J/ApJS/268/54 Continuous opt. monitoring of BL Lac from 2009-2021 (Xu+, 2023)
A small-scale structure model of a jet based on observations of
microvariability.
Xu J., Hu S., Chen X., Jiang Y., Alexeeva S.
<Astrophys. J. Suppl. Ser., 268, 54 (2023)>
=2023ApJS..268...54X 2023ApJS..268...54X
ADC_Keywords: BL Lac objects; Photometry, UBVRI
Keywords: Blazars ; BL Lacertae objects ; Jets
Abstract:
We developed a multiregion radiation model for the evolution of flux
and spectral index with time. In this model, each perturbation
component in the jet produces an independent flare. The model can be
used to study the decomposition of microvariability, the structural
scale of the perturbed components, and the physical parameters of the
acceleration processes. Based on the shock acceleration model for a
relativistic jet, the influence of the acceleration parameters on
multiband flare parameters is calculated. We present the results of
multiband optical microvariability of the blazar BL Lacertae observed
during 89 nights in the period from 2009 to 2021, and use them as a
sample for model fitting. The results show that both the amplitude and
duration of flares decomposed from the microvariability light curves
conform to a log-normal distribution. The time delays between the
optical bands follow a normal distribution and amount to several
minutes, which corroborate with both predictions from the theoretical
model and the calculation of the discrete correlation function. Using
the spectral index evolution and the simultaneous fitting of the
multiband variability curves, we obtain the acceleration and radiation
parameters to constrain and distinguish the origins of different
flares. Based on the flare decomposition, we can effectively reproduce
the time-domain evolution trends of the optical variations and energy
spectrum, and explain the various redder-when-brighter and
bluer-when-brighter behaviors.
Description:
Photometric observations were carried out with the 1.0m telescope at
Weihai Observatory of Shandong University from 2009 to 2021
(MJD55070--59352) in standard B and V (Johnson) and R and I (Cousins)
filters.
Objects:
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RA (ICRS) DE Designation(s)
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22 02 43.29 +42 16 39.9 BL Lacertae = NAME BL Lac
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 33 24899 Light curves of BL Lac from Weihai observatory
of Shandong University
table2.dat 53 1108 Flare parameters used to fit the data
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See also:
J/PAZh/30/243 : BV(RI)c-JHK phot. of BL Lac in 1999-2001 (Hagen-Thorn+, 2004)
J/AZh/71/717 : Polarimetric Observations of BL Lac (Gagen-Torn+ 1994)
J/A+AS/116/403 : VRI photometry of stars in 12 BL Lac objects (Fiorucci+, 1996)
J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)
J/A+AS/136/455 : BVRI photometry of 3 BL Lac objects (Bai+, 1999)
J/ApJ/522/846 : Optical monitoring of GeV loud blazars (Xie+, 1999)
J/A+A/369/758 : VRI photometry of BL Lac (1997-1999) (Fan+, 2001)
J/A+A/385/55 : Long-Term Polarization of BL Lac (Hagen-Thorn+ 2002)
J/MNRAS/373/209 : BATC eim photometry of BL Lac (Hu+, 2006)
J/A+A/450/39 : BVRI photometry of 8 red blazars (Gu+, 2006)
J/AJ/134/799 : Multiwaveband polarimetry of 15 AGN (Jorstad+, 2007)
J/ApJ/743/171 : The 2LAC catalog (Ackermann+, 2011)
J/A+A/558/A92 : S5 0716+714 microvariability observation (Bhatta+, 2013)
J/ApJ/787/151 : Fitted jet components in BL Lacertae (Cohen+, 2014)
J/ApJ/816/53 : Multiwavelength obs. of BL Lac in 2012-2013 (Wehrle+, 2016)
J/A+A/609/A68 : Full-Stokes polarimetry of 5 radio sources (Myserlis+, 2018)
J/A+A/620/A185 : Long-term optical monitoring of TeV Blazars (Nilsson+, 2018)
J/A+A/623/A175 : 2015 BL Lac VHE gamma-ray flare (MAGIC Collaboration, 2019)
J/ApJ/884/92 : 7yrs of VRI obs. of S5 0716+714 and its flares (Xu+, 2019)
J/A+A/649/A153 : BL Lac 86GHz images (Casadio+, 2021)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d JD [2455128.9/2459206.0] Julian date
18 A1 --- Band Observational band (B, V, R or I)
20- 26 F7.4 mag mag [10.8/14.7] Apparent magnitude in Band after the
galactic extinction correction
28- 33 F6.4 mag e_mag [0.0007/0.05] Uncertainty in mag
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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- 9 F9.1 d JD [2455128.9/2459206.0] Julian Date
11 I1 --- ID [1/7] Flare index identifier
13 A1 --- Band Observational band (V, R or I)
15- 21 F7.4 h Center [-3.1/14.7] Central time of the flare
23- 29 F7.4 mJy Amp [0.039/19.41] Flare amplitude in Band
31- 38 F8.4 10-5/s/m3 dN [0.08/161.5] Enhanced electron number density
40- 45 F6.4 h Width [0.25/5.72] Flare width/duration, τflare
47- 53 F7.4 AU Size [2.88/65.54] Size of the radiation region,
Scell (Equation 3)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 12-Jan-2024