We present the results from our time-series imaging data taken with the 1.3m Devasthal fast optical telescope and 0.81m Tenagara telescope in V, Rc, and Ic bands covering an area of ~18.4x18.4 toward the star-forming region Sh 2-190. This photometric data helped us to explore the nature of the variability of pre-main-sequence (PMS) stars. We have identified 85 PMS variables, i.e., 37 Class II and 48 Class III sources. Forty-five of the PMS variables show periodicity in their light curves. We show that the stars with thicker disks and envelopes rotate slower and exhibit larger photometric variations compared to their diskless counterparts. This result suggests that rotation of the PMS stars is regulated by the presence of circumstellar disks. We also found that the periods of the stars show a decreasing trend with increasing mass in the range of ~0.5-2.5M_{sun}_. Our result indicates that most of the variability in Class II sources is ascribed to the presence of a thick disk, while the presence of cool spots on the stellar surface causes the brightness variation in Class III sources. X-ray activities in the PMS stars were found to be at the saturation level reported for the main-sequence stars. The younger counterparts of the PMS variables show less X-ray activity, hinting at a less significant role of a stellar disk in X-ray generation.

Cone search capability for table J/ApJ/921/165/table2 (Sh 2-190 members catalog)

Cone search capability for table J/ApJ/921/165/table3 (PMS variables and their physical parameters)