Unveiling the Variability and Chemical Composition of AL Col

Ghosh, Surath C.; Joshi, Santosh; Ghosh, Samrat; Dileep, Athul; Trust, Otto; Sarkar, Mrinmoy; Rosales, Jereme A.; Castro, Nicholas E.; Malkov, Oleg; Singh, Harinder P.; Tan, Kefeng; Bedi, Sarabjeet S.

doi:10.3390/galaxies13040093

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Open AccessArticle

Unveiling the Variability and Chemical Composition of AL Col

by

Surath C. Ghosh

^1,2,*

,

Santosh Joshi

¹

,

Samrat Ghosh

¹

,

Athul Dileep

¹

,

Otto Trust

^3,4

,

Mrinmoy Sarkar

¹

,

Jereme A. Rosales

⁵

,

Nicholas E. Castro

⁵

,

Oleg Malkov

⁶

,

Harinder P. Singh

⁷

,

Kefeng Tan

⁸

and

Sarabjeet S. Bedi

²

¹

Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital 263001, India

²

Department of Computer Science and Information Technology, MJP Rohilkhand University, Bareilly 243006, India

³

Department of Physics, Mbarara University of Science and Technology, Mbarara P.O. Box 1410, Uganda

⁴

Department of Physics, Faculty of Science, Kyambogo University, Kyambogo P.O. Box 1, Uganda

⁵

Departamento de Física, Universidad de Concepción (UdeC), Concepcion 4070412, Chile

⁶

Institute of Astronomy of the Russian Academy of Sciences (INASAN), Moscow 119017, Russia

⁷

Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India

⁸

National Astronomical Observatories, Chinese Academy of Sciences (NAOC), Beijing 100101, China

^*

Author to whom correspondence should be addressed.

Galaxies 2025, 13(4), 93; https://doi.org/10.3390/galaxies13040093 (registering DOI)

Submission received: 17 June 2025 / Revised: 1 August 2025 / Accepted: 5 August 2025 / Published: 14 August 2025

(This article belongs to the Special Issue Stellar Spectroscopy, Molecular Astronomy and Atomic Astronomy)

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Abstract

In this study, we present analysis of TESS photometry, spectral energy distribution (SED), high-resolution spectroscopy, and spot modeling of the

α^{2}

CVn-type star AL Col (HD 46462). The primary objective is to determine its fundamental physical parameters and investigate its surface activity characteristics. Using TESS short-cadence (120 s) SAP flux, we identified a rotational frequency of 0.09655

d^{- 1}

(

P_{rot} = 10.35733

d). Wavelet analysis reveals that while the amplitudes of the harmonic components vary over time, the strength of the primary rotational frequency remains stable. A SED analysis of multi-band photometric data yields an effective temperature (

T_{eff}

) of 11,750 K. High-resolution spectroscopic observations covering wavelengthrange 4500–7000 Å provide refined estimates of

T_{eff}

= 13,814 ± 400 K,

log g

= 4.09 ± 0.08 dex, and

υ sin i

= 16 ± 1 km s

^{- 1}

. Abundance analysis shows solar-like composition of O ii, Mg ii, S ii, and Ca ii, while helium is under-abundant by 0.62 dex. Rare earth elements (REEs) exhibit over-abundances of up to 5.2 dex, classifying the star as an Ap/Bp-type star. AL Col has a radius of

R = 3.74 \pm 0.48 R_{⊙}

, with its H–R diagram position estimating a mass of

M = 4.2 \pm 0.2 M_{⊙}

and an age of

0.12 \pm 0.01

Gyr, indicating that the star has slightly evolved from the main sequence. The TESS light curves were modeled using a three-evolving-spot configuration, suggesting the presence of differential rotation. This star is a promising candidate for future investigations of magnetic field diagnostics and the vertical stratification of chemical elements in its atmosphere.

Keywords: stars—chemically peculiar; He weak; techniques—TESS photometry; high resolution spectroscopy; abundance; individual—AL Col; variable—α2CVn

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MDPI and ACS Style

Ghosh, S.C.; Joshi, S.; Ghosh, S.; Dileep, A.; Trust, O.; Sarkar, M.; Rosales, J.A.; Castro, N.E.; Malkov, O.; Singh, H.P.; et al. Unveiling the Variability and Chemical Composition of AL Col. Galaxies 2025, 13, 93. https://doi.org/10.3390/galaxies13040093

AMA Style

Ghosh SC, Joshi S, Ghosh S, Dileep A, Trust O, Sarkar M, Rosales JA, Castro NE, Malkov O, Singh HP, et al. Unveiling the Variability and Chemical Composition of AL Col. Galaxies. 2025; 13(4):93. https://doi.org/10.3390/galaxies13040093

Chicago/Turabian Style

Ghosh, Surath C., Santosh Joshi, Samrat Ghosh, Athul Dileep, Otto Trust, Mrinmoy Sarkar, Jereme A. Rosales, Nicholas E. Castro, Oleg Malkov, Harinder P. Singh, and et al. 2025. "Unveiling the Variability and Chemical Composition of AL Col" Galaxies 13, no. 4: 93. https://doi.org/10.3390/galaxies13040093

APA Style

Ghosh, S. C., Joshi, S., Ghosh, S., Dileep, A., Trust, O., Sarkar, M., Rosales, J. A., Castro, N. E., Malkov, O., Singh, H. P., Tan, K., & Bedi, S. S. (2025). Unveiling the Variability and Chemical Composition of AL Col. Galaxies, 13(4), 93. https://doi.org/10.3390/galaxies13040093

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