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(Note: this is a shortened version of the original "structured" A&A formatabstract.) We performed a large optical spectroscopic and photometric survey ofthe Lynds~1630N and 1641 clouds. We provide a catalog of 132 confirmed youngstars in L1630N and 267 such objects in L1641. We identify 28 transition disksystems, 20 of which were previously unknown, as well as 42 new transition diskcandidates for which we have broad-band photometry but no optical spectroscopy.We estimate mass accretion rates M_acc from the equivalent widths of theH_alpha, H_beta, and HeI 5876\AA emission lines, and find a dependence onstellar mass of M_acc propto Mstar^alpha, with alpha~3.1 in the subsolar massrange that we probe. An investigation of a large literature sample of massaccretion rate estimates yields a similar slope of alpha~2.8 in the subsolarregime, but a shallower slope of alpha~2.0 if the whole mass range of 0.04M_sun-5 Msun is included. Among the transition disk objects, the fraction ofstars that show significant accretion activity is relatively low compared tostars with still optically thick disks (26\pm11% vs. 57\pm6%, respectively).However, those transition disks that do show significant accretion have thesame median accretion rate as normal optically thick disks of 3-4*10^{-9}M_sun/yr. We find that the ages of the transition disks and the WTTSs withoutdisks are statistically indistinguishable, and both groups are significantlyolder than the CTTSs. These results argue against disk-binary interaction orgravitational instability as mechanisms causing a transition disk appearance.Our observations indicate that disk lifetimes in the clustered population areshorter than in the distributed population. We propose refined Halphaequivalent width criteria to distinguish WTTSs from CTTSs.

Star and protoplanetary disk properties in Orion's suburbs