Multiwavelength Study of Blue Straggler Stars in Tombaugh 2: Evidence for Binary Mass Transfer and Constraints on Cluster Dynamical State
Fuente:
arXiv
Saved in:
| Main Authors: | , , , , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2026
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866910128517677056 |
|---|---|
| author | Bisht, D. Jiang, Ing-Guey Belwal, K. Cınar, D. C. Dattatrey, Arvind K. Rangwal, Geeta Raj, A. Biswas, Shraddha Bisht, Mohit Singh Durgapal, Alok |
| author_facet | Bisht, D. Jiang, Ing-Guey Belwal, K. Cınar, D. C. Dattatrey, Arvind K. Rangwal, Geeta Raj, A. Biswas, Shraddha Bisht, Mohit Singh Durgapal, Alok |
| contents | We present a focused multiwavelength study of blue straggler stars (BSSs) in the intermediate-age open cluster Tombaugh 2, located in the outer Galactic disk, to constrain the dominant formation pathways of BSSs in a low-density environment. Cluster members are identified using Gaia DR3 astrometry through a Gaussian Mixture Model, yielding a clean sample of high-probability members. Color-magnitude diagram analysis indicates an age of 1.74 Gyr. The radial surface density profile is well described by a King model, indicating a centrally concentrated overall structure, while the cluster exhibits only weak or no clear evidence of mass segregation among its stellar populations. We identify 26 BSS candidates and 2 YSS candidates. Spectral energy distributions constructed from ultraviolet, optical, and infrared photometry reveal that 9 BSSs (32%) exhibit significant ultraviolet excess, indicating an additional hot component. Binary SED decomposition identifies stripped companions with effective temperatures Teff $\sim$ (1.5-8) $\times$ 10$^4$ K and radii R $\sim$ 0.04-0.28 R_$\odot$, consistent with proto-white dwarfs, extremely low-mass pre-helium white dwarfs, and young hot remnants formed through recent mass transfer. A slight central concentration of BSSs, together with stripped companions, suggests that binary mass transfer is an important formation channel, with no evidence for merger-driven formation. Multi-epoch VLT/FLAMES spectroscopy reveals radial-velocity variability in several systems, providing independent evidence for binarity. Our results highlight that optical-infrared photometric analyses alone may fail to detect hot compact companions, while spectroscopy and ultraviolet observations provide complementary constraints, with ultraviolet data offering a direct probe of such companions in intermediate-age open clusters. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_12494 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Multiwavelength Study of Blue Straggler Stars in Tombaugh 2: Evidence for Binary Mass Transfer and Constraints on Cluster Dynamical State Bisht, D. Jiang, Ing-Guey Belwal, K. Cınar, D. C. Dattatrey, Arvind K. Rangwal, Geeta Raj, A. Biswas, Shraddha Bisht, Mohit Singh Durgapal, Alok Solar and Stellar Astrophysics Astrophysics of Galaxies We present a focused multiwavelength study of blue straggler stars (BSSs) in the intermediate-age open cluster Tombaugh 2, located in the outer Galactic disk, to constrain the dominant formation pathways of BSSs in a low-density environment. Cluster members are identified using Gaia DR3 astrometry through a Gaussian Mixture Model, yielding a clean sample of high-probability members. Color-magnitude diagram analysis indicates an age of 1.74 Gyr. The radial surface density profile is well described by a King model, indicating a centrally concentrated overall structure, while the cluster exhibits only weak or no clear evidence of mass segregation among its stellar populations. We identify 26 BSS candidates and 2 YSS candidates. Spectral energy distributions constructed from ultraviolet, optical, and infrared photometry reveal that 9 BSSs (32%) exhibit significant ultraviolet excess, indicating an additional hot component. Binary SED decomposition identifies stripped companions with effective temperatures Teff $\sim$ (1.5-8) $\times$ 10$^4$ K and radii R $\sim$ 0.04-0.28 R_$\odot$, consistent with proto-white dwarfs, extremely low-mass pre-helium white dwarfs, and young hot remnants formed through recent mass transfer. A slight central concentration of BSSs, together with stripped companions, suggests that binary mass transfer is an important formation channel, with no evidence for merger-driven formation. Multi-epoch VLT/FLAMES spectroscopy reveals radial-velocity variability in several systems, providing independent evidence for binarity. Our results highlight that optical-infrared photometric analyses alone may fail to detect hot compact companions, while spectroscopy and ultraviolet observations provide complementary constraints, with ultraviolet data offering a direct probe of such companions in intermediate-age open clusters. |
| title | Multiwavelength Study of Blue Straggler Stars in Tombaugh 2: Evidence for Binary Mass Transfer and Constraints on Cluster Dynamical State |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2604.12494 |