CaltechAUTHORS
Published December 10, 2023 | Version Published
Journal Article Open

A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set

Creators

  • 1. ROR icon California Institute of Technology

Abstract

In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.

Copyright and License

© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We are grateful to the anonymous referee for the review and providing suggestions that improved the manuscript. We thank the staff at the participating observatories and correlator centers that made possible the EHT 2017 observations. P.T. thanks Pablo Mellado and William Robertson for their support through several stages of the data reduction in the IRAM servers. R.P.E. is funded by the Chinese Academy of Sciences President's International Fellowship Initiative, grant No. 2021FSM0004. S.M.R. is a CIFAR Fellow and is supported by the NSF Physics Frontiers Center awards 1430284 and 2020265. This work was supported by the European Research Council Synergy Grant "BlackHoleCam: Imaging the Event Horizon of Black Holes" (grant 610058). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.01404.V. ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), NSF, and National Institutes of Natural Sciences of Japan, together with National Research Council (Canada), Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, Associated Universities, Inc. (AUI)/NRAO, and the National Astronomical Observatory of Japan (NAOJ). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The LMT is a project operated by the Instituto Nacional de Astrófisica, Óptica, y Electrónica (Mexico) and the University of Massachusetts at Amherst (USA). This work is partly based on observations carried out with the IRAM 30 m Telescope under project No. 084-17. The IRAM 30 m Telescope on Pico Veleta, Spain is operated by IRAM and supported by CNRS (Centre National de la Recherche Scientifique, France), MPG (Max-Planck-Gesellschaft, Germany), and IGN (Instituto Geográfico Nacional, Spain). This research has made use of NASA's Astrophysics Data System Bibliographic Services. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The Event Horizon Telescope Collaboration thanks the following organizations and programs: the Academia Sinica; the Academy of Finland (projects 274477, 284495, 312496, and 315721); the Agencia Nacional de Investigación y Desarrollo (ANID), Chile via NCN19_058 (TITANs) and Fondecyt 1221421, the Alexander von Humboldt Stiftung; an Alfred P. Sloan Research Fellowship; Allegro, the European ALMA Regional Centre node in the Netherlands, the NL astronomy research network NOVA and the astronomy institutes of the University of Amsterdam, Leiden University and Radboud University; the ALMA North America Development Fund; the Astrophysics and High Energy Physics program by MCIN (with funding from European Union NextGenerationEU, PRTR-C17I1); the Black Hole Initiative, which is funded by grants from the John Templeton Foundation and the Gordon and Betty Moore Foundation (although the opinions expressed in this work are those of the author(s) and do not necessarily reflect the views of these Foundations); the Brinson Foundation; Chandra DD7-18089X and TM6-17006X; the China Scholarship Council; the China Postdoctoral Science Foundation fellowships (2020M671266, 2022M712084); Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects U0004-246083, U0004-259839, F0003-272050, M0037-279006, F0003-281692, 104497, 275201, and 263356); the Consejería de Economía, Conocimiento, Empresas y Universidad of the Junta de Andalucía (grant P18-FR-1769), the Consejo Superior de Investigaciones Científicas (grant 2019AEP112); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General de Asuntos del Personal Académico-Universidad Nacional Autónoma de México (DGAPA-UNAM, projects IN112417 and IN112820); the Dutch Organization for Scientific Research (NWO) for VICI award (grant 639.043.513), grant OCENW.KLEIN.113 and the Dutch black hole Consortium (with project No. NWA 1292.19.202) of the research program the National Science Agenda; the Dutch National Supercomputers, Cartesius and Snellius (NWO grant 2021.013); the EACOA Fellowship awarded by the East Asia Core Observatories Association, which consists of the Academia Sinica Institute of Astronomy and Astrophysics, the National Astronomical Observatory of Japan, Center for Astronomical Mega-Science, Chinese Academy of Sciences, and the Korea Astronomy and Space Science Institute; the European Union Horizon 2020 research and innovation program under grant agreements RadioNet (No 730562) and M2FINDERS (No 101018682); the Horizon ERC Grants 2021 program under grant agreement No. 101040021; the Generalitat Valenciana (grants APOSTD/2018/177 and ASFAE/2022/018) and GenT Program (project CIDEGENT/2018/021); MICINN Research Project PID2019-108995GB-C22; the European Research Council for advanced grant "JETSET: Launching, propagation and emission of relativistic jets from binary mergers and across mass scales" (grant No. 884631); the Institute for Advanced Study; the Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche TEONGRAV; the International Max Planck Research School for Astronomy and Astrophysics at the Universities of Bonn and Cologne; DFG research grant "Jet physics on horizon scales and beyond" (grant No. FR 4069/2-1); Joint Columbia/Flatiron Postdoctoral Fellowship, research at the Flatiron Institute is supported by the Simons Foundation; the Japan Ministry of Education, Culture, Sports, Science and Technology (MEXT; grant JPMXP1020200109); the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); the Joint Institute for Computational Fundamental Science, Japan; the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJSSW-SYS008, ZDBS-LY-SLH011); the Leverhulme Trust Early Career Research Fellowship; the Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP21H01137, JP18H03721, JP18K13594, 18K03709, JP19K14761, 18H01245, 25120007); the Malaysian Fundamental Research Grant Scheme (FRGS) FRGS/1/2019/STG02/UM/02/6; the MIT International Science and Technology Initiatives (MISTI) Funds; the Ministry of Science and Technology (MOST) of Taiwan (103-2119-M-001-010-MY2, 105-2112-M-001-025-MY3, 105-2119-M-001-042, 106-2112-M-001-011, 106-2119-M-001-013, 106-2119-M-001-027, 106-2923-M-001-005, 107-2119-M-001-017, 107-2119-M-001-020, 107-2119-M-001-041, 107-2119-M-110-005, 107-2923-M-001-009, 108-2112-M-001-048, 108-2112-M-001-051, 108-2923-M-001-002, 109-2112-M-001-025, 109-2124-M-001-005, 109-2923-M-001-001, 110-2112-M-003-007-MY2, 110-2112-M-001-033, 110-2124-M-001-007, and 110-2923-M-001-001); the Ministry of Education (MoE) of Taiwan Yushan Young Scholar Program; the Physics Division, National Center for Theoretical Sciences of Taiwan; the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC20K1567, NASA Astrophysics Theory Program grant 80NSSC20K0527, NASA NuSTAR award 80NSSC20K0645); NASA Hubble Fellowship grants HST-HF2-51431.001-A, HST-HF2-51482.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555; the National Institute of Natural Sciences (NINS) of Japan; the National Key Research and Development Program of China (grant 2016YFA0400704, 2017YFA0402703, 2016YFA0400702); the National Science Foundation (NSF, grants AST-0096454, AST-0352953, AST-0521233, AST-0705062, AST-0905844, AST-0922984, AST-1126433, AST-1140030, DGE-1144085, AST-1207704, AST-1207730, AST-1207752, MRI-1228509, OPP-1248097, AST-1310896, AST-1440254, AST-1555365, AST-1614868, AST-1615796, AST-1715061, AST-1716327, AST-1716536, OISE-1743747, AST-1816420, AST-1935980, AST-2034306); NSF Astronomy and Astrophysics Postdoctoral Fellowship (AST-1903847); the Natural Science Foundation of China (grants 11650110427, 10625314, 11721303, 11725312, 11873028, 11933007, 11991052, 11991053, 12192220, 12192223); the Natural Sciences and Engineering Research Council of Canada (NSERC, including a Discovery Grant and the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program); the National Youth Thousand Talents Program of China; the National Research Foundation of Korea (the Global PhD Fellowship Grant: grants NRF-2015H1A2A1033752, the Korea Research Fellowship Program: NRF-2015H1D3A1066561, Brain Pool Program: 2019H1D3A1A01102564, Basic Research Support Grant 2019R1F1A1059721, 2021R1A6A3A01086420, 2022R1C1C1005255); Netherlands Research School for Astronomy (NOVA) Virtual Institute of Accretion (VIA) postdoctoral fellowships; Onsala Space Observatory (OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-00648); the Perimeter Institute for Theoretical Physics (research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development and by the Province of Ontario through the Ministry of Research, Innovation and Science); the Princeton Gravity Initiative; the Spanish Ministerio de Ciencia e Innovación (grants PGC2018-098915-B-C21, AYA2016-80889-P, PID2019-108995GB-C21, and PID2020-117404GB-C21); the University of Pretoria for financial aid in the provision of the new Cluster Server nodes and SuperMicro (USA) for an SEEDING grant approved toward these nodes in 2020; the Shanghai Pilot Program for Basic Research, Chinese Academy of Science, Shanghai Branch (JCYJ-SHFY-2021-013); the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the Spinoza Prize SPI 78-409; the South African Research Chairs Initiative, through the South African Radio Astronomy Observatory (SARAO, grant ID 77948), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Innovation (DSI) of South Africa; the Toray Science Foundation; the Swedish Research Council (VR); the US Department of Energy (USDOE) through the Los Alamos National Laboratory (operated by Triad National Security, LLC, for the National Nuclear Security Administration of the USDOE (contract 89233218CNA000001); and the YCAA Prize Postdoctoral Fellowship. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract No. DE-AC05-00OR22725. We also thank the Center for Computational Astrophysics, National Astronomical Observatory of Japan. The computing cluster of Shanghai VLBI correlator supported by the Special Fund for Astronomy from the Ministry of Finance in China is acknowledged. This work was partially supported by FAPESP (Fundação de Amparo á Pesquisa do Estado de São Paulo) under grant 2021/01183-8. APEX is a collaboration between the Max-Planck-Institut für Radioastronomie (Germany), ESO, and the Onsala Space Observatory (Sweden). The SMT is operated by the Arizona Radio Observatory, a part of the Steward Observatory of the University of Arizona, with financial support of operations from the State of Arizona and financial support for instrumentation development from the NSF. Support for SPT participation in the EHT is provided by the National Science Foundation through award OPP-1852617 to the University of Chicago. Partial support is also provided by the Kavli Institute of Cosmological Physics at the University of Chicago. The SPT hydrogen maser was provided on loan from the GLT, courtesy of ASIAA. The SMA is a joint project between the SAO and ASIAA and is funded by the Smithsonian Institution and the Academia Sinica. The JCMT is operated by the East Asian Observatory on behalf of the NAOJ, ASIAA, and KASI, as well as the Ministry of Finance of China, Chinese Academy of Sciences, and the National Key Research and Development Program (No. 2017YFA0402700) of China and Natural Science Foundation of China grant 11873028. Additional funding support for the JCMT is provided by the Science and Technologies Facility Council (UK) and participating universities in the UK and Canada. We acknowledge the significance that Maunakea, where the SMA and JCMT EHT stations are located, has for the indigenous Hawaiian people. The EHTC has received generous donations of FPGA chips from Xilinx Inc., under the Xilinx University Program. The EHTC has benefited from technology shared under an open-source license by the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER). The EHT project is grateful to T4Science and Microsemi for their assistance with Hydrogen Masers. We gratefully acknowledge the support provided by the extended staff of the ALMA, both from the inception of the ALMA Phasing Project through the observational campaigns of 2017 and 2018. We would like to thank A. Deller and W. Brisken for EHT-specific support with the use of DiFX.

Facilities

ALMA - Atacama Large Millimeter Array, LMT - , IRAM:30m - Institute de Radioastronomie Millimetrique 30 meter telescope

Software References

MPIvdif2psrfits, presto (Ransom 2011), riptide (Morello et al. 2020), numpy (Harris et al. 2020), scipy (Virtanen et al. 2020), matplotlib (Hunter 2007), tempo (Nice et al. 2015), sigpyproc (Lorimer 2011)

Files

Torne_2023_ApJ_959_14.pdf

Files (2.8 MB)

Name Size Download all
md5:0c4908339cc63f6d16c3a82af7e80b3a
2.8 MB Preview Download

Additional details

Identifiers

ISSN
1538-4357

Funding

Chinese Academy of Sciences
2021FSM0004
Canadian Institute for Advanced Research
National Science Foundation
PHY-1430284
National Science Foundation
PHY-2020265
European Research Council
610058
Centre National de la Recherche Scientifique
Max Planck Society
Instituto Geográfico Nacional
Academia Sinica
Research Council of Finland
274477
Research Council of Finland
284495
Research Council of Finland
312496
Research Council of Finland
315721
Agencia Nacional de Investigación y Desarrollo
NCN19_058
Agencia Nacional de Investigación y Desarrollo
Fondecyt 1221421
Alexander von Humboldt Foundation
Alfred P. Sloan Foundation
John Templeton Foundation
Gordon and Betty Moore Foundation
Brinson Foundation
National Aeronautics and Space Administration
DD7-18089X
National Aeronautics and Space Administration
TM6-17006X
China Scholarship Council
China Postdoctoral Science Foundation
2020M671266
China Postdoctoral Science Foundation
2022M712084
Consejo Nacional de Humanidades, Ciencias y Tecnologías
U0004-246083
Consejo Nacional de Humanidades, Ciencias y Tecnologías
U0004-246083
Consejo Nacional de Humanidades, Ciencias y Tecnologías
U0004-259839
Consejo Nacional de Humanidades, Ciencias y Tecnologías
F0003-272050
Consejo Nacional de Humanidades, Ciencias y Tecnologías
M0037-279006
Consejo Nacional de Humanidades, Ciencias y Tecnologías
F0003-281692
Consejo Nacional de Humanidades, Ciencias y Tecnologías
104497
Consejo Nacional de Humanidades, Ciencias y Tecnologías
275201
Consejo Nacional de Humanidades, Ciencias y Tecnologías
263356
Consejería de Economía, Conocimiento, Empresas y Universidad
P18-FR-1769
Consejo Superior de Investigaciones Científicas
2019AEP112
Perimeter Institute
Universidad Nacional Autónoma de México
DGAPA-UNAM IN112417
Universidad Nacional Autónoma de México
IN112820 DGAPA-UNAM
Dutch Research Council
639.043.513
Dutch Research Council
OCENW.KLEIN.113
Dutch Research Council
NWA 1292.19.202
Dutch Research Council
2021.013
National Astronomical Observatory of Japan
European Research Council
730562
European Research Council
101018682
European Research Council
101040021
Generalitat Valenciana
APOSTD/2018/177
Generalitat Valenciana
ASFAE/2022/018
Generalitat Valenciana
CIDEGENT/2018/021
Ministerio de Ciencia, Innovación y Universidades
PID2019-108995GB-C22
European Research Council
884631
Institute for Advanced Study
Istituto Nazionale di Fisica Nucleare
Deutsche Forschungsgemeinschaft
FR 4069/2-1
Columbia University
Simons Foundation
Ministry of Education, Culture, Sports, Science and Technology
JPMXP1020200109
Japan Society for the Promotion of Science
JP17J08829
Chinese Academy of Sciences
QYZDJ-SSW-SLH057
Chinese Academy of Sciences
QYZDJSSW-SYS008
Chinese Academy of Sciences
ZDBS-LY-SLH011
Leverhulme Trust
Japan Society for the Promotion of Science
18KK0090
Japan Society for the Promotion of Science
JP18H03721
Japan Society for the Promotion of Science
JP18K13594
Japan Society for the Promotion of Science
18K03709
Japan Society for the Promotion of Science
JP19K14761
Japan Society for the Promotion of Science
18H01245
Japan Society for the Promotion of Science
25120007
Ministry of Science, Technology and Innovation
FRGS/1/2019/STG02/UM/02/6
Massachusetts Institute of Technology
National Center for Theoretical Sciences
National Aeronautics and Space Administration
80NSSC20K1567
National Aeronautics and Space Administration
80NSSC20K0527
National Aeronautics and Space Administration
80NSSC20K0645
National Aeronautics and Space Administration
NASA Hubble Fellowship HST-HF2-51431.001-A
National Aeronautics and Space Administration
NASA Hubble Fellowship HST-HF2-51482.001-A
National Aeronautics and Space Administration
NAS5-26555
National Institutes of Natural Sciences
National Natural Science Foundation of China
2016YFA0400704
National Natural Science Foundation of China
2017YFA0402703
National Natural Science Foundation of China
2016YFA0400702
National Science Foundation
AST-0096454
National Science Foundation
AST-0352953
National Science Foundation
AST-0521233
National Science Foundation
AST-0705062
National Science Foundation
AST-0905844
National Science Foundation
AST-0922984
National Science Foundation
AST-1126433
National Science Foundation
AST-1140030
National Science Foundation
NSF Graduate Research Fellowship DGE-1144085
National Science Foundation
AST-1207704
National Science Foundation
AST-1207730
National Science Foundation
AST-1207752
National Science Foundation
AST-1228509
National Science Foundation
OPP-1248097
National Science Foundation
AST-1310896
National Science Foundation
AST-1440254
National Science Foundation
AST-1555365
National Science Foundation
AST-1614868
National Science Foundation
AST-1615796
National Science Foundation
AST-1715061
National Science Foundation
AST-1716327
National Science Foundation
AST-1716536
National Science Foundation
OISE-1743747
National Science Foundation
AST-1816420
National Science Foundation
AST-1935980
National Science Foundation
AST-2034306
National Science Foundation
NSF Astronomy and Astrophysics Fellowship AST-1903847
National Natural Science Foundation of China
11650110427
National Natural Science Foundation of China
10625314
National Natural Science Foundation of China
11721303
National Natural Science Foundation of China
11725312
National Natural Science Foundation of China
11873028
National Natural Science Foundation of China
11933007
National Natural Science Foundation of China
11991052
National Natural Science Foundation of China
11991053
National Natural Science Foundation of China
12192220
National Natural Science Foundation of China
12192223
Natural Sciences and Engineering Research Council
National Research Foundation of Korea
NRF-2015H1A2A1033752
National Research Foundation of Korea
NRF-2015H1D3A1066561
National Research Foundation of Korea
2019H1D3A1A01102564
National Research Foundation of Korea
2019R1F1A1059721
National Research Foundation of Korea
2021R1A6A3A01086420
National Research Foundation of Korea
2022R1C1C1005255
Swedish Research Council
2017-00648
Innovation, Science and Economic Development Canada
Princeton University
Ministerio de Ciencia, Innovación y Universidades
PGC2018-098915-B-C21
Ministerio de Ciencia, Innovación y Universidades
AYA2016-80889-P
Ministerio de Ciencia, Innovación y Universidades
PID2019-108995GB-C21
Ministerio de Ciencia, Innovación y Universidades
PID2020-117404GB-C21
University of Pretoria
Chinese Academy of Sciences
JCYJ-SHFY-2021-013
Agencia Estatal de Investigación
SEV-2017-0709
Dutch Research Council
SPI 78-409
South African Radio Astronomy Observatory
77948
Department of Science and Innovation
United States Department of Energy
89233218CNA000001
Yale University
United States Department of Energy
DE-AC05-00OR22725
Fundação de Amparo à Pesquisa do Estado de São Paulo
2021/01183-8
National Science Foundation
OPP-1852617
University of Chicago
Smithsonian Astrophysical Observatory
National Natural Science Foundation of China
2017YFA0402700
National Natural Science Foundation of China
11873028
Xilinx (United States)

Caltech Custom Metadata

Caltech groups
Astronomy Department