A revisit to the enigmatic variable star 21 Comae

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F19%3A00111171" target="_blank" >RIV/00216224:14310/19:00111171 - isvavai.cz</a>

Result on the web

<a href="https://academic.oup.com/mnras/article-abstract/485/3/4247/5319136?redirectedFrom=PDF" target="_blank" >https://academic.oup.com/mnras/article-abstract/485/3/4247/5319136?redirectedFrom=PDF</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/mnras/stz413" target="_blank" >10.1093/mnras/stz413</a>

Result language

angličtina

Original language name

A revisit to the enigmatic variable star 21 Comae

Original language description

The magnetic chemically peculiar (Ap/CP2) star 21 Com has been extensively studied in the past, albeit with widely differing and sometimes contradictory results, in particular concerning the occurrence of short-term variability between about 5 to 90 min. We have performed a new investigation of 21 Com using Microvariability and Oscillations of Star (MOST) satellite and high-cadence ground-based photometry, time series spectroscopy, and evolutionary and pulsational modelling. Our analysis confirms that 21 Com is a classical CP2 star showing increased abundances of, in particular, Cr and Sr. From spectroscopic analysis, we have derived T-eff = 8 900 +/- 200 K, log g = 3.9 +/- 0.2, and nu sin i = 63 +/- 2 kms(-1). Our modelling efforts suggest that 21 Com is a main sequence (MS) star seen equator-on with a mass of 2.29 +/- 0.10 M-circle dot and a radius of R = 2.6 +/- 0.2 R-circle dot. Our extensive photometric data confirm the existence of rotational light variability with a period of 2.052 19(2) d. However, no significant frequencies with a semi-amplitude exceeding 0.2 mmag were found in the frequency range from 5 to 399 d(-1). Our RV data also do not indicate short-term variability. We calculated pulsational models assuming different metallicities and ages, which do not predict the occurrence of unstable modes. The star 18 Com, often employed as comparison star for 21 Com in the past, has been identified as a periodic variable (P=1.416 45 d). While it is impossible to assess whether 21 Com has exhibited short-term variability in the past, the new observational data and several issues/inconsistencies identified in previous studies strongly suggest that 21 Com is neither a delta Scuti nor a roAp pulsator but a 'well-behaved' CP2 star exhibiting its trademark rotational variability.

Czech name

—

Czech description

—

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

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2019

Confidentiality

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

Name of the periodical

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

e-ISSN

1365-2966

Volume of the periodical

485

Issue of the periodical within the volume

3

Country of publishing house

GB - UNITED KINGDOM

Number of pages

13

Pages from-to

4247-4259

UT code for WoS article

000474902000095

EID of the result in the Scopus database

2-s2.0-85067010195