UVIT Open Cluster Study. X. Rich Collection of Post Mass Transfer Systems in NGC 6791

Abstract

NGC 6791 is one of the richest old open clusters in the Milky Way. Its position above the Galactic plane and the number density makes it an interesting middle ground between Galactic open and globular clusters. We aim to detect the UV bright population of NGC 6791 using \textit{AstroSat}/UVIT images in near-UV and far-UV filters and characterise the known post mass transfer systems such as blue straggler stars (BSSs). We identified 20 members with large UV flux (out of 91 cluster members among 1180 detections), suggestive of binarity, interactions or stellar activity using multi-wavelength spectral energy distribution analysis. We characterised 62 isolated cluster members, including five hot subdwarfs (sdA/sdB). Additionally, we detected ten sdA/sdB/extremely low mass white dwarf (ELM) type candidates hidden alongside other cluster members. Additionally, we report the discovery of four candidate blue lurkers, which are main sequence stars with mass accretion history. We report that this cluster has a variety of stellar (pre-)remnants, such as sdBs, sdAs, and ELM white dwarfs, that are by-products of binary evolution. The above are likely to be post mass transfer binaries found throughout the evolutionary phases from the main sequence to the post horizontal branch. Therefore, this dynamically old open cluster is unique, making it an ideal testbed for dynamical studies.

8 pages, 2 figures, catalogue available in CDS, accepted in A&A

References in corpus (22)

• The Gaia mission
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Painting a portrait of the Galactic disc with its stellar clusters
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• Age determination for 269 $Gaia$ DR2 Open Clusters
• Gaia Data Release 3. The first Gaia catalogue of eclipsing binary candidates
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIII. Proper-motion catalogs and internal kinematics
• Blue Straggler Stars in Open Clusters using Gaia: Dependence on Cluster Parameters and Possible Formation Pathways
• UVIT Open Cluster Study. II. Detection of extremely low mass white dwarfs and post-mass transfer binaries in M67
• WIYN Open Cluster Study. LIX. Radial-Velocity Membership of the Evolved Population of the Old Open Cluster NGC 6791
• UOCS VII. Blue Straggler Populations of Open Cluster NGC 7789 with UVIT/AstroSat
• The Swift/UVOT Stars Survey. III. Photometry and Color-Magnitude Diagrams of 103 Galactic Open Clusters
• Detection of a White Dwarf companion to a Blue Straggler Star in the outskirts of globular cluster NGC 5466 with the Ultraviolet Imaging Telescope (UVIT)
• Rotationally Driven Ultraviolet Emission of Red Giant Stars
• UOCS. IV. Discovery of diverse hot companions to blue stragglers in the old open cluster King 2
• UOCS.VI. UVIT/AstroSat detection of low-mass white dwarf companions to 4 more blue stragglers in M67
• UOCS-VIII. UV Study of the open cluster NGC 2506 using ASTROSAT
• Characterization of hot populations of Melotte 66 open cluster using Swift/UVOT
• New insights in the origin and evolution of the old, metal-rich open cluster NGC 6791
• GlobULeS-IV. UVIT/AstroSat detection of extremely low mass white dwarf companions to blue straggler stars in NGC 362
• Pulsating subdwarf B stars in the oldest open cluster NGC6791
• Photometric variability of blue straggler stars in M67 with TESS and K2

Cited by in corpus (4)

• Hunting Down White Dwarf--Main Sequence Binaries Using Multi-Wavelength Observations
• UOCS. XIV. Uncovering extremely low mass white dwarfs and blue lurkers in NGC 752
• A rotation-based census of blue lurker candidates in open clusters
• Evidence for Dynamical Filtering: High Binary Fraction, Hard-binary Excess, and Unresolved Triples in the Surviving Core of NGC 6791