A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companion

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26620%2F18%3APU135433" target="_blank" >RIV/00216305:26620/18:PU135433 - isvavai.cz</a>

Result on the web

<a href="https://arxiv.org/abs/1710.06709" target="_blank" >https://arxiv.org/abs/1710.06709</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/mnras/stx2737" target="_blank" >10.1093/mnras/stx2737</a>

Result language

angličtina

Original language name

A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companion

Original language description

We present a comprehensive study of Z CVn, an RR Lyrae star that shows long-term cyclic variations of its pulsation period. A possible explanation suggested from the shape of the O-C diagram is the light travel-time effect, which we thoroughly examine. We used original photometric and spectroscopic measurements and investigated the period evolution using available maximum times spanning more than one century. If the binary hypothesis is valid, Z CVn orbits around a black hole with minimal mass of 56.5 M-circle dot on a very wide (P-orbit = 78.3 yr) and eccentric orbit (e = 0.63). We discuss the probability of the formation of a black hole-RR Lyrae pair, and, although we found it possible, there is no observational evidence of the black hole in the direction to Z CVn. However, the main objection against the binary hypothesis is the comparison of the systemic radial velocity curve model and spectroscopic observations that clearly show that Z CVn cannot be bound in such a binary. Therefore, the variations of pulsation period are likely intrinsic to the star. This finding represents a discovery/confirmation of a new type of cyclic period changes in RR Lyrae stars. By the analysis of our photometric data, we found that the Blazhko modulation with period of 22.931 d is strongly dominant in amplitude. The strength of the phase modulation varies and is currently almost undetectable. We also estimated photometric physical parameters of Z CVn and investigated their variations during the Blazhko cycle using the inverse Baade-Wesselink method.

Czech name

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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

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OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

<a href="/en/project/LQ1601" target="_blank" >LQ1601: CEITEC 2020</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

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

474

Issue of the periodical within the volume

1

Country of publishing house

GB - UNITED KINGDOM

Number of pages

14

Pages from-to

824-837

UT code for WoS article

000424339500060

EID of the result in the Scopus database

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