Diffuse Low-Ionization Gas in the Galactic Halo Casts Doubts on $zsimeq 0.03$ WHIM Detections

In this Letter we demonstrate that the two claims of $zsimeq 0.03$ OVII K$alpha$ absorption lines from Warm Hot Intergalactic Medium (WHIM) along the lines of sight to the blazars H~2356-309 (Buote et al., 2009; Fang et al., 2010) and Mkn~501 (Ren, Fang & Buote, 2014) are likely misidentifications of the $z=0$ OII K$beta$ line produced by a diffuse Low-Ionization Metal Medium in the Galaxys Interstellar and Circum-Galactic mediums. We perform detailed modeling of all the available high signal-to-noise Chandra LETG and XMM-Newton RGS spectra of H 2356-309 and Mkn 501 and demonstrate that the $zsimeq 0.03$ WHIM absorption along these two sightlines is statistically not required. Our results, however, do not rule out a small contribution from the $zsimeq 0.03$ OVII K$alpha$ absorber along the line of sight to H~2356-309. In our model the temperature of the putative $z = 0.031$ WHIM filament is T$= 3times 10^5$ K and the OVII column density is N$_{OV II} le 4times 10^{15}$ cm$^{-2}$, twenty times smaller than the OVII column density previously reported, and now more consistent with the expectations from cosmological hydrodynamical simulations.