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Post Info TOPIC: NGC 1893
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Title: Main-sequence variable stars in young open cluster NGC 1893
Author: Sneh Lata, Ram Kesh Yadav, A. K. Pandey, Andrea Richichi, C. Eswaraiah, Brajesh Kumar, Norbert Kappelmann, Saurabh Sharma

In this paper we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using (U-B)/(B-V) and (J-H)/(H-K) two colour diagrams, and V/(V-I) colour magnitude diagram. Forty five stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as beta Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. (2013). These variable candidates show ~0.005 to ~0.02 mag brightness variations with periods of  < 1.0 d. Seventeen new class variables are located in the H-R diagram between the slowly pulsating B stars and delta Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al. (2003).

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Blobrana


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Title: Pre-main sequence variable stars in young open cluster NGC 1893
Authors: Sneh Lata, A. K. Pandey, W. P. Chen, G. Maheswar, Neelam Chauhan

We present results of multi-epoch (fourteen nights during 2007-2010) V-band photometry of the cluster NGC 1893 region to identify photometric variable stars in the cluster. The study identified a total of 53 stars showing photometric variability. The members associated with the region are identified on the basis of spectral energy distribution, J-H/H-K two colour diagram and V/V-I colour-magnitude diagram. The ages and masses of the majority of pre-main-sequence sources are found to be \lesssim 5 Myr and in the range 0.5 \lesssim M/solar masses \lesssim 4, respectively. These pre-main-sequence sources hence could be T Tauri stars. We also determined the physical parameters like disk mass and accretion rate from the spectral energy distribution of these T Tauri stars. The periods of majority of the T Tauri stars range from 0.1 to 20 day. The brightness of Classical T Tauri stars is found to vary with larger amplitude in comparison to Weak line T Tauri stars. It is found that the amplitude decreases with increase in mass, which could be due to the dispersal of disks of massive stars.

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