Visual and ultraviolet flux variability of the bright CP star
theta Aurigae

J 2015

Visual and ultraviolet flux variability of the bright CP star theta Aurigae

KRTIČKA, Jiří, Zdeněk MIKULÁŠEK, Theresa LUFTINGER a Miroslav JAGELKA

Základní údaje

Originální název

Visual and ultraviolet flux variability of the bright CP star theta Aurigae

Název česky

Vizuální a ultrafialová proměnnost hasné CP hvězdy theta Aurigae

Autoři

KRTIČKA, Jiří (203 Česká republika, garant, domácí), Zdeněk MIKULÁŠEK (203 Česká republika, domácí), Theresa LUFTINGER (40 Rakousko) a Miroslav JAGELKA (703 Slovensko, domácí)

Vydání

ASTRONOMY & ASTROPHYSICS, LES ULIS CEDEX A, EDP SCIENCES S A, 2015, 0004-6361

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10308 Astronomy

Stát vydavatele

Francie

Utajení

není předmětem státního či obchodního tajemství

Impakt faktor

Impact factor: 4.378 v roce 2014

Kód RIV

RIV/00216224:14310/15:00081641

Organizační jednotka

Přírodovědecká fakulta

DOI

http://dx.doi.org/10.1051/0004-6361/201425097

UT WoS

000357274600017

Klíčová slova anglicky

stars: chemically peculiar; stars: early-type; stars: variables: general; stars: individual: theta Aurigae

Štítky

AKR, rivok

Příznaky

Mezinárodní význam, Recenzováno

Změněno: 14. 4. 2016 15:38, Ing. Andrea Mikešková

Anotace

V originále

Context. Chemically peculiar stars of the upper part of the main sequence show periodical variability in line intensities and continua, modulated by the stellar rotation, which is attributed to the existence of chemical spots on the surface of these stars. The flux variability is caused by the changing redistribution rate of the radiative flux predominantly from the short-wavelength part of the spectra to the long-wavelength part, which is a result of abundance anomalies. Many details of this process are still unknown. Aims. We study the nature of the multi-spectral variability of one of the brightest chemically peculiar stars, theta Aur. Methods. We predict the flux variability of theta Aur from the emerging intensities calculated for individual surface elements of the star taking into account horizontal variation of chemical composition. The surface chemical composition was derived from Doppler abundance maps. Results. The simulated optical variability in the Stromgren photometric system and the ultraviolet flux variability agree well with observations. The IUE flux distribution is reproduced in great detail by our models in the near ultraviolet region. A minor disagreement remains between the observed and predicted fluxes in the far ultraviolet region. The resonance lines of magnesium and possibly also some lines of silicon are relatively weak in the ultraviolet domain, which indicates non-negligible vertical abundance gradients in the atmosphere. We also derive a new period of the star, P = 3.618 664(10) d, from all available photometric and magnetic measurements and show that the observed rotational period is constant over decades. Conclusions. The ultraviolet and visual variability of theta Aur is mostly caused by silicon bound-free absorption and chromium and iron line absorption. Manganese also contributes to the variability, but to a lesser extent. These elements redistribute the flux mainly from the far-ultraviolet region to the near-ultraviolet and optical regions in the surface abundance spots. The light variability is modulated by the stellar rotation. The ultraviolet domain is key for understanding the properties of chemically peculiar stars. It provides a detailed test for surface abundance models and comprises many lines that originate from states with a low excitation potential, which enable detecting vertical abundance gradients.

Návaznosti

GAP209/12/0217, projekt VaV

Název: Multispektrální proměnnost horkých hvězd a její příčiny

Investor: Grantová agentura ČR, Multispektrální proměnnost horkých hvězd a její příčiny

7AMB14AT015, projekt VaV

Název: Nový pohled na magnetické hvězdy (Akronym: MAGSTARS)

Investor: Ministerstvo školství, mládeže a tělovýchovy ČR, Nový pohled na magnetické hvězdy

Citovat

KRTIČKA, Jiří, Zdeněk MIKULÁŠEK, Theresa LUFTINGER a Miroslav JAGELKA. Visual and ultraviolet flux variability of the bright CP star theta Aurigae. ASTRONOMY & ASTROPHYSICS. LES ULIS CEDEX A: EDP SCIENCES S A, 2015, roč. 576, april, s. "nestránkováno", 11 s. ISSN 0004-6361. Dostupné z: https://dx.doi.org/10.1051/0004-6361/201425097.

@article{1338894,
   author = {Krtička, Jiří and Mikulášek, Zdeněk and Luftinger, Theresa and Jagelka, Miroslav},
   article_location = {LES ULIS CEDEX A},
   article_number = {april},
   doi = {http://dx.doi.org/10.1051/0004-6361/201425097},
   keywords = {stars: chemically peculiar; stars: early-type; stars: variables: general; stars: individual: theta Aurigae},
   language = {eng},
   issn = {0004-6361},
   journal = {ASTRONOMY & ASTROPHYSICS},
   title = {Visual and ultraviolet flux variability of the bright CP star theta Aurigae},
   volume = {576},
   year = {2015}
}

TY  - JOUR
ID  - 1338894
AU  - Krtička, Jiří - Mikulášek, Zdeněk - Luftinger, Theresa - Jagelka, Miroslav
PY  - 2015
TI  - Visual and ultraviolet flux variability of the bright CP star theta Aurigae
JF  - ASTRONOMY & ASTROPHYSICS
VL  - 576
IS  - april
SP  - "nestránkováno"
EP  - "nestránkováno"
PB  - EDP SCIENCES S A
SN  - 00046361
KW  - stars: chemically peculiar
KW  - stars: early-type
KW  - stars: variables: general
KW  - stars: individual: theta Aurigae
N2  - Context. Chemically peculiar stars of the upper part of the main sequence show periodical variability in line intensities and continua, modulated by the stellar rotation, which is attributed to the existence of chemical spots on the surface of these stars. The flux variability is caused by the changing redistribution rate of the radiative flux predominantly from the short-wavelength part of the spectra to the long-wavelength part, which is a result of abundance anomalies. Many details of this process are still unknown. Aims. We study the nature of the multi-spectral variability of one of the brightest chemically peculiar stars, theta Aur. Methods. We predict the flux variability of theta Aur from the emerging intensities calculated for individual surface elements of the star taking into account horizontal variation of chemical composition. The surface chemical composition was derived from Doppler abundance maps. Results. The simulated optical variability in the Stromgren photometric system and the ultraviolet flux variability agree well with observations. The IUE flux distribution is reproduced in great detail by our models in the near ultraviolet region. A minor disagreement remains between the observed and predicted fluxes in the far ultraviolet region. The resonance lines of magnesium and possibly also some lines of silicon are relatively weak in the ultraviolet domain, which indicates non-negligible vertical abundance gradients in the atmosphere. We also derive a new period of the star, P = 3.618 664(10) d, from all available photometric and magnetic measurements and show that the observed rotational period is constant over decades. Conclusions. The ultraviolet and visual variability of theta Aur is mostly caused by silicon bound-free absorption and chromium and iron line absorption. Manganese also contributes to the variability, but to a lesser extent. These elements redistribute the flux mainly from the far-ultraviolet region to the near-ultraviolet and optical regions in the surface abundance spots. The light variability is modulated by the stellar rotation. The ultraviolet domain is key for understanding the properties of chemically peculiar stars. It provides a detailed test for surface abundance models and comprises many lines that originate from states with a low excitation potential, which enable detecting vertical abundance gradients.
ER  -

KRTIČKA, Jiří, Zdeněk MIKULÁŠEK, Theresa LUFTINGER a Miroslav JAGELKA. Visual and ultraviolet flux variability of the bright CP star theta Aurigae. \textit{ASTRONOMY \&{}amp; ASTROPHYSICS}. LES ULIS CEDEX A: EDP SCIENCES S A, 2015, roč.~576, april, s.~''nestránkováno'', 11 s. ISSN~0004-6361. Dostupné z: https://dx.doi.org/10.1051/0004-6361/201425097.

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