Extracting the 21 cm EoR signal using MWA drift scan data
  The detection of redshifted hyperfine line of neutral hydrogen (HI) is the
most promising probe of the Epoch of Reionization (EoR). We report an analysis
of 55 hours of Murchison Widefield Array (MWA) Phase II drift scan EoR data.
The data correspond to a central frequency $\nu_0 = 154.24 \, \rm MHz$
($z\simeq 8.2$ for the redshifted HI hyperfine line) and bandwidth $B = 10.24
\, \rm MHz$. As one expects greater system stability in a drift scan, we test
the system stability by comparing the extracted power spectra from data with
noise simulations and show that the power spectra for the cleanest data behave
as thermal noise. We compute the HI power spectrum as a function of time in one
and two dimensions. The best upper limit on the one-dimensional power spectrum
are: $\Delta^2(k) \simeq (1000~\rm mK)^2$ at $k \simeq 0.2$$h~{\rm Mpc}^{-1}$
and at $k \simeq 1$$h~{\rm Mpc}^{-1}$. The cleanest modes, which might be the
most suited for obtaining the optimal signal-to-noise, correspond to $k \gtrsim
1$$h~{\rm Mpc}^{-1}$. We also study the time-dependence of the
foreground-dominated modes in a drift scan and compare with the expected
behaviour.
