3 X-ray Brightness Changes

Figure 1 (upper panel) displays the 0.4-8 keV light curves of PG1211+143 measured by the HETGS , which were obtained from a combination of the MEG and HEG data. The observation numbers are labeled (with “1-6”) according to the time sequence of the exposures listed in the first column of Table 1. The source appeared to be at its lowest brightness at the beginning, while it reached the highest brightness on April 13 (4th observation). It then returned to a lower brightness on April 15. As can be seen, there were only moderate changes in brightness over the 9-day observation.

Figure 1 (lower panel) displays the FUV continua of PG1211+143 measured by the HST-COS . The G140L continuum light curve has an average flux of $F_{\lambda}$(1430Å $)=(2.14 \pm 0.09) \times 10^{-14}$ ergcm$^{-2}$s$^{-1}$Å$^{-1}$, and shows very small variations in two days, which is consistent with the G130M continuum $F_{\lambda}$(1430Å $)=2.18 \times 10^{-14}$ ergcm$^{-2}$s$^{-1}$Å$^{-1}$. The G140L data combined with X-ray, infrared, and radio were used for constructing the ionizing SED for the photoionization modeling discussed in §5.1.

Figure: Upper panel: long-term light curve of PG1211+143 in the 0.4-8 keV broad band observed with the Chandra -HETGS from 2015 April 9 to 17 (MJD: 57121.362-57130.351) binned using 5000-s time intervals. Lower panels: HST-COS sampling light curve. The time unit is day and zero corresponds to MJD 57121.