Accurate fundamental parameters and distance to a massive early-type eclipsing binary in the Danks 2 cluster

TL;DR

This study precisely determines the fundamental parameters and distance of a massive eclipsing binary in the Danks 2 cluster, enhancing understanding of stellar properties and cluster distance with high accuracy.

Contribution

The paper provides the first detailed measurement of masses, radii, and distance for an eclipsing binary in Danks 2, using near-infrared spectroscopy and spectral energy distribution fitting.

Findings

Masses: 24.5 and 21.7 solar masses

Distance: 3.52 kpc with 2% precision

Both stars are main-sequence O6.5–O7 types

Abstract

We present a study of the properties of the O-type, massive eclipsing binary 2MASS J13130841-6239275 located in the outskirts of the Danks 2 cluster in the G305 star-forming complex, using near-infrared spectroscopy from VLT/ISAAC. We derive the masses and radii to be 24.5$\pm$0.9 M$_{\odot}$ and 9.2$\pm$0.1 R$_{\odot}$ for the primary and 21.7$\pm$0.8 M$_{\odot}$ and 8.7$\pm$0.1 R$_{\odot}$ for the secondary component. In addition, we evaluate the sensitivity of our parameters to the choice of the spectral features used to determine the radial velocities. Both components appear to be main-sequence O6.5$-$O7 type stars at an age of $\sim$5 Myr, which is in agreement with the age of the cluster. A high visual extinction of A$_{5495}$=11.9$\pm$0.1 mag is reported, which is likely attributed to the cold molecular gas contaminating the north-east region of the cluster. By fitting the spectral energy distribution of the system to the available $BVI_{c}JHK_{s}$ photometry, we determine a distance to the system of 3.52$\pm$0.08 kpc with a precision of 2$\%$, which is the most well-determined distance to the Danks 2 cluster and the host complex reported in the literature.