J/MNRAS/483/1125 Radius inflation in Praesepe active M-dwarfs (Jackson+, 2019)
A search for radius inflation among active M-dwarfs in Praesepe.
Jackson R.J., Jeffries R.D., Deliyannis C.P., Sun Q., Douglas S.T.
<Mon. Not. R. Astron. Soc., 483, 1125-1138 (2019)>
=2019MNRAS.483.1125J 2019MNRAS.483.1125J (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, pre-main sequence ; Stars, masses ;
Stars, diameters ; Magnitudes ; Radial velocities ; Optical
Keywords: stars: evolution - stars: low-mass - stars: pre-main-sequence -
starspots
Abstract:
Rotation periods from Kepler K2 are combined with projected rotation
velocities from the WIYN 3.5m telescope to determine projected radii
for fast-rotating, low-mass (0.1≤M/M☉≤0.6) members of the
Praesepe cluster. A maximum likelihood analysis that accounts for
observational uncertainties, binarity, and censored data yields
marginal evidence for radius inflation - the average radius of these
stars is 6±4 per cent larger at a given luminosity than predicted by
commonly used evolutionary models. This overradius is smaller (at
2σ confidence) than was found for similar stars in the younger
Pleiades using a similar analysis; any decline appears due to changes
occurring in higher mass (>0.25M☉) stars. Models incorporating
magnetic inhibition of convection predict an overradius, but do not
reproduce this mass dependence unless superequipartition surface
magnetic fields are present at lower masses. Models incorporating flux
blocking by starspots can explain the mass dependence but there is no
evidence that spot coverage diminishes between the Pleiades and
Praesepe samples to accompany the decline in overradius. The fastest
rotating stars in both Praesepe and the Pleiades are significantly
smaller than the slowest rotators for which a projected radius can be
measured. This may be a selection effect caused by more efficient
angular momentum loss in larger stars leading to their progressive
exclusion from the analysed samples. Our analyses assume random
spin-axis orientations; any alignment in Praesepe, as suggested by
Kovacs, is strongly disfavoured by the broad distribution of projected
radii.
Description:
Candidate targets were selected from a list of high-probability
Praesepe members (Kraus & Hillenbrand 2007AJ....134.2340K 2007AJ....134.2340K, Cat.
J/AJ/134/2340) with rotation periods reported by Douglas et al.
(2017ApJ...842...83D 2017ApJ...842...83D, Cat. J/ApJ/842/83). The large majority of these
periods (92 per cent) are based on K2 light curves from campaign 5
(Howell et al. 2014PASP..126..398H 2014PASP..126..398H, Cat. IV/34) and the completeness
of the rotation period data is 86 per cent. Stars with rotation
periods were matched with the 2MASS catalogue (Skrutskie et al.
2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233) to define the target names,
coordinates, and K2MASS and with the Gaia catalogue (DR1; Gaia
collaboration 2016A&A...595A...1G 2016A&A...595A...1G, Cat. I/337) for G magnitudes.
Targets for our fibre spectroscopy were selected from a 10 square
degree area with the highest target density, with a faint limit of
K2MASS<14.5.
The luminosity of each target was estimated from its KCIT magnitude
(hereafter referred to as K) assuming a conversion of K=K2MASS+0.024
(Carpenter 2001AJ....121.2851C 2001AJ....121.2851C), zero reddening (Cummings et al.
2017AJ....153..128C 2017AJ....153..128C, Cat. J/AJ/153/128), and a distance modulus of
6.35±0.04 (Gaia Collaboration 2018A&A...616A..10G 2018A&A...616A..10G, Cat.
J/A+A/616/A10) and taking bolometric corrections as a function of
(V-K) from a 625Myr BHAC15 isochrone.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 99 230 Properties of observed science targets in
Praesepe
table4.dat 76 230 Estimated values of relative RV, vsini, and
Rsini
--------------------------------------------------------------------------------
See also:
J/AJ/134/2340 : Membership of Praesepe and Coma Berenices clusters
(Kraus+, 2007)
J/ApJ/842/83 : Praesepe members rotational periods from K2 LCs
(Douglas+, 2017)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- ID Target name (2MASS JHHMMSSss+DDMMSSs)
25- 26 I2 h RAh Right ascension (J2000)
28- 29 I2 min RAm Right ascension (J2000)
31- 36 F6.3 s RAs Right ascension (J2000)
38 A1 --- DE- Declination sign (J2000)
39- 40 I2 deg DEd Declination (J2000)
42- 43 I2 arcmin DEm Declination (J2000)
45- 49 F5.2 arcsec DEs Declination (J2000)
51- 55 F5.2 mag Kmag 2MASS K-band magnitude
57- 60 F4.2 mag V-K V-K color excess (1)
62- 65 A4 --- n_V-K V-K estimation source
67- 71 F5.2 d Period Rotation period from Douglas et al.
(2017ApJ...842...83D 2017ApJ...842...83D, Cat. J/ApJ/842/83)
73- 76 F4.2 mag BCKmag K-band bolometric correction (2)
78- 82 F5.2 [Lsun] logLstar Star luminosity (2)
84- 87 F4.2 Msun Mstar Star mass (2)
89- 93 F5.3 Rsun Rstar Star radius (2)
95- 99 F5.2 km/s vsini Projected equatorial velocity (3)
--------------------------------------------------------------------------------
Note (1): (V-K) estimated from G-K2MASS color where no V magnitude is
available. V magnitudes were only available for 54 per cent of the
stars. This subset was used to define a second-order polynomial
relationship between V-K and G-K.
Note (2): Values estimated using a BHAC15 model isochrone (Baraffe et al.
2015A&A...577A..42B 2015A&A...577A..42B)
Note (3): Targets were prioritized according to a predicted projected equatorial
velocity, vsini=50πR/4P in km/s, where R is the stellar radius in
solar units estimated from the 625Myr BHAC15 isochrone and π/4 is a
simple average value for the (unknown) sini if the spin axes are
randomly oriented.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- ID Target name (2MASS JHHMMSSss+DDMMSSs)
25- 28 F4.2 mag KMag K-band absolute magnitude
30- 34 F5.2 [Lsun] logLstar Star luminosity
36- 40 F5.2 d Period Rotation period from Douglas et al.
(2017ApJ...842...83D 2017ApJ...842...83D, Cat. J/ApJ/842/83)
42- 44 I3 --- SNR Signal to noise ratio
46- 51 F6.2 km/s RVrel ?=999 Relative radial velocity
53- 58 F6.2 km/s e_RVrel ?=999 Error on RVrel
60- 63 F4.1 km/s vsini Projected equatorial velocity
65- 67 F3.1 km/s e_vsini Error on vsini
69 A1 --- l_Rsini Upper limit in Rsini (1)
71- 76 F6.4 Rsun Rsini ? Projected radius (2)
--------------------------------------------------------------------------------
Note (1): Where the relative uncertainty in vsini is >30 per cent, an upper
limit is shown along with corresponding upper limits in Rsini
Note (2): Rsini is estimated using the rotation Period (P) and vsini:
Rsini/R_☉=0.0198Pvsini. Rsini values are shown where vsini>8km/s
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 12-Jul-2022