GlobULeS. IV. UVIT/AstroSat Detection of Extremely Low Mass White Dwarf Companions to Blue Straggler Stars in NGC 362

Dattatrey, Arvind K.; Yadav, R. K. S.; Rani, Sharmila; Subramaniam, Annapurni; Singh, G. N.; Sahu, Snehalata; Singh, Ravi Shankar

doi:10.3847/1538-4357/acade0

Cited by 4 publications

(2 citation statements)

References 73 publications

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“…Ferraro et al (2009) claimed that bluer BSSs in the globular cluster M 30 are formed via collisional mergers, while redder BSSs are formed via mass transfer. Similar double BSS sequences have been seen in other globular clusters (NGC 362: Dalessandro et al 2013;Dattatrey et al 2023, NGC 2173: Li et al 2018. Similarly, the UV excess of BSSs has been linked to binarity (Gosnell et al 2015;Sindhu et al 2019;Pandey et al 2021).…”

Section: Discussionsupporting

confidence: 75%

Uocs

Jadhav¹,

Subramaniam²,

Sagar³

2023

A&A

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Aims. NGC 6791 is one of the richest old open clusters in the Milky Way. Its position above the Galactic plane and its number density make it an interesting middle ground between Galactic open and globular clusters. We aim to detect the UV-bright population of NGC 6791 using AstroSat/UVIT images in near-UV and far-UV filters and characterise the known post-mass-transfer systems such as blue straggler stars (BSSs). Methods. We identified 20 members with large UV flux (out of 91 cluster members among 1180 detections) – which is suggestive of binarity, interactions, or stellar activity – using a multi-wavelength spectral energy distribution analysis. Results. We characterised 62 isolated cluster members, including five hot subdwarfs (sdA/sdB). Additionally, we detected ten sdA/sdB/extremely low-mass (ELM) white dwarf-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. Conclusions. We report that this cluster has a variety of stellar (pre-)remnants, such as sdBs, sdAs, and ELM white dwarfs, which are by-products of binary evolution. These 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 test bed for dynamical studies.

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Section: Discussionsupporting

confidence: 75%

Uocs

Jadhav¹,

Subramaniam²,

Sagar³

2023

A&A

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“…In recent studies, it was also proposed that BSSs formed from the merger of mainsequence stars previously in a hierarchical triple system as a result of the eccentric Kozai-Lidov mechanism (Perets & Fabrycky 2009;Naoz & Fabrycky 2014), which has a significant role in BSS formation in open clusters (Li et al 2023). Many studies have been presented to describe the BSS populations and their formation scenarios in open and globular clusters (Mathieu & Latham 1986;Ferraro et al 2009;Dattatrey et al 2023).…”

Section: Introductionmentioning

confidence: 99%

UOCS. XIII. Study of the Far-ultraviolet Bright Stars in the Open Cluster NGC 2420 Using AstroSat

Yadav,

Dattatrey,

Rangwal

et al. 2024

ApJ

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We present the study of four far-ultraviolet (FUV) bright stars in the field of the open cluster NGC 2420 using the Ultra Violet Imaging Telescope mounted on AstroSat. The three stars 525, 527, and 560 are members, while star 646 is a nonmember of the cluster. To characterize and determine the parameters of these stars, multiwavelength spectral energy distributions (SEDs) are analyzed using UV, optical, and IR data sets. For all four FUV bright stars, a two-component SED model fits well. Our findings indicate that two stars, 525 and 560, are binary blue straggler star (BSS) systems. These BSS systems may have formed in a tertiary system due to mass transfer from an evolved outer tertiary companion. Star 527 is a binary system of a BSS and an extremely low-mass (ELM) white dwarf, while star 646 is a binary system of a horizontal branch star and an ELM white dwarf. The effective temperatures, radii, luminosities, and masses of the two ELMs are (10250, 11500) K (0.42, 0.12) R ⊙, (1.61, 0.23) L ⊙, and (0.186, 0.170) M ⊙, respectively. The star 527 could be a post-mass-transfer system and may have originated through the Case A/B mass-transfer process in a low-density environment. The cooling age of the ELMs is < 1 Myr, indicating that they have only recently formed.

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Field blue straggler stars: discovery of white dwarf companions to blue metal-poor stars using UVIT/AstroSat

Panthi,

Subramaniam,

Vaidya

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Blue metal-poor (BMP) stars are the main-sequence stars that appear bluer and more luminous than normal turn-off stars of metal-poor globular clusters. They are believed to be either field blue straggler stars (FBSS) formed via post-mass transfer mechanism or accreted from dwarf satellite galaxies of the Milky Way. A significant fraction of BMP stars are discovered to be potential binaries. We observed 27 BMP stars using UVIT/AstroSat in two FUV filters, F148W and F169M. We report the discovery of white dwarf (WD) companions of 12 BMP stars for the first time. The WD companions have estimated temperatures Teff ∼10500 − 18250 K, and masses 0.17 M⊙ − 0.8 M⊙. Based on [Fe/H] and space velocity, we group the 12 BMP/FBSS stars as the thick disk (5) and halo (5), whereas two stars appear to be in-between. All the 5 thick disk BMP/FBSS have extremely low-mass (M < 0.2 M⊙) WDs as companions, whereas the 5 halo BMP/FBSS have low (0.2 M⊙ < M < 0.4 M⊙), normal (0.4 M⊙ < M < 0.6M⊙), and high mass (M > 0.6 M⊙) WD companions. Our analysis suggests that at least ∼44 ${{\%}}$ of BMP stars are FBSS, and these stars hold the key to understand the details of mass transfer, binary properties, and chemical enrichment among the FBSS.

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GlobULeS. IV. UVIT/AstroSat Detection of Extremely Low Mass White Dwarf Companions to Blue Straggler Stars in NGC 362

Cited by 4 publications

References 73 publications

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UOCS. XIII. Study of the Far-ultraviolet Bright Stars in the Open Cluster NGC 2420 Using AstroSat

Field blue straggler stars: discovery of white dwarf companions to blue metal-poor stars using UVIT/AstroSat

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