OVII and Temperature Limits on the Local Component of the Soft X-ray Diffuse Background

The local component of the ¼ keV soft X-ray diffuse background (SXDB) is believed to have its origins in a pocket of hot ionized gas, centered roughly on the Sun, known as the Local Hot Bubble (LHB). There is often disagreement on the temperature of this local component. Due to its abundance in observations of the SXDB, the flux of the OVII emission line (568 eV) is a valuable tool in assessing limits to this temperature. By correlating variations in the OVII surface brightness in observations devoid of point sources from the Suzaku X-Ray telescope with variations observed in the ¼ keV intensity from the ROSAT All Sky Survey, limits can be set on the amount of OVII originating from the LHB, and temperature limits can be drawn from these. In this research, we take twelve OVII surface brightnesses from Yoshino et al., add an additional eighteen Suzaku observations, and correlate all of the surface brightnesses with the corresponding ¼ keV ROSAT intensities. From how much correlation is seen, limits on OVII originating from the LHB are drawn, and an upper limit to the temperature is set. These limits help to further refine our model of the interstellar medium and can be used as checks for future work.

This work was supported by the National Science Foundation's REU program through NSF Award AST-1004881.