J/AJ/165/12 FUMES. III. HST/STIS measurements of 9 M-dwarfs (Duvvuri+, 2023)
FUMES.
III. Ultraviolet and Optical Variability of M-dwarf Chromospheres.
Duvvuri G.M., Pineda J.S., Berta-Thompson Z.K., France K., Youngblood A.
<Astron. J., 165, 12 (2023)>
=2023AJ....165...12D 2023AJ....165...12D
ADC_Keywords: Stars, M-type; Spectra, ultraviolet
Keywords: M dwarf stars ; Stellar activity ; Stellar rotation
Abstract:
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 3.5m 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 Hα to H10
and the CaII 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 NV, SiIV, and
CIV resonance line doublets, and the CII and HeII 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.
Description:
The Far Ultraviolet M-dwarf Evolution Survey (FUMES) program collected
UV spectra using the Space Telescope Imaging Spectrograph (STIS) on
Hubble Space Telescope (HST). Spectra were obtained using the FUV-MAMA
detector and the G140L grating for the majority of the targets except
HIP112312 and HIP17695, for which we used the echelle E140M grating
instead.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 9 *Stellar parameters for the subset of the FUMES
sample considered in this work
table9.dat 91 30 Ultraviolet integrated flux measurements and
intrinsic variability fits
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Note on table1.dat: All parameters are from Pineda+, 2021ApJ...911..111P 2021ApJ...911..111P.
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See also:
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/MNRAS/421/3189 : CaII and Hα data for dK5/dM4 stars (Houdebine, 2012)
J/ApJS/207/15 : M dwarf flare spectra (Kowalski+, 2013)
J/ApJS/211/9 : Variability in UV line emission of F-M stars (Loyd+, 2014)
J/ApJ/821/93 : Rotation & Galactic kinematics mid M dwarfs (Newton+, 2016)
J/ApJ/837/96 : Rotation-Activity Corr. in K-M dwarfs II. (Houdebine+, 2017)
J/ApJ/834/85 : Hα emission in nearby M dwarfs (Newton+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Stellar identifier
12- 16 F5.3 Msun Mass [0.23/0.79] Stellar mass
18- 22 F5.3 Msun e_Mass [0.002/0.02] Negative error on Msun
24- 28 F5.3 Msun E_Mass [0.002/0.02] Positive error on Msun
30- 34 F5.3 Rsun Rad [0.25/0.94] Stellar radius
36- 40 F5.3 Rsun e_Rad [0.003/0.03] Negative error on Rad
42- 46 F5.3 Rsun E_Rad [0.003/0.03] Positive error on Rad
48- 51 I4 K Teff [3173/3886] Effective temperature
53- 54 I2 K e_Teff [6/83] Negative error on Teff
56- 57 I2 K E_Teff [8/89] Positive error on Teff
59- 64 F6.3 d Prot [1.28/53.5] Rotation period
66- 71 F6.4 --- Ro [0.02/1] Rossby Number
73- 77 F5.3 --- EW [0.15/0.56] Hα quiescent equivalent width
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Filt Filter used
18- 23 F6.1 0.1nm Wavemin [1227/1628] Minimum wavelength in filter (added
by VizieR team from table7)
25- 30 F6.1 0.1nm Wavemax [1254/1654] Maximum wavelength in filter (added
by VizieR team from table7)
32- 41 A10 --- Name Stellar identifier
43- 47 F5.2 --- Flux [4.32/92.4] Integrated flux (10-15erg/s/cm2)
49- 53 F5.2 --- e_Flux [0.3/15] Negative error on Flux
55- 59 F5.2 --- E_Flux [0.5/26] Positive error on Flux
61 A1 --- l_aVar [<] Limit on aVar
63- 68 F6.3 --- aVar [0.67/83.1] Absolute intrinsic variability
(10-15erg/s/cm2)
70 A1 --- l_fVar [<] Limit on fVar
72- 76 F5.3 --- fVar [0.06/0.61] Fractional intrinsic variability
(10-15erg/s/cm2)
78- 82 F5.3 --- e_fVar [0.08/0.2]? Negative error on fVar
84- 88 F5.3 --- E_fVar [0.1/0.3]? Positive error on fVar
90- 91 I2 --- Nobs [4/23] Number of measurement
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History:
From electronic version of the journal
References:
Youngblood et al. Paper II: 2021ApJ...911..112Y 2021ApJ...911..112Y
(End) Prepared by Coralie Fix [CDS], 07-Nov-2023