FUMES. III. Ultraviolet and Optical Variability of M-dwarf Chromospheres

被引:5
|
作者
Duvvuri, Girish M. [1 ,2 ,3 ]
Pineda, J. Sebastian [1 ,3 ]
Berta-Thompson, Zachory K. [1 ,2 ]
France, Kevin [1 ,2 ,3 ]
Youngblood, Allison [4 ]
机构
[1] Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA
[2] Univ Colorado, Ctr Astrophys & Space Astron, 593 UCB, Boulder, CO 80309 USA
[3] Univ Colorado, Lab Atmospher & Space Phys, 600 UCB, Boulder, CO 80309 USA
[4] NASA, Goddard Space Flight Ctr, Exoplanets & Stellar Astrophys Lab, Greenbelt, MD 20771 USA
来源
ASTRONOMICAL JOURNAL | 2023年 / 165卷 / 01期
基金
美国国家科学基金会;
关键词
H-ALPHA; SURVEY; I; EMISSION; ROTATION; ASTROPY; FLARES; STARS; LINES; YOUNG;
D O I
10.3847/1538-3881/ac9b49
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We obtained ultraviolet and optical spectra for nine M dwarfs across a range of rotation periods to determine whether they showed stochastic intrinsic variability distinguishable from flares. The ultraviolet spectra were observed during the Far Ultraviolet M-dwarf Evolution Survey Hubble Space Telescope program using the Space Telescope Imaging Spectrograph. The optical observations were taken from the Apache Point Observatory 3.5 m telescope using the Dual Imaging Spectrograph and from the Gemini South Observatory using the Gemini Multi-Object Spectrograph. We used the optical spectra to measure multiple chromospheric lines: the Balmer series from H alpha to H10 and the Ca ii H and K lines. We find that after excising flares, these lines vary on the order of 1%-20% at minute-cadence over the course of an hour. The absolute amplitude of variability was greater for the faster rotating M dwarfs in our sample. Among the five stars for which we measured the weaker Balmer lines, we note a tentative trend that the fractional amplitude of the variability increases for higher-order Balmer lines. We measured the integrated flux of multiple ultraviolet emission features formed in the transition region: the N v, Si iv, and C iv resonance line doublets, and the C ii and He ii multiplets. The signal-to-noise ratio of the UV data was too low for us to detect nonflare variability at the same scale and time cadence as the optical. We consider multiple mechanisms for the observed stochastic variability and propose both observational and theoretical avenues of investigation to determine the physical causes of intrinsic variability in the chromospheres of M dwarfs.
引用
收藏
页数:18
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