J/ApJ/929/29 Open cluster nondegenerate stars analysis (Gutierrez+, 2022)
Detection of gravitational redshift in open cluster nondegenerate stars.
Gutierrez C.M., Ramos-Chernenko N.
<Astrophys. J., 929, 29 (2022)>
=2022ApJ...929...29G 2022ApJ...929...29G
ADC_Keywords: Radial velocities; Clusters, open; Optical
Keywords: Gravitation ; General relativity ; Radial velocity ;
Open star clusters ; Redshifted
Abstract:
A key observational prediction of Einstein's Equivalence Principle is
that light undergoes redshift when it escapes from a gravitational
field. Although astrophysics provides a wide variety of physical
conditions in which this redshift should be significant, until very
recently the observational evidence for this gravitational effect was
limited to the light emitted by the Sun and white dwarfs. Gaia-DR2
astrometric and kinematic data, in combination with other
spectroscopic observations, provides a test bench to validate such
predictions in statistical terms. The aim of this paper is to analyze
several thousand main-sequence and giant stars in open clusters (OCs)
in order to measure the gravitational redshift effect.
Observationally, a spectral shift will depend on the stellar
mass-to-radius ratio as expected from the theoretical estimation of
relativity. After the analysis, the obtained correlation coefficient
between theoretical predictions and observations for 28 (51) OCs is
a=0.977±0.218 (0.899±0.137). The result has proven to be
statistically robust and with little dependence on the details of the
methodology or sample selection criteria. This study represents one of
the more extensive validations of a fundamental prediction of gravity
theories.
Description:
A total sample of 86 open clusters (OCs) and 8899 stars was selected
from Tarricq+ 2021 (Cat. J/A+A/647/A19) for analysis. The initial 1382
OCs data were completed with stellar parameters from the Gaia
DR2-based StarHorse catalog (Anders+ 2019, I/349).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 86 Full results for Method B (see Section 3.2) with
and without modeling the convective shift (CS)
contribution for 47 clusters
table2.dat 106 8899 The base sample used in the paper for 86 open clusters
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/349 : StarHorse, Gaia DR2 photo-astrometric distances (Anders+, 2019)
J/A+A/322/460 : NGC 3680 photometry and radial velocities (Nordstrom+ 1997)
J/A+A/381/446 : Astrometric Radial Velocities. III. (Madsen+, 2002)
J/A+A/526/A127 : Velocities of M67 MS and giant stars (Pasquini+, 2011)
J/A+A/550/A103 : Model 1D (LHD) and 3D (CO5BOLD) sp. (Allende Prieto+, 2013)
J/A+A/619/A155 : Open cluster kinematics with Gaia DR2 (Soubiran+, 2018)
J/A+A/627/A119 : Extended halo of NGC 2682 (M 67) (Carrera+ 2019)
J/MNRAS/483/5026 : Radial velocities of Hyades stars (Leao+, 2019)
J/A+A/633/A99 : Gaia DR2 open clusters in the MW. II (Cantat-Gaudin+, 2020)
J/A+A/640/A1 : Portrait Galactic disc (Cantat-Gaudin+, 2020)
J/A+A/643/A146 : The solar gravitational redshift (Gonzalez Hernandez+, 2020)
J/A+A/647/A19 : 3D Kinematics and age of OCs (Tarricq+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Cl Host cluster identifier
15- 21 F7.3 km/s RVel [-61.6/106.3] Radial velocity
23- 27 F5.3 km/s e_RVel [0.049/0.4] Uncertainty in RVel
29- 33 F5.3 km/s rms [0.7/2.8] Standard deviation
35- 37 I3 --- Ngr [50/581] Number of stars with the gravitational
redshift (GR) estimation
39- 45 F7.3 --- aGR [-13.7/9.8] Slope result of fit with only GR
considered
47- 51 F5.3 --- e_aGR [0.3/9] Uncertainty in aGR
53- 58 F6.3 km/s bGR [-2.5/2.6] Intercept result of fit with only
GR considered
60- 64 F5.3 km/s e_bGR [0.15/2.2] Uncertainty in bGR with only GR
considered
66- 68 I3 --- Ncs [1/478] Number of stars with the CS estimation
70- 75 F6.3 --- aCS [-2/5.2]? Slope result of fit with GR & CS
considered
77- 81 F5.3 --- e_aCS [0.39/6]? Uncertainty in aCS
83- 88 F6.3 km/s bCS [-1.3/1.3]? Intercept result of fit with GR &
CS considered
90- 94 F5.3 km/s e_bCS [0.18/1.5]? Uncertainty in bCS
96- 100 A5 --- Flag Result flag (1)
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Note (1): Flag as follows:
True = GR+CS;
False = only GR considered.
NULL value for clusters added by CDS to complete the sample of
hosts given in Table 2.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR2 Gaia DR2 identifier
21- 40 F20.16 deg RAdeg DR2 Right Ascension (J2000)
42- 61 F20.16 deg DEdeg [-72/86] DR2 Declination (J2000)
63- 75 A13 --- Cl Host cluster identifier
77- 84 F8.3 km/s RVel [-922/998] Radial velocity (1)
86- 91 F6.4 km/s e_RVel [0/1] Uncertainty in RVel (1)
93- 99 F7.4 km/s CS [-0.33/0.81]? Convective shift (2)
101-106 F6.4 km/s GR [0.004/1.3] Gravitational shift (2)
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Note (1): From Tarricq+ (2021, J/A+A/647/A19).
Note (2): Positive/negative values for red/blueshift, respectively.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Mar-2024