J/AJ/137/5022 Variability of radio-bright BL Lac objects (Nieppola+, 2009)
Long-term variability of radio-bright BL Lacertae objects.
Nieppola E., Hovatta T., Tornikoski M., Valtaoja E., Aller M.F., Aller H.D.
<Astron. J., 137, 5022-5036 (2009)>
=2009AJ....137.5022N 2009AJ....137.5022N
ADC_Keywords: BL Lac objects ; Radio sources
Keywords: BL Lacertae objects: general - galaxies: active -
methods: statistical - radiation mechanisms: non-thermal -
radio continuum: galaxies
Abstract:
Radio-bright BL Lacertae objects (BLOs) are typically very variable
and exhibit prominent flaring. We use a sample of 24 BLOs, regularly
monitored at Metsahovi Radio Observatory, to get a clear idea of their
flaring behavior in the radio domain and to find possible
commonalities in their variability patterns. Our goal was to compare
the results given by computational timescales and the observed
variability parameters determined directly from the flux curves. Also,
we wanted to find out if the BLO flares adhere to the generalized
shock model, which gives a schematic explanation for the physical
process giving rise to the variability. We use long-term monitoring
data from 4.8, 8, 14.5, 22, 37, 90, and 230GHz, obtained mainly from
the University of Michigan and Metsahovi Radio Observatories. The
structure function, discrete correlation function, and Lomb-Scargle
periodogram timescales, calculated in a previous study, are analyzed
in more detail. Also, we determine flare durations, rise and decay
times, and absolute and relative peak fluxes from the monitoring data.
Description:
Our sample has been selected from the BLO sample monitored at the
Metsahovi Radio Observatory for more than 20 years.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 24 The source sample of 24 BLOs
table2.dat 56 128 The most significant timescales obtained for the
sample sources using the structure function,
the discrete correlation function and the
Lomb-Scargle periodogram
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See also:
J/A+A/445/441 : SED of BL Lacertae objects (Nieppola+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Source Source name (HHMM+DDMM)
10- 21 A12 --- OName Other name
24- 25 I2 h RAh Right ascension (J2000)
27- 28 I2 min RAm Right ascension (J2000)
30- 33 F4.1 s RAs Right ascension (J2000)
35 A1 --- DE- Declination sign (J2000)
36- 37 I2 deg DEd Declination (J2000)
39- 40 I2 arcmin DEm Declination (J2000)
42- 45 F4.1 arcsec DEs Declination (J2000)
47- 51 F5.3 --- z ?=- Redshift
53- 56 F4.1 --- Dvar ?=- Doppler boosting factor of the source
taken from Hovatta et al. (2009A&A...494..527H 2009A&A...494..527H)
58- 60 A3 --- Class [HILBL] BLO class (High, Intermediate or Low
energy-peaked BL Lac) according to
Nieppola et al. (2006, Cat. J/A+A/445/441)
62 A1 --- Flare [*] Flare analysis (1)
64- 65 I2 --- r_z ?=- Redshift reference (2)
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Note (1): indicates whether the source is included in the flare analysis.
See the text for details.
Note (2): References as follows:
1 = Britzen et al., 2008, Cat. J/A+A/484/119
2 = Carangelo et al., 2003A&A...412..651C 2003A&A...412..651C
3 = Cohen et al., 1987ApJ...318..577C 1987ApJ...318..577C
4 = De Grijp et al., 1992, Cat. J/A+AS/96/389
5 = Hewitt & Burbidge, 1987ApJS...63....1H 1987ApJS...63....1H
6 = Hewitt & Burbidge, 1989ApJS...69....1H 1989ApJS...69....1H
7 = Lawrence et al., 1986AJ.....91..494L 1986AJ.....91..494L
8 = Nilsson et al., 2008A&A...487L..29N 2008A&A...487L..29N
9 = Smith & Nair, 1995PASP..107..863S 1995PASP..107..863S
10 = Sowards-Emmerd et al., 2005, Cat. J/ApJ/626/95
11 = Stickel et al., 1988A&A...191L..16S 1988A&A...191L..16S
12 = Stickel et al., 1989, Cat. III/175
13 = Stickel et al., 1991ApJ...374..431S 1991ApJ...374..431S
14 = Stickel et al., 1993, Cat. J/A+AS/98/393
15 = Tytler & Fan, 1992ApJS...79....1T 1992ApJS...79....1T
16 = Ulrich et al., 1975ApJ...198..261U 1975ApJ...198..261U
17 = Vermeulen et al., 1995ApJ...452L...5V 1995ApJ...452L...5V
18 = Weistrop et al., 1984BAAS...16..521W 1984BAAS...16..521W
19 = Wiklind & Combes, 1997A&A...328...48W 1997A&A...328...48W
20 = Wright et al., 1983MNRAS.205..793W 1983MNRAS.205..793W.
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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- 8 A8 --- Source Source name (HHMM+DDMM)
10- 21 A12 --- OName Other name
23- 27 F5.1 GHz nu Observation frequency
29- 30 A2 --- l_TSF [≥] Limit flag on TSF
32- 37 F6.3 yr TSF ? Structure function timescale (1)
39- 44 F6.3 yr TDCF ? Discrete correlation function timescale (1)
46- 51 F6.3 yr TP ? Lomb-Scargle periodogram timescale (1)
53- 56 A4 --- Note Note(s) on timescales (2)
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Note (1): All time scales are in the observer's frame.
Note (2): Note on timescales as follows:
1 = faint source
2 = multiple time scales
3 = exceptionally large errors in TDCF
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Nov-2011