J/MNRAS/532/3069ivo://CDS.VizieR/J/MNRAS/532/3069doi:10.26093/cds/vizier.75323069CDSJarvela E.Savolainen T.Berton M.Lahteenmaki A.Kiehlmann S.,Hovatta T.Varglund I.Readhead A.C.S.Tornikoski M.Max-moerbeck W.,Reeves R.A.Suutarinen S.2025-02-12T20:12:13Z2024-10-17T14:18:49ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiradio-galaxiesseyfert-galaxiesWe report on the discovery of one of the most extreme cases of high-frequency radio variability ever measured in active galactic nuclei (AGNs), observed on time-scales of days and exhibiting variability amplitudes of 3-4 orders of magnitude. These sources, all radio-weak narrow-line Seyfert 1 (NLS1) galaxies, were discovered some years ago at Aalto University Metsahovi Radio Observatory (MRO) based on recurring flaring at 37 GHz, strongly indicating the presence of relativistic jets. In subsequent observations with the Karl G. Jansky Very Large Array (JVLA) at 1.6, 5.2, and 9.0GHz no signs of jets were seen. To determine the cause of their extraordinary behaviour, we observed them with the JVLA at 10, 15, 22, 33, and 45GHz, and with the Very Long Baseline Array (VLBA) at 15GHz. These observations were complemented with single-dish monitoring at 37 GHz at MRO, and at 15GHz at Owens Valley Radio Observatory (OVRO). Intriguingly, all but one source either have a steep radio spectrum up to 45GHz, or were not detected at all. Based on the 37GHz data, the time-scales of the radio flares are a few days, and the derived variability brightness temperatures and variability Doppler factors are comparable to those seen in blazars. We discuss alternative explanations for their extreme behaviour, but so far no definite conclusions can be made. These sources exhibit radio variability at a level rarely, if ever, seen in AGN. They might represent a new type of jetted AGN, or a new variability phenomenon, and thus deserve our continued attention.2024MNRAS.532.3069Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/532/3069CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/532/3069https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/532/3069http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/532/3069https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/532/3069https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/532/3069http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/532/3069GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/532/3069/sample (Basic properties of the (table 1))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/532/3069/sample?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/532/3069/sample?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/532/3069/sample?GETtext/xml+votable180.050000true157.27787555.94034720.0055555555555555566/6066 9427 9868 10975 11374 11483https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/532/3069?format=asciiRadiodefaultJ/MNRAS/532/3069/sampleBasic properties of the (table 1)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNoteBand the coordinates are from (1)meta.notecharSNameShort aliasmeta.idcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainzredshiftsrc.redshiftfloatScaleScale at the redshift of the sourcekpc/arcmininstr.scalefloatlogMBHlogarithmic black hole mass (2)log(solMass)phys.massfloatLSenvlarge-scale environment (3)meta.notecharHostHost galaxy morphology (4)src.morph.typecharSimbadNameSimbad column added by the CDSmeta.idcharnullableSDSSSource SDSS namemeta.id;meta.maincharJ/MNRAS/532/3069/table3Interferometric data (JVLA, VLBA)e_Fint? Integrated flux density errormJystat.errorfloatnullablermsrmsuJy/beamstat.errorintBeamMajBeam major axisarcsecphys.angSizedoubleBeamMinBeam minor axisarcsecphys.angSize;srcdoubleBeamPA[] Beam position angledegpos.posAng;instr.beamfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSource SDSS namemeta.id;meta.maincharFreqFrequency (10,15,22,33,43,45)GHzem.freqintTimeTime of the observationyrtime.epochdoublel_FpeakUpper limit flag for peak flux densitymeta.code.errorcharFpeakPeak flux densitymJy/beamphot.fluxfloate_Fpeak? Peak flux density errormJy/beamstat.errorfloatnullableFint? Integrated flux densitymJyphot.fluxfloatnullableJ/MNRAS/532/3069/table4Single dish data (MRO and OVRO)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSource SDSS namemeta.id;meta.maincharFreq[15 37] Frequency (15 for OVRO, 37 for MRO)GHzem.freqintTimeTime of the observationyrtime.epochdoublel_FluxUpper limit flag for flux densitymeta.code.error;phot.fluxcharFluxFlux densitymJyphot.fluxdoublee_Flux? Flux density errormJystat.error;phot.fluxfloatnullable