English

Optical Photometric Variable Stars towards the Galactic \hii region NGC 2282

Astrophysics of Galaxies 2018-04-04 v1 Solar and Stellar Astrophysics

Abstract

We report here CCD II-band time-series photometry of a young (2-5 Myr) cluster NGC 2282 to identify and understand the variability of pre-main-sequence (PMS) stars. The II-band photometry, down to \sim 20.5 mag, enables us to probe the variability towards the lower mass end (\sim 0.1 M_\odot) of the PMS stars. From the light curves of 1627 stars, we identified 62 new photometric variable candidates. Their association with the region was established from Hα\alpha emission and infrared (IR) excess. Among 62 variables, 30 young variables exhibit Hα\alpha emission, near-IR (NIR)/mid-IR (MIR) excess or both, and they are candidate members of the cluster. Out of 62 variables, 41 are periodic variables with the rotation rate ranging from 0.2 to 7 days. The period distribution exhibits a median period at \sim 1-day as in many young clusters (e.g., NGC~2264, ONC, etc.), but it follows a uni-modal distribution unlike others having bimodality with the slow rotators peaking at \sim 6-8 days. To investigate the rotation-disk and variability-disk connection, we derived NIR excess from Δ\Delta(I-K) and MIR excess from SpitzerSpitzer [3.6]-[4.5] μ\mum data. No conclusive evidence of slow rotation with the presence of disks around stars and fast rotation for diskless stars is obtained from our periodic variables. A clear increasing trend of the variability amplitude with the IR excess is found for all variables.

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Cite

@article{arxiv.1802.02303,
  title  = {Optical Photometric Variable Stars towards the Galactic \hii region NGC 2282},
  author = {Somnath Dutta and Soumen Mondal and Santosh Joshi and Jessy Jose and Ramkrishna Das and Supriyo Ghosh},
  journal= {arXiv preprint arXiv:1802.02303},
  year   = {2018}
}