14 research outputs found
Relations Between Neutron-Star Parameters in the Hartle-Thorne Approximation
Using stellar structure calculations in the Hartle-Thorne approximation, we
derive analytic expressions connecting the ellipticity of the stellar surface
to the compactness, the spin angular momentum, and the quadrupole moment of the
spacetime. We also obtain empirical relations between the compactness, the spin
angular momentum, and the spacetime quadrupole. Our formulae reproduce the
results of numerical calculations to within a few percent and help reduce the
number of parameters necessary to model the observational appearance of
moderately spinning neutron stars. This is sufficient for comparing theoretical
spectroscopic and timing models to observations that aim to measure the masses
and radii of neutron stars and to determine the equation of state prevailing in
their interiors.Comment: 6 pages, 5 figures, to appear in Ap
Atmospheric Structure and Radiation Pattern for Neutron-Star Polar Caps Heated by Magnetospheric Return Currents
The Neutron-star Interior Composition ExploreR (NICER) is collecting data to
measure the radii of neutron stars by observing the pulsed emission from their
surfaces. The primary targets are isolated, rotation-powered pulsars, in which
the surface polar caps are heated by bombardment from magnetospheric currents
of electrons and positrons. We investigate various stopping mechanisms for the
beams of particles that bombard the atmosphere and calculate the heat
deposition, the atmospheric temperature profiles, and the energy spectra and
beaming of the emerging radiation. We find that low-energy particles with
{\gamma} deposit most of their energy in the upper regions of the
atmosphere, at low optical depth, resulting in beaming patterns that are
substantially different than those of deep-heated, radiative equilibrium
models. Only particles with energies {\gamma} penetrate to high
optical depths and fulfill the conditions necessary for a deep-heating
approximation. We discuss the implications of our work for modeling the pulse
profiles from rotation-powered pulsars and for the inference of their radii
with NICER observations.Comment: 13 pages, 12 figures, submitted to Ap
Measuring Neutron Star Radii via Pulse Profile Modeling with NICER
The Neutron-star Interior Composition Explorer (NICER) is an X-ray
astrophysics payload that will be placed on the International Space Station.
Its primary science goal is to measure with high accuracy the pulse profiles
that arise from the non-uniform thermal surface emission of rotation-powered
pulsars. Modeling general relativistic effects on the profiles will lead to
measuring the radii of these neutron stars and to constraining their equation
of state. Achieving this goal will depend, among other things, on accurate
knowledge of the source, sky, and instrument backgrounds. We use here simple
analytic estimates to quantify the level at which these backgrounds need to be
known in order for the upcoming measurements to provide significant constraints
on the properties of neutron stars. We show that, even in the
minimal-information scenario, knowledge of the background at a few percent
level for a background-to-source countrate ratio of 0.2 allows for a
measurement of the neutron star compactness to better than 10% uncertainty for
most of the parameter space. These constraints improve further when more
realistic assumptions are made about the neutron star emission and spin, and
when additional information about the source itself, such as its mass or
distance, are incorporated.Comment: Submitted to Ap
Rotation in Event Horizon Telescope Movies
The Event Horizon Telescope (EHT) has produced images of M87* and Sgr A*, and
will soon produce time sequences of images, or movies. In anticipation of this,
we describe a technique to measure a rotation rate, or pattern speed
, from movies using an autocorrelation technique. We validate the
technique on Gaussian random field models with a known rotation rate and apply
it to a library of synthetic images of Sgr A* based on general relativistic
magnetohydrodynamics (GRMHD) simulations. We predict that EHT movies will have
degree per , which is of order
of the Keplerian orbital frequency in the emitting region. We can plausibly
attribute the slow rotation seen in our models to the pattern speed of
inward-propagating spiral shocks. We also find that depends strongly
on inclination. Application of this technique will enable us to compare future
EHT movies with the clockwise rotation of Sgr A* seen in near-infrared flares
by GRAVITY. Pattern speed analysis of future EHT observations of M87* and Sgr
A* may also provide novel constraints on black hole inclination and spin, as
well as an independent measurement of black hole mass
First Sagittarius A Event Horizon Telescope results. IV. Variability, morphology, and black hole mass
REST OF AUTHORS : Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dhruv, Vedant; Doeleman, Sheperd S.; Dougal, Sean; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; Garcia, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gomez-Ruiz, Arturo, I; Gomez, Jose L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Haworth, Kari; Hecht, Michael H.; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C. M. Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Joshi, Abhishek, V; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; 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; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng-Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang-Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lu, Ru-Sen; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Marti-Vidal, Ivan; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Muller, Cornelia; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Fuentes, Santiago Navarro; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares, Hector; Ortiz-Leon, Gisela N.; Oyama, Tomoaki; Palumbo, Daniel C. M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Pietu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Potzl, Felix M.; Prather, Ben; Preciado-Lopez, Jorge A.; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Romero-Canizales, Cristina; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sanchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Souccar, Kamal; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Torne, Pablo; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, Maciek; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yamaguchi, Paul; Yoon, Doosoo; Young, Andre; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang-Yao; Zhao, Shan-Shan; Chang, Dominic O.Please read abstract in the article.We thank an anonymous referee for insightful and
constructive comments that helped improve the quality of this
paper.
The Event Horizon Telescope Collaboration thanks the
following organizations and programs: the Academia Sinica;
the Academy of Finland (projects 274477, 284495, 312496,
315721); the Agencia Nacional de InvestigaciĂłn 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
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); Chandra DD7-18089X and TM6-17006X;
the China Scholarship Council; China Postdoctoral Science Foundation fellowship (2020M671266); Consejo Nacional de
Ciencia y TecnologĂa (CONACYT, Mexico, projects U0004-
246083, U0004-259839, F0003-272050, M0037-279006,
F0003-281692, 104497, 275201, 263356); the ConsejerĂa de
EconomĂa, Conocimiento, Empresas y Universidad of the Junta
de AndalucĂa (grant P18-FR-1769), the Consejo Superior de
Investigaciones CientĂficas (grant 2019AEP112); the Delaney
Family via the Delaney Family John A. Wheeler Chair at
Perimeter Institute; DirecciĂłn General de Asuntos del Personal
Académico-Universidad Nacional Autónoma de México
(DGAPA-UNAM, projects IN112417 and IN112820); the
Dutch Organization for Scientific Research (NWO) VICI
award (grant 639.043.513) and grant OCENW.KLEIN.113;
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 Research Council (ERC) Synergy
Grant âBlackHoleCam: Imaging the Event Horizon of Black
Holesâ (grant 610058); the European Union Horizon 2020
research and innovation programme under grant agreements
RadioNet (No 730562) and M2FINDERS (No 101018682); the
Generalitat Valenciana postdoctoral grant APOSTD/2018/177
and GenT Program (project CIDEGENT/2018/021); MICINN
Research Project PID2019-108995GB-C22; the European
Research Council for advanced grant âJETSET: Launching,
propagation and emission of relativistic jets from binary
mergers and across mass scalesâ (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 âJet physics on horizon
scales and beyondâ (Grant No. FR 4069/2-1); Joint Princeton/
Flatiron and Joint Columbia/Flatiron Postdoctoral Fellowships,
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 Japanese Government (Monbukagakusho: MEXT) Scholarship;
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 grant
HST-HF2-51431.001-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 Spanish
Ministerio de Ciencia e InnovaciĂłn (grants PGC2018-098915-
B-C21, AYA2016-80889-P, PID2019-108995GB-C21,
PID2020-117404GB-C21); the University of Pretoria for
financial aid in the provision of the new Cluster Server nodes
and SuperMicro (USA) for a SEEDING GRANT approved
towards 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 âCenter of
Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica
de AndalucĂa (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; 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. We thank the staff at the participating observatories,
correlation centers, and institutions for their enthusiastic
support. This paper makes use of the following ALMA data:
ADS/JAO.ALMA#2016.1.01154.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 NRAO is a facility of the NSF operated
under cooperative agreement by AUI. 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. APEX is a collaboration between the Max-Planck-Institut fĂŒr
Radioastronomie (Germany), ESO, and the Onsala Space
Observatory (Sweden). 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. The LMT is a project operated
by the Instituto Nacional de AstrĂłfisica, Ăptica, y ElectrĂłnica
(Mexico) and the University of Massachusetts at Amherst
(USA). 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 GeogrĂĄfico Nacional,
Spain). 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.
This work used the Extreme Science and Engineering
Discovery Environment (XSEDE), supported by NSF grant
ACI-1548562, and CyVerse, supported by NSF grants DBI-
0735191, DBI-1265383, and DBI-1743442. XSEDE Stampede2
resource at TACC was allocated through TG-AST170024 and
TG-AST080026N. XSEDE JetStream resource at PTI and
TACC was allocated through AST170028. This research is part
of the Frontera computing project at the Texas Advanced
Computing Center through the Frontera Large-Scale Community
Partnerships allocation AST20023. Frontera is made possible by
National Science Foundation award OAC-1818253. This
research was carried out using resources provided by the Open
Science Grid, which is supported by the National Science
Foundation and the U.S. Department of Energy Office of
Science. Additional work used ABACUS2.0, which is part of
the eScience center at Southern Denmark University. Simulations
were also performed on the SuperMUC cluster at the LRZ
in Garching, on the LOEWE cluster in CSC in Frankfurt, on the
HazelHen cluster at the HLRS in Stuttgart, and on the Pi2.0 and
Siyuan Mark-I at Shanghai Jiao Tong University. The computer
resources of the Finnish IT Center for Science (CSC) and the
Finnish Computing Competence Infrastructure (FCCI) project
are acknowledged. This research was enabled in part by support
provided by Compute Ontario (http://computeontario.ca),
Calcul Quebec (http://www.calculquebec.ca) and Compute
Canada (http://www.computecanada.ca).
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 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. This research has made use of NASAÊŒs Astrophysics
Data System. 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. We thank Martin
Shepherd for the addition of extra features in the Difmap software
that were used for the CLEAN imaging results presented in this
paper. We acknowledge the significance that Maunakea, where
the SMA and JCMT EHT stations are located, has for the
indigenous Hawaiian people. IMV acknowledges the use of LLuis
Vives HPC resources of the University of Valencia.http://iopscience.iop.org/2041-8205am2023Physic
First Sagittarius A Event Horizon Telescope results. VI. Testing the black hole metric
REST OF AUTHORS : Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dhruv, Vedant; Doeleman, Sheperd S.; Dougal, Sean; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; Garcia, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gomez-Ruiz, Arturo, I; Gomez, Jose L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Haworth, Kari; Hecht, Michael H.; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C. M. Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Joshi, Abhishek, V; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; 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; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng-Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang-Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lu, Ru-Sen; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Marti-Vidal, Ivan; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Muller, Cornelia; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Fuentes, Santiago Navarro; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares, Hector; Ortiz-Leon, Gisela N.; Oyama, Tomoaki; Ozel, Feryal; Palumbo, Daniel C. M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Pietu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Potzl, Felix M.; Prather, Ben; Preciado-Lopez, Jorge A.; Psaltis, Dimitrios; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Romero-Canizales, Cristina; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sanchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Souccar, Kamal; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Torne, Pablo; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, Maciek; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yamaguchi, Paul; Yoon, Doosoo; Young, Andre; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang-Yao; Zhao, Shan-Shan.Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum,
axisymmetric metric, without electromagnetic charge, that satisfies Einsteinâs equations and does not have
pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr
prediction based on 2017 EHT observations of Sagittarius A* (Sgr A*). We calibrate the relationship between the
geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes
both Kerr and non-Kerr simulations. We use the exquisite prior constraints on the mass-to-distance ratio for Sgr A*
to show that the observed image size is within âŒ10% of the Kerr predictions. We use these bounds to constrain
metrics that are parametrically different from Kerr, as well as the charges of several known spacetimes. To consider
alternatives to the presence of an event horizon, we explore the possibility that Sgr A* is a compact object with a
surface that either absorbs and thermally reemits incident radiation or partially reflects it. Using the observed image
size and the broadband spectrum of Sgr A*, we conclude that a thermal surface can be ruled out and a fully
reflective one is unlikely. We compare our results to the broader landscape of gravitational tests. Together with the
bounds found for stellar-mass black holes and the M87 black hole, our observations provide further support that
the external spacetimes of all black holes are described by the Kerr metric, independent of their mass.The authors thank the anonymous referee for comments that
improved the manuscript.
The Event Horizon Telescope Collaboration thanks the
following organizations and programs: the Academia Sinica;
the Academy of Finland (projects 274477, 284495, 312496,
315721); the Agencia Nacional de InvestigaciĂłn 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
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); Chandra DD7-18089X and TM6-17006X;
the China Scholarship Council; China Postdoctoral Science
Foundation fellowship (2020M671266); Consejo Nacional de
Ciencia y TecnologĂa (CONACYT, Mexico, projects U0004-
246083, U0004-259839, F0003-272050, M0037-279006,
F0003-281692, 104497, 275201, 263356); the ConsejerĂa de
EconomĂa, Conocimiento, Empresas y Universidad of the Junta
de AndalucĂa (grant P18-FR-1769), the Consejo Superior de Investigaciones CientĂficas (grant 2019AEP112); the Delaney
Family via the Delaney Family John A. Wheeler Chair at
Perimeter Institute; DirecciĂłn General de Asuntos del Personal
Académico-Universidad Nacional Autónoma de México
(DGAPA-UNAM, projects IN112417 and IN112820); the
Dutch Organization for Scientific Research (NWO) VICI
award (grant 639.043.513) and grant OCENW.KLEIN.113;
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 Research Council (ERC) Synergy
Grant âBlackHoleCam: Imaging the Event Horizon of Black
Holesâ (grant 610058); the European Union Horizon 2020
research and innovation programme under grant agreements
RadioNet (No 730562) and M2FINDERS (No 101018682); the
Generalitat Valenciana postdoctoral grant APOSTD/2018/177
and GenT Program (project CIDEGENT/2018/021); MICINN
Research Project PID2019-108995GB-C22; the European
Research Council for advanced grant âJETSET: Launching,
propagation and emission of relativistic jets from binary
mergers and across mass scalesâ (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 âJet physics on horizon
scales and beyondâ (Grant No. FR 4069/2-1); Joint Princeton/
Flatiron and Joint Columbia/Flatiron Postdoctoral Fellowships,
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 Japanese Government (Monbukagakusho: MEXT) Scholarship;
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 grant
HST-HF2-51431.001-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 Spanish
Ministerio de Ciencia e InnovaciĂłn (grants PGC2018-098915-
B-C21, AYA2016-80889-P, PID2019-108995GB-C21,
PID2020-117404GB-C21); the University of Pretoria for
financial aid in the provision of the new Cluster Server nodes
and SuperMicro (USA) for a SEEDING GRANT approved
towards 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 âCenter of
Excellence Severo Ochoaâ award for the Instituto de AstrofĂsica
de AndalucĂa (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; 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.
We thank the staff at the participating observatories,
correlation centers, and institutions for their enthusiastic
support. This paper makes use of the following ALMA data:
ADS/JAO.ALMA#2016.1.01154.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 NRAO is a facility of the NSF operated
under cooperative agreement by AUI. 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.
APEX is a collaboration between the Max-Planck-Institut fĂŒr
Radioastronomie (Germany), ESO, and the Onsala Space
Observatory (Sweden). 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. The LMT is a project operated
by the Instituto Nacional de AstrĂłfisica, Ăptica, y ElectrĂłnica
(Mexico) and the University of Massachusetts at Amherst
(USA). 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 GeogrĂĄfico Nacional,
Spain). 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.
This work used the Extreme Science and Engineering
Discovery Environment (XSEDE), supported by NSF grant
ACI-1548562, and CyVerse, supported by NSF grants DBI-
0735191, DBI-1265383, and DBI-1743442. XSEDE Stampede2
resource at TACC was allocated through TGAST170024
and TG-AST080026N. XSEDE JetStream
resource at PTI and TACC was allocated through
AST170028. This research is part of the Frontera computing
project at the Texas Advanced Computing Center through the
Frontera Large-Scale Community Partnerships allocation
AST20023. Frontera is made possible by National Science
Foundation award OAC-1818253. This research was carried
out using resources provided by the Open Science Grid, which
is supported by the National Science Foundation and the U.S.
Department of Energy Office of Science. Additional work used ABACUS2.0, which is part of the
eScience center at Southern Denmark University. Simulations
were also performed on the SuperMUC cluster at the LRZ in
Garching, on the LOEWE cluster in CSC in Frankfurt, on the
HazelHen cluster at the HLRS in Stuttgart, and on the Pi2.0 and
Siyuan Mark-I at Shanghai Jiao Tong University. The computer
resources of the Finnish IT Center for Science (CSC) and the
Finnish Computing Competence Infrastructure (FCCI) project
are acknowledged. This research was enabled in part by support
provided by Compute Ontario (http://computeontario.ca),
Calcul Quebec (http://www.calculquebec.ca) and Compute
Canada (http://www.computecanada.ca).
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 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. This research has made use of NASAÊŒs Astrophysics
Data System. 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. We thank Martin
Shepherd for the addition of extra features in the Difmap software
that were used for the CLEAN imaging results presented in this
paper. We acknowledge the significance that Maunakea, where
the SMA and JCMT EHT stations are located, has for the
indigenous Hawaiian people. IMV acknowledges the use of LLuis
Vives HPC resources of the University of Valencia.http://iopscience.iop.org/2041-8205am2023Physic
Resolving the inner parsec of the blazar J1924â2914 with the Event Horizon Telescope
Rest of authors: Ikeda, Shiro; Impellizzeri, C. M. Violette; Inoue, Makoto; James, David J.; Jannuzi, Buell T.; Jeter, Britton; Jiang, Wu; Jimenez-Rosales, Alejandra; Johnson, Michael D.; Joshi, Abhishek, V; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; 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; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Michael; Kuo, Cheng-Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang-Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lindahl, Greg; Lindqvist, Michael; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Lonsdale, Colin; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Mueller, Cornelia; 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, Hector; Ortiz-Leon, Gisela N.; Oyama, Tomoaki; Ozel, Feryal; Palumbo, Daniel C. M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Pietu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Potzl, Felix M.; Prather, Ben; Preciado-Lopez, Jorge A.; Psaltis, Dimitrios; Pu, Hung-Yi; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Romero-Canizales, Cristina; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L. J.; Sanchez, Salvador; Sanchez-Arguelles, David; Sanchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Souccar, Kamal; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tilanus, Remo P. J.; Titus, Michael; Torne, Pablo; Trent, Tyler; Trippe, Sascha; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael; Wong, George N.; Wu, Qingwen; Yamaguchi, Paul; Yoon, Doosoo; Young, Andre; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Shan-Shan.The blazar J1924â2914 is a primary Event Horizon Telescope (EHT) calibrator for the Galactic centerâs black hole
Sagittarius A*. Here we present the first total and linearly polarized intensity images of this source obtained with
the unprecedented 20 ÎŒas resolution of the EHT. J1924â2914 is a very compact flat-spectrum radio source with
strong optical variability and polarization. In April 2017 the source was observed quasi-simultaneously with the
EHT (April 5â11), the Global Millimeter VLBI Array (April 3), and the Very Long Baseline Array (April 28),
giving a novel view of the source at four observing frequencies, 230, 86, 8.7, and 2.3 GHz. These observations
probe jet properties from the subparsec to 100 pc scales. We combine the multifrequency images of J1924â2914 to
study the source morphology. We find that the jet exhibits a characteristic bending, with a gradual clockwise
rotation of the jet projected position angle of about 90° between 2.3 and 230 GHz. Linearly polarized intensity
images of J1924â2914 with the extremely fine resolution of the EHT provide evidence for ordered toroidal
magnetic fields in the blazar compact core.We thank the anonymous reviewer for their thoughtful and
helpful comments. The Event Horizon Telescope Collaboration
thanks the following organizations and programs: the Academy
of Finland (projects 274477, 284495, 312496, 315721); the
Agencia Nacional de InvestigaciĂłn y Desarrollo (ANID), Chile
via NCN19_058 (TITANs) and Fondecyt 3190878, 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
black hole Initiative at Harvard University, through a grant
(60477) from the John Templeton Foundation; the China Scholarship Council; Consejo Nacional de Ciencia y TecnologĂa
(CONACYT, Mexico, projects U0004-246083, U0004-
259839, F0003-272050, M0037-279006, F0003-281692,
104497, 275201, 263356); the Delaney Family via the Delaney
Family John A. Wheeler Chair at Perimeter Institute; DirecciĂłn
General de Asuntos del Personal Académico-Universidad
Nacional AutĂłnoma de MĂ©xico (DGAPA-UNAM, projects
IN112417 and IN112820); the European Research Council
Synergy Grant âBlackHoleCam: Imaging the Event Horizon of
Black Holesâ (grant 610058); the Generalitat Valenciana
postdoctoral grant APOSTD/2018/177 and GenT Program
(project CIDEGENT/2018/021); MICINN Research Project
PID2019-108995GB-C22; the Gordon and Betty Moore
Foundation (grant GBMF-3561); 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; Joint Princeton/Flatiron and Joint Columbia/
Flatiron Postdoctoral Fellowships, research at the Flatiron
Institute is supported by the Simons Foundation; the Japanese
Government (Monbukagakusho: MEXT) Scholarship; the
Japan Society for the Promotion of Science (JSPS) Grant-in-
Aid for JSPS Research Fellowship (JP17J08829); the Key
Research Program of Frontier Sciences, Chinese Academy of
Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJSSWSYS008,
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,
JP18K13594, JP18K03656, JP18H03721, 18K03709,
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 (105-2112-M-001-025-MY3, 106-2112-M-001-011,
106-2119- M-001-027, 107-2119-M-001-017, 107-2119-M-
001-020, 107-2119-M-110-005, 108-2112-M-001-048, and
109-2124-M-001-005); the National Aeronautics and Space
Administration (NASA, Fermi Guest Investigator grant
80NSSC20K1567, NASA Astrophysics Theory Program grant
80NSSC20K0527, NASA NuSTAR award 80NSSC20K0645);
the National Institute of Natural Sciences (NINS) of Japan; the
National Key Research and Development Program of China
(grant 2016YFA0400704, 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-1555365,AST-1615796, AST-
1715061, AST-1716327, AST-1903847,AST-2034306); the
Natural Science Foundation of China (grants 11573051,
11633006, 11650110427, 10625314, 11721303, 11725312,
11933007, 11991052, 11991053); a fellowship of China
Postdoctoral Science Foundation (2020M671266); 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, 2015- R1D1A1A01056807, the Korea
Research Fellowship Program: NRF-2015H1D3A1066561, Basic Research Support Grant 2019R1F1A1059721); the
Netherlands Organization for Scientific Research (NWO) VICI
award (grant 639.043.513) and Spinoza Prize SPI 78-409; the
New Scientific Frontiers with Precision Radio Interferometry
Fellowship awarded by the South African Radio Astronomy
Observatory (SARAO), which is a facility of the National
Research Foundation (NRF), an agency of the Department of
Science and Technology (DST) of South Africa; the 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 Spanish Ministerio de EconomĂa y Competitividad
(grants PGC2018-098915-B-C21, AYA2016-80889-P,
PID2019-108995GB-C21); the State Agency for Research of
the Spanish MCIU through the âCenter of Excellence Severo
Ochoaâ award for the Instituto de AstrofĂsica de AndalucĂa
(SEV-2017-0709); the Toray Science Foundation; the ConsejerĂa
de EconomĂa, Conocimiento, Empresas y Universidad of the
Junta de AndalucĂa (grant P18-FR-1769), the Consejo Superior
de Investigaciones CientĂficas (grant 2019AEP112); 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); the European UnionÊŒs Horizon
2020 research and innovation program under grant
agreement No 730562 RadioNet; ALMA North America
Development Fund; the Academia Sinica; Chandra DD7-
18089X and TM6-17006X; the GenT Program (Generalitat
Valenciana) Project CIDEGENT/2018/021. This work used the
Extreme Science and Engineering Discovery Environment
(XSEDE), supported by NSF grant ACI-1548562, and CyVerse,
supported by NSF grants DBI-0735191, DBI-1265383, and
DBI-1743442. XSEDE Stampede2 resource at TACC was
allocated through TG-AST170024 and TG-AST080026N.
XSEDE JetStream resource at PTI and TACC was allocated
through AST170028. The simulations were performed in part on
the SuperMUC cluster at the LRZ in Garching, on the LOEWE
cluster in CSC in Frankfurt, and on the HazelHen cluster at the
HLRS in Stuttgart. This research was enabled in part by support
provided by Compute Ontario (http://computeontario.ca),
Calcul Quebec (http://www.calculquebec.ca) and Compute
Canada (http://www.computecanada.ca). We thank the staff at
the participating observatories, correlation centers, and institutions
for their enthusiastic support. This paper makes use of the
following ALMA data: ADS/JAO.ALMA#2016.1.01154.V
and ADS/JAO.ALMA2016.1.00413.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 cooperationwith
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
NRAO is a facility of the NSF operated under cooperative
agreement by AUI. APEX is a collaboration between the Max-
Planck-Institut fĂŒr Radioastronomie (Germany), ESO, and the
Onsala Space Observatory (Sweden). 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 R&D Program (No.
2017YFA0402700) of China. Additional funding support for the
JCMT is provided by the Science and Technologies Facility
Council (UK) and participating universities in the UK and
Canada. The LMT is a project operated by the Instituto Nacional
de AstrĂłfisica, Ăptica, y ElectrĂłnica (Mexico) and the University
of Massachusetts at Amherst (USA). 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
GeogrĂĄfico Nacional, Spain). 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 EHTC has received generous donations of
FPGA chips from Xilinx Inc., under the Xilinx University
Program. The EHTC has benefited from technology shared under 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. This research has made use of
NASAÊŒs Astrophysics Data System. 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. We acknowledge the significance that
Maunakea, where the SMA and JCMT EHT stations are located,
has for the indigenous Hawaiian people.
We also thank Alexandra Elbakyan for her contributions to
the open science initiative. This research has made use of data
obtained with the Global Millimeter VLBI Array (GMVA),
coordinated by the VLBI group at the Max-Planck-Institut fĂŒr
Radioastronomie (MPIfR). The GMVA consists of telescopes
operated by MPIfR, IRAM, Onsala, Metsahovi, Yebes, the
Korean VLBI Network, the Green Bank Observatory, and the
Very Long Baseline Array (VLBA). The VLBA and the GBT
are facilities of the National Science Foundation under
cooperative agreement by Associated Universities, Inc. The
data were correlated at the DiFX correlator of the MPIfR in
Bonn, Germany. We thank the National Science Foundation
(awards OISE-1743747, AST-1816420, AST-1716536, AST-
1440254, AST-1935980) and the Gordon and Betty Moore
Foundation (GBMF-5278) for financial support of this work.
Support for this work was also provided by the NASA Hubble
Fellowship grant HST-HF2-51431.001-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.http://iopscience.iop.org/0004-637Xam2023Physic
Constraining the Neutron Star MassâRadius Relation and Dense Matter Equation of State with . I. The Millisecond Pulsar X-Ray Data Set
International audienceWe present the set of deep Neutron Star Interior Composition Explorer (NICER) X-ray timing observations of the nearby rotation-powered millisecond pulsars PSRs J0437â4715, J0030+0451, J1231â1411, and J2124â3358, selected as targets for constraining the massâradius relation of neutron stars and the dense matter equation of state (EoS) via modeling of their pulsed thermal X-ray emission. We describe the instrument, observations, and data processing/reduction procedures, as well as the series of investigations conducted to ensure that the properties of the data sets are suitable for parameter estimation analyses to produce reliable constraints on the neutron star massâradius relation and the dense matter EoS. We find that the long-term timing and flux behavior and the Fourier-domain properties of the event data do not exhibit any anomalies that could adversely affect the intended measurements. From phase-selected spectroscopy, we find that emission from the individual pulse peaks is well described by a single-temperature hydrogen atmosphere spectrum, with the exception of PSR J0437â4715, for which multiple temperatures are required