J/A+A/704/A198ivo://CDS.VizieR/J/A+A/704/A198CDSBaglio M.C.Alabarta K.Russell D.M.Masetti N.Messa M.M.,Munoz-Darias T.Vincentelli F.M.Rout S.K.Saikia P.Gabuya A.,Chavushyan V.Al Qaissieh T.Palado A.2026-03-02T06:25:50Z2025-12-09T11:47:45ZCDS support team

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

cds-question@unistra.frx-ray-binary-starsblack-holesphotometryvisible-astronomyspectroscopyultraviolet-astronomyWe present a study of the evolution of the minute-timescale optical variability and of the optical spectroscopic signatures of outflows in the black hole X-ray binary MAXI J1820+070 during its main 2018 outburst and subsequent re-brightenings. Multi-filter, minute-cadence optical light curves were obtained with the Las Cumbres Observatory network and the Al Sadeem Observatory (UAE) over 2018-2020, complemented by archival X-ray data from Swift/BAT and XRT and from MAXI. We also acquired contemporaneous low-resolution optical spectra with the 2.1 m OAN San Pedro Martir (Mexico), the 2.1m OAGH Cananea (Mexico), and the "G.D. Cassini" 1.5m telescope at Loiano (Italy). The optical fractional rms is highest in the hard state and is best described by short time-scale flickering that is stronger at longer wavelengths. This suggests that the minute-timescale optical variability is driven by the jet in the hard state. In this scenario, the variability could be due to variations in the inflow that inject velocity fluctuations at the base of the jet (internal shock model). The variability is then quenched in the soft state, with any residual signal likely associated with variability in the accretion flow. This is in agreement with the accretion-ejection coupling in black hole binaries and confirms that the variability signature of the jet is present at optical wavelengths in all hard states. In the dimmest hard states, any residual optical variability may instead be linked to cyclo-synchrotron emission from the hot flow. The optical spectra reveal double-peaked emission lines and possible signatures of cold winds during the hard state. Such winds were previously reported in this source during the main 2018 outburst; here we provide one of the first tentative detections of their presence also during the subsequent re-brightenings. The absence of optical wind signatures in the soft state likely reflects a higher level of disc ionisation driven by the increased X-ray flux, which suppresses the low-ionisation features detectable in the optical band.2025A&A...704A.198Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/704/A198CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/889/142 : MAXI J1820+070 Swift/XRT & NICER timing study (Stiele+, 220)J/MNRAS/493/L81 : Radio astrometry of MAXI J1820+070 (Atri+, 2020)J/MNRAS/496/L96 : Polarization of LMXB MAXI J1820+070 (Kosenkov+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/704/A198https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/704/A198http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/704/A198https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/704/A198https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/704/A198http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/704/A198GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/704/A198/list (List of fits spectra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/704/A198/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/704/A198/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/704/A198/list?GETtext/xml+votable180.050000true275.09141677.18533330.0055555555555555566/31817https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/704/A198?format=asciiX-rayUVOpticaldefaultJ/A+A/704/A198/gbandLCO g'-band (AB) photometry from the XB-NEWS pipelinerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, mid-exposure (UTC)dtime.epochdoublemag? Magnitude in Band (1)magphot.magfloatnullablee_mag? Magnitude uncertainty on Bandmagstat.error;phot.magfloatnullableBand[griRV] Observed bandinstr.bandpasscharJ/A+A/704/A198/ibandLCO i'-band (AB) photometry from the XB-NEWS pipelinerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, mid-exposure (UTC)dtime.epochdoublemag? Magnitude in Band (1)magphot.magfloatnullablee_mag? Magnitude uncertainty on Bandmagstat.error;phot.magfloatnullableBand[griRV] Observed bandinstr.bandpasscharJ/A+A/704/A198/gbandaAl Sadeem Observatory Blue (g'-band, AB) photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, mid-exposure (UTC)dtime.epochdoublemag? Magnitude in Band (1)magphot.magfloatnullablee_mag? Magnitude uncertainty on Bandmagstat.error;phot.magfloatnullableBand[griRV] Observed bandinstr.bandpasscharJ/A+A/704/A198/rbandaAl Sadeem Observatory Red (R-band, Vega) photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, mid-exposure (UTC)dtime.epochdoublemag? Magnitude in Band (1)magphot.magfloatnullablee_mag? Magnitude uncertainty on Bandmagstat.error;phot.magfloatnullableBand[griRV] Observed bandinstr.bandpasscharJ/A+A/704/A198/vbandaAl Sadeem Observatory Green (V-band, Vega) photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJDModified Julian Date, mid-exposure (UTC)dtime.epochdoublemag? Magnitude in Band (1)magphot.magfloatnullablee_mag? Magnitude uncertainty on Bandmagstat.error;phot.magfloatnullableBand[griRV] Observed bandinstr.bandpasscharJ/A+A/704/A198/listList of fits spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Simbad right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Simbad declination (J2000)pos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablebLambdaLower value of wavelength interval0.1nmem.wlfloatBLambdaUpper value of wavelength interval0.1nmem.wlfloatdLambdaWavelength resolution0.1nm/pixspect.resolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTelTelescope (1)meta.id;instr.telcharInstInstrumentmeta.id;instrcharExpTimeExposure timestime.duration;obs.exposureintAirmassAirmassobs.airMassfloat