J 2016

The nature of the light variability of magnetic Of?p star HD 191612

KRTIČKA, Jiří

Basic information

Original name

The nature of the light variability of magnetic Of?p star HD 191612

Authors

KRTIČKA, Jiří (203 Czech Republic, guarantor, belonging to the institution)

Edition

Astronomy and Astrophysics, EDP Sciences, 2016, 0004-6361

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10308 Astronomy

Country of publisher

France

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

Impact factor

Impact factor: 4.378 in 2014

RIV identification code

RIV/00216224:14310/16:00088249

Organization unit

Faculty of Science

DOI

UT WoS

000385832200121

Keywords (in Czech)

hvězdné větry, ztráta hmoty, proměnné hvězdy, hydrodynamika

Keywords in English

stars winds outflows; stars mass-loss; stars early-type; stars variables general; hydrodynamics

Tags

Tags

Reviewed
Změněno: 14/4/2017 15:05, Ing. Andrea Mikešková

Abstract

V originále

A small fraction of hot OBA stars host global magnetic fields with field strengths of the order of 0.1-10 kG. This leads to the creation of persistent surface structures (spots) in stars with sufficiently weak winds as a result of the radiative diffusion. These spots become evident in spectroscopic and photometric variability. This type of variability is not expected in stars with strong winds, where the wind inhibits the radiative diffusion. Therefore, a weak photometric variability of the magnetic Of?p star HD 191612 is attributed to the light absorption in the circumstellar clouds. We study the nature of the photometric variability of HD 191612. We assume that the variability results from variable wind blanketing induced by surface variations of the magnetic field tilt and modulated by stellar rotation. We used our global kinetic equilibrium (NLTE) wind models with radiative force determined from the radiative transfer equation in the comoving frame (CMF) to predict the stellar emergent flux. Our models describe the stellar atmosphere in a unified manner and account for the influence of the wind on the atmosphere. The models are calculated for different wind mass-loss rates to mimic the effect of magnetic field tilt on the emergent fluxes. We integrate the emergent fluxes over the visible stellar surface for individual rotational phases, and calculate the rotationally modulated light curve of HD 191612. The wind blanketing that varies across surface of HD 191612 is able to explain a part of the observed light variability in this star. The mechanism is able to operate even at relatively low mass-loss rates. The remaining variability is most likely caused by the flux absorption in circumstellar clouds. The variable wind blanketing is an additional source of the light variability in massive stars. The presence of the rotational light variability may serve as a proxy for the magnetic field.

Links

GA16-01116S, research and development project
Name: Atmosféry a okolohvězdné prostředí magnetických horkých hvězd
Investor: Czech Science Foundation