UOCS –VIII. UV study of the open cluster NGC 2506 using <i>ASTROSAT</i>★

Panthi, Anju; Vaidya, Kaushar; Jadhav, Vikrant V.; Rao, Khushboo K; Subramaniam, Annapurni; Agarwal, Manan; Pandey, S. B.

doi:10.1093/mnras/stac2421

Cited by 8 publications

(2 citation statements)

References 122 publications

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“…The temperature range of BSSs in OC M67 (4 Gyr) is 6250 −9000 K (Jadhav et al 2019), in King 2 (6 Gyr) it is 5750-8500 K , and in OC NGC 188 (7 Gyr) it is 6100−6800 K (Gosnell et al 2015). In intermediate-age OCs such as NGC 7789 (1.6 Gyr) (Vaidya et al 2022) and NGC 2506 (2.2 Gyr) (Panthi et al 2022), BSSs span a temperature range from 7250 to 10,250 K, and 7750−9750 K, respectively. The SEDs of all BSSs are well-fitted with a single model, and we suggest that collisions leading to mergers might explain their formation in this cluster.…”

Section: Discussionmentioning

confidence: 99%

UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership

Rani

Pandey

Subramaniam

et al. 2023

ApJ

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We present the first far-UV (FUV) imaging results of the intermediate-age Galactic open cluster NGC 2818 that has a planetary nebula (PN) within the field using images taken from the Ultra Violet Imaging Telescope (UVIT) aboard AstroSat. We identify cluster members by combining UVIT-detected sources with Gaia EDR3 data. We detect four bright and hot blue straggler stars (BSSs) and two yellow straggler stars (YSSs) based on their location in optical and FUV–optical color–magnitude diagrams. Based on the parameters estimated using spectral energy distributions, we infer that BSSs are either collisional products or might have undetectable white dwarf (WD) companions. Our photometric analysis of YSSs confirms their binarity, consistent with the spectroscopic results. We find YSSs to be formed through a mass-transfer scenario and the hot components are likely to be A-type subdwarfs. A comparison of the radial velocity, Gaia EDR3 proper motion of the PN with the cluster, and reddening toward the PN and the cluster does not rule out the membership of the PN. Comparing the central star’s position with theoretical post‐AGB (pAGB) models suggest that it has already entered the WD cooling phase, and its mass is deduced to be ∼0.66 M ⊙. The corresponding progenitor mass turns out to be ∼2.1 M ⊙, comparable to the turn-off mass of the cluster, implying that the progenitor could have formed in the cluster. We suggest that the NGC 2818 might be one of the few known clusters to host a PN, providing a unique opportunity to test stellar evolution models.

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Section: Discussionmentioning

confidence: 99%

UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership

Rani

Pandey

Subramaniam

et al. 2023

ApJ

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“…It has been revealed through spectroscopic and UV observations that in many OCs, such as NGC 188 (Geller et al 2008;Gosnell et al 2015), M67 (Geller et al 2015;Sindhu et al 2019;Jadhav et al 2019), NGC 6819 (Milliman et al 2015, and NGC 7789 (Nine et al 2020;Vaidya et al 2022), ∼33% -85% of BSS formed via binary system evolution, primarily through the mass-transfer channel. The triple-mediated interactions are also considered as an important formation channel for some BSS of OCs, such as M67 and NGC 188 (Leigh & Sills 2011;Leiner et al 2016;Bertelli Motta et al 2018), Melotte 66 (Rao et al 2022), and NGC 2506 (Panthi et al 2022). Furthermore, Ferraro et al (2009) and Dalessandro et al (2013) found that blue sequences of M30 and NGC 1261 contain W UMa binaries.…”

Section: Discussionmentioning

confidence: 99%

Discovery of double BSS sequences in the old Galactic open cluster Berkeley 17

Rao

Bhattacharya

Vaidya

et al. 2022

Monthly Notices of the Royal Astronomical Society: Letters

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Blue straggler stars (BSS) are peculiar objects which normally appear as a single broad sequence along the extension of the main sequence. Only four globular clusters (GCs) have been observed to have two distinct and parallel BSS sequences. For the first time for any open cluster (OC), we report double BSS sequences in Berkeley 17. Using the machine-learning based membership algorithm ML-MOC on Gaia EDR3 data, we identify 627 cluster members, including 21 BSS candidates out to 15′ from the cluster center. Both the BSS sequences are almost equally populated and parallel to one another in Gaia as well as in Pan-STARRS colour-magnitude diagram (CMD). We statistically confirm their presence and report that both BSS sequences are highly segregated compared to the reference population out to ∼5.5′ and not segregated thereafter. The lower densities of OCs make BSS formation impossible via the collisional channel. Therefore, mass transfer seems to be the only viable channel for forming candidates of both sequences. The gap between the red and blue BSS sequences, on the other hand, is significant and presents a great opportunity to understand the connection between BSS formation and internal as well as external dynamics of the parent clusters.

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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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UOCS –VIII. UV study of the open cluster NGC 2506 using ASTROSAT★

Cited by 8 publications

References 122 publications

UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership

UOCS-IX. AstroSat/UVIT Study of the Open Cluster NGC 2818: Blue Stragglers, Yellow Stragglers, Planetary Nebula, and their Membership

Discovery of double BSS sequences in the old Galactic open cluster Berkeley 17

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