J/ApJ/914/47ivo://CDS.VizieR/J/ApJ/914/47doi:10.26093/cds/vizier.19140047CDSKashi A.Principe D.A.Soker N.Kastner J.H.2023-01-16T09:38:37Z2022-12-28T15:25:04ZCDS support team

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

cds-question@unistra.frmultiple-starsx-ray-sourceschemical-abundancesThe massive binary system Eta Carinae is characterized by intense colliding winds that form shocks and emit X-rays. The system is highly eccentric (e~0.9), resulting in modulated X-ray emission during its 5.54yr orbit. The X-ray flux increases in the months prior to periastron passage, exhibiting strong flares, then rapidly declines to a flat minimum lasting a few weeks, followed by a gradual recovery. We present the Neutron Star Interior Composition Explorer telescope spectra obtained before, during, and after the 2020 X-ray minimum, and perform spectral analysis to establish the temporal behavior of the X-ray flux and X-ray-absorbing column density (N_H_(t)) for the 2-10keV and 5-10keV energy ranges. The latter range is dominated by the stellar wind-collision region and, therefore, these spectral parameters-in particular, N_H_(t)-serve as potentially stringent constraints on the binary orientation. We compare the observed N_H_(t) results to the behavior predicted by a simple geometrical model in an attempt to ascertain which star is closer to us at periastron: the more massive primary ({omega}~240{deg}-270{deg}) or the secondary ({omega}~90{deg}). We find that the variations in column density, both far from periastron and around periastron passage, support the latter configuration ({omega}~90{deg}). The 2020 X-ray minimum showed the fastest recovery among the last five minima, providing additional evidence for a recent weakening of the primary star's wind.2021ApJ...914...47Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/914/47CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/133/299 : Long-term spectroscopy of eta Carinae (Damineli+ 1998)J/A+A/343/847 : Geneva Photometry of Eta Car (van Genderen+ 1999)J/A+A/419/215 : Emission lines of Sr filament near {eta} Car (Hartman+, 2004)J/AJ/129/2018 : RXTE scaled fluxes of eta Car (Corcoran+, 2005)J/ApJS/157/138 : UV spectrum of eta Car (Nielsen+, 2005)J/ApJS/163/173 : UV spectrum of eta Car in 2003.5 (Gull+, 2006)J/ApJS/168/289 : NUV spectrum of eta Car in 2003.5 (Nielsen+, 2007)J/AJ/135/1249 : The early spectra of eta Carinae (Humphreys+, 2008)J/ApJS/181/473 : Analysis of the spectrum of {eta} Car (Nielsen+, 2009)J/A+A/493/1093 : BVRI light curves of {eta} Car (Fernandez-Lajus+, 2009)J/other/NewA/15.108 : eta Car UBVRIHa LCs in 2009 (Fernandez-Lajus+ 2010)J/ApJS/194/2 : Chandra Carina Complex Project (CCCP) cat. (Broos+, 2011)J/A+A/540/A133 : {eta} Car emission spectrum (1700-10400{AA}) (Zethson+, 2012)J/ApJ/751/73 : Equivalent widths in {eta} Cat in 1998-2012 (Mehner+, 2012)J/A+A/564/A14 : Near-infrared photometry of {eta} Carinae (Mehner+, 2014)J/A+A/578/A122 : eta Carinae's 2014.6 spectroscopic event (Mehner+, 2015)J/AJ/150/109 : Spectroscopy of {eta} Car in 2009 (Richardson+, 2015)J/A+A/594/A106 : eta Car velocity-resolved imaging (Weigelt+, 2016)J/ApJ/838/45 : eta Car obs. around the 2014 X-ray min. (Corcoran+, 2017)http://heasarc.gsfc.nasa.gov/W3Browse/nicer/nicermastr.html : NICER home pagehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/914/47https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/914/47http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/914/47https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/914/47https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/914/47http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/914/47GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-raydefaultJ/ApJ/914/47/table1Best-fit model parameters to the 2-10keV NICER X-ray spectra of Eta Car between July 2017 and July 2020 and their 90% confidence valuesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateNICER Observation Date, UT, ISO-8601stime.epoch;obsnullableObsIDUnique observation numbermeta.id;obsl_NHLimit flag on NH (G1)meta.code.errorcharNH[0.7/34.7]? Absorbing column density1e+22cm**-2phys.columnDensityfloatnullableE_NH[0.1/490]? Upper 90% confidence interval on NH1e+22cm**-2stat.error;stat.maxfloatnullablee_NH[0.1/21]? Lower 90% confidence interval on NH1e+22cm**-2stat.errorfloatnullablel_kTLimit flag on kT (G1)meta.code.error;phys.energycharkT[0.7/7.4]? Plasma energykeVphys.temperature;em.X-rayfloatnullableE_kT[0.1/34.5]? Upper 90% confidence interval on kTkeVstat.error;stat.maxfloatnullablee_kT[0.1/3.7]? Lower 90% confidence interval on kTkeVstat.error;phys.energyfloatnullablel_FeLimit flag on Fe (G1)meta.code.error;phys.abund.FecharFe[0.12/49.38]? Iron abundance, relative to Solarlog(Sun)phys.abundfloatnullableE_Fe[0.02/1.2]? Upper 90% confidence interval on Felog(Sun)stat.error;stat.maxfloatnullablee_Fe[0.02/0.8]? Lower 90% confidence interval on Felog(Sun)stat.error;phys.abund.FefloatnullablelogEM[56.53/58.56] Log of the emission measurelog(cm**-3)phys.emissMeasurefloatE_logEM[0.01/1.7] Upper 90% confidence interval on logEMlog(cm**-3)stat.error;stat.maxfloate_logEM[0.01/1.2] Lower 90% confidence interval on logEMlog(cm**-3)stat.errorfloatFlux[0.1/30] Observed flux in the 2-10keV band, 10-11 erg/s/cm2 (G2)1e-14W.m**-2phot.flux;em.X-ray.mediumfloatE_Flux[0.03/5.5] Upper 90% confidence interval on Flux1e-14W.m**-2stat.error;stat.maxfloate_Flux[0.04/5.6] Lower 90% confidence interval on Flux1e-14W.m**-2stat.error;phot.fluxfloatchi2[0.44/1.5] Reduced {chi}^2 value associated with the best fit modelstat.fit.chi2floatJ/ApJ/914/47/table2Best-fit model parameters to the 5-10keV NICER X-ray spectra of Eta Car between July 2017 and July 2020 and their 90% confidence valuesE_Flux[0.1/28]? Upper 90% confidence interval on Flux1e-14W.m**-2stat.error;stat.maxfloatnullablee_Flux[0.03/10]? Lower 90% confidence interval on Flux1e-14W.m**-2stat.error;phot.fluxfloatnullableIntFlux[0.1/56] Intrinsic (i.e., unabsorbed) flux in the 5-10keV band, 10^-11^erg/s/cm2 (G2)1e-14W.m**-2phot.flux;em.X-ray.mediumfloatE_IntFlux[0.1/50] Upper 90% confidence interval on Flux1e-14W.m**-2stat.error;stat.maxfloate_IntFlux[0.08/49] Lower 90% confidence interval on Flux1e-14W.m**-2stat.errorfloatchi2[0.3/2.94] Reduced {chi}^2 value associated with the best fit modelstat.fit.chi2floatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateNICER Observation Date, UT, ISO-8601stime.epoch;obsnullableObsIDUnique observation numbermeta.id;obsl_NHLimit flag on NH (G1)meta.code.errorcharNH[8/430]? Absorbing column density1e+22cm**-2phys.columnDensityintnullableE_NH[4/293]? Upper 90% confidence interval on NH1e+22cm**-2stat.error;stat.maxintnullablee_NH[4/78]? Lower 90% confidence interval on NH1e+22cm**-2stat.errorintnullablel_kTLimit flag on kT (G1)meta.code.error;phys.energycharkT[0.3/8]? Plasma energykeVphys.temperature;em.X-rayfloatnullableE_kT[0.2/13.7]? Upper 90% confidence interval on kTkeVstat.error;stat.maxfloatnullablee_kT[0.1/5.1]? Lower 90% confidence interval on kTkeVstat.error;phys.energyfloatnullablel_FeLimit flag on Fe (G1)meta.code.error;phys.abund.FecharFe[0.13/6.72]? Iron abundance, relative to Solarlog(Sun)phys.abundfloatnullableE_Fe[0.04/2.3]? Upper 90% confidence interval on Felog(Sun)stat.error;stat.maxfloatnullablee_Fe[0.04/0.7]? Lower 90% confidence interval on Felog(Sun)stat.error;phys.abund.FefloatnullablelogEM[56.47/60.24] Log of the emission measurelog(cm**-3)phys.emissMeasurefloatE_logEM[0.07/3.2] Upper 90% confidence interval on logEMlog(cm**-3)stat.error;stat.maxfloate_logEM[0.05/2.3] Lower 90% confidence interval on logEMlog(cm**-3)stat.errorfloatl_FluxLimit flag on Flux (G1)meta.code.error;phot.fluxcharFlux[0.03/14]? Observed flux in the 5-10keV band, 10^-11^erg/s/cm2 (G2)1e-14W.m**-2phot.flux;em.X-ray.mediumfloatnullable