Long-term photometric observations of pre-main sequence objects in the field of North America/Pelican Nebula^⋆

¹ Physics Department, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
e-mail: jurdana@phy.uniri.hr
² Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria

Received: 1 November 2013
Accepted: 16 June 2014

Abstract

To broaden the search and study stars in the early evolutionary phase, we investigated a sample of 17 pre-main sequence objects previously detected as either Hα emission-line pre-main sequence stars or T Tauri variables located in the field of the North America/Pelican Nebula complex. Johnson-Cousins B, V, R_c, I_c magnitudes and mean color indices for the program stars are determined from more than 12 400 measurements from archive photographic plates and from CCD data collected at 7 observatories covering the period of almost 60 years from 1954 up to 2013. We complemented previously rare insights on the photometry of the program stars and presented their photometric history, which for almost all program stars is the first long term photometric monitoring on a timescale of 6 decades. Eight program stars are found to be classical T Tauri stars of variability type II, while 6 program stars are weak-line T Tauri stars of variability type I. For the first time, periodicity is found for three stars: V1716 Cyg indicates a 4.15 day period, V2051 Cyg indicates a 384 day period, and V521 Cyg a period of 503 days.