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Po-Chieh Huang, Wen-Ping Chen, Chia-Ling Hu, Otabek Burkhonov, Shuhrat Ehgamberdiev, Jinzhong Liu, Hiroyuki Naito, Erika Pakstiene, Jan Kare Trandem Qvam, Stefanie Rätz, Evgeni Semkov & Collaboration YETY

Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps

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Mots-clés : astronomie, astrophysique, photométrie, polarimétrie, stars, variability

Abstract

UX Orionis stars are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such an UX Orionis star in the young ( 4 Myr) open cluster Trumpler 37 at 900 pc, showing a prominent infrared access, H-alpha emission, and flare activity. Our multi-color photometric monitoring from 2009 to 2016 showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) cyclic, but not strictly periodical, occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual ”blueing” phenomena near the brightness minima, during which the star appeared bluer when dimmer, and (v) a noticeable polarization, from 3 to 9 percent in g’, r’, and i’ -bands. The occultation events may be caused by dust clumps, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. The level of polarization was anti-correlated with the brightness in the bright state, when the dust clump backscattered stellar light. We discussed two potential hypotheses: orbiting dust clumps versus dust clumps along a spiral arm structure.

Keywords : astronomy, astrophysics, photometry, polarimetry, stars, variability

To cite this article

Po-Chieh Huang, Wen-Ping Chen, Chia-Ling Hu, Otabek Burkhonov, Shuhrat Ehgamberdiev, Jinzhong Liu, Hiroyuki Naito, Erika Pakstiene, Jan Kare Trandem Qvam, Stefanie Rätz, Evgeni Semkov & Collaboration YETY, «Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps», Bulletin de la Société Royale des Sciences de Liège [En ligne], Volume 87 - Année 2018, Actes de colloques, First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop - November 2016 - Nainital, India, 145 - 149 URL : https://popups.uliege.be:443/0037-9565/index.php?id=7594.

About: Po-Chieh Huang

Graduate Institute of Astronomy, National Central University, Taiwan, pochiehhuang1@gmail.com

About: Wen-Ping Chen

Graduate Institute of Astronomy, National Central University, Taiwan

About: Chia-Ling Hu

Taipei Astronomical Museum, Taiwan

About: Otabek Burkhonov

Ulugh Beg Astronomical Institute, Uzbekistan

About: Shuhrat Ehgamberdiev

Ulugh Beg Astronomical Institute, Uzbekistan

About: Jinzhong Liu

Nanshan 1m telescope of Xinjiang Astronomical Observatory, China

About: Hiroyuki Naito

Nayoro Observatory, Japan

About: Erika Pakstiene

Institute of Theoretical Physics and Astronomy, Vilnius University, Lithuania

About: Jan Kare Trandem Qvam

Mathematics and Natural Sciences, Department of Physics, University of Oslo, Norway

About: Stefanie Rätz

Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Germany

About: Evgeni Semkov

Institute of Astronomy and National Astronomical Observatory, Bulgaria