J/ApJ/818/105ivo://CDS.VizieR/J/ApJ/818/105doi:10.26093/cds/vizier.18180105CDSMooley K.P.Hallinan G.Bourke S.Horesh A.Myers S.T.Frail D.A.,Kulkarni S.R.Levitan D.B.Kasliwal M.M.Cenko S.B.Cao Y.Bellm E.,Laher R.R.2018-07-02T15:15:39Z2018-01-11T12:41:52ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frWe have commenced a multiyear program, the Caltech-NRAO Stripe 82 Survey (CNSS), to search for radio transients with the Jansky VLA in the Sloan Digital Sky Survey Stripe 82 region. The CNSS will deliver five epochs over the entire ~270deg^2^ of Stripe 82, an eventual deep combined map with an rms noise of ~40{mu}Jy and catalogs at a frequency of 3 GHz, and having a spatial resolution of 3". This first paper presents the results from an initial pilot survey of a 50deg^2^ region of Stripe 82, involving four epochs spanning logarithmic timescales between 1 week and 1.5yr, with the combined map having a median rms noise of 35{mu}Jy. This pilot survey enabled the development of the hardware and software for rapid data processing, as well as transient detection and follow-up, necessary for the full 270deg^2^ survey. Data editing, calibration, imaging, source extraction, cataloging, and transient identification were completed in a semi-automated fashion within 6 hr of completion of each epoch of observations, using dedicated computational hardware at the NRAO in Socorro and custom-developed data reduction and transient detection pipelines. Classification of variable and transient sources relied heavily on the wealth of multiwavelength legacy survey data in the Stripe 82 region, supplemented by repeated mapping of the region by the Palomar Transient Factory. A total of 3.9_-0.9_^+0.5^% of the few thousand detected point sources were found to vary by greater than 30%, consistent with similar studies at 1.4 and 5 GHz. Multiwavelength photometric data and light curves suggest that the variability is mostly due to shock-induced flaring in the jets of active galactic nuclei (AGNs). Although this was only a pilot survey, we detected two bona fide transients, associated with an RS CVn binary and a dKe star. Comparison with existing legacy survey data (FIRST, VLA-Stripe 82) revealed additional highly variable and transient sources on timescales between 5 and 20yr, largely associated with renewed AGN activity. The rates of such AGNs possibly imply episodes of enhanced accretion and jet activity occurring once every ~40,000yr in these galaxies. We compile the revised radio transient rates and make recommendations for future transient surveys and joint radio-optical experiments.2016ApJ...818..105Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/818/105CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/wds : Washington Visual Double Star Catalog (Mason+ 2001-2014)IX/10A : ROSAT All-Sky Bright Source Catalog (1RXS) (Voges+ 1999)I/259 : The Tycho-2 Catalogue (Hog+ 2000)II/294 : SDSS Photometric Catalog, DR7 (Adelman- McCarthy+, 2009)VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)VIII/59 : The FIRST Survey, version 1999Jul (White+ 1999)VIII/87 : Allen Tel. Array 20cm Survey (ATATS). I. (Croft+ 2010)J/A+AS/132/305 : Extragal. radio sources at 22, 37 and 87GHzJ/ApJS/143/1 : FIRST-APM Source Catalog (McMahon+, 2002)J/AJ/127/2565 : Faint FIRST variable radio sources (De Vries+, 2004)J/AJ/130/1373 : Radio observations of the HDFS region. II (Huynh+, 2005)J/AJ/135/2470 : Radio observations of the HDFS region. IV (Huynh+, 2008)J/ApJ/689/108 : MASIV survey. II. First four epochs (Lovell+, 2008)J/ApJ/696/870 : Catalina Real-time Transient Survey CRTS (Drake+, 2009)J/ApJ/740/65 : VLA search for 5GHz radio transients (Ofek+, 2011)J/ApJS/194/29 : Observations of blazars at 15GHz (Richards+, 2011)J/ApJ/742/49 : Variable and transient radio sources in FIRSTJ/ApJS/203/15 : Counterparts to 1.4GHz ECDF-S sources (Bonzini+, 2012)J/ApJ/746/156 : Radio afterglow observations of GRBs (Chandra+, 2012)J/MNRAS/421/1644 : 843MHz MOST ATLAS catalogue (Randall+, 2012)J/A+A/553/A107 : Variability of 198 extragal. radio sources (Chen+, 2013)J/ApJ/769/125 : 1.4GHz radio variability in FIRST & SDSS Stripe 82J/MNRAS/453/4020 : ATLAS 1.4GHz Data Release 3 (Franzen+, 2015)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/818/105https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/818/105http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/818/105https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/818/105https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/818/105http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/818/105GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/818/105/table3 (Summary of the radio transient and variable sources found in this work)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/818/105/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/818/105/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/818/105/table3?GETtext/xml+votable180.050000true330.5399-0.034251940.0055555555555555565/4698 4713 4757 4758 6/18685 18686 18687 18749 18751 18766 18786 18787 18788 18790 18791 18798 18829 18830 18834 18835 18837 18838 18839 18840 18841 18842 18844 18845 18846 18851 18856 18859 18860 18862 18866 18880 19023 19025 19026 19027 19037 19038 19045 19046 19047 19052 19053 19056 19057 19058 19200 19201 192022.85864675833786e-19 3.5010283109654867e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/818/105?format=asciiRadiodefaultJ/ApJ/818/105/table3Summary of the radio transient and variable sources found in this workDEJ2000[-1.193/1.197] Declination (J2000)degpos.eq.dec;meta.mainSE1[0.09/359.852] Flux density at epoch E1mJyphot.flux.densityfloate_SE1[0.054/1.2] Error in SE1mJystat.errorfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeTimescale of search (less than 1 week, 1 month, 1.5yr, 20yr)meta.notecharVTCVTC name (VTC JHHMMSS+DDMMSS in SIMBAD)meta.id;meta.maincharRAJ2000[329.252/353.256] Right ascension (J2000)degpos.eq.ra;meta.mainSE2[0.271/324.569] Flux density at epoch E2mJyphot.flux.densityfloate_SE2[0.044/0.769] Error in SE2mJystat.errorfloatSE3[0.046/362.536] Flux density at epoch E3mJyphot.flux.densityfloate_SE3[0.047/1.024] Error in SE3mJystat.errorfloatSE4[0.098/545.119] Flux density at epoch E4mJyphot.flux.densityfloate_SE4[0.041/0.403] Error in SE4mJystat.errorfloatm[-0.81/1.61] Modulation indexsrc.var.indexfloatl_Sf[<] Limit flag on Sf (1)meta.code.errorcharSf[0.49/617.48] FIRST flux densitymJyphot.flux.density;em.radio.750-1500MHzfloate_Sf[0.09/0.89]? Error in SfmJystat.errorfloatnullablel_Sh[<] Limit flag on Sh (1)meta.code.errorcharSh[0.17/397.62]? Hodge et al. (2011, Cat. J/AJ/142/3) flux densitymJyphot.flux.density;em.radio.750-1500MHzfloatnullablee_Sh[0.05/5.57]? Error in ShmJystat.errorfloatnullablermag[8.9/25.3]? SDSS r magnitudemagphot.mag;em.opt.RfloatnullablePTF[nv/V ] Variability of optical counterpart (2)meta.code;src.varcharzsp[0.06/2.99]? Spectroscopic redshift (3)src.redshiftfloatnullablen_zsp[a] Photometric redshift estimate from SDSSmeta.notecharLum[29.1/34.7]? Radio luminosity (4)0.001W.m**-2phys.luminosity;em.radiofloatnullableIdIdentification (AGN QSO)src.classcharRCatDisplay data from the FIRST survey (Cat. VIII/92) and from Hodge et al. (Cat. J/AJ/142/3), within 1.5"meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlchar