J/ApJ/933/136 0.4-10keV X-ray monitoring of Eta Car (Espinoza-Galeas+, 2022) ================================================================================ NICER X-ray observations of Eta Carinae during its most recent periastron Passage. Espinoza-Galeas D., Corcoran M.F., Hamaguchi K., Russell C.M.P., Gull T.R., Moffat A.F.J., Richardson N.D., Weigelt G., Hillier D.J., Damineli A., Stevens I.R., Madura T., Gendreau K., Arzoumanian Z., Navarete F. =2022ApJ...933..136E ================================================================================ ADC_Keywords: Binaries, X-ray ; X-ray sources Keywords: Stellar winds ; X-ray sources ; Stellar evolution Abstract: We report high-precision X-ray monitoring observations in the 0.4-10keV band of the luminous, long-period colliding wind binary Eta Carinae, up to and through its most recent X-ray minimum/periastron passage in 2020 February. Eta Carinae reached its observed maximum X-ray flux on 2020 January 7, at a flux level of 3.30x10^-10^ergs/s/cm2, followed by a rapid plunge to its observed minimum flux, 0.03x10^-10^ergs/s/cm2, near 2020 February 17. The NICER observations show an X-ray recovery from the minimum of only ~16 days, the shortest X-ray minimum observed so far. We provide new constraints for the "deep" and "shallow" minimum intervals. Variations in the characteristic X-ray temperatures of the hottest observed X-ray emission indicate that the apex of the wind-wind "bow shock" enters the companion's wind acceleration zone about 81 days before the start of the X-ray minimum. There is a steplike increase in column density just before the X-ray minimum, probably associated with the presence of dense clumps near the shock apex. During the recovery and after, the column density shows a smooth decline, which agrees with previous NH measurements made by Swift at the same orbital phase, indicating that the changes in the mass-loss rate are only a few percent over the two cycles. Finally, we use the variations in the X-ray flux of the outer ejecta seen by NICER to derive a kinetic X-ray luminosity of the ejecta of ~10^41^ergs/s near the time of the "Great Eruption." Description: NICER (the Neutron Star Interior Composition Explorer) is an X-ray astronomy facility attached to the International Space Station (ISS). NICER is devoted to time-resolved X-ray spectrometry in the 0.2-12.0keV energy band (see table 2 for characteristics of NICER). NICER was launched on 2017-June-3 and deployed at the ISS on 2017-June-16. NICER's primary mission is to obtain X-ray spectrometry with high time, moderate spectral resolution and and 30arcmin^2 restricted field of view of cosmic X-ray sources, primarily of X-ray binary pulsars. NICER's combination of a large effective area, a restricted field of view, and a broad bandpass in the thermal X-ray range makes it especially well suited to observing X-ray variables like long-period colliding wind binaries (and other sources), in addition to X-ray pulsars. NICER observed {eta} Car between 2017-July-20 and 2021-February-21 and has provided frequent measurements of {eta} Car's X-ray spectrum, typically twice per month, with appropriately increased sampling near the periastron, when the variation in the X-ray spectrum occurs on timescales of days. In order to obtain a better estimation of the temperatures and the column densities from the NICER spectra, we used an {eta} Car spectrum template with all the available dispersed spectra from Chandra HETG (High Energy Transmission Grating). We combined the 32 CHANDRA HETG observations in Table 4 to obtain a high-precision dispersed X-ray spectrum, with a total exposure of 2Ms and an exposure-weighted average phase of 0.73. See section 4.1. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 10 45 03.54 -59 41 03.9 * eta Car = TYC 8626-2809-1 ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table4.dat 50 39 HETG Chandra observations (0.4-10.0 keV) table6.dat 99 265 Log of NICER observations and rates table7.dat 102 265 NICER spectral modeling parameters -------------------------------------------------------------------------------- See also: B/chandra : The Chandra Archive Log (CXC, 1999-2014) B/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017) J/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/A+A/465/993 : Spectral atlas of massive stars around He I (Groh+, 2007) 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/A+A/493/1093 : BVRI light curves of {eta} Car (Fernandez-Lajus+, 2009) J/ApJS/181/473 : Analysis of the spectrum of {eta} Car (Nielsen+, 2009) J/other/NewA/15.108 : UBVRIHa of {eta} Car in 2009 (Fernandez-Lajus+ 2010) 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/ApJ/808/174 : FeII radiative transition rates (Bautista+, 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 minimum (Corcoran+, 2017) J/ApJ/914/47 : ISS/NICER X-ray observations of eta Car (Kashi+, 2021) Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 5 I5 --- ObsID [632/23131] Observation identifier 7- 15 F9.2 s Exptime [14703.7/102189.1] Exposure time 17- 35 A19 "datime" Date Date of observation (UT) 37- 44 F8.2 d MJD [51867.6/58875.9] Modified Julian Date 46- 50 F5.3 --- Phase [0.527/3.991] Phase -------------------------------------------------------------------------------- Byte-by-byte Description of file: table6.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 I10 --- OBSID [1110010101/3651032801] NICER Observation identifier 12- 21 F10.4 d MJD-Start [57954/59176] Modified Julian Date at observation start 23- 32 F10.4 d MJD-End [57954/59176] Modified Julian Date at observation end 34- 39 F6.4 --- Phase [3.534/4.138] Phase 41- 46 F6.1 s Exptime [109/9946] Exposure time 48- 52 F5.2 ct/s CR2-10keV [0.25/32.42] Total Rate, 2.0-10.0 keV 54 A1 --- l_CR2-10keVNet Limit flag for CR2-10keVNet 55- 59 F5.2 ct/s CR2-10keVNet [0.02/31.87] Net Rate, 2.0-10.0 keV 61- 64 F4.2 ct/s e_CR2-10keVNet [0.01/0.4]? Uncertainty in CR2-10keVNet 66- 70 F5.2 ct/s CR2-3keV [0.05/13.07] Total Rate, 2.0-3.0 keV 72 A1 --- l_CR2-3keVNet Limit flag for CR2-3keVNet 73- 77 F5.2 ct/s CR2-3keVNet [0.01/12.96] Net Rate, 2.0-3.0 keV 79- 82 F4.2 ct/s e_CR2-3keVNet [0.01/0.25]? Uncertainty in CR2-3keVNet 84- 87 F4.2 ct/s CR5-7keV [0.05/4.24] Total Rate, 5.0-7.0 keV 89 A1 --- l_CR5-7keVNet Limit flag for CR5-7keVNet 91- 94 F4.2 ct/s CR5-7keVNet [0.01/4.16] Net Rate, 5.0-7.0 keV 96- 99 F4.2 ct/s e_CR5-7keVNet [0.01/0.15]? Uncertainty in CR5-7keVNet -------------------------------------------------------------------------------- Byte-by-byte Description of file: table7.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 I10 --- OBSID [1110010101/3651032801] NICER Observation identifier 12- 15 F4.2 --- Phase [3.53/4.14] Phase 17- 21 F5.2 10-14W/m2 Flux [0.01/30.43] Flux, 10^-11^ergs/cm2/s 23- 26 F4.2 10+22cm-2 NH3 [3.0/5.0]? Column density, NH3 28- 31 F4.2 10+22cm-2 e_NH3 [0.02/5.25]? Uncertainty in NH3 33- 33 A1 --- l_kT4 Limit flag for kT4 35- 38 F4.2 keV kT4 [1.0/2.0]? weighted average temperature 40- 43 F4.2 keV e_kT4 [0.01/2.08]? Uncertainty in kT4 45- 48 F4.2 10+58cm-3 EM4 [0.0/6.33]? Emission measure 50- 54 F5.2 10+58cm-3 e_EM4 [0.0/11.73]? Uncertainty in EM4 56- 61 F6.2 10+22cm-2 NH5 [3.0/200.0]? Column density, NH5 63- 68 F6.2 10+22cm-2 e_NH5 [0.05/182.9]? Uncertainty in NH5 70- 70 A1 --- l_kT6 Limit flag for kT6 72- 75 F4.2 keV kT6 [2.0/6.0]? weighted average temperature 77- 80 F4.2 keV e_kT6 [0.1/4.02]? Uncertainty in kT6 82- 85 F4.2 10+58cm-3 EM6 [0.04/3.88]? Emission measure 87- 90 F4.2 10+58cm-3 e_EM6 [0.02/7.42]? Uncertainty in EM6 92- 96 F5.2 10-5ph/cm2/s Flux-FeK [0.74/51.31]? Flux, FeK 98-102 F5.2 10-5ph/cm2/s e_Flux-FeK [0.6/14.8]? Uncertainty in Flux-FeK -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Katia van der Woerd [CDS] 17-Jul-2024