Optical photometric variable stars towards the Galactic H ii region NGC 2282. Issue 2 (20th March 2018)

• Record Type: Journal Article
• Authors: Dutta, Somnath; Mondal, Soumen; Joshi, Santosh; Jose, Jessy; Das, Ramkrishna; Ghosh, Supriyo
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 476:Issue 2(2018)
• Page Start: 2813
• Page End: 2824
• Publication Date: 2018-03-20
• Subjects: methods: observational -- stars: formation -- stars: pre-main-sequence -- stars: variables: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty329
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We report here CCD I -band time series photometry of a young (2–5 Myr) cluster NGC 2282, in order to identify and understand the variability of pre-main-sequence (PMS) stars. The I -band photometry, down to ∼20.5 mag, enables us to probe the variability towards the lower mass end (∼0.1 M⊙ ) of PMS stars. From the light curves of 1627 stars, we identified 62 new photometric variable candidates. Their association with the region was established from H α emission and infrared (IR) excess. Among 62 variables, 30 young variables exhibit H α emission, near-IR (NIR)/mid-IR (MIR) excess or both and are candidate members of the cluster. Out of 62 variables, 41 are periodic variables, with a rotation rate ranging from 0.2–7 d. The period distribution exhibits a median period at ∼1 d, as in many young clusters (e.g. NGC 2264, ONC, etc.), but it follows a unimodal distribution, unlike others that have bimodality, with slow rotators peaking at ∼6–8 d. To investigate the rotation–disc and variability–disc connection, we derived the NIR excess from Δ( I − K ) and the MIR excess from Spitzer [3.6]–[4.5] $\mu$ m data. No conclusive evidence of slow rotation with the presence of discs around stars and fast rotation for discless stars is obtained from our periodic variables. A clear increasing trend of the variability amplitude with IR excess is found for all variables.