Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397: High-precision multiple-pass photometry and astrometry

M Griggio; M Libralato; R Gerasimov; L.R Bedin; A Bellini; J Anderson; E Dalessandro; E Vesperini; H Baumgardt; D Massari; M Cadelano; R.E Ryan; I Mcdonald; F Annibali; E Balbinot; J.-C Cuillandre; D Erkal; A.M.N Ferguson; T Saifollahi; M Kluge; M Schirmer; P.B Kuzma; K Voggel; B Altieri; S Andreon; N Auricchio; C Baccigalupi; M Baldi; A Balestra; S Bardelli; P Battaglia; A Biviano; E Branchini; M Brescia; S Camera; V Capobianco; C Carbone; J Carretero; M Castellano; G Castignani; S Cavuoti; A Cimatti; C Colodro-Conde; G Congedo; C.J Conselice; L Conversi; Y Copin; F Courbin; H.M Courtois; M Cropper; G de Lucia; F Dubath; X Dupac; M Farina; R Farinelli; S Ferriol; E Franceschi; S Galeotta; K George; C Giocoli; J Gracia-Carpio; A Grazian; F Grupp; S.V.H Haugan; H Hoekstra; W Holmes; F Hormuth; A Hornstrup; K Jahnke; M Jhabvala; S Kermiche; A Kiessling; B Kubik; M Kümmel; H Kurki-Suonio; A.M.C Le Brun; S Ligori; P.B Lilje; V Lindholm; G Mainetti; I Lloro; O Marggraf; M Martinelli; N Martinet; F Marulli; R.J Massey; E Medinaceli; S Mei; M Meneghetti; E Merlin; G Meylan; A Mora; M Moresco; L Moscardini; R Nakajima; S.-M Niemi; C Padilla; S Paltani; F Pasian; K Pedersen

doi:10.1051/0004-6361/202660441

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Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397: High-precision multiple-pass photometry and astrometry

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Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397: High-precision multiple-pass photometry and astrometry

M Griggio, M Libralato, R Gerasimov, L.R Bedin, A Bellini, J Anderson, E Dalessandro, E Vesperini, H Baumgardt, D Massari, …

Astronomy & Astrophysics, Vol.Forthcoming articles(Forthcoming articles)

2026

DOI: https://doi.org/10.1051/0004-6361/202660441

Abstract

globular clusters: individual: NGC 6397

stars: kinematics and dynamics

stars: luminosity function, mass function

stars: low-mass

stars: interiors

proper-motions

Astrophysics

We present a `multiple-pass' data-reduction tool designed for Euclid, based on software developed for the Space Telescope (HST), which improves the astrometric and photometric precision for faint sources and in crowded fields. In this work, we apply it to Euclid Early Release Observations of the Galactic globular cluster NGC,6397. By combining our new catalogue with archival HST data, separated by a time span of approximately 20 years, we were able to measure high-precision proper motions and investigate the radial variations in the energy equipartition and velocity anisotropy of the cluster. The combination of deep and wide-field observations also allowed us to derive the present-day local mass function of NGC,6397 and to study the radial dependence of mass segregation and binary fraction. Finally, we report the discovery of a subtle under-density of stars in the colour-magnitude diagram of NGC,6397 around a stellar mass of 0.35,M_(⊙) with a more than 5σ confidence level. This feature is consistent with the Hubble Gaia M-dwarf gap discovered in Galactic field stars, but it has never previously been observed in a globular cluster. The gap is caused by the onset of full convection in stellar interiors. We demonstrate that the properties of the gap provide tight constraints on the distance to NGC,6397 and its intrinsic metallicity dispersion, offering a new benchmark for stellar evolution models.

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Title: Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397
Creators: M Griggio - Space Telescope Science Institute
M Libralato - Osservatorio Astronomico di Padova
R Gerasimov - University of Notre Dame
L.R Bedin - Osservatorio Astronomico di Padova
A Bellini - Space Telescope Science Institute
J Anderson - Space Telescope Science Institute
E Dalessandro - Osservatorio di Astrofisica e Scienza dello Spazio
E Vesperini - Indiana University Bloomington
H Baumgardt - The University of Queensland
D Massari - Osservatorio di Astrofisica e Scienza dello Spazio
M Cadelano - Osservatorio di Astrofisica e Scienza dello Spazio
R.E Ryan - Space Telescope Science Institute
I Mcdonald - University of Manchester
F Annibali - Osservatorio di Astrofisica e Scienza dello Spazio
E Balbinot - Leiden University
J.-C Cuillandre - Université Paris Cité
D Erkal - University of Surrey, School of Maths and Physics
A.M.N Ferguson - University of Edinburgh
T Saifollahi - Observatoire astronomique de Strasbourg
M Kluge - Max Planck Institute for Extraterrestrial Physics
M Schirmer - Max Planck Institute for Astronomy
P.B Kuzma - National Astronomical Observatory of Japan
K Voggel - Observatoire astronomique de Strasbourg
B Altieri - European Space Astronomy Centre
S Andreon - Brera Astronomical Observatory
N Auricchio - Osservatorio di Astrofisica e Scienza dello Spazio
C Baccigalupi - Scuola Internazionale Superiore di Studi Avanzati
M Baldi - Istituto Nazionale di Fisica Nucleare, Sezione di Bologna
A Balestra - Osservatorio Astronomico di Padova
S Bardelli - Osservatorio di Astrofisica e Scienza dello Spazio
P Battaglia - Centre National d'Études Spatiales
A Biviano - Institute for Fundamental Physics of the Universe
E Branchini - Brera Astronomical Observatory
M Brescia - Astronomical Observatory of Capodimonte
S Camera - Osservatorio Astrofisico di Torino
V Capobianco - Osservatorio Astrofisico di Torino
C Carbone - National Institute for Astrophysics
J Carretero - Port d'Informació Científica
M Castellano - Astronomical Observatory of Rome
G Castignani - Osservatorio di Astrofisica e Scienza dello Spazio
S Cavuoti - Astronomical Observatory of Capodimonte
A Cimatti - University of Bologna
C Colodro-Conde - Instituto de Astrofísica de Canarias
G Congedo - European Space Agency
C.J Conselice - University of Manchester
L Conversi - European Space Astronomy Centre
Y Copin - Université de Lille
F Courbin - Federal Reserve
H.M Courtois - Université Claude Bernard Lyon 1
M Cropper - UCL Australia
G de Lucia - Institut d'Astrophysique Spatiale
F Dubath - University of Geneva
X Dupac - European Space Astronomy Centre
M Farina - Institute of Nuclear Physics of Lyon
R Farinelli - Osservatorio di Astrofisica e Scienza dello Spazio
S Ferriol - Université Claude Bernard Lyon 1
E Franceschi - Osservatorio di Astrofisica e Scienza dello Spazio
S Galeotta - Trieste Astronomical Observatory
K George - LMU Klinikum
C Giocoli - Istituto Nazionale di Fisica Nucleare, Sezione di Bologna
J Gracia-Carpio - Max Planck Institute for Extraterrestrial Physics
A Grazian - Osservatorio Astronomico di Padova
F Grupp - Ludwig-Maximilians-Universität München
S.V.H Haugan - University of Oslo
H Hoekstra - Leiden University
W Holmes - California Institute of Technology
F Hormuth - Felix Hormuth Engineering (Leimen, Germany)
A Hornstrup - Technical University of Denmark
K Jahnke - Max Planck Institute for Astronomy
M Jhabvala - Goddard Space Flight Center
S Kermiche - Institute of Nuclear Physics of Lyon
A Kiessling - Jet Propulsion Laboratory
B Kubik - Université Claude Bernard Lyon 1
M Kümmel - Ludwig-Maximilians-Universität München
H Kurki-Suonio - Observatoire de Paris
A.M.C Le Brun - Laboratoire d’étude de l’Univers et des phénomènes eXtrèmes
S Ligori - Osservatorio Astrofisico di Torino
P.B Lilje - University of Oslo
V Lindholm - University of Helsinki
G Mainetti - Centre National de la Recherche Scientifique
I Lloro - SKA Observatory
O Marggraf - University of Bonn
M Martinelli - Astronomical Observatory of Rome
N Martinet - Aix-Marseille Université
F Marulli - Université Paris Cité
R.J Massey - Durham University
E Medinaceli - Institut d'Astrophysique de Paris
S Mei - Université Paris Cité
M Meneghetti - Institut d'Astrophysique de Paris
E Merlin - Astronomical Observatory of Rome
G Meylan - École Polytechnique Fédérale de Lausanne
A Mora - European Space Agency
M Moresco - Osservatorio di Astrofisica e Scienza dello Spazio
L Moscardini - Istituto Nazionale di Fisica Nucleare, Sezione di Bologna
R Nakajima - European Space Agency
S.-M Niemi - European Space Research and Technology Centre
C Padilla - Institute for High Energy Physics
S Paltani - University of Geneva
F Pasian - European Space Agency
K Pedersen - University of Copenhagen
Publication Details: Astronomy & Astrophysics, Vol.Forthcoming articles(Forthcoming articles)
Publisher: EDP Sciences
Number of pages: 18
First online publication date: 21/05/2026
Publication Date: 2026
Date accepted for publication: 12/05/2026
Grants: National Aeronautics and Space Administration (United States, Washington) - NASA
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (Germany, Cologne) - DLR
United Kingdom Space Agency (United Kingdom, Swindon) - UKSA
Ministerio de Ciencia, Innovación y Universidades (Spain, Madrid) - MICINN
State Secretariat for Education, Research and Innovation (Switzerland, Bern)
Fundação para a Ciência e Tecnologia (Portugal, Lisbon) - FCT
European Space Agency (France, Paris) - ASE
Agenzia Spaziale Italiana (Italy, Rome) - ASI
Austrian Forschungsförderungsgesellschaft
DTU Space (Denmark, Kongens Lyngby)
Centre National d'Études Spatiales (France, Paris) - CNES
Hungarian Academy of Sciences (Hungary, Budapest) - MTA
National Astronomical Observatory of Japan (Japan, Mitaka-shi) - NAOJ
Nederlandse Onderzoekschool Voor Astronomie (The Netherlands, Amsterdam) - NOVA
Norwegian Space Agency (Norway, Oslo) - NSC
Research Council of Finland (Finland, Helsinki)
Romanian Space Agency (Romania, Bucharest) - ROSA
DRF grant, D0101.90373, Schnörringen Telescope Science Institute (Germany, Waldbröl) - STScI
IData analysis Research Grant (PI E. Dalessandro), (PI E. Dalessandro), National Institute for Astrophysics (Italy, Rome) - INAF
Grant note: The Euclid Consortium acknowledges the European Space Agency and a number of agencies and institutes that have supported the development of Euclid, in particular the Agenzia Spaziale Italiana, the Austrian Forschungsförderungsgesellschaft funded through BMIMI, the Belgian Science Policy, the Canadian Euclid Consortium, the Deutsches Zentrum für Luft- und Raumfahrt, the DTU Space and the Niels Bohr Institute in Denmark, the French Centre National d’Etudes Spatiales, the Fundação para a Ciência e a Tecnologia, the Hungarian Academy of Sciences, the Ministerio de Ciencia, Innovación y Universidades, the National Aeronautics and Space Administration, the National Astronomical Observatory of Japan, the Netherlandse Onderzoekschool Voor Astronomie, the Norwegian Space Agency, the Research Council of Finland, the Romanian Space Agency, the Swiss Space Office (SSO) at the State Secretariat for Education, Research, and Innovation (SERI), and the United Kingdom Space Agency. A complete and detailed list is available on the Euclid web site (www.euclid-ec.org/consortium/community/). This work has made use of the Early Release Observations (ERO) data from the Euclid mission of the European Space Agency (ESA), 2024, https://doi.org/10.57780/esa-qmocze3. Based on observations with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space TelescopeScience Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. MG acknowledges support from STScI DRF grant D0101.90373. ED acknowledges financial support from the INAF Data analysis Research Grant (PI E. Dalessandro) of the “Bando Astrofisica Fondamentale 2024”.
Identifiers: 991130394702346
Academic Unit: School of Maths and Physics
Language: English
Resource Type: Journal article

Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397: High-precision multiple-pass photometry and astrometry

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