J/A+A/689/A262 APT photometry for V889 Her and LQ Hya (Tuomi+, 2024)
Characterising the stellar differential rotation based on largest-spot
statistics from ground-based photometry.
Tuomi M., Lehtinen J.J., Henry G.W., Hackman T.
<Astron. Astrophys. 689, A262 (2024)>
=2024A&A...689A.262T 2024A&A...689A.262T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Photometry, UBV
Keywords: methods: statistical - stars: activity - stars: individual: V889 Her -
stars: individual: LQ Hya - stars: rotation - starspots
Abstract:
Stellar spot distribution has consequences on the observable periodic
signals in long-time baseline ground-based photometry. We model the
statistics of the dominating spots of two young and active Solar-type
stars, V889 Her and LQ Hya, in order to obtain information on the
underlying spot distribution, rotation of the star, as well as the
orientation of the stellar axis of spin. By calculating estimates for
spot-induced periodicities in independent subsets of photometric data,
we obtain statistics based on the dominating spots in each subset,
giving rise to largest-spot statistics accounting for stellar geometry
and rotation, including differential rotation. Our simple statistical
models are able to reproduce the observed distribution of photometric
signals rather well. This also enables us to estimate the dependence
of angular velocity of the spots as a function of latitude. Our
results indicate that V889 Her has a non-monotonic differential
rotation curve with a maximum angular velocity between latitudes of
37-40 deg and lower angular velocity at the pole than the equator. Our
results for LQ Hya indicate that the star rotates much like a rigid
body. Furthermore, the results imply that the monotonic Solar
differential rotation curve may not be a universal model for other
solar-type stars. The non-monotonicity of the differential rotation of
V889 Her is commonly produced in magnetohydrodynamic simulations,
which indicates that our results are realistic from a theoretical
perspective.
Description:
The B- and V-band light curves for the stars V889 Her and LQ Hya are
provided in the files v889her_b.dat, lqhya_b.dat, v889her_v.dat and
lqhya_v.dat as differential photometry against the comparison stars
HD 171286 (V889 Her) and HD 82477 (LQ Hya). The time points are given
as reduced HJD, i.e. HJD-2400000.0. The data was obtained with the T3
0.4m APT at the Fairborn Observatory, Arizona.
Objects:
-------------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------------
18 34 20.1 +18 41 24.2 V* V889 Her = HD 171488
09 32 25.6 -11 11 04.7 V* LQ Hya = HD 82558
-------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
lqhyab.dat 19 3730 LQ Hya B-band light curve
lqhyav.dat 19 3653 LQ Hya V-band light curve
v889herb.dat 19 2780 V889 Her B-band light curve
v889herv.dat 19 2755 V889 Her V-band light curve
--------------------------------------------------------------------------------
See also:
J/A+A/276/345 : Photometry of variable LQ Hya (Jestu 1993)
J/A+A/394/505 : UBV photometry of LQ Hya (Berdyugina+, 2002)
J/A+A/542/A38 : LQ Hya V-band differential light curve (Lehtinen+, 2012)
J/A+A/575/A57 : LQ Hya activity and Li variations (Flores Soriano+, 2015)
J/A+A/577/A120 : Carrier fit analysis of LQ Hya photometry (Olspert+, 2015)
J/A+A/660/A141 : Light curve of the active star LQ Hya (Lehtinen+, 2022)
J/A+A/622/A170 : V-band differential photometry for V889 Her (Willamo+, 2019)
Byte-by-byte Description of file: lqhya?.dat v889her?.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 F10.4 d HJD Reduced Heliocentric Julian Date (HJD-2400000)
13- 17 F5.3 mag dmag Differential band Johnson (B or V) photometry
19 A1 --- Band [BV] Observed band
--------------------------------------------------------------------------------
Acknowledgements:
Mikko Tuomi, mikko.tuomi(at)helsinki.fi
Thoma Hackman, thomas.hackman(at)helsinki.fi
(End) Patricia Vannier [CDS] 02-Sep-2024