J/A+A/667/A50 Anti-solar differentially rotating stars (Noraz+, 2022)
Hunting for anti-solar differentially rotating stars using the Rossby number.
An application to the Kepler field.
Noraz Q., Breton S.N., Brun A.S., Garcia R.A., Strugarek A., Santos A.R.G.,
Mathur S., Amard L.
<Astron. Astrophys. 667, A50 (2022)>
=2022A&A...667A..50N 2022A&A...667A..50N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, G-type
Keywords: stars: rotation - stars: solar-type - Sun: evolution -
methods: analytical - methods: data analysis - methods: observational
Abstract:
Anti-solar differential rotation profiles have been found for decades
in numerical simulations of convective envelopes of solar-type stars.
These profiles are characterized by a slow equator and fast poles
(i.e., reversed with respect to the Sun) and have been found in
simulations for high Rossby numbers. Rotation profiles like this have
been reported in evolved stars, but have never been unambiguously
observed for cool solar-type stars on the main sequence. As solar-type
stars age and spin down, their Rossby numbers increase, which could
therefore induce a transition toward an anti-solar differential
rotation regime before the end of the main sequence. Such a rotational
transition will impact the large-scale dynamo process and the magnetic
activity. In this context, detecting this regime in old main-sequence
solar-type stars would improve our understanding of their
magnetorotational evolution.
The goal of this study is to identify the most promising cool
main-sequence stellar candidates for anti-solar differential rotation
in the Kepler sample.
First, we introduce a new theoretical formula to estimate fluid Rossby
numbers, Rof, of main-sequence solar-type stars. We derived it from
observational quantities such as Teff and Prot, and took the influence
of the internal structure into account. Then, we applied it on a
subset of the most recent catalog of Kepler rotation periods, after
removing subgiants and selecting targets with solar metallicity. Next,
we considered the highest computed Rof and inspected each target
individually to select the most reliable anti-solar candidate.
Finally, we extended our study to stars with metallicities different
from that of the Sun. To this end, we developed a formulation for Rof
dependent on the metallicity index [Fe/H] by using 1D stellar grids,
and we also considered this compositional aspect for the selection of
the targets.
We obtain a list of the most promising stars that are likely to show
anti-solar differential rotation. We identify two samples: one at
solar metallicity, including 14 targets, and another for other
metallicities, including 8 targets. We find that the targets with the
highest Rof are likely to be early-G or late-F stars at about
log10g=4.37dex.
We conclude that cool main-sequence stellar candidates for anti-solar
differential rotation exist in the Kepler sample. The most promising
candidate is KIC 10907436, and two other particularly interesting
candidates are the solar analog KIC 7189915 and the seismic target KIC
12117868. Future characterization of these 22 stars is expected to
help us understand how dynamics can impact magnetic and rotational
evolution of old solar-type stars at high Rossby number.
Description:
We presented a novel approach for highlighting the most promising
candidates for the detection of anti-solar DR regime in MS cool stars.
We proposed a first application of our method to the Kepler field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec1.dat 20 99 Results of individual visual inspections
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC Kepler Input Catalog identifier
10 I1 --- HaloFlag [0/1] Target in bright Halo (1)
12 I1 --- NeighFlag [0/3] Neighbors in FoV (2)
14 I1 --- ShapeFlag [0/1] Suspicious shape (3)
16 I1 --- loggFlag [0/1] High logg uncertainties (4)
18 I1 --- ProtFlag [0/3] Uncertain rotation period (5)
20 I1 --- CandFlag [0/1] Antisolar candidate (6)
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Note (1): Target in bright Halo flag as follows:
0 = No pollution from the halo of another star
1 = The target is in the light-halo of a brighter star from the visual
inspection of 2MASS images (Skrutskie et al., 2006AJ....131.1163S 2006AJ....131.1163S,
Cat. VII/233)
Note (2): Neighbors in FoV flag as follows:
0 = There is no neighbor visible in the Kepler acquisition field of view
(FoV)
1 = There is at least a neighbor visible in the Kepler acquisition FoV,
which is not polluting the rotational signal of the target
2 = There is at least a neighbor visible in the Kepler acquisition FoV,
which is possibly polluting the rotational signal of the target
3 = There is at least a neighbor visible in the Kepler acquisition FoV,
which is surely polluting the rotational signal of the target
Note (3): Suspicious shape flag as follows:
0 = The shape of the target in the FoV is not suspicious
1 = The shape of the target in the FoV is deformed or elongated
Note (4): High logg uncertainties flag as follows:
0 = logg uncertainties taken from Santos et al. (2019ApJS..244...21S 2019ApJS..244...21S,
Cat. J/ApJS/244/21; 2021ApJS..255...17S 2021ApJS..255...17S, Cat. J/ApJS/255/17)
are standard
1 = logg uncertainties taken from Santos et al. (2019ApJS..244...21S 2019ApJS..244...21S,
Cat. J/ApJS/244/21; 2021ApJS..255...17S 2021ApJS..255...17S, Cat. J/ApJS/255/17)
are too large (e_logg>0.7dex) to decipher whether the target
is in its MS phase or in its subgiant phase
Note (5): Uncertain rotation period flag as follows:
0 = The rotation period (Prot) value extracted by
Santos et al. (2019ApJS..244...21S 2019ApJS..244...21S, Cat. J/ApJS/244/21;
2021ApJS..255...17S 2021ApJS..255...17S, Cat. J/ApJS/255/17)
(S19-21) clearly comes from the rotational signal of the target
1 = The Prot value extracted by S19-21 possibly does not come from the
rotational signal of the target
2 = We compute a new reliable Prot value from the rotational signal of the
target, but the corresponding new Rossby value is too low to consider
the target in the optimistic sample
3 = We compute a new reliable Prot value from the rotational signal of the
target and the corresponding new Rossby value is high enough to keep
the target in the optimistic sample
Note (6): Antisolar candidate flag as follows:
0 = We do not consider the target as an anti-solar DR candidate
1 = We consider the target as an anti-solar DR candidate
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Acknowledgements:
Quentin Noraz, quentin.noraz-73(at)hotmail.fr
(End) Patricia Vannier [CDS] 09-Aug-2022