J/A+A/656/A103 NGC 3532 stars chromospheric activity (Fritzewski+, 2021)
A detailed understanding of the rotation-activity relationship using the 300 Myr
old open cluster NGC 3532.
Fritzewski D.J., Barnes S.A., James D.J., Jarvinen S.P., Strassmeier K.G.
<Astron. Astrophys. 656, A103 (2021)>
=2021A&A...656A.103F 2021A&A...656A.103F (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, late-type ; Equivalent widths ;
Spectroscopy ; Optical
Keywords: stars: chromospheres -
open clusters and associations: individual: NGC 3532 -
stars: late-type - stars: activity - techniques: spectroscopic -
techniques: photometric
Abstract:
The coeval stars of young open clusters provide insights into the
formation of the rotation-activity relationship that elude studies of
multi-age field populations.
We measure the chromospheric activity of cool stars in the 300 Myr old
open cluster NGC 3532 in concert with their rotation periods to study
the mass-dependent morphology of activity for this transitional coeval
population. Using multi-object spectra of the Ca II infrared triplet
region obtained with the AAOmega spectrograph at the 4m Anglo-
Australian Telescope, we measure the chromospheric emission ratios
R'IRT for 454 FGKM cluster members of NGC3532.
The morphology of activity against colour appears to be a near-mirror
image of the cluster's rotational behaviour. In particular, we
identify a group of 'desaturated transitional rotators' that branches
off from the main group of unsaturated FGK slow rotators, and from
which it is separated by an 'activity gap'. The few desaturated gap
stars are identical to the ones in the rotational gap. Nevertheless,
the rotation-activity diagram is completely normal. In fact, the
relationship is so tight that it allows us to predict rotation periods
for many additional stars. We then precisely determine these periods
from our photometric light curves, allowing us to construct an
enhanced colour-period diagram that represents 66% of the members in
our sample. Our activity measurements show that all fast rotators of
near-solar mass (F-G type) have evolved to become slow rotators,
demonstrating that the absence of fast rotators in a colour-period
diagram is not a detection issue but an astrophysical fact. We also
identify a new population of low-activity stars among the early
Mdwarfs, enabling us to populate the extended slow rotator sequence in
the colour-period diagram.
The joint analysis of chromospheric activity and photometric time
series data thus enables comprehensive insights into the evolution of
the rotation and activity of stars during the transitional phase
between the Pleiades and Hyades ages.
Description:
Measurements of chromospheric activity for cool star members of the
open cluster NGC 3532. In addition to the equivalent widths and
chromospheric emission ratios, the table contains photometric rotation
periods for 258 stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 99 454 Chromospheric emission ratios and rotation
periods for 454 member cool star members of
the open cluster NGC 3532
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See also:
J/AJ/141/115 : BV(RI)c photometry on NGC 3532 (Clem+ 2011)
J/A+A/622/A110 : Spectroscopic membership for NGC 3532 (Fritzewski+ 2019)
J/A+A/652/A60 : Rotation periods for NGC 3532 (Fritzewski+ 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right ascension (J2000) from Clem et al.
(2011AJ....141..115C 2011AJ....141..115C, Cat. J/AJ/141/115)
11- 19 F9.5 deg DEdeg Declination (J2000) from Clem et al.
(2011AJ....141..115C 2011AJ....141..115C, Cat. J/AJ/141/115)
21- 26 I6 --- CLHW ID from Clem et al. (2011AJ....141..115C 2011AJ....141..115C,
Cat. J/AJ/141/115),
[CLH2011b] NNNNNN in Simbad
28- 32 F5.3 mag (V-Ks)0 (V-Ks)_0 colour based on Vmag from Clem et
al. (2011AJ....141..115C 2011AJ....141..115C,
Cat. J/AJ/141/115) and 2MASS Ks (1)
34- 37 I4 K Teff Effective temperature estimated from
(V-Ic)0 (2)
39- 41 F3.1 0.1nm excessEW Sum of the chromospheric excess equivalent
widths measured in the Ca II IRT line cores
43- 46 F4.2 0.1nm e_excessEW Uncertainty of excess_EW
48- 53 F6.4 10+3W/m2 FIRT excessEW converted to flux in the IRT
(106erg/s/cm2)
55- 61 F7.5 10+3W/m2 e_FIRT Uncertainty of FIRT (106erg/s/cm2)
63- 68 F6.3 [-] logRIRT Logarithm of normalized excess flux
(chromospheric emission ratio)
70- 74 F5.3 [-] e_logRIRT Uncertainty of logRIRT
76- 80 F5.2 d Prot ? Photometric rotation period from
Fritzewski et al.
(2021A&A...652A6..0F 2021A&A...652A6..0F, Cat. J/A+A/652/A60)
82- 85 F4.2 d e_Prot ? Uncertainty of Prot
87- 92 F6.4 --- Ro ? Rossby number (3)
94- 99 F6.4 --- e_Ro ? Uncertainty of Ro
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Note (1): Dereddened with E(B-V)=0.034, E(V-Ks)=0.095
(Fritzewski et al., 2019A&A...622A.110F 2019A&A...622A.110F, Cat. J/A+A/622/A110).
Note (2): Teff estimated from (V-Ic)0 with Mann et al.
(2015ApJ...804...64M 2015ApJ...804...64M, Cat. J/ApJ/804/64)
Note (3): Calculated with convective turnover time from Barnes & Kim
(2010ApJ...721..675B 2010ApJ...721..675B)
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Acknowledgements:
Dario Fritzewski, dfritzewski(at)aip.de
(End) Patricia Vannier [CDS] 02-Nov-2021