The optical variability of steep-spectrum radio quasars in the SDSS
  Stripe 82 region
  While there are a lot of investigations on the optical variability of
flat-spectrum radio quasars (FSRQs), not much work has been done on the optical
variability of steep-spectrum radio quasars (SSRQs). We investigate the optical
variability of 18 SSRQs and 15 FSRQs in the SDSS Stripe 82 region using SDSS
DR7 released multi-epoch data covering about nine years. For all SSRQs studied,
we detect variations in r band flux of overall amplitude between 0.22 mag and
0.92 mag in different sources. Eight of 18 SSRQs display a bluer-when-brighter
(BWB) trend. In contrast, the variability amplitude of 15 FSRQs in r band
ranges from 0.18 to 0.97 mag, and 11 of 15 sources show a BWB trend. We found
an anti-correlation between the Eddington ratio and the variability amplitude
in r band for SSRQs, which is similar to that in radio quiet AGNs. This implies
that the thermal emission from accretion disk may be responsible for the
variability in SSRQs, although the jet nonthermal emission cannot be excluded.
In contrast, there is no correlation in FSRQs, which implies that the
mechanisms of variability in FSRQs may be different from that in SSRQs. The
optical continuum variability of radio loud broad absorption line quasars
(BALQs) are investigated for the first time here on two sources with steep
radio spectrum. Both radio loud BALQs show variations with amplitude of about
0.3 mag at r band. Their spectral variability all show a BWB trend. In a
combined sample (18 SSRQs, and 44 FSRQs) of our sample with the FSRQs in Gu &
Ai (2011), we found a trend of a broader line width of broad Mg II emission
line with steeper radio spectral index. It implies a disc-like broad line
region (BLR) geometry may present in these quasars. In these 62 quasars, we
found a ~ 57% source percentage showing BWB trend in FSRQs, whereas it is ~ 44%
in SSRQs.
