J/ApJ/839/97 HeI 5876 & 10830Å EWs of solar-type stars (Andretta+, 2017)
Estimates of active region area coverage through simultaneous measurements of
the He I λλ5876 and 10830 lines.
Andretta V., Giampapa M.S., Covino E., Reiners A., Beeck B.
<Astrophys. J., 839, 97 (2017)>
=2017ApJ...839...97A 2017ApJ...839...97A
ADC_Keywords: Stars, G-type ; Equivalent widths ; Rotational velocities
Keywords: stars: activity ; stars: magnetic field ; stars: solar-type ;
techniques: spectroscopic
Abstract:
Simultaneous, high-quality measurements of the neutral helium triplet
features at 5876Å and 10830Å in a sample of solar-type stars are
presented. The observations were made with ESO telescopes at the La
Silla Paranal Observatory under program ID 088.D-0028(A) and MPG
Utility Run for Fiber Extended-range Optical Spectrograph
088.A-9029(A). The equivalent widths of these features combined with
chromospheric models are utilized to infer the fractional area
coverage, or filling factor, of magnetic regions outside of spots. We
find that the majority of the sample is characterized by filling
factors less than unity. However, discrepancies occur among the
coolest K-type and the warmest and most rapidly rotating F-type dwarf
stars. We discuss these apparently anomalous results and find that in
the case of K-type stars, they are an artifact of the application of
chromospheric models best suited to the Sun than to stars with
significantly lower Teff. The case of the F-type rapid rotators can be
explained by the measurement uncertainties of the equivalent widths,
but they may also be due to a non-magnetic heating component in their
atmospheres. With the exceptions noted above, preliminary results
suggest that the average heating rates in the active regions are the
same from one star to the other, differing in the spatially
integrated, observed level of activity due to the area coverage.
Hence, differences in activity in this sample are mainly due to the
filling factor of active regions.
Description:
A total of 134 FEROS spectra (R=48000) of our targets (including
telluric standards) were acquired on the night of UT 2011 December
6-7; spectral coverage from 3500 to 9200Å. The Fiber Extended-range
Optical Spectrograph (FEROS) was mounted at the 2.2m Max-Planck
Gesellschaft/European Southern Observatory (MPG/ESO) telescope at La
Silla (Chile).
The HeIλ10830 spectroscopic observations were carried out on
the same night as the FEROS D3 observations, using the CRyogenic
high-resolution InfraRed Echelle Spectrograph (CRIRES), mounted at
Unit Telescope 1 (Antu) of the VLT array at Cerro Paranal.
The details of the observations is given in table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 62 134 Journal of observations for 41 HD stars
table3.dat 100 18 Helium equivalent width measurements and data
for program stars: B-V≤0.5
table4.dat 100 16 Helium equivalent width measurements and data
for program stars: B-V>0.5
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See also:
V/50 : Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
III/244 : Catalog of Stellar Rotational Velocities (Glebocki+ 2005)
J/A+AS/132/155 : Main-sequence and subgiants ROSAT data (Huensch+ 1998)
J/A+AS/135/319 : ROSAT data of Nearby Stars (Huensch+ 1999)
J/A+A/397/147 : Activity-rotation relationship in stars (Pizzolato+ 2003)
J/A+A/493/1099 : CaII HK emission in rapidly rotating stars (Schroeder+, 2009)
J/A+A/511/A54 : Magnetic cycles & radial-velocity for 8 stars (Santos+, 2010)
J/A+A/542/A116 : Rotation in A-F stars (Ammler-von Eiff+, 2012)
J/A+A/557/L10 : Rotation periods of 12000 Kepler stars (Nielsen+, 2013)
J/A+A/560/A4 : Rotation periods of active Kepler stars (Reinhold+, 2013)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/A+A/579/A136 : HAT-P-36 and WASP-11/HAT-P-10 light curves (Mancini+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [HD]
4- 9 I6 --- HD HD number
10 A1 --- m_HD HD component
12- 26 A15 --- SpType MK spectral type (A0V to K2.5V) (1)
28- 31 F4.2 mag B-V [0.02/1] The (B-V) color index (1)
33- 34 I2 h FEROS.h Hour of FEROS start time; UT (2)
36- 37 I2 min FEROS.m Minute of FEROS start time; UT (2)
39- 40 I2 s FEROS.s Second of FEROS start time; UT (2)
42- 43 I2 h CRIRES.h ? Hour of CRIRES start time; UT (2)
45- 46 I2 min CRIRES.m ? Minute of CRIRES start time; UT (2)
48- 49 I2 s CRIRES.s ? Second of CRIRES start time; UT (2)
51 A1 --- NodPos [AB] CRIRES nodding position
53- 62 A10 --- Notes Additional note(s) (3)
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Note (1): From the Bright Star Catalog (Hoffleit & Jaschek 1991bsc..book.....H 1991bsc..book.....H ;
see V/50) or the Simbad data base.
Note (2): The UT date for all start times is 2011 December 7.
Note (3): Note as follows:
std = telluric standards;
No AO = CRIRES AO off.
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Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- --- [HD]
4- 9 I6 --- HD HD number
10 A1 --- m_HD HD component
12- 15 F4.2 mag B-V [0.3/1] B-V color index
17- 21 F5.1 km/s vsini [1/118] Rotational velocity (1)
23- 27 F5.2 [10-7W] logLx [26/30] Log of X-ray luminosity (2)
29- 32 F4.1 10-13m WHeI5876 [3/77] HeIλ5876 equivalent width
34- 36 F3.1 10-13m e_WHeI5876 [1/7] WHeI5876 uncertainty
38- 41 F4.1 10-13m WHeI5876c [3/65] Corrected HeIλ5876
equivalent width
43- 45 F3.1 10-13m e_WHeI5876c [1/8] WHeI5876c uncertainty
47- 50 F4.1 10-13m WHeI5876b [1/13]? Undetected stellar blends in the line
profile
52- 54 F3.1 10-13m e_WHeI5876b [0.7/3]? WHeI5876b uncertainty
56- 60 F5.1 10-13m W10830 [51/410]? HeIλ10830 equivalent width
62- 65 F4.1 10-13m e_W10830 [1/21]? W10830 uncertainty
67- 70 F4.1 10-13m W10829 [12/70]? HeIλ10829.1 equivalent width
72- 75 F4.1 10-13m e_W10829 [1/16]? W10829 uncertainty
77- 80 F4.2 --- f(C) [0.1/1]? Filling factor f for the C serie of
models derived from Equation 1 (3)
82- 85 F4.2 --- e_f(C) [0.03/0.2]? f(C) uncertainty
87- 90 F4.2 --- f(C-np) [0.1/1]? Filling factor f for the C-np serie
of models derived from Equation 1 (3)
92- 95 F4.2 --- e_f(C-np) [0.02/0.2]? f(C-np) uncertainty
97-100 F4.2 --- fmin [0.03/1]? The minimum filling factor (4)
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Note (1): From Ammler-von Eiff & Reiners (2012, J/A+A/542/A116) when available,
otherwise from Glebocki & Gnacinski (2005, III/244)
or (HD 48189A) from Schroder et al. (2009, J/A+A/493/1099).
Note (2): From Hunsch et al. (1999, J/A+AS/135/319).
Note (3): The two series of theoretical models, labeled C and C-np, are
described in Section 2.1 and shown in Figure 4.
Equation 1 (in Section 2):
Wobs=(1-f)Wq+f.Wa where Wobs is the observed
equivalent width of a line, Wq is the contributions from
the quiescent atmosphere and Wa the active (plage-like)
atmosphere.
Note (4): The minimum filling factor from Equation 2 obtained from the
measurement of the λ10830 line only. Equation 2 (in Section 2):
f≥ (Wobs-Wq)/(Wmax-Wq) with Wobs, the observed equivalent
width of a line and Wq the contributions from the quiescent
atmosphere.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Nov-2017