Characterizing and mitigating intraday variability: Reconstructing source structure in accreting black holes with mm-VLBI

Avery E. Broderick, Roman Gold, Boris Georgiev, Dominic W. Pesce, Paul Tiede, Chunchong Ni, Kotaro Moriyama, Kazunori Akiyama, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Baloković, John Barrett, Michi BauböckBradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Hope Boyce, Michael Bremer, Christiaan D. Brinkerink, Roger Brissenden, Silke Britzen, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, Do-Young Byun, John E. Carlstrom, Chiara Ceccobello, Andrew Chael, Chi-kwan Chan, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, John E. Conway, James M. Cordes, Thomas M. Crawford, The Event Horizon Telescope Collaboration

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

1 Downloads (Pure)

Abstrakt

The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87 * and Sgr A *. However, with this leap in resolution has come a new set of practical complications. Sgr A * exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A * and M87 *. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87 *, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.

OriginalsprogEngelsk
ArtikelnummerL21
TidsskriftThe Astrophysical Journal Letters
Vol/bind930
Udgave nummer2
Antal sider30
ISSN2041-8205
DOI
StatusUdgivet - 10. maj 2022

Fingeraftryk

Dyk ned i forskningsemnerne om 'Characterizing and mitigating intraday variability: Reconstructing source structure in accreting black holes with mm-VLBI'. Sammen danner de et unikt fingeraftryk.

Citationsformater