VLTI observations of Orion Belt stars: I. ε Orionis

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F25%3A10510254" target="_blank" >RIV/00216208:11320/25:10510254 - isvavai.cz</a>

Result on the web

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=3PK2ChWZIr" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=3PK2ChWZIr</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202556154" target="_blank" >10.1051/0004-6361/202556154</a>

Result language

angličtina

Original language name

VLTI observations of Orion Belt stars: I. ε Orionis

Original language description

Context. Massive stars play a decisive role in the evolution of the Universe. They are the primary sources of ionising radiation, generating strong stellar winds that affect the interstellar medium. They ultimately end their lives as supernovae, ejecting synthesised, r-process elements. Aims. To constrain their current state and structure, we need access to sufficiently complex models, constrained by astrometric, interferometric, and spectroscopic observations. However, such tools are not available for distant stars. Therefore, we focused on the nearest massive stars in Orion&apos;s Belt for the purposes of this work. Methods. We obtained VLTI interferometric observations of the stars of Orion&apos;s Belt and calibrated visibility data from the GRAVITY and PIONIER instruments. Additionally, we obtained spectroscopic data from the CFHT and CTIO observatories. For the modelling, we used a modified version of PHOEBE2, extended with new interferometric and spectroscopic modules. To describe non-spherical, rotating, or Roche-like stars, we needed to compute integrals over triangular meshes, using extensive grids of synthetic spectra (OSTAR, BSTAR, ATLAS). For the fitting, we used the simplex algorithm and chi 2 mapping of the parameter space. Results. In this paper, the first in a series, we present single-star models of the B0 Ia supergiant epsilon Ori. Interferometric visibilities indicate that the star is not spherical, but it is rotating close to its critical velocity. The preferred distance, d=(384 +/- 8)pc, corresponds to the median of distances for the Orion OB1b association. Specifically, we obtained the following parameters: mass of m=(28.4 +/- 2.0)M circle dot, equivalent radius of R=(27.6 +/- 1.5)R circle dot, where the polar and equatorial values are 22.3 R-circle dot and 33.6 R-circle dot, respectively, effective temperature of Teff similar or equal to 25 000K, inclination of the rotation axis of i similar or equal to 45deg, longitude of the ascending node (of the equator) of Omega similar or equal to 300deg, and a period of Prot=4.3-0.0+1.0d. This ?compromise? model provides a reasonable fit to wind-free Balmer line profiles (H gamma, H delta, H epsilon, etc.). However, there is still some tension between the interferometric and spectroscopic datasets when comparing a faster rotating star versus a slower one. Conclusions. Our fast-rotating model implies that circumstellar matter should naturally be present, taking the form of wind or disk, and ought to contribute to the continuum radiation. The fast rotation of epsilon Ori is compatible with a merger, formed from a multiple system of comparable mass, such as delta, zeta, or sigma Ori.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

—

Continuities

S - Specificky vyzkum na vysokych skolach

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Astronomy &amp; Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

704

Issue of the periodical within the volume

prosinec

Country of publishing house

FR - FRANCE

Number of pages

16

Pages from-to

A204

UT code for WoS article

001635819700005

EID of the result in the Scopus database

2-s2.0-105025769692