Detection of White Dwarf Companions to Blue Stragglers in the Open Cluster NGC 188: Direct Evidence for Recent Mass Transfer

Gosnell, Natalie M.; Geller, Aaron M.; Sills, Alison; Leigh, Nathan W. C.; Knigge, Christian

doi:10.1088/2041-8205/783/1/l8

Cited by 87 publications

(106 citation statements)

References 29 publications

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“…V228 in 47 Tuc, Kaluzny et al 2007) and those have finished mass transfer (e.g. WOCS 4348, 4540 and 5379 in NGC 188, Gosnell et al 2014). The blue-straggler binaries during the mass-transfer phase have a "low-luminosity boundary" (about 0.75 mag brighter than the ZAMS) given by Tian et al (2006), and can match the observed red-sequence blue stragglers in globular cluster M30 (Ferraro et al 2009;Xin et al 2015).…”

Section: Introductionmentioning

confidence: 69%

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

Jiang

Chen

et al. 2017

ApJ

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Two blue-straggler sequences discovered in globular cluster M30 provide a strong constraint on the formation mechanisms of blue stragglers. We study the formation of the blue-straggler binaries through binary evolution, and find that binary evolution can contribute to the blue stragglers in both of the sequences. Whether a blue straggler is located in the blue sequence or red sequence depends on the contribution of the mass donor to the total luminosity of the binary, which is generally observed as a single star in globular clusters. The blue stragglers in the blue sequence have a cool white-dwarf companion, while the majority (∼ 60%) of the objects in the red sequence are the binaries that are still experiencing mass transfer, but there are also some objects that the donors have just finished the mass transfer (the stripped-core stars, ∼ 10%) or the blue stragglers (the accretors) have evolved away from the blue sequence (∼ 30%). Meanwhile, W UMa contact binaries found in both sequences may be explained by various mass ratios, that is, W UMa contact binaries in the red sequence have two components with comparable masses (e.g. mass ratio q ∼ 0.3-1.0), while those in the blue sequence have low mass ratio (e.g. q < 0.3). However, the fraction of blue sequence in M30 cannot be reproduced by binary population synthesis if we assumed the initial parameters of a binary sample to be the same as that of the field. This possible indicates that dynamical effects on binary systems is very important in globular clusters.

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Section: Introductionmentioning

confidence: 69%

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

Jiang

Chen

et al. 2017

ApJ

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“…First, Santana et al (2013) showed observationally that the fraction of blue stragglers in dwarf galaxies can be of the order of 10× higher than those in globular clusters, which, according to the authors, is because of the higher prevalence of binaries from which blue stragglers are formed in the low-density environments present in local dSph galaxies. Second, Milky Way globular clusters are old stellar populations (older than ∼10-11 Gyr according to recent reviews such as Gratton et al 2012 Gosnell et al (2014) have confirmed the presence of three hot and young white dwarfs as companion stars in binary systems for three blue straggler stars in the open cluster NGC188. These white dwarfs would correspond to former RGB or AGB stars that transferred mass in the recent past to their companion stars in the binary system, hence transforming them into blue stragglers.…”

Section: Young Population Versus Blue Straggler Populationmentioning

confidence: 96%

A Megacam Survey of Outer Halo Satellites. Vi. The Spatially Resolved Star-Formation History of the Carina Dwarf Spheroidal Galaxy*

Santana¹,

Muñoz²,

Boer³

et al. 2016

ApJ

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We present the spatially resolved star-formation history (SFH) of the Carina dwarf spheroidal galaxy, obtained from deep, wide-field g andr imaging and a metallicity distribution from the literature. Our photometry covers ∼2 deg 2 , reaching up to ∼10 times the half-light radius of Carina with a completeness higher than 50% at g∼24.5, more than one magnitude fainter than the oldest turnoff. This is the first time a combination of depth and coverage of this quality has been used to derive the SFH of Carina, enabling us to trace its different populations with unprecedented accuracy. We find that Carina's SFH consists of two episodes well separated by a star-formation temporal gap. These episodes occurred at old (>10 Gyr) and intermediate (2-8 Gyr) ages. Our measurements show that the old episode comprises the majority of the population, accounting for 54±5% of the stellar mass within 1.3 times the King tidal radius, while the total stellar mass derived for Carina is ´ M 1.60 0.09 10 6, and the stellar mass-to-light ratio is 1.8±0.2. The SFH derived is consistent with no recent star formation, which hints that the observed blue plume is due to blue stragglers. We conclude that the SFH of Carina evolved independently of the tidal field of the Milky Way, since the frequency and duration of its star-formation events do not correlate with its orbital parameters. This result is supported by the age-metallicity relation observed in Carinaand the gradients calculated indicating that outer regions are older and more metal-poor.

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“…Recently, Gosnell et al (2014Gosnell et al ( , 2015 used HST to study BSSs in NGC188 in the UV region, detecting white dwarf (WD) companions to seven BSS and thereby confirming that at least some BSSs can form by mass transfer. Three of their BSSs were found to have cool WD companions; four were found to have hotter WDs.…”

Section: Arxiv:161202535v1 [Astro-phsr] 8 Dec 2016mentioning

confidence: 99%

A Hot Companion to a Blue Straggler in NGC 188 as Revealed by the Ultra-Violet Imaging Telescope (Uvit) on Astrosat

Subramaniam

Sindhu

Tandon

et al. 2016

ApJL

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We present early results from the Ultra-Violet Imaging Telescope (UVIT) onboard the ASTROSAT observatory. We report the discovery of a hot companion associated with one of the blue straggler stars (BSSs) in the old open cluster, NGC188. Using fluxes measured in four filters in UVIT's Far-UV (FUV) channel, and two filters in the near-UV (NUV) channel, we have constructed the spectral energy distribution (SED) of the star WOCS-5885, after combining with flux measurements from GALEX, UIT, UVOT, SPITZER, WISE and several ground-based facilities. The resulting SED spans a wavelength range of 0.15 µm to 7.8 µm. This object is found to be one of the brightest FUV sources in the cluster. An analysis of the SED reveals the presence of two components. The cooler component is found to have a temperature of 6 000±150 K, confirming that it is a BSS. Assuming it to be a main-sequence star, we estimate its mass to be ∼ 1.1 -1.2M . The hotter component, with an estimated temperature of 17 000±500 K, has a radius of ∼ 0.6R and L ∼ 30L . Bigger and more luminous than a white dwarf, yet cooler than a sub-dwarf, we speculate that it is a post-AGB/HB star that has recently transferred its mass to the BSS, which is known to be a rapid rotator. This binary system, which is the first BSS with a post-AGB/HB companion identified in an open cluster, is an ideal laboratory to study the process of BSS formation via mass transfer.

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Detection of White Dwarf Companions to Blue Stragglers in the Open Cluster NGC 188: Direct Evidence for Recent Mass Transfer

Cited by 87 publications

References 29 publications

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

A Megacam Survey of Outer Halo Satellites. Vi. The Spatially Resolved Star-Formation History of the Carina Dwarf Spheroidal Galaxy*

A Hot Companion to a Blue Straggler in NGC 188 as Revealed by the Ultra-Violet Imaging Telescope (Uvit) on Astrosat

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