A quasar shedding its dust cocoon at redshift 2
  We present the first near-IR spectroscopy and joint analyses of
multi-wavelength observations for SDSS J082747.14+425241.1, a dust-reddened,
weak broad emission-line quasar (WLQ) undergoing a remarkable broad absorption
line (BAL) transformation. The systemic redshift is more precisely measured to
be $z=2.070\pm0.001$ using H$\beta$ compared to $z=2.040\pm0.003$ using \mgii\
from the literature, signifying an extreme \mgii\ blueshift of $2140\pm530$
\kms\ relative to H$\beta$. Using the H$\beta$-based single-epoch scaling
relation with a systematic uncertainty of 0.3 dex, its black hole (BH) mass and
Eddington ratio are estimated to be $M_{\rm BH}\sim6.1\times10^8M_\odot$ and
$\lambda_{\rm Edd}\sim0.71$, indicative of being in a rapidly accreting phase.
Our investigations confirm the WLQ nature and the LoBAL$\rightarrow$HiBAL
transformation, along with a factor of 2 increase in the \mgii+\feii\ emission
strength and a decrease of 0.1 in $E(B-V)$ over two decades. The kinetic power
of this LoBAL wind at $R\sim$15 pc from its BH is estimated to be $\sim$43\% of
the Eddington luminosity, sufficient for quasar feedback upon its host galaxy
albeit with an order-of-magnitude uncertainty. This quasar provides a clear
example of the long-sought scenario where LoBAL quasars are surrounded by dust
cocoons, and wide-angle nuclear winds play a key role in the transition for red
quasars evolving into the commonly seen blue quasars.
