The distance to the young cluster NGC 7129 and its age

Abstract

The dust cloud TGU H645 P2 and embedded in it young open cluster NGC 7129 are investigated using the results of medium-band photometry of 159 stars in the Vilnius seven-colour system down to V = 18.8 mag. The photometric data were used to classify about 50 % of the measured stars in spectral and luminosity classes. The extinction A V vs. distance diagram for the 20 ′ × 20 ′ area is plotted for 155 stars with two-dimensional classification from the present and the previous catalogues. The extinction values found range between 0.6 and 3.4 mag. However, some red giants, located in the direction of the dense parts of the cloud, exhibit the infrared extinction equivalent up to A V = 13 mag. The distance to the cloud (and the cluster) is found to be 1.15 kpc (the true distance modulus 10.30 mag). For determining the age of NGC 7129, a luminosity vs. temperature diagram for six cluster members of spectral classes B3 to A1 was compared with the Pisa pre-main-sequence evolution tracks and the Palla birthlines. The cluster can be as old as about 3 Myr, but star forming continues till now as witnessed by the presence in the cloud of many younger pre-main-sequence objects identified with photometry from 2MASS, Spitzer and WISE infrared surveys.

Distances and Kinematics of Gould Belt Star-forming Regions with Gaia DR2 Results

“…Many of the pre-main sequence stars found in the Cepheus flare are part of this region (Kun et al 2008). NGC 7129, however, seems to be at a larger distance of 1 kpc (Racine 1968;Straižys et al 2014).…”

An Optical Survey of the Partially Embedded Young Cluster in NGC 7129

“…the Hα emission and X-ray detected sources, are superposed in the figure. The zero age main sequence (ZAMS) of Siess et al (2000) is overplotted using the dwarf colors presented by Kenyon & Hartmann (1995) and assuming a distance of 1150 pc (Straižys et al 2014). The cluster sequence is welldefined by the activity-selected sample and lies at least two magnitudes above the ZAMS, even for the early-type members.…”

“…Magakian et al (2004) concluded that most of the detected Hα emission sources were T Tauri stars. Vilnius 7color photometry down to V =18.8 is provided by Straižys et al (2014) for 159 stars in the cluster region. The photometric data was used to classify about half of the detected sources, assigning spectral types, luminosity classes and deriving extinction estimates.…”

“…The extinction across a 23 ′ ×23 ′ area varies between 0.6 and 2.8 mag, but in the densest parts of the molecular cloud, A V approaches ∼13 mag. Straižys et al (2014) determine the age of the cluster to be between 0.2 and 3 Myr by plotting six early-type cluster members on the HR diagram and using the evolutionary models of Palla (2005).…”

Membership Determination of van den Bergh Open Clusters vdB92, vdB146 (NGC 7129) and vdB150

“…Only five members fulfil both astrometric and photometric condition, they are stars No. 1 (UCAC4 781-037989 Straižys et al [11] find that the young age of the cluster makes that only six While comparing our results with these six cluster members, it can be seen that only star No. 105 (UCAC4 781-037982) does not fulfil the astrometric membership condition due to its proper motion.…”