LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC): the
  second release of value-added catalogues
  We present the second release of value-added catalogues of the LAMOST
Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues
present values of radial velocity $V_{\rm r}$, atmospheric parameters ---
effective temperature $T_{\rm eff}$, surface gravity log$g$, metallicity
[Fe/H], $\alpha$-element to iron (metal) abundance ratio [$\alpha$/Fe]
([$\alpha$/M]), elemental abundances [C/H] and [N/H], and absolute magnitudes
${\rm M}_V$ and ${\rm M}_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4
million unique stars targeted by the LSS-GAC since September 2011 until June
2014. The catalogues also give values of interstellar reddening, distance and
orbital parameters determined with a variety of techniques, as well as proper
motions and multi-band photometry from the far-UV to the mid-IR collected from
the literature and various surveys. Accuracies of radial velocities reach
5kms$^{-1}$ for late-type stars, and those of distance estimates range between
10 -- 30 per cent, depending on the spectral signal-to-noise ratios. Precisions
of [Fe/H], [C/H] and [N/H] estimates reach 0.1dex, and those of [$\alpha$/Fe]
and [$\alpha$/M] reach 0.05dex. The large number of stars, the contiguous sky
coverage, the simple yet non-trivial target selection function and the robust
estimates of stellar radial velocities and atmospheric parameters, distances
and elemental abundances, make the catalogues a valuable data set to study the
structure and evolution of the Galaxy, especially the solar-neighbourhood and
the outer disk.
