EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Westerlund 1 and 2 Open Clusters Survey^★

¹ Istituto Nazionale di Astrofisica (INAF) -- Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
e-mail: mario.guarcello@inaf.it
² Universidad de Rio Negro, Sede Atlántica – CONICET, Viedma CP8500, Río Negro, Argentina
³ Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisbon, Portugal
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁵ Department of Physics and Chemistry, University of Palermo, Palermo, Italy
⁶ Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Guipuzkoa, Spain
⁷ IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
⁸ Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
⁹ Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Liège, Quartier Agora, 19c, Allée du 6 Aôut, B5c, 4000 Sart Tilman, Belgium
¹⁰ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹¹ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹² Departamento de Astrofísica, Centro de Astrobiología, (CSIC-INTA), Ctra. Torrejón a Ajalvir, km 4, Torrejón de Ardoz, 28850 Madrid, Spain
¹³ School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
¹⁴ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹⁵ Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Barcelona, Spain
¹⁶ Institut d’Estudis Espacials de Catalunya (IEEC), Carrer Gran Capitá 2–4, 08034 Barcelona, Spain
¹⁷ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
¹⁸ Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL 32611-2055, USA
¹⁹ Istituto Nazionale di Astrofisica (INAF) – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, Italy
²⁰ Universität Heidelberg, Zentrum für Astronomie, Institut für The-oretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
²¹ Physics and Astronomy Department Galileo Galilei, University of Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
²² Univ. Grenoble-Alpes, CNRS, IPAG, 38000 Grenoble, France
²³ Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Alicante, Carretera de San Vicente s/n, 03690, San Vicente del Raspeig, Spain
²⁴ Dipartimento di Fisica e Astronomia, Università di Bologna, Via Gobetti 93/2, Bologna 40129, Italy
²⁵ Istituto Nazionale di Astrofisica (INAF) – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, Bologna 40129, Italy
²⁶ Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA
²⁷ School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
²⁸ Istituto Nazionale di Astrofisica (INAF) — Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123 Catania, Italy
²⁹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, 06300 Nice, France; Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³⁰ Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK
³¹ University of Split, Faculty of Science, Department of Physics, Rudera Boškovića 33, 21000 Split, Croatia
³² Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
³³ Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003, USA
³⁴ AURA for the European Space Agency (ESA), ESA Office, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³⁵ The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
³⁶ Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA
³⁷ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn VIC 3122, Australia
³⁸ Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK
³⁹ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12–14, 69120 Heidelberg, Germany

Received: 22 August 2023
Accepted: 21 November 2023

Abstract

Context. With a mass exceeding several 10⁴ M_⊙ and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions among stars.

Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars. The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.

Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically, the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec. Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation were carried out using the ACIS-Extract software.

Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a photon flux threshold of approximately 2 × 10⁻⁸ photons cm⁻² s⁻¹. The X-ray sources exhibit a highly concentrated spatial distribution, with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.