J/ApJ/874/13 24yr of radio observations of V404 Cygni (Plotkin+, 2019)
Radio variability from a quiescent stellar-mass black hole jet.
Plotkin R.M., Miller-Jones J.C.A., Chomiuk L., Strader J., Bruzewski S.,
Bundas A., Smith K.R., Ruan J.J.
<Astrophys. J., 874, 13 (2019)>
=2019ApJ...874...13P 2019ApJ...874...13P
ADC_Keywords: Binaries, X-ray; Black holes; Radio sources
Keywords: accretion, accretion disks ; stars: black holes ;
stars: individual (V404 Cygni) ; X-rays: binaries
Abstract:
Relativistic outflows are believed to be a common feature of black
hole X-ray binaries (BHXBs) at the lowest accretion rates, when they
are in their "quiescent" spectral state. However, we still lack a
detailed understanding of how quiescent jet emission varies with time.
Here we present 24yr of archival radio observations (from the Very
Large Array and the Very Long Baseline Array) of the BHXB V404 Cygni
in quiescence (totaling 150 observations from 1.4 to 22GHz). The
observed flux densities follow lognormal distributions with means and
standard deviations of (<logfν>,σlogfν)=(-0.53,0.19) and
(-0.53,0.30) at 4.9 and 8.4GHz, respectively (where fν is the flux
density in units of mJy). As expected, the average radio spectrum is
flat with a mean and standard deviation of
(<αr,σαr)=(0.02,0.65), where
fν∝ναr_^. We find that radio flares that increase
the flux density by factors of 2-4 over timescales as short as <10
minutes are commonplace, and that long-term variations (over 10-4000
day timescales) are consistent with shot-noise impulses that decay to
stochastic variations on timescales ≲10 days (and perhaps as short as
tens of minutes to several hr). We briefly compare the variability
characteristics of V404 Cygni to jetted active galactic nuclei, and we
conclude with recommendations on how to account for variability when
placing quiescent BHXB candidates with radio luminosities comparable
to V404 Cygni (LR∼1028erg/s) onto the radio/X-ray luminosity plane.
Description:
In this paper, we reanalyze all observations of the black hole X-ray
binary V404 Cygni in quiescence with the VLA through 2015, and we also
consider observations with the Very Long Baseline Array (VLBA).
We monitored V404 Cygni with the VLBA over 13 (approximately)
fortnightly observations between 2014 February 3 and August 22 under
program code BM399 (PI: Miller-Jones). Each observation lasted 2hr,
yielding ∼56min on source. We observed with all available antennas,
using 256MHz of bandwidth centered on a frequency of 4.98GHz.
We also identified an additional VLBA observation at 8.4GHz reported
by Miller-Jones+ (2009ApJ...706L.230M 2009ApJ...706L.230M) taken on 2008 November 17 under
program code BM290 which we rereduced.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
20 24 03.82 +33 52 01.9 V404 Cygni = V* V404 Cyg
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 100 163 Catalog of radio observations
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See also:
VIII/99 : Catalogue of Radio Stars (Wendker, 2001)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/A+A/493/339 : XMM-Newton serendipitous Survey. V. (Watson+, 2009)
J/AJ/138/1874 : MOJAVE. VI. Kinematic analysis of blazar jets (Lister+, 2009)
J/ApJ/722/520 : Gamma-ray light curves of Fermi blazars (Abdo+, 2010)
J/MNRAS/428/2500 : GX 339-4 radio/X-ray flux correlation (Corbel+, 2013)
J/ApJ/764/135 : Spectroscopic redshifts of BL Lac objects (Shaw+, 2013)
J/ApJS/210/18 : X-ray survey of the Galactic Bulge (CXOGBS) (Jonker+, 2014)
J/BaltA/24/395 : X-ray and radio sources in binaries (Malkov+, 2015)
J/A+A/587/A61 : BlackCAT, stellar-mass BH in X-ray (Corral-Santana+, 2016)
J/ApJ/826/37 : Fermi/GBM obs. of V404 Cygni 2015 outburst (Jenke+, 2016)
J/ApJS/222/15 : WATCHDOG: an all-sky database of Gal. BHXBs (Tetarenko+, 2016)
J/MNRAS/471/1468 : Transient BH X-ray binaries XMM obs. (Eckersall+, 2017)
J/ApJ/853/150 : Spectral analysis of low-mass X-ray binaries (Sonbas+, 2018)
J/ApJ/869/171 : Chandra observations of NuSTAR sources (Tomsick+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y [1991/2015] Year of observation
6- 7 I2 "month" Obs.M Month of observation
9- 10 I2 d Obs.D Day of observation
12- 20 F9.3 d MJD [48524.9/57239.2] Modified Julian day
22- 28 A7 --- PID Program identifier
30- 33 A4 --- Config Configuration (1)
35- 39 F5.1 min Tos [4.2/540] Dwell time on V404 Cygni
41- 44 F4.1 GHz Freq [1.4/22.5] Central observing frequency
46 A1 --- l_fnu Upper limit flag on fnu
48- 53 F6.3 mJy fnu [0.1/37]? Flux density or 5σ upper limit
55- 59 F5.3 mJy e_fnu [0.005/0.18]? Error in fnu
61 A1 --- l_Sp+Index Limit flag on Sp+Index
63- 67 F5.2 --- Sp+Index [-1.97/1.8]? Spectral index alpha
(fν~ν+alpha)
69- 72 F4.2 --- e_Sp+Index [0.03/0.44]? Error in Sp+Index
74- 78 A5 --- Fluxcal Source used for flux calibration
(3C286 or 3C48)
80- 87 A8 --- Phasecal Source used to solve complex gains (2007+404,
2023+318 or 2025+337)
89-100 A12 --- PI Principal investigator of VLA program
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Note (1): The configuration of the VLA during the observation, except
for "vlba", which denotes that the observation was taken
with the VLBA .
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Aug-2020