H$\alpha$ Reverberation Mapping of the Intermediate-Mass Active Galactic
  Nucleus in NGC 4395
  We present the results of a high-cadence spectroscopic and imaging monitoring
campaign of the active galactic nucleus (AGN) of NGC 4395. High
signal-to-noise-ratio spectra were obtained at the Gemini-N 8 m telescope using
the GMOS integral field spectrograph (IFS) on 2019 March 7, and at the Keck-I
10 m telescope using the Low-Resolution Imaging Spectrometer (LRIS) with
slitmasks on 2019 March 3 and April 2. Photometric data were obtained with a
number of 1 m-class telescopes during the same nights. The narrow-line region
(NLR) is spatially resolved; therefore, its variable contributions to the slit
spectra make the standard procedure of relative flux calibration impractical.
We demonstrate that spatially-resolved data from the IFS can be effectively
used to correct the slit-mask spectral light curves. While we obtained no
reliable lag owing to the lack of strong variability pattern in the light
curves, we constrain the broad line time lag to be less than 3 hr, consistent
with the photometric lag of $\sim80$ min reported by Woo et al. (2019). By
exploiting the high-quality spectra, we measure the second moment of the broad
component of the H$\alpha$ emission line to be $586\pm19$ km s$^{-1}$,
superseding the lower value reported by Woo et al. (2019). Combining the
revised line dispersion and the photometric time lag, we update the black hole
mass as $(1.7\pm 0.3)\times10^4$ M$_{\odot}$.
