Diffuse Low-Ionization Gas in the Galactic Halo Casts Doubts on $z\simeq
  0.03$ WHIM Detections
  In this Letter we demonstrate that the two claims of $z\simeq 0.03$ 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 Galaxy's 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 $z\simeq 0.03$
WHIM absorption along these two sightlines is statistically not required. Our
results, however, do not rule out a small contribution from the $z\simeq 0.03$
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$= 3\times 10^5$ K
and the OVII column density is N$_{OV II} \le 4\times 10^{15}$ cm$^{-2}$,
twenty times smaller than the OVII column density previously reported, and now
more consistent with the expectations from cosmological hydrodynamical
simulations.
