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.
| Original language | English |
|---|---|
| Article number | 14 |
| Journal | Astrophysical Journal |
| Volume | 959 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Dec 2023 |
| MoE publication type | A1 Journal article-refereed |
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In: Astrophysical Journal, Vol. 959, No. 1, 14, 01.12.2023.
Research output: Contribution to journal › Article › Scientific › peer-review
TY - JOUR
T1 - A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
AU - Torne, Pablo
AU - Liu, Kuo
AU - Eatough, Ralph P.
AU - Wongphechauxsorn, Jompoj
AU - Cordes, James M.
AU - Desvignes, Gregory
AU - De Laurentis, Mariafelicia
AU - Kramer, Michael
AU - Ransom, Scott M.
AU - Chatterjee, Shami
AU - Wharton, Robert
AU - Karuppusamy, Ramesh
AU - Blackburn, Lindy
AU - Janssen, Michael
AU - Chan, Chi Kwan
AU - Crew, Geoffrey, B.
AU - Matthews, Lynn D.
AU - Goddi, Ciriaco
AU - Rottmann, Helge
AU - Wagner, Jan
AU - Sánchez, Salvador
AU - Ruiz, Ignacio
AU - Abbate, Federico
AU - Bower, Geoffrey C.
AU - Salamanca, Juan J.
AU - Gómez-Ruiz, Arturo I.
AU - Herrera-Aguilar, Alfredo
AU - Jiang, Wu
AU - Lu, Ru Sen
AU - Pen, Ue Li
AU - Raymond, Alexander W.
AU - Shao, Lijing
AU - Shen, Zhiqiang
AU - Paubert, Gabriel
AU - Sanchez-Portal, Miguel
AU - Kramer, Carsten
AU - Castillo, Manuel
AU - Navarro, Santiago
AU - John, David
AU - Schuster, Karl Friedrich
AU - Johnson, Michael D.
AU - Rygl, Kazi L.J.
AU - Akiyama, Kazunori
AU - Alberdi, Antxon
AU - Alef, Walter
AU - Algaba, Juan Carlos
AU - Anantua, Richard
AU - Asada, Keiichi
AU - Azulay, Rebecca
AU - Bach, Uwe
AU - Baczko, Anne Kathrin
AU - Ball, David
AU - Baloković, Mislav
AU - Barrett, John
AU - Bauböck, Michi
AU - Benson, Bradford A.
AU - Bintley, Dan
AU - Blundell, Raymond
AU - Bouman, Katherine L.
AU - Boyce, Hope
AU - Bremer, Michael
AU - Brinkerink, Christiaan D.
AU - Brissenden, Roger
AU - Britzen, Silke
AU - Broderick, Avery E.
AU - Broguiere, Dominique
AU - Bronzwaer, Thomas
AU - Bustamante, Sandra
AU - Byun, Do Young
AU - Carlstrom, John E.
AU - Ceccobello, Chiara
AU - Chael, Andrew
AU - Chang, Dominic O.
AU - Chatterjee, Koushik
AU - Chen, Ming Tang
AU - Chen, Yongjun
AU - Cheng, Xiaopeng
AU - Cho, Ilje
AU - Christian, Pierre
AU - Conroy, Nicholas S.
AU - Conway, John E.
AU - Crawford, Thomas M.
AU - Cruz-Osorio, Alejandro
AU - Cui, Yuzhu
AU - Dahale, Rohan
AU - Davelaar, Jordy
AU - Deane, Roger
AU - Dempsey, Jessica
AU - Dexter, Jason
AU - Dhruv, Vedant
AU - Doeleman, Sheperd S.
AU - Dougal, Sean
AU - Dzib, Sergio A.
AU - Emami, Razieh
AU - Falcke, Heino
AU - Farah, Joseph
AU - Fish, Vincent L.
AU - Fomalont, Ed
AU - Ford, H. Alyson
AU - Foschi, Marianna
AU - Fraga-Encinas, Raquel
AU - Freeman, William T.
AU - Friberg, Per
AU - Fromm, Christian M.
AU - Fuentes, Antonio
AU - Galison, Peter
AU - Gammie, Charles F.
AU - García, Roberto
AU - Gentaz, Olivier
AU - Georgiev, Boris
AU - Gold, Roman
AU - Gómez, José L.
AU - Gu, Minfeng
AU - Gurwell, Mark
AU - Hada, Kazuhiro
AU - Haggard, Daryl
AU - Haworth, Kari
AU - Hecht, Michael H.
AU - Hesper, Ronald
AU - Heumann, Dirk
AU - Ho, Luis C.
AU - Ho, Paul
AU - Honma, Mareki
AU - Huang, Chih Wei L.
AU - Huang, Lei
AU - Hughes, David H.
AU - Ikeda, Shiro
AU - Impellizzeri, C. M.Violette
AU - Inoue, Makoto
AU - Issaoun, Sara
AU - James, David J.
AU - Jannuzi, Buell T.
AU - Jeter, Britton
AU - Jiménez-Rosales, Alejandra
AU - Jorstad, Svetlana
AU - Joshi, Abhishek V.
AU - Jung, Taehyun
AU - Karami, Mansour
AU - Kawashima, Tomohisa
AU - Keating, Garrett K.
AU - Kettenis, Mark
AU - Kim, Dong Jin
AU - Kim, Jae Young
AU - Kim, Jongsoo
AU - Kim, Junhan
AU - Kino, Motoki
AU - Koay, Jun Yi
AU - Kocherlakota, Prashant
AU - Kofuji, Yutaro
AU - Koyama, Shoko
AU - Krichbaum, Thomas P.
AU - Kuo, Cheng Yu
AU - La Bella, Noemi
AU - Lauer, Tod R.
AU - Lee, Daeyoung
AU - Lee, Sang Sung
AU - Leung, Po Kin
AU - Levis, Aviad
AU - Li, Zhiyuan
AU - Lico, Rocco
AU - Lindahl, Greg
AU - Lindqvist, Michael
AU - Lisakov, Mikhail
AU - Liu, Jun
AU - Liuzzo, Elisabetta
AU - Lo, Wen Ping
AU - Lobanov, Andrei P.
AU - Loinard, Laurent
AU - Lonsdale, Colin J.
AU - MacDonald, Nicholas R.
AU - Mao, Jirong
AU - Marchili, Nicola
AU - Markoff, Sera
AU - Marrone, Daniel P.
AU - Marscher, Alan P.
AU - Martí-Vidal, Iván
AU - Matsushita, Satoki
AU - Medeiros, Lia
AU - Menten, Karl M.
AU - Michalik, Daniel
AU - Mizuno, Izumi
AU - Mizuno, Yosuke
AU - Moran, James M.
AU - Moriyama, Kotaro
AU - Moscibrodzka, Monika
AU - Müller, Cornelia
AU - Müller, Hendrik
AU - Mus, Alejandro
AU - Musoke, Gibwa
AU - Myserlis, Ioannis
AU - Nadolski, Andrew
AU - Nagai, Hiroshi
AU - Nagar, Neil M.
AU - Nakamura, Masanori
AU - Narayan, Ramesh
AU - Narayanan, Gopal
AU - Natarajan, Iniyan
AU - Nathanail, Antonios
AU - Neilsen, Joey
AU - Neri, Roberto
AU - Ni, Chunchong
AU - Noutsos, Aristeidis
AU - Nowak, Michael A.
AU - Oh, Junghwan
AU - Okino, Hiroki
AU - Olivares, Héctor
AU - Ortiz-León, Gisela N.
AU - Oyama, Tomoaki
AU - Özel, Feryal
AU - Palumbo, Daniel C.M.
AU - Paraschos, Georgios Filippos
AU - Park, Jongho
AU - Parsons, Harriet
AU - Patel, Nimesh
AU - Pesce, Dominic W.
AU - Piétu, Vincent
AU - Plambeck, Richard
AU - PopStefanija, Aleksandar
AU - Porth, Oliver
AU - Pötzl, Felix M.
AU - Prather, Ben
AU - Preciado-López, Jorge A.
AU - Psaltis, Dimitrios
AU - Pu, Hung Yi
AU - Ramakrishnan, Venkatessh
AU - Rao, Ramprasad
AU - Rawlings, Mark G.
AU - Rezzolla, Luciano
AU - Ricarte, Angelo
AU - Ripperda, Bart
AU - Roelofs, Freek
AU - Rogers, Alan
AU - Ros, Eduardo
AU - Romero-Cañizales, Cristina
AU - Roshanineshat, Arash
AU - Roy, Alan L.
AU - Ruszczyk, Chet
AU - Sánchez-Argüelles, David
AU - Sasada, Mahito
AU - Satapathy, Kaushik
AU - Savolainen, Tuomas
AU - Schloerb, F. Peter
AU - Schonfeld, Jonathan
AU - Small, Des
AU - Sohn, Bong Won
AU - SooHoo, Jason
AU - Souccar, Kamal
AU - Sun, He
AU - Tetarenko, Alexandra J.
AU - Tiede, Paul
AU - Tilanus, Remo P.J.
AU - Titus, Michael
AU - Toscano, Teresa
AU - Traianou, Efthalia
AU - Trent, Tyler
AU - Trippe, Sascha
AU - Turk, Matthew
AU - van Bemmel, Ilse
AU - van Langevelde, Huib Jan
AU - van Rossum, Daniel R.
AU - Vos, Jesse
AU - Ward-Thompson, Derek
AU - Wardle, John
AU - Weintroub, Jonathan
AU - Wex, Norbert
AU - Wielgus, Maciek
AU - Wiik, Kaj
AU - Witzel, Gunther
AU - Wondrak, Michael F.
AU - Wong, George N.
AU - Wu, Qingwen
AU - Yadlapalli, Nitika
AU - Yamaguchi, Paul
AU - Yfantis, Aristomenis
AU - Yoon, Doosoo
AU - Young, André
AU - Young, Ken
AU - Younsi, Ziri
AU - Yu, Wei
AU - Yuan, Feng
AU - Yuan, Ye Fei
AU - Zensus, J. Anton
AU - Zhang, Shuo
AU - Zhao, Guang Yao
AU - Zhao, Shan Shan
N1 - Funding Information: 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. Publisher Copyright: © 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/12/1
Y1 - 2023/12/1
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85179827016&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/acf4f2
DO - 10.3847/1538-4357/acf4f2
M3 - Article
AN - SCOPUS:85179827016
SN - 0004-637X
VL - 959
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 14
ER -