A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
Authors: Torne Pablo , Liu Kuo , Eatough Ralph P. , Wongphechauxsorn Jompoj , Cordes James M. , Desvignes Gregory , De Laurentis Mariafelicia , Kramer Michael , Ransom Scott M. , Chatterjee Shami , Wharton Robert , Karuppusamy Ramesh , Blackburn Lindy , Janssen Michael , Chan Chi-kwan , Crew Geoffrey, B. , Matthews Lynn D. , Goddi Ciriaco , Rottmann Helge , Wagner Jan , Sánchez Salvador , Ruiz Ignacio , Abbate Federico , Bower Geoffrey C. , Salamanca Juan J. , Gómez-Ruiz Arturo I. , Herrera-Aguilar Alfredo , Jiang 江 Wu 悟 , Lu 路 Ru-Sen 如森 , Pen Ue-Li , Raymond Alexander W. , Shao Lijing , Shen 沈 Zhiqiang 志强 , Paubert Gabriel , Sanchez-Portal Miguel , Kramer Carsten , Castillo Manuel , Navarro Santiago , John David , Schuster Karl-Friedrich , Johnson Michael D. , Rygl Kazi L. J. , Akiyama Kazunori , Alberdi Antxon , Alef Walter , Algaba Juan Carlos , Anantua Richard , Asada Keiichi , Azulay Rebecca , Bach Uwe , Baczko Anne-Kathrin , Ball David , Baloković Mislav , Barrett John , Bauböck Michi , Benson Bradford A. , Bintley Dan , Blundell Raymond , Bouman Katherine L. , Boyce Hope , Bremer Michael , Brinkerink Christiaan D. , Brissenden Roger , Britzen Silke , Broderick Avery E. , Broguiere Dominique , Bronzwaer Thomas , Bustamante Sandra , Byun Do-Young , Carlstrom John E. , Ceccobello Chiara , Chael Andrew , Chang Dominic O. , Chatterjee Koushik , Chen Ming-Tang , Chen 陈 Yongjun 永军 , Cheng Xiaopeng , Cho Ilje , Christian Pierre , Conroy Nicholas S. , Conway John E. , Crawford Thomas M. , Cruz-Osorio Alejandro , Cui 崔 Yuzhu 玉竹 , Dahale Rohan , Davelaar Jordy , Deane Roger , Dempsey Jessica , Dexter Jason , Dhruv Vedant , Doeleman Sheperd S. , Dougal Sean , Dzib Sergio A. , Emami Razieh , Falcke Heino , Farah Joseph , Fish Vincent L. , Fomalont Ed , Ford H. Alyson , Foschi Marianna , Fraga-Encinas Raquel , Freeman William T. , Friberg Per , Fromm Christian M. , Fuentes Antonio , Galison Peter , Gammie Charles F. , García Roberto , Gentaz Olivier , Georgiev Boris , Gold Roman , Gómez José L. , Gu 顾 Minfeng 敏峰 , Gurwell Mark , Hada Kazuhiro , Haggard Daryl , Haworth Kari , Hecht Michael H. , Hesper Ronald , Heumann Dirk , Ho 何 Luis C. 子山 , Ho Paul , Honma Mareki , Huang Chih-Wei L. , Huang 黄 Lei 磊 , Hughes David H. , Ikeda Shiro , Impellizzeri C. M. Violette , Inoue Makoto , Issaoun Sara , James David J. , Jannuzi Buell T. , Jeter Britton , Jiménez-Rosales Alejandra , Jorstad Svetlana , Joshi Abhishek V. , Jung Taehyun , Karami Mansour , Kawashima Tomohisa , Keating Garrett K. , Kettenis Mark , Kim Dong-Jin , Kim Jae-Young , Kim Jongsoo , Kim Junhan , Kino Motoki , Koay Jun Yi , Kocherlakota Prashant , Kofuji Yutaro , Koyama Shoko , Krichbaum Thomas P. , Kuo Cheng-Yu , La Bella Noemi , Lauer Tod R. , Lee Daeyoung , Lee Sang-Sung , Leung Po Kin , Levis Aviad , Li 李 Zhiyuan 志远 , Lico Rocco , Lindahl Greg , Lindqvist Michael , Lisakov Mikhail , Liu 刘 Jun 俊 , Liuzzo Elisabetta , Lo Wen-Ping , Lobanov Andrei P. , Loinard Laurent , Lonsdale Colin J. , MacDonald Nicholas R. , Mao 毛 Jirong 基荣 , Marchili Nicola , Markoff Sera , Marrone Daniel P. , Marscher Alan P. , Martí-Vidal Iván , Matsushita Satoki , Medeiros Lia , Menten Karl M. , Michalik Daniel , Mizuno Izumi , Mizuno Yosuke , Moran James M. , Moriyama Kotaro , Moscibrodzka Monika , Müller Cornelia , Müller Hendrik , Mus Alejandro , Musoke Gibwa , Myserlis Ioannis , Nadolski Andrew , Nagai Hiroshi , Nagar Neil M. , Nakamura Masanori , Narayan Ramesh , Narayanan Gopal , Natarajan Iniyan , Nathanail Antonios , Neilsen Joey , Neri Roberto , Ni Chunchong , Noutsos Aristeidis , Nowak Michael A. , Oh Junghwan , Okino Hiroki , Olivares Héctor , Ortiz-León Gisela N. , Oyama Tomoaki , Özel Feryal , Palumbo Daniel C. M. , Paraschos Georgios Filippos , Park Jongho , Parsons Harriet , Patel Nimesh , Pesce Dominic W. , Piétu Vincent , Plambeck Richard , PopStefanija Aleksandar , Porth Oliver , Pötzl Felix M. , Prather Ben , Preciado-López Jorge A. , Psaltis Dimitrios , Pu Hung-Yi , Ramakrishnan Venkatessh , Rao Ramprasad , Rawlings Mark G. , Rezzolla Luciano , Ricarte Angelo , Ripperda Bart , Roelofs Freek , Rogers Alan , Ros Eduardo , Romero-Cañizales Cristina , Roshanineshat Arash , Roy Alan L. , Ruszczyk Chet , Sánchez-Argüelles David , Sasada Mahito , Satapathy Kaushik , Savolainen Tuomas , Schloerb F. Peter , Schonfeld Jonathan , Small Des , Sohn Bong Won , SooHoo Jason , Souccar Kamal , Sun 孙 He 赫 , Tetarenko Alexandra J. , Tiede Paul , Tilanus Remo P. J. , Titus Michael , Toscano Teresa , Traianou Efthalia , Trent Tyler , Trippe Sascha , Turk Matthew , van Bemmel Ilse , van Langevelde Huib Jan , van Rossum Daniel R. , Vos Jesse , Ward-Thompson Derek , Wardle John , Weintroub Jonathan , Wex Norbert , Wielgus Maciek , Wiik Kaj , Witzel Gunther , Wondrak Michael F. , Wong George N. , Wu 吴 Qingwen 庆文 , Yadlapalli Nitika , Yamaguchi Paul , Yfantis Aristomenis , Yoon Doosoo , Young André , Young Ken , Younsi Ziri , Yu 于 Wei 威 , Yuan 袁 Feng 峰 , Yuan 袁 Ye-Fei 业飞 , Zensus J. Anton , Zhang Shuo , Zhao Guang-Yao , Zhao 赵 Shan-Shan 杉杉 
Published: November 2023

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.