Identification

Title

Deconvolving the HD 81809 binary: Rotational and activity evidence for a subgiant with a sun-like cycle

Abstract

HD 81809 has one of the highest quality activity cycles from the sample of stars synoptically observed in the Mount Wilson Observatory HK Project. However, this object is in fact a binary system, raising the question as to which of the components is responsible for the observed cyclic activity and what are the properties of that active component. The Hipparcos spacecraft obtained resolved two-color photometry for this system that indicates that both components are near the solar temperature. Combined with the precise Gaia parallax and empirical bolometric corrections we derive component the luminosities of L-A = 5.8 +/- 0.3 L-circle dot(N), and L-B = 1.025 +/- 0.055 L-circle dot(N), and radii R-A 2.42 +/- 0.08 R-circle dot(N) and R-B 1.04 +/- 0.04 R-circle dot(N), confirming that the primary component is a subgiant. We perform an independent estimate of the rotation period of the A component based on v sin i and find that it agrees with the 40.2 days period previously measured from the Ca HK time series. We explore plausible scenarios for the deconvolved S-index and find that a cycling A component would have an activity level within the bounds of ensemble activity-rotation trends, while a cycling B component likely does not. Based on the available rotation and activity evidence, we find the most likely characterization of the system is a subgiant primary component responsible for the smooth cyclic behavior in Ca HK with log(R'(HK)) similar to -4.89, while the secondary component has relatively flat activity at log(R'(HK)) similar to -5.02.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7959mh7

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2018-10-15T00:00:00Z

Frequency of update

Quality and validity

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Conformity

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version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact