J/A+A/702/A116 K2 data of M4 RR Lyraes and RGB parameters (Molnar+, 2025)
Matching seismic masses for RR Lyrae-type and oscillating red horizontal branch
stars in M4.
Molnar L., Netzel H., Howell M., Kalup Cs., Joyce M.
<Astron. Astrophys. 702, A116 (2025)>
=2025A&A...702A.116M 2025A&A...702A.116M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry ; Optical
Keywords: asteroseismology - stars: horizontal-branch -
stars: variables: RR Lyrae - globular clusters: individual: M4
Abstract:
Globular clusters offer a powerful way to test the properties of
stellar populations and the late stages of low-mass stellar evolution.
In this paper we study oscillating giant stars and overtone RR
Lyrae-type pulsators in the nearest globular cluster, M4, with the
help of high-precision, continuous light curves collected by the
Kepler space telescope in the K2 mission. We determine the frequency
composition of five RRc stars and model their physical parameters from
linear pulsation models. We are able, for the first time, to compare
seismic masses of RR Lyrae stars directly to the masses of the very
similar red horizontal branch stars in the same stellar population,
independently determined from asteroseismic scaling relations. We find
average seismic masses of 0.648±0.028M☉ for RR Lyrae stars and
0.657±0.034M☉ for red horizontal-branch stars. While the
accuracy of our RR Lyrae masses still relies on the accuracy of
evolutionary mass differences of neighboring horizontal branch
subgroups, this result strongly indicates that RRc stars may indeed
exhibit high-degree, l=8 and 9 non-radial modes, and modeling these
modes can provide realistic mass estimates. We compare the seismic
masses of our red horizontal branch and RR Lyrae stars to evolutionary
models and to theoretical mass relations and highlight the limitations
of these relations.
Description:
The Kepler space telescope observed five overtone RR Lyrae stars in M4
during the K2 mission. Differential photometry with Gaia-based
reference fluxes are presented here. We also list the updated physical
parameters of the evolved stars (RGB, RHB, AGB) based on asteroseismic
scaling relations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
rrlyr.dat 57 5 List of M4 RR Lyraes studied
tablec1.dat 35 15037 K2SC- and trend-corrected photometric data
for the five RRc stars
tablec4.dat 99 75 The updated global seismic properties and
calculated physical parameters for the
giants in M4
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See also:
J/MNRAS/515/3184 : Asteroseismology M4 study with K2 data (Howell+, 2022)
Byte-by-byte Description of file: rrlyr.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Variable star designation, VNN,
Cl* NGC 6121 Saw VNN
5- 6 I2 h RAh Simbad right ascension (J2000)
8- 9 I2 min RAm Simbad right ascension (J2000)
11- 15 F5.2 s RAs Simbad right ascension (J2000)
17 A1 --- DE- Simbad declination sign (J2000)
18- 19 I2 deg DEd Simbad declination (J2000)
21- 22 I2 arcmin DEm Simbad declination (J2000)
24- 27 F4.1 arcsec DEs Simbad declination (J2000)
29- 36 F8.6 d P1O Pulsation perdiod (from table 1)
38- 57 A20 --- SName Simbad name
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Byte-by-byte Description of file: tablec1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- ID Variable star designation
6- 16 F11.6 d BJD Time of observation (BJD-2454833)
19- 26 F8.5 mag Kpmag Brightness in the Kepler passband
29- 35 F7.5 mag e_Kpmag Brightness uncertainty
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Byte-by-byte Description of file: tablec4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Giant designation, from Howell et al.,
2022MNRAS.515.3184H 2022MNRAS.515.3184H, Cat. J/MNRAS/515/3184
11- 13 A3 --- Type Evolutionary stage
16- 17 A2 --- QF [D MD] Qality Flag (1)
20- 24 F5.2 mag Gmag Gaia DR2 brightness
27- 32 F6.2 uHz numax Frequency at maximum amplitude (microHz)
35- 38 F4.2 uHz e_numax Uncertainty of numax
41- 44 I4 K Teff Effective temperature
47- 49 I3 K e_Teff Uncertainty of Teff
52- 56 F5.1 Lsun L Luminosity
58- 61 F4.1 Lsun e1_L Random error in luminosity
64- 67 F4.1 Lsun e_L Systematic error in luminosity
70- 73 F4.2 Msun M Seismic mass
76- 79 F4.2 Msun e_M Uncertainty of the seismic mass
81- 99 I19 --- GaiaDR2 Gaia DR2 source_id
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Note (1): Qality Flag as follows:
D = Detection
MD = Marginal Detection
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Acknowledgements:
Laszlo Molnar, molnar.laszlo(at)csfk.org
(End) Patricia Vannier [CDS] 25-Aug-2025