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Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

Huang, P. C. and Chen, W. P. and Mugrauer, M. and Bischoff, R. and Budaj, J. and Garai, Zoltán (2019) Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei. ASTROPHYSICAL JOURNAL, 871 (2). ISSN 1538-4357

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Abstract

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM Cephei is such a UXor in the young (similar to 4 Myr) open cluster Trumpler 37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008-2018) detects (1) an similar to 3.43 day period, likely arising from rotational modulation by surface starspots, (2) sporadic brightening on timescales of days due to accretion, (3) irregular minor flux drops due to circumstellar dust extinction, and (4) major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting <= 50 days) events, is proportional to the duration, a consequence of varying clump sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying similar to 3%-8%, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring- or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.

Item Type: Article
Subjects: Q Science / természettudomány > Q1 Science (General) / természettudomány általában
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 13 Feb 2023 14:50
Last Modified: 13 Feb 2023 14:50
URI: http://real.mtak.hu/id/eprint/158959

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