J/AJ/170/316ivo://CDS.VizieR/J/AJ/170/316CDSO'Brien S.M.Schwamb M.E.Watson C.A.Nielsen L.D.Bryant E.M.,Casewell S.L.Burleigh M.R.Fortson L.Gill S.Lintott C.J.,Hobbs K.L.Apergis I.Bayliss D.Fernandez Fernandez J.Gunther M.N.,Hawthorn F.Jenkins J.S.Kendall A.McCormac J.de Mooij E.J.W.,Rodel T.Saha S.Trouille L.West R.G.Wheatley P.J.Agafitei M.C.,Apaydin D.R.Baeten E.Baller B.Carabott J.Chesson S.,Freigeiro S.A.Gonano V.Hanke M.Hermes P.Hildebrand A.,Langley J.S.Lim S.M.McCarthy L.R.Mitchell G.O'Neill K.,Pearson C.R.Reket N.Riethmiller J.Saeftel J.Sainio A.Steiner C.,Strickland A.Tanner C.Terentev I.A.Tiu E.J.P.Tumanov S.Y.,Urszula M.Vahlenkamp P.de Vroome F.Wantuch P.Woodruff T.2026-08-27T12:30:33Z2026-08-27T12:06:52ZCDS support team

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

cds-question@unistra.freclipsing-binary-starsmultiple-starsphotometryvisible-astronomym-starsdwarf-starsWe report the identification and characterization of a new binary system composed of two near-equal mass M-dwarfs. The binary NGTS-EB-8 was identified as a planet candidate in data from the Next Generation Transit Survey (NGTS) by citizen scientists participating in the Planet Hunters NGTS project. High-resolution spectroscopic observations reveal the system to be a double-lined binary. By modeling the photometric and radial velocity observations, we determine an orbital period of 4.2days and the masses and radii of both stars to be M_A_=0.250_-0.004_^+0.005^M_{sun}_, M_B_=0.208_-0.004_^+0.005^M_{sun}_, and R_A_=0.255_-0.005_^+0.004^R_{sun}_, R_B_=0.233_-0.005_^+0.006^R_{sun}_, respectively. We detect Balmer line emission from at least one of the stars but no significant flare activity. We note that both components lie in the fully convective regime of low-mass stars (<=0.35M_{sun}_); therefore, they can be a valuable test for stellar evolutionary models. We demonstrate that the photometric observations, speckle imaging, and initial radial velocity measurements were unable to identify the true nature of this system and highlight that high-resolution spectroscopic observations are crucial in determining whether systems such as this are in fact binaries.2025AJ....170..316Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/170/316CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/322A : UCAC4 Catalogue (Zacharias+, 2012)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)IV/39 : TESS Input Catalog version 8.2 (TIC v8.2) (Paegert+, 2021)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)V/152 : The DEBCat detached eclipsing binary catalogue (Southworth, 2015)J/AJ/123/3356 : Palomar/MSU nearby star spectr. survey. III. (Gizis+, 2002)J/A+A/415/1153 : [Fe/H] for 98 extra-solar planet-host stars (Santos+, 2004)J/ApJ/648/629 : Radio observations of late M, L, and T dwarfs (Berger+, 2006)J/AJ/134/2398 : Stellar SEDs in SDSS and 2MASS filters (Covey+, 2007)J/ApJ/684/635 : New low-mass eclipsing binary from SDSS-II (Blake+, 2008)J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)J/AJ/140/1402 : M dwarf flares from SDSS spectra (Hilton+, 2010)J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)J/AJ/141/166 : HATNet variability survey of K and M dwarfs (Hartman+, 2011)J/AJ/142/19 : Speckle observations of KOI (Howell+, 2011)J/ApJ/728/48 : Multicolor eclipse data for 6 new binaries (Kraus+, 2011)J/MNRAS/426/1507 : Detached M dwarf eclipsing binaries in WTS (Birkby+, 2012)J/ApJ/771/129 : Submillimetric Class II sources of Taurus (Andrews+, 2013)J/ApJ/767/95 : Improved stellar param. of smallest KIC stars (Dressing+, 2013)J/A+A/551/A112 : Metallicity-giant planet correlation (Mortier+, 2013)J/ApJ/785/126 : HIRES radial velocity measurements (Knutson+, 2014)J/A+A/566/A103 : Kepler planet host candidates imaging (Lillo-Box+, 2014)J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs (Mann+, 2015)J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)J/AJ/151/68 : Kepler Mission. VII. Eclipsing binaries in DR3 (Kirk+, 2016)J/A+A/587/A64 : Physical properties of giant exoplanets (Santerne+, 2016)J/AJ/152/180 : Bol. fluxes of eclipsing binaries in Tycho-2 (Stassun+, 2016)J/ApJS/230/16 : O5-L3 empirical stellar spectra from SDSS (Kesseli+, 2017)J/AJ/156/234 : KELT transit false positive catalog for TESS (Collins+, 2018)J/MNRAS/476/5253 : LCs for 5 LMEBs in WFCAM Transit Survey (Cruz+, 2018)J/A+A/616/A10 : 46 open clust. GaiaDR2 HR diagrams (Gaia Collaboration, 2018)J/AJ/155/114 : HAT-TR-318-007: a double-lined M dwarf binary (Hartman+, 2018)J/AJ/155/225 : M dwarf stars rotational broadening measur. (Kesseli+, 2018)J/AJ/156/102 : The TESS Input Catalog & Candidate Target List (Stassun+, 2018)J/ApJ/867/105 : ATLAS all-sky stellar ref. cat, ATLAS-REFCAT2 (Tonry+, 2018)J/ApJ/871/63 : How to constrain M dwarf. II. Nearby binaries (Mann+, 2019)J/MNRAS/488/4905 : SuperWASP transit false positive catalog (Schanche+, 2019)J/A+A/625/A68 : Radii and masses of the CARMENES targets (Schweitzer+, 2019)J/A+A/625/A150 : 10 very-low-mass stars photometry (von Boetticher+, 2019)J/AJ/159/60 : 8695 flares from 1228 stars in TESS S1 & S2 (Gunther+, 2020)J/ApJ/905/107 : Spectr. activity indicators of TIC stars (Medina+, 2020)J/ApJS/254/39 : Exoplanet candidates from TESS first 2yr obs (Guerrero+, 2021)J/AJ/162/75 : Speckle obs. TESS exoplanet host stars. II. (Lester+, 2021)J/A+A/649/A3 : Gaia EDR3 photometric passbands (Riello+, 2021)J/ApJS/258/16 : TESS Eclipsing Binary stars. I. Sectors 1-26 (Prsa+, 2022)J/A+A/693/A228 : CARMENES input catalogue of M dwarfs. IX. (Cifuentes+, 2025)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/170/316https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/170/316http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/170/316https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/170/316https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/170/316http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/170/316GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/170/316/table7 (Parameters for double-lined eclipsing binaries composed of two M-dwarfs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/170/316/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/170/316/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/170/316/table7?GETtext/xml+votable180.050000true113.656030831.86949440.0055555555555555566/3512 4298 4694 4708 6340 6544 7675 9929 10169 10739 14555 14558 14757 16490 18895 20713 21016 21676 22289 22868 23182 23229 27405 31182-31183 34301 40347 42979 44390 46796https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/170/316?format=asciiOpticaldefaultJ/AJ/170/316/table7Parameters for double-lined eclipsing binaries composed of two M-dwarfsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameSystem namemeta.id;meta.maincharPer[0.22/41.03] Perioddtime.periodfloatMassA[0.11/0.6] A star stellar masssolMassphys.massfloatE_MassA[3e-4/0.02] Upper uncertainty in MassAsolMassstat.error;stat.max;phys.massdoublee_MassA[3e-4/0.02] Lower uncertainty in MassAsolMassstat.error;stat.min;phys.massdoubleMassB[0.08/0.6] B star stellar masssolMassphys.massfloatE_MassB[3e-4/0.03] Upper uncertainty in MassBsolMassstat.error;stat.max;phys.massdoublee_MassB[3e-4/0.03] Lower uncertainty in MassBsolMassstat.error;stat.min;phys.massdoubleRadA[0.17/0.88] A star stellar radiussolRadphys.size.radiusfloatE_RadA[2e-4/0.1] Upper uncertainty in RadAsolRadstat.error;stat.max;phys.size.radiusfloate_RadA[2e-4/0.1] Lower uncertainty in RadAsolRadstat.error;stat.min;phys.size.radiusfloatRadB[0.1/0.84] B star stellar radiussolRadphys.size.radiusfloatE_RadB[2e-4/0.11] Upper uncertainty in RadBsolRadstat.error;stat.max;phys.size.radiusfloate_RadB[2e-4/0.11] Lower uncertainty in RadBsolRadstat.error;stat.min;phys.size.radiusfloatRefsReferences (1)meta.refcharSimbadNameSimbad column added by the CDSmeta.idcharnullable_RAPosition from Simbad (right ascension part)degpos.eq.ra;meta.main_DEPosition from Simbad (declination part)degpos.eq.dec;meta.mainJ/AJ/170/316/fig8Combined table from original tablesFluxNormalized Fluxphot.flux;arith.ratio;em.optdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBJDTimestamp of observation in BJDdtime.epochdoublee_FluxUncertainty on fluxstat.error;phot.flux;arith.ratiodoubleInstSource of the data (instrument/filter/sector; added by CDS) (1)meta.id;instrchar