The disintegrating old open cluster Czernik 3

Abstract

We have performed a detailed analysis of the Czernik 3 (Cz3) open cluster by using deep near-infrared photometry taken with TIRCAM2 on 3.6m Devasthal optical telescope along with the recently available high quality proper motion data from the Gaia DR2 and deep photometric data from Pan-STARRS1. The cluster has a highly elongated morphology with fractal distribution of stars. The core and cluster radii of the cluster are estimated as 0.5 pc and 1.2 pc, respectively. We have identified 45 stars as cluster members using the Gaia proper motion data. The distance and age of the cluster are found to be 3.5 ± 0.9 kpc and $0.9^{+0.3}_{-0.1}$ Gyr, respectively. The slope of the mass function `Γ′ in the cluster region, in the mass range ∼0.95 <M/M⊙<2.2, is found to be −1.01 ± 0.43. The cluster shows the signatures of mass-segregation and is dynamically relaxed (dynamical age=10 Myr). This along with its small size, big tidal radius, low density/large separation of stars, and elongated and distorted morphology, indicate that the Cz3 is a loosely bound disintegrating cluster under the influence of external tidal interactions.

Quest for the upcoming periastron passage of an episodic dust maker and particle accelerating colliding wind binary: WR 125

“…The aperture photometry was performed in all the J, H, and K bands as WR 125 was isolated in all the science frames. The instrumental magnitudes of WR 125 at each epoch of observations were calibrated by using color equations generated from the instrumental and 2MASS photometry of the other stars in the same field of view (see Sharma et al 2020). The absolute JHK magnitudes obtained for WR 125 are given in Table 5. 6.…”

Sh 2-301: a blistered H II region undergoing star formation

“…We have used the Gaia proper motion (PM) data with σ P M <3 mas/yr to determine the membership probability of the stars belonging to the NE-cluster found in the S301 region using the method described in Balaguer-Núnez et al (1998). This method has been extensively used recently (for example, Sinha et al 2020;Sharma et al 2020;Kaur et al 2020;Pandey et al 2020b). PMs in RA and Dec are plotted as vector-point diagrams (VPDs) in the top panels of Figure 4.…”

“…Two-color diagrams (TCDs) and CMDs of the member stars have been proven to be very good tools to constrain reddening, distance and age of a cluster (for example, Phelps & Janes 1994;Sharma et al 2006Sharma et al , 2020. In the left panel of Figure 6, we have shown (U − B) versus (B − V ) TCD of the stars located within the boundary of the NE-cluster (radius < 3 .3).…”

Gaia 20eae: A newly discovered episodically accreting young star

“…We have used standard data reduction procedures for the image cleaning, photometry, and astrometry (for details, see Sharma et al 2020). We have derived following color transformation equations using the available magnitudes in different filters (i.e., APASS DR10 archive 5 or Two Micron All Sky Survey (2MASS) archive 6 ) of all the stars in the frame at epoch JD = 2459141 (for optical) and JD = 2459144 (for NIR).…”