J/ApJ/946/98 HST/COS obs. of main-sequence FGKM dwarfs (Cruz Aguirre+, 2023)
Disentangling stellar and airglow emission lines from Hubble Space Telescope
(HST) Cosmic Origins Spectrograph (COS) spectra.
Cruz Aguirre F., Youngblood A., France K., Bourrier V.
<Astrophys. J., 946, 98 (2023)>
=2023ApJ...946...98C 2023ApJ...946...98C
ADC_Keywords: Stars, dwarfs; Spectra, ultraviolet; Radial velocities;
Stars, diameters; Stars, distances
Keywords: Dwarf stars ; Main sequence stars ; Hubble Space Telescope ;
Ultraviolet spectroscopy ; Stellar activity
Abstract:
HI Lyα (1215.67Å) and the OI triplet (1302.17, 1304.86, and
1306.03Å) are bright far-ultraviolet (FUV) emission lines that
trace the stellar chromosphere. Observations of stellar Lyα and
OI using the Hubble Space Telescope's (HST) most sensitive FUV
spectrograph, the Cosmic Origins Spectrograph (COS), are contaminated
with geocoronal emission, or airglow. This study demonstrates that
airglow emission profiles as observed by COS are sufficiently stable
to create airglow templates that can be reliably subtracted from the
data, recovering the underlying stellar flux. We developed a graphical
user interface to implement the airglow subtraction on a sample of
171 main-sequence F-, G-, K-, and M-type dwarfs from the COS data
archive. Correlations between recovered stellar emission and measures
of stellar activity were investigated. Several power-law relationships
are presented for predicting the stellar Lyα and OI emission.
The apparent brightness of the stellar emission relative to the
airglow is a critical factor in the success or failure of an airglow
subtraction. We developed a predictor for the success of an airglow
subtraction using the signal-to-noise ratio of the nearby
chromospheric emission line SiIII (1206.51Å). The minimum
attenuated Lyα flux that was successfully recovered is
1.39x10-14erg/cm2/s, and we recommend this as a minimum flux for
COS Lyα recoveries.
Description:
We identified 171 stars of F, G, K, or M type from available HST
Cosmic Origins Spectrograph (COS) G130M spectra in the Mikulski
Archive for Space Telescopes (MAST) data archive. All COS observations
analyzed in this work can be accessed through the MAST portal via
doi:10.17909/0sc9-b207. There are 78 confirmed exoplanet host stars in
this sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb2.dat 319 171 Observing programs of the stellar COS and
literature values
tableb4.dat 379 410 Best fit results
refs.dat 67 153 References
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See also:
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Byte-by-byte Description of file: tableb2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- Name Star name
24- 40 A17 --- SpT Spectral type
42- 43 I2 --- r_SpT [0/69]? Reference for SpT (see refs.dat file)
45- 62 A18 --- ObsID Observing Program identifier
64- 73 A10 "M/D/Y" Obs.date Date of First Observation UTC
75- 79 A5 "h:m" Obs.time Time of First Observation UTC
81- 83 A3 --- Host Exoplanet Host? ("Yes"=78 occurrences)
85- 91 F7.3 km/s RVel [-99/913]? Radial Velocity
93- 94 I2 --- r_RVel [1/65]? Reference for RVel
(see refs.dat file)
96-101 F6.2 km/s RVISM [-29.3/27.4] ISM radial velocity
103-107 F5.2 [cm-2] logNHI [17.46/19.3]? Log, HI column density
109-112 F4.2 [cm-2] E_logNHI [0.02/0.9]? Upper Uncertainty on logNHI (2)
114-117 F4.2 [cm-2] e_logNHI [0.02/0.5]? Lower Uncertainty on logNHI (2)
119-120 I2 --- r_logNHI [70/81]? Reference for logNHI
(see refs.dat file)
121 A1 --- f_logNHI [d] Flag on logNHI (1)
123-130 E8.3 mW/m2 FLya [1.3e-14/2e-12]? Lyα Flux, erg/s/cm2
132-139 E8.3 mW/m2 E_FLya [4e-15/2.2e-12]? Upper Uncertainty on FLya
(2)
141-148 E8.3 mW/m2 e_FLya [3e-15/9e-13]? Lower Uncertainty on FLya (2)
150-151 I2 --- r_FLya [70/81]? Reference for FLya
(see refs.dat file)
153-164 F12.9 [-] RHK [-5.7/-3.9]? Log, R'HK activity indicator
166-176 F11.9 [-] E_RHK [0.016/0.3]? Upper Uncertainty on RHK (2)
178-185 F8.6 [-] e_RHK [0.016/0.3]? Lower Uncertainty on RHK (2)
187-188 I2 --- r_RHK [9/93]? Reference for RHK (see refs.dat file)
190-198 F9.4 K Teff [2515/6831]? Surface effective temperature
200-211 F12.8 K E_Teff [3.8/119]? Upper Uncertainty on Teff (2)
213-219 F7.3 K e_Teff [3.8/105]? Lower Uncertainty on Teff (2)
221-223 I3 --- r_Teff [19/110]? Reference for Teff
(see refs.dat file)
225-230 F6.4 Rsun Rstar [0.1/2.7]? Stellar radius
232-242 F11.9 Rsun E_Rstar [0.0057/0.3]? Upper Uncertainty on Rstar (2)
244-249 F6.4 Rsun e_Rstar [0.0057/0.3]? Lower Uncertainty on Rstar (2)
251-253 I3 --- r_Rstar [36/120]? Reference for Rstar
(see refs.dat file)
255-262 F8.4 pc Dist [3.2/104] Distance
264-270 F7.4 pc E_Dist [0.0004/10] Upper Uncertainty on Dist (2)
272-278 F7.4 pc e_Dist [0.0004/10] Lower Uncertainty on Dist (2)
280-282 I3 --- r_Dist [2/121]? Reference for Dist
(see refs.dat file)
284-291 F8.3 d Prot [0.4/1015]? Rotational Period
293-305 F13.9 d E_Prot [0.001/160]? Upper Uncertainty on FLya (2)
307-312 F6.3 d e_Prot [0.001/13.5]? Lower Uncertainty on FLya (2)
314-316 I3 --- r_Prot [54/152]? Reference for FLya
(see refs.dat file)
318-319 A2 --- l_Prot [dd] dd: Prot is an upper limit based on
vsini
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Note (1): References and notes as follows:
d = Calculated using Lyα reconstruction method developed in
Youngblood+ 2016ApJ...824..101Y 2016ApJ...824..101Y
Note (2): When a value has an upper limit, but the lower limit is null (blank),
this indicates that the upper and lower uncertainties are equal/symmetric
and were calculated based on other reported errors in the literature.
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Byte-by-byte Description of file: tableb4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- Name Star Name
24- 33 A10 --- Line Emission Line
35- 47 F13.9 km/s RVel [-96/243] Radial Velocity
49- 61 F13.9 km/s E_RVel [0.001/398] Upper Uncertainty on RVel
63- 75 F13.9 km/s e_RVel [0.001/417] Lower Uncertainty on RVel
77- 88 F12.8 km/s FWHM-G [10/291] Gaussian Full width at half maximum
90-103 F14.9 km/s E_FWHM-G [6.4e-06/1555] Upper Uncertainty on FWHM-G
105-116 F12.9 km/s e_FWHM-G [0.04/64.6] Lower Uncertainty on FWHM-G
118-130 F13.9 km/s FWHM-L [1.8/190]? Lorentzian Full width at
half maximum
132-144 F13.9 km/s E_FWHM-L [0.79/882]? Upper Uncertainty on FWHM-L
146-157 F12.9 km/s e_FWHM-L [0.75/58]? Lower Uncertainty on FWHM-L
159-171 F13.9 [-] logFamp [-16/-9.5] log, Flux Amplitude
173-183 F11.9 [-] E_logFamp [0.004/2] Upper Uncertainty on logFamp
185-195 F11.9 [-] e_logFamp [0.005/3.2] Lower Uncertainty on logFamp
197-207 F11.8 [cm-2] logNHI [17/19.1]? log, HI column density
209-219 F11.9 [cm-2] E_logNHI [0.03/1.2]? Upper Uncertainty on logNHI
221-231 F11.9 [cm-2] e_logNHI [0.001/2]? Lower Uncertainty on logNHI
233-245 F13.9 km/s RVISM [-49/45]? ISM radial velocity
247-258 F12.9 km/s E_RVISM [0.0001/44]? Upper Uncertainty on RVISM
260-271 F12.9 km/s e_RVISM [0.38/68]? Lower Uncertainty on RVISM
273-284 F12.9 0.1nm SH [-1.5/1.5] Airglow Shift, Angstroms
286-296 F11.9 0.1nm E_SH [0.0005/1] Upper Uncertainty on SH
298-308 F11.9 0.1nm e_SH [0.0007/1] Lower Uncertainty on SH
310-323 F14.12 --- SC [2.1e-10/6.5] Airglow Scale Factor
325-335 F11.9 --- E_SC [0.0003/0.3] Upper Uncertainty on SC
337-347 F11.9 --- e_SC [3.3e-06/0.3] Lower Uncertainty on SC
349-356 E8.2 mW/m2 RF [2e-17/5.2e-12] Rec. Flux, erg/s/cm2
358-365 E8.2 mW/m2 E_RF [5.4e-18/5.3e-12] Upper Uncertainty on RF
367-374 E8.2 mW/m2 e_RF [1.2e-35/3e-12] Lower Uncertainty on RF
376-379 A4 --- Morph Morphological category (1)
--------------------------------------------------------------------------------
Note (1): Morphological category of the observed Lyα and OI profiles
as follows:
DS;S = Definite Stellar, Strong (15 occurrences)
DS;W = Definite Stellar, Weak (32 occurrences)
QS;S = Questionable Stellar, Strong (14 occurrences)
QS;W = Questionable Stellar, Weak (31 occurrences)
SD = Stellar Dominant (126 occurrences)
ME = Mixed Emission (156 occurrences)
AD = Airglow Dominant (36 occurrences)
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Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Ref Reference code
5- 23 A19 --- BibCode Bibcode of the reference
25- 45 A21 --- Auth Author's name(s)
47- 67 A21 --- Cat VizieR catalog's reference
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Feb-2025