No planet around the K giant star 42 Draconis

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00645234" target="_blank" >RIV/67985815:_____/25:00645234 - isvavai.cz</a>

Result on the web

<a href="https://hdl.handle.net/11104/0375072" target="_blank" >https://hdl.handle.net/11104/0375072</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202554197" target="_blank" >10.1051/0004-6361/202554197</a>

Result language

angličtina

Original language name

No planet around the K giant star 42 Draconis

Original language description

Published radial-velocity (RV) measurements of the K giant star 42 Dra taken over a three-year time span reveal variations consistent with a 3.9 Jupiter-mass companion in a 479-d orbit. Aims. This exoplanet can be confirmed if these variations are long-lived and coherent. Continued monitoring may also reveal additional companions. Methods. We acquired additional RV measurements of 42 Dra, the data now span 15 years. Standard periodogram analyses were used to investigate the stability of the planet's RV signal. We also investigated variations in the spectral line shapes using the bisector velocity span as well as infrared photometry from the COBE mission. Results. The recent RV measurements do not follow the published planet orbit. An orbital solution using the 2004 2011 data yields a period and eccentricity consistent with the published values, but the RV amplitude decreased by a factor of four since the earlier measurements. Including some additional RV measurements taken between 2014 and 2018 reveals a second period at 530 d. The interference (beating) of this period with the one at 479 d may account for the observed amplitude variations. The planet hypothesis is conclusively ruled out by COBE/DIRBE 1.25 μ photometry, which shows variations with the planet orbital period as well as a 170 d period. Conclusions. The RV of 42 Dra shows significant amplitude variations, which along with the COBE/DIRBE photometry firmly established that there is no giant planet around this star. The presence of multi-periodic variations suggests that we are seeing stellar oscillations in this star, most likely oscillatory convection modes. These oscillations may account for some of the long-period RV variations attributed to planets around K giant stars that may skew the statistics of planet occurrence around intermediate-mass stars. Long-term monitoring with excellent sampling is required to exclude amplitude variations in the long periods found in the RV of K giant stars.

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

2025

Confidentiality

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

Name of the periodical

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

699

Issue of the periodical within the volume

July

Country of publishing house

FR - FRANCE

Number of pages

7

Pages from-to

A260

UT code for WoS article

001690931400001

EID of the result in the Scopus database

2-s2.0-105011143699