Open clusters in AurOB2
  We study the area around the HII region Sh 2-234, including the young open
cluster Stock 8, to investigate the extent and definition of the association
Aur OB2 and the possible role of triggering in massive cluster formation. We
obtained Str\"omgren and J,H,Ks photometry for Stock 8 and Str\"omgren
photometry for two other cluster candidates in the area, which we confirm as
young open clusters and name Alicante 11 and Alicante 12. We took spectroscopy
of 33 early-type stars in the area, including the brightest cluster members. We
calculate a common distance of $2.80^{+0.27}_{-0.24}$ kpc for the three open
clusters and surrounding association. We derive an age 4-6 Ma for Stock 8, and
do not find a significantly different age for the other clusters or the
association. The star LSV +34 23, with spectral type O8 II(f), is likely the
main source of ionization of Sh 2-234. We observe an important population of
pre-main sequence stars, some of them with disks, associated with the B-type
members lying on the main-sequence. We interpret the region as an area of
recent star formation with some residual and very localized ongoing star
formation. We do not find evidence for sequential star formation on a large
scale. The classical definition of Aur OB2 has to be reconsidered, because its
two main open clusters, Stock 8 and NGC 1893, are not at the same distance.
Stock 8 is probably located in the Perseus arm, but other nearby HII regions
whose distances also place them in this arm show quite different distances and
radial velocities and, therefore, are not connected.
