J/ApJ/764/3 Hα indices in M low-mass stars (Robertson+, 2013)
Hα activity of old M dwarfs: stellar cycles and mean activity levels
for 93 low-mass stars in the solar neighborhood.
Robertson P., Endl M., Cochran W.D., Dodson-Robinson S.E.
<Astrophys. J., 764, 3 (2013)>
=2013ApJ...764....3R 2013ApJ...764....3R
ADC_Keywords: Stars, M-type ; Spectroscopy
Keywords: planetary systems; stars: activity; stars: kinematics and dynamics;
stars: late-type; techniques: radial velocities;
techniques: spectroscopic
Abstract:
Through the McDonald Observatory M Dwarf Planet Search, we have
acquired nearly 3000 high-resolution spectra of 93 late-type (K5-M5)
stars over more than a decade using the High Resolution Spectrograph
on the Hobby-Eberly Telescope. This sample provides a unique
opportunity to investigate the occurrence of long-term stellar
activity cycles for low-mass stars. In this paper, we examine the
stellar activity of our targets as reflected in the Hα feature.
We have identified periodic signals for six stars, with periods
ranging from days to more than 10 years, and find long-term trends for
seven others. Stellar cycles with P≥1 year are present for at least
5% of our targets. Additionally, we present an analysis of the
time-averaged activity levels of our sample, and search for
correlations with other stellar properties. In particular, we find
that more massive, earlier type (M0-M2) stars tend to be more active
than later type dwarfs. Furthermore, high-metallicity stars tend to be
more active at a given stellar mass. We also evaluate Hα
variability as a tracer of activity-induced radial velocity (RV)
variation. For the M dwarf GJ 1170, Hα variation reveals stellar
activity patterns matching those seen in the RVs, mimicking the signal
of a giant planet, and we find evidence that the previously identified
stellar activity cycle of GJ 581 may be responsible for the recently
retracted planet f in that system. In general, though, we find that
Hα is not frequently correlated with RV at the precision
(typically 6-7m/s) of our measurements.
Description:
The McDonald Observatory Planet Search has monitored nearby stars for
RV variation induced by exoplanets with the Hobby-Eberly Telescope
(HET) since 2001. After removing double-lined spectroscopic binaries
(SB2s), the M dwarf survey has amassed 2933 high-resolution spectra of
93 stars as of 2012 July. Our HET M dwarf spectra are taken with the
High Resolution Spectrograph (HRS). Nearly all the spectra are taken
at a resolving power R=60000, with a small number of bright targets
which we observed at R=120000.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 25 14 List of stars (from table 1)
table2.dat 54 457 Hα and Ca I indices shown in Figures 4 and 6
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See also:
J/A+A/541/A9 : M dwarfs activity & radial velocity (Gomes da Silva+, 2012)
J/A+A/540/A82 : CaIIHK emission in stars with planets (Krejcova+, 2012)
J/AJ/143/93 : Rotational velocities in early-M stars (Reiners+, 2012)
J/ApJ/743/48 : Stellar rotation periods & X luminosities (Wright+, 2011)
J/A+A/521/A12 : RVs of nearby late-type stars (Maldonado+, 2010)
J/A+A/514/A97 : HR spectra of Late-type stars (Lopez-Santiago+ 2010)
J/A+A/511/A54 : Magnetic cycles & RV for 8 stars (Santos+, 2010)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/ApJ/723/954 : HIRES radial velocities of GJ 581 (Vogt+, 2010)
J/A+A/507/487 : GJ 581 radial velocity curve (Mayor+, 2009)
J/A+A/505/859 : M dwarfs radial velocities (Zechmeister+, 2009)
J/AJ/135/785 : SDSS-DR5 low-mass star spectroscopic sample (West+, 2008)
J/A+A/469/309 : Late-type stars chromospheric activity (Cincunegui+, 2007)
J/MNRAS/367/1329 : Elemental abundances for 176 stars (Reddy+, 2006)
J/AJ/128/426 : Subdwarfs in the SDSS (West+, 2004)
J/A+AS/135/319 : ROSAT data of Nearby Stars (Huensch+ 1999)
J/A+A/327/1039 : Structure and evolution of low-mass stars (Chabrier+ 1997)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
9 A1 --- n_Name Notes on the fit (1)
11 A1 --- l_Per Limit flag on Per
12- 18 F7.2 d Per [3/2687]? Period for periodic signals
20- 25 F6.2 d e_Per ? Per uncertainty
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Note (1): Flag as follows:
a = three-day fit
b = 994 day fit
l = linear trends
q = quadratic trends
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name
10- 22 F13.8 d BJD Barycentric Julian Date; BJD-2450000
24- 30 F7.5 --- Ha [0.0495/0.087] Hα index
32- 38 F7.5 --- e_Ha [0.0002/0.002] Uncertainty in Ha index
40- 46 F7.5 --- CaI [0.0214/0.028] Ca I index
48- 54 F7.5 --- e_CaI [0.0001/0.002] Uncertainty in CaI index
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Oct-2014