Decline of the 2-10 keV Emission from Eta Carinae
ATel #6338; Jamar Liburd (U. VI), Michael F. Corcoran (NASA/GSFC-CRESST/USRA), Kenji Hamaguchi (NASA/GSFC-CRESST/UMBC), Theodore Gull (NASA/GSFC), Thomas Madura (NASA/GSFC/NPP), Mairan Teodoro (NASA/GSFC/CNPq), Anthony Moffat and Noel Richardson (U. Montreal), Chris Russell (U. Delaware), Andrew Pollock (ESA), Stan Owocki (U. Delaware)
on 23 Jul 2014; 21:23 UT
Credential Certification: Michael Corcoran (michael.f.corcoran@nasa.gov)
Subjects: X-ray, Binary, Star
Analysis of Eta Car's X-ray spectrum in the 2-10 keV band using processed data from the X-ray Telescope on Swift reveals a peak flux on July 16, 2014 of 0.046 photons s-1cm-2 (3.37±0.15×10-10 ergs s-1cm-2). This flux is similar to the previous maximum flux seen by the XRT, 3.53±0.13×10-10 ergs s-1cm-2 (0.049 photons s-1cm-2, ATEL #6298).
Since this peak on July 16, the most recent Swift XRT quicklook data show a drop in flux. On July 20, 2014 the XRT flux as seen in the quicklook data was 0.011 photons s-1cm-2 (8.3±0.5×10-11 ergs s-1cm-2). This most likely indicates that the 2-10 keV flux is in its declining phase as Eta Car approaches its deep X-ray minimum stage (Hamaguchi et al., 2014, ApJ, 784, 125) associated with periastron passage of the 2024-day binary orbit. The column density derived from analysis of the July 20 XRT quicklook data is 7.2×1022 cm-2. This is consistent with the column density seen near the same orbital phase in 2003 (7.7×1022 cm-2, Hamaguchi et al., 2007, ApJ, 663, 522). Eta Car's deep X-ray minimum phase is expected to begin on July 30, 2014. Weekly Swift/XRT observations of Eta Car in the 2-10 keV band are planned throughout the X-ray minimum.
Recent Swift/XRT fluxes of Eta Carinae, compared to the RXTE/PCA flux from the previous orbital cycle.
