flux [4.3e-8/2.8e-5] Flux, erg/s/cm2
117-124 E8.2 mW/m2 e_Flux [7e-9/7e-7] Uncertainty in Flux, erg/s/cm2
126-129 F4.2 --- chi2 [0.7/2] Reduced χ2
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- GRB GRB trigger name (bnYYMMDDddd)
12 I1 --- m_GRB ? GRB pulse segment fit
14- 19 F6.2 s Tmin [-2/105] Time bin, minimum
21- 26 F6.2 s Tmax [1.7/150] Time bin, maximum
28- 29 A2 --- Bin Energy Bin (1)
31- 35 F5.2 s tau-cat [-2.5/9.7] Spectral lag
37- 40 F4.2 s e_tau-cat [0.01/1.7] Uncertainty in spectral lag
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Note (1): Energy Bin as follows:
N2 = 25-50keV (NaI)
N3 = 50-100keV (NaI)
N4 = 100-300keV (NaI)
N5 = 300-1000keV (NaI)
N6 = 25-40keV (NaI)
N7 = 40-60keV (NaI)
N8 = 60-100keV (NaI)
N9 = 16-25keV (NaI)
B1 = 300-1000keV (BGO)
B2 = 1000-5000keV (BGO)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- GRB GRB trigger name (bnYYMMDDddd)
12 I1 --- m_GRB ? GRB Pulse segment fit
14- 14 A1 --- Evol Evolution (1)
16- 20 F5.2 --- tau31 [-1/8.7] Spectral lag (τ31)
22- 26 F5.2 --- e_tau31 [0.01/14] Uncertainty in tau31
28- 32 F5.2 --- W [0.3/55.7] Pulse width
34- 38 F5.2 --- ktau [-1.9/14.8] Fit slope, tau31-logE relation
40- 43 F4.2 --- e_ktau [0.02/4] Uncertainty in ktau
45- 49 F5.2 --- kE [-2/0.8] Fit slope, logEp to t relation
51- 54 F4.2 --- e_kE [0.02/0.6] Uncertainty in kE
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Note (1): Code as follows:
H = the hard-to-soft (H2S) spectral evolution pattern:
Equation (3): logEp=a+kElogt wiht kE<0
T = the tracking spectral evolution pattern (see Equation (4) in section 4)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Sep-2019