J/A+A/592/A120ivo://CDS.VizieR/J/A+A/592/A120doi:10.26093/cds/vizier.35920120CDSFiguera Jaimes R.Bramich D.M.Kains N.Skottfelt J.Jorgensen U.G.,Horne K.Dominik M.Alsubai K.A.Bozza V.Burgdorf M.J.,Calchi Novati S.Ciceri S.D'Ago G.Evans D.F.Galianni P.Gu S.H.,Harpsoe K.B.WHaugbolle T.Hinse T.C.Hundertmark M.Juncher D.,Kerins E.Korhonen H.Kuffmeier M.Mancini L.Peixinho N.Popovas A.,Rabus M.Rahvar S.Scarpetta G.Schmidt R.W.Snodgrass C.,Southworth J.Starkey D.Street R.A.Surdej J.Tronsgaard R.,Unda-Sanzana E.von Essen C.Wang X. B.Wertz O.,(The MiNDSTEp Consortium)2018-07-02T11:07:41Z2016-08-09T07:50:53ZCDS support team

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

cds-question@unistra.frglobular-star-clustersvariable-starsphotometryWe show the benefits of using Electron-Multiplying CCDs and the shift-and-add technique as a tool to minimise the effects of the atmospheric turbulence such as blending between stars in crowded fields and to avoid saturated stars in the fields observed. We intend to complete, or improve, the census of the variable star population in globular cluster NGC 6715. Our aim is to obtain high-precision time-series photometry of the very crowded central region of this stellar system via the collection of better angular resolution images than has been previously achieved with conventional CCDs on ground-based telescopes. Observations were carried out using the Danish 1.54-m Telescope at the ESO La Silla observatory in Chile. The telescope is equipped with an Electron-Multiplying CCD that allowed to obtain short-exposure-time images (ten images per second) that were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). The high precision photometry was performed via difference image analysis employing the DanDIA pipeline. We attempted automatic detection of variable stars in the field. We statistically analysed the light curves of 1405 stars in the crowded central region of NGC 6715 to automatically identify the variable stars present in this cluster. We found light curves for 17 previously known variable stars near the edges of our reference image (16 RR Lyrae and 1 semi-regular) and we discovered 67 new variables (30 RR Lyrae, 21 long-period irregular, 3 semi-regular, 1 W Virginis, 1 eclipsing binary, and 11 unclassified).2016A&A...592A.120Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/592/A120CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/140/1500 : RR Lyrae variables in central region of M54 (Montiel+, 2010)J/AcA/64/177 : VI light curves of Galactic Bulge RR Lyrae (Soszynski+, 2014)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/592/A120https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/592/A120http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/592/A120https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/592/A120https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/592/A120http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/592/A120GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/592/A120/table3 (Ephemerides and main characteristics of the variable stars in the field of globular cluster NGC 6715)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/592/A120/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/592/A120/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/592/A120/table3?GETtext/xml+votable180.050000true283.758375-30.4764250.0055555555555555566/48035https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/592/A120?format=asciidefaultJ/A+A/592/A120/table3Ephemerides and main characteristics of the variable stars in the field of globular cluster NGC 6715recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLCPlot of the light curvesmeta.ref.urlcharVNameVariable star ID (VNNN)meta.id;meta.maincharprimaryNote[a] a: Epochs, periods, mean magnitudes, amplitudes, and classifications taken from OGLE databasemeta.notecharONamePreviously known ID assigned to the stars (1)meta.idcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainEpoch? Epoch used (HJD)dtime.epoch;instr.setupdoublenullablePer? Period measured in this work unless the variable is an OGLE star, in which case we use their perioddtime.perioddoublenullablee_Per? rms uncertainty on Perdstat.errordoublenullableImag? Median I magnitudemagphot.mag;em.opt.Ifloatnullablen_Imag[d] d: Peak magnitudemeta.notecharAmp(i+z)? Peak-to-peak amplitude in the light curve (i'+z')magsrc.var.amplitudefloatnullableNNumber of epochsmeta.numberintTypeClassification of the variablesrc.classcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/592/A120/table1Time series I photometry for all the variables studied in this workrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintVNameVariable star ID (VNNN)meta.id;meta.maincharFilt[I] Observation filterobs.param;obscharHJDHeliocentric Julian date at mid-exposuredtime.epochdoublemag.s? Standard magnitude (I band)magphot.mag;em.opt.Ifloatnullablemag.i? Instrumental magnitude (I band)magphot.mag;em.opt.Ifloatnullablee_mag.i? Magnitude uncertainty (standard or instrumental)magstat.errorfloatnullableFref? Reference flux (I band) (in ADU/s unit) (1)s**-1phot.flux.density;em.optdoublenullablee_Fref? Reference flux uncertainty (in ADU/s unit)s**-1stat.errordoublenullableDFluxDifference flux (I band) (in ADU/s unit) (1)s**-1phot.flux;arith.ratiodoublee_DFluxDifference flux uncertainty (in ADU/s unit)s**-1stat.errordoublepPhotometric scale factor (1)arith.factorfloatJ/A+A/592/A120/tableb1Cross-identification between the RR Lyrae variables listed by the CVSGGC, the variable star candidates from Montiel & Mighell and the OGLE RR Lyrae starsSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCVSGGCCVSGGC designation (VNNN), Clement et al., 2001AJ....122.2587C, Cl* NGC 6715 SAW VNNN in Simbadmeta.id;meta.maincharOGLEOGLE designation (RRLYR-NNNNN), Soszynski et al., 2014, Cat. J/AcA/64/177, OGLE BLG-RRLYR-NNNNN in Simbadmeta.idcharVCMontiel designation (VCNN), Montiel & Mighell, 2010, Cat. J/AJ/140/1500 [MM2010] VCNN in Simbadmeta.idchar