First black hole mass estimation for the quadruple lensed system
  WGD2038-4008
  The quadruple lensed system WGD2038-4008 was recently discovered with the
help of new techniques and observations. Even though black hole mass has been
estimated for lensed quasars, it has been calculated mostly for one broad
emission line of one image, but the images could be affected by microlensing,
affecting the results. We present black hole mass (MBH) estimations for images
A and B using the three most prominent broad emission lines (H$\alpha$,
H$\beta$ and MgII) obtained in one single-epoch spectra. This is the first time
the mass is estimated in a lensed quasar in two images, allowing us to
disentangle the effects of microlensing. We used the X-shooter instrument
mounted in VLT, to observe this system taking advantage of its wide spectral
range. Using the flux ratio between the continuum and the core of the emission
lines we analyzed if microlensing was present in the continuum source. We
obtained MBH using the single-epoch method with the H$\alpha$ and H$\beta$
emission lines from the monochromatic luminosity and the velocity width. The
luminosity at 3000 \r{A} was obtained using the Spectral Energy Distribution
(SED) of image A while the luminosity at 5100 \r{A} was estimated directly from
the spectra. The average MBH between the images obtained was $\rm
log_{10}$(M$_{BH}/M_{\odot}$) = 8.27 $\pm$ 1.05, 8.25 $\pm$ 0.32 and 8.59 $\pm$
0.35 for MgII, H$\beta$ and H$\alpha$ respectively. We find Eddington ratios
similar to those measured in the literature for unlensed low-luminosity
quasars. Microlensing of -0.16 $\pm$ 0.06 mag. in the continuum was found but
the induced error in the MBH is minor compared to the one associated to the
macromodel magnification. We also obtained the accretion disk size using the
MBH for the three emission lines, obtaining an average value of $\rm
log_{10}(r_{s}/cm)$ = 15.3 +/- 0.63, which is in agreement with theoretical
estimates.
