# The double Blue Straggler sequence in NGC2173: yes, a field contamination artefact!

## TL;DR

This study confirms that the previously claimed double blue straggler sequence in NGC2173 is actually a field star contamination artifact, after addressing concerns about data analysis methods and field star distribution.

## Contribution

The paper demonstrates that the double BSS sequence in NGC2173 is a result of field contamination, clarifying previous conflicting claims through robust data analysis.

## Key findings

- The double BSS sequence is caused by field star contamination.
- Decontamination procedure is unaffected by different HST instruments.
- Field stars show no significant radial segregation.

## Abstract

Li et al. (2018a; Li18a) claimed that the young stellar cluster NGC2173 in the Large Magellanic Cloud (LMC) harbours a bifurcated sequence of blue straggler stars (BSSs), similar to those detected in a few dynamically old globular clusters. However, Dalessandro et al. (2019; D19) re-analyzed the data by taking into account the contamination of the cluster population from LMC field stars, which was completely neglected by L18a. D19 showed that $\sim40\%$ of the selected BSS sample (and especially the population observed along one of the two sequences) is composed of field star interlopers, concluding that the double BSS sequence is most likely a field contamination artefact. In a recent note Li et al. (2018b) argued that the analysis by D19 is affected by two issues related to (1) the use of different HST instruments/filters in the decontamination procedure, and (2) a presumed overestimate of the number of field stars, which show a central radial segregation. Here we demonstrate that the D19 decontamination procedure is completely unaffected by the use of different HST instruments, and that, the field stars removed by D19 have no significant radial segregation toward the cluster center. Hence, we confirm that the claimed double sequence is just a field contamination artefact.