J/AJ/154/42 BVRI photometry of S5 0716+714 in 2012 (Hong+, 2017)
Multicolor optical monitoring of the BL Lacertae object S5 0716+714 during the
2012 outburst.
Hong S., Xiong D., Bai J.
<Astron. J., 154, 42-42 (2017)>
=2017AJ....154...42H 2017AJ....154...42H (SIMBAD/NED BibCode)
ADC_Keywords: BL Lac objects ; Photometry, UBVRI
Keywords: BL Lacertae objects: individual: S5 0716+714 - galaxies: active -
galaxies: photometry
Abstract:
We monitored the BL Lacertae object S5 0716+714 in the optical bands
during 2012 January and February with long time spans on intraday
timescales (>5hr) and high time resolutions. During this monitoring
period, the object shows violent flaring activity in both short and
intraday timescales. The object has a high duty cycle. The light
curves detected as intraday variability show variability of various
shapes. The variability amplitude is from 12.81% to 33.22%, and the
average value is 19.92%±5.87%. The overall magnitude variabilities
are ΔB=1.24m, ΔV=1.42m, ΔR=1.3m, and
ΔI=1.23m. During the observations, the average change rate is
=0.035±0.009Mag/h during the ascent and
=0.035±0.014Mag/h during the descent. However, different cases
are found on certain nights. There are good interband correlations but
no significant time lags for intraday and short timescales. The
results of the autocorrelation function show that the variability
timescales range from 0.054 to 0.134 day. Most nights show a
bluer-when-brighter (BWB) chromatic trend, a weak redder-when-brighter
(RWB) trend is found, and a few nights show no correlation between
magnitude and color index. The BWB trend appears in short timescales.
During the flare, the spectral index exhibits a clockwise loop for
internights. A shock-in-jet model and the shock wave propagating along
a helical path are likely to explain the variability and color index
variability.
Description:
Our optical observations were carried out using the 60cm BOOTES-4
auto-telescope that is located at the Lijiang Observatory of the
Yunnan Observatories of the Chinese Academy of Sciences, where the
longitude is 100°01'51''E and the latitude is 26°42'32''N,
with an altitude of 3193m. The telescope's main objective is to
observe gamma-ray bursts and blazars.
During our observations (2012 Jan 27-2012 Feb 08), the telescope was
equipped with standard Johnson UBV and Cousins RI filters. The optical
observations in the B, V, R, and I bands were in a corresponding
cyclic mode. Time resolutions for most of the nights are less than 6
minutes, and time spans on a night are more than 5hr. The time
intervals between the V and R bands range from 30 to 131s, and most of
the nights have time intervals less than 50s. The typical exposure
times in the B, V, R, and I bands are 60, 40, 40, and 40s,
respectively.
Please refer to Section 2 in the paper for additional details about
the observations.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
07 21 53.45 +71 20 36.4 S5 0716+714 = 2E 1802
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 37 683 Data of B band
table4.dat 37 871 Data of V band
table5.dat 37 874 Data of R band
table6.dat 37 878 Data of I band
table7.dat 56 49 *Results of IntraDay Variability (IDV)
observations of S5 0716+714
table8.dat 38 58 Results of change rate
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Note on table7.dat: Brightness changes of a few tenths or hundredths of a
magnitude during hours or less are often known as intraday variability (IDV) or
microvariability (Wagner & Witzel 1995ARA&A..33..163W 1995ARA&A..33..163W).
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See also:
J/ApJS/229/21 : VRI monitoring of the QSO 3C 273 in 2005-2016 (Xiong+, 2017)
J/ApJS/222/24 : 2010-2015 VRI LCs of BL Lac object Mrk 501 (Xiong+, 2016)
J/ApJS/218/18 : 2004-2012 BVRI observations of blazar S5 0716+714 (Dai+, 2015)
J/ApJ/783/83 : BVRI photometry of S5 0716+714 (Liao+, 2014)
J/ApJ/768/40 : R-band and polarimetry of blazar S5 0716+71 (Larionov+, 2013)
J/AJ/143/108 : B'V'R' photometry of the BL Lac object S5 0716+714 (Wu+, 2012)
J/ApJ/731/118 : R-band variability in blazar S5 0716+71 (Chandra+, 2011)
J/ApJS/185/511 : Optical microvariability of S5 0716+714 (Poon+, 2009)
J/AJ/136/1846 : BVRI light curves of S5 0716+714 (Zhang+, 2008)
J/AJ/135/1384 : R-band variability in 5 blazars (Gupta+, 2008)
J/AJ/133/1599 : B'V'R' photometry of S5 0716+714 (Wu+, 2007)
J/A+A/451/435 : BV(RI)c photometry of S5 0716+714 (Montagni+, 2006)
J/A+A/450/39 : BVRI photometry of 8 red blazars (Gu+, 2006)
J/AJ/129/1818 : Photometry of S5 0716+714 (Wu+, 2005)
J/A+A/402/151 : S5 0716+714 UBVRI photometry (Raiteri+, 2003)
J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)
J/A+A/327/61 : BV(RI)c photometry of S5 0716+714 (Ghisellini+ 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "Y:M:D" Date Universal Time (UT) date of the observation
13- 22 F10.4 d MJD [55953.6/55963] Modified Julian Date of observation
24- 30 F7.4 mag Bmag [13.65/14.9] Johnson B band magnitude
32- 37 F6.4 mag e_Bmag [0.013/0.086] The RMS uncertainty in Bmag
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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 "Y:M:D" Date Universal Time (UT) date of the observation
13- 22 F10.4 d MJD [55953.6/55966] Modified Julian Date of observation
24- 30 F7.4 mag Vmag [13/14.5] Johnson V band magnitude
32- 37 F6.4 mag e_Vmag [0.01/0.078] The RMS uncertainty in Vmag
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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- 11 A11 "Y:M:D" Date Universal Time (UT) date of the observation
13- 22 F10.4 d MJD [55953.6/55966] Modified Julian Date of observation
24- 30 F7.4 mag Rmag [12.64/13.95] Cousins R band magnitude
32- 37 F6.4 mag e_Rmag [0.0076/0.047] The RMS uncertainty in Rmag
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "Y:M:D" Date Universal Time (UT) date of the observation
13- 22 F10.4 d MJD [55953.6/55966] Modified Julian Date of observation
24- 30 F7.4 mag Imag [12.16/13.39] Cousins I band magnitude
32- 37 F6.4 mag e_Imag [0.0073/0.047] The RMS uncertainty in Imag
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "Y:M:D" Date Universal Time (UT) date of the observation
13 A1 --- Band [BVRI] Observed band
15- 18 F4.2 --- C [0.77/8.26] Value of the C-test (1)
20- 24 F5.2 --- [0.61/68.23] Average F-value (1)
26- 29 F4.2 --- FC99 [1.53/2.51] The critical F-value with 99%
confidence level (1)
31- 36 F6.2 --- FA [1/164.48] THe F-value of one-way ANalysis Of
VAriance (ANOVA) (1)
38- 41 F4.2 --- FA99 [1.98/4] The critical F-value of one-way ANalysis
Of VAriance (ANOVA) with 99% confidence level (1)
43- 44 A2 --- Var Variability status (V=Variable, PV=Probable
Variable, or N=Nonvariable)
46- 50 F5.2 % Amp [12.81/33.22]? Variability amplitude (2)
52- 56 F5.2 mag [12.3/14.8] Daily average magnitude
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Note (1):
In order to quantify the IntraDay Variability (IDV) of the object, we
have employed three statistical analysis techniques: the C-test, F-test,
and one-way ANalysis Of VAriance (ANOVA) (e.g., de Diego
2010AJ....139.1269D 2010AJ....139.1269D; Goyal et al. 2012A&A...544A..37G 2012A&A...544A..37G; Hu et al.
2014MNRAS.443.2940H 2014MNRAS.443.2940H; Agarwal & Gupta 2015MNRAS.450..541A 2015MNRAS.450..541A; Dai et al. 2015,
Cat. J/ApJS/218/18; Xiong et al. 2016, Cat. J/ApJS/222/24). The blazar is
considered variable (V) if the light curve satisfies the criteria of the
C-test, F-test, and ANOVA. The blazar is considered probably variable (PV)
if only one of the above three criteria is satisfied. The blazar is
considered nonvariable (N) if none of the criteria are met.
Romero et al. (1999A&AS..135..477R 1999A&AS..135..477R) introduced the variability parameter,
C, as the average value between C1 and C2:
C1=σ(BL-StarA)/σ(StarA-StarB),
C2=σ(BL-StarB)/σ(StarA-StarB), Eq. (2), where:
(BL-StarA),(BL-StarB), and (StarA-StarB) are the differential
instrumental magnitudes of the blazar and comparison star A, the blazar and
comparison star B, and comparison stars A and B, respectively.
Here σ is the standard deviation of the differential instrumental
magnitudes.
The value of F is calculated as:
F1=Var(BL-StarA)/Var(StarA-StarB),F2=Var(BL-StarB)/Var(StarA-StarB),
where:
Var(BL-StarA),Var(BL-StarB), and Var(StarA-StarB) are the variances
of the differential instrumental magnitudes.
The F-value from the average of F1 and F2 is compared with the critical
F-value:
Fανbl,ν*, where:
νbl and ν* are the number of degrees of freedom for the blazar and
comparison star, respectively (ν=N-1),
and α is the significance level set as 0.01 (2.6σ).
If the average F-value is larger than the critical value, the blazar is
variable at a confidence level of 99%.
De Diego (2010AJ....139.1269D 2010AJ....139.1269D) reported that the ANOVA is a powerful and
robust estimator for microvariations. It does not rely on error measurement
but derives the expected variance from subsamples of the data. The one-way
ANOVA test divides the data into many groups. Then, it compares the
variances between intergroups and intragroups. See Section 2 in the paper
for further details.
Note (2):
The variability amplitude (Amp) can be calculated by (Heidt & Wagner
1996A&A...305...42H 1996A&A...305...42H):
Amp=100*[(Amax-Amin)2-2σ2%]1/2, Eq. (6), where:
Amax and Amin are the maximum and minimum magnitude,
respectively, of the light curve for the night being considered,
and σ is the rms error.
When estimating the variability amplitude, we only consider the nights
detected as variability.
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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- 11 A11 "Y:M:D" Date Universal Time (UT) date of the observation
13 A1 --- Band [BVRI] Observed band
15- 24 F10.4 d MJD [55953.6/55966] Modified Julian Date
(increasing/decreasing time points)
26- 31 F6.3 mag mag [12.16/14.89] Magnitude
33- 38 F6.3 mag/h CR [-0.075/0.054]? Change rate (1)
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Note (1): When calculating the change rate, we consider the coefficients of
correlation >0.7; for CR, the positive and negative signs are increasing
brightness and decreasing brightness, respectively.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 12-Oct-2017