The putative old, nearby cluster Lodén 1 does not exist

Abstract

Astronomers have access to precious few nearby, middle-aged benchmark star clusters. Within 500 pc, there are only NGC 752 and Ruprecht 147 (R147), at 1.5 and 3 Gyr respectively. The Database for Galactic Open Clusters (WEBDA) also lists Lodén 1 as a 2 Gyr cluster at a distance of 360 pc. If this is true, Lodén 1 could become a useful benchmark cluster. This work details our investigation of Lodén 1. We assembled archival astrometry (PPMXL) and photometry (2MASS, Tycho-2, APASS), and acquired medium resolution spectra for radial velocity measurements with the Robert Stobie Spectrograph (RSS) at the Southern African Large Telescope. We observed no sign of a cluster main-sequence turnoff or red giant branch amongst all stars in the field brighter than $J<11$. Considering the 29 stars identified by L.O. Lodén and listed on SIMBAD as the members of Lodén 1, we found no compelling evidence of kinematic clustering in proper motion or radial velocity. Most of these candidates are A stars and red giants, and their observed properties are consistent with distant field stars in the direction of Lodén 1 in the Galactic plane. We conclude that the old nearby cluster Lodén 1 is neither old, nor nearby, nor a cluster.

Accepted to AJ

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