Article
Astronomy & Astrophysics
Mengye Wang, Yiqiu Ma, Qingwen Wu
Summary: In this study, the effects of gas accretion on the mass distribution and migration of stellar-mass black holes and stars in the accretion disc of active galactic nuclei are simulated and explored. It is found that stellar-mass black holes can grow up to several tens solar mass and form heavier black hole binaries. This can help us understand the black-hole mass distribution observed by ground-based gravitational wave detectors such as LIGO/Virgo, ET, and Cosmic Explorer.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
O. Porth, Y. Mizuno, Z. Younsi, C. M. Fromm
Summary: Based on 3D general relativistic magnetohydrodynamic simulations, this study examines a model for magnetic flux eruptions from the black hole magnetosphere. The results suggest that the erupted flux bundles can power infrared and X-ray flares, and the motion within the magnetically supported flow is significantly sub-Keplerian.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Thomas Bronzwaer, Jordy Davelaar, Ziri Younsi, Monika Moscibrodzka, Hector Olivares, Yosuke Mizuno, Jesse Vos, Heino Falcke
Summary: Accreting black holes often display a dark central region called the black hole shadow, conveying information about the black hole's mass and spin. The observed central brightness depression, or image shadow, can differ from the black hole shadow due to factors such as evacuation of the innermost region of the accretion flow and obscuration by optically thick regions. The study found that a compact and optically thin emission region allows for measurement of the black hole shadow size with an accuracy of 5%, indicating that certain conditions must be met for accurate measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Indrani Banerjee, Bhaswati Mandal, Soumitra SenGupta
Summary: String inspired models have the potential to replace general relativity in high-energy/high-curvature regimes, with interesting implications for cosmology and acceleration. Studies on the Einstein-Maxwell dilaton-axion theory provide insights into astrophysical observations and the properties of black holes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ramesh Narayan, Andrew Chael, Koushik Chatterjee, Angelo Ricarte, Brandon Curd
Summary: We present the results of nine simulations of radiatively inefficient magnetically arrested discs (MADs) with different black hole spin parameters. Our study finds that the saturated magnetic flux level and jet power of MAD discs strongly depend on the black hole spin. Prograde discs have higher magnetic flux and more powerful jets compared to retrograde discs. Moreover, MADs with spinning black holes launch jets with generalized parabolic profiles, and the width of the jets varies with distance from the black hole according to a power-law function. We also observe a strong correlation between the disc-jet geometry and the dimensionless magnetic flux, with prograde systems displaying thinner equatorial accretion flows near the black hole and wider jets compared to retrograde systems. Additionally, we find different trends in disc variability between prograde and retrograde MADs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Shihong Liao, Peter H. Johansson, Matias Mannerkoski, Dimitrios Irodotou, Francesco Paolo Rizzuto, Stuart McAlpine, Antti Rantala, Alexander Rawlings, Till Sawala
Summary: We propose a new model to study the accretion and feedback of SMBH binaries, which allows us to investigate the evolution of SMBH binaries in gas-rich galaxy mergers. Our model includes preferential mass accretion on to the secondary SMBH and can resolve SMBH binaries down to separations of tens of Schwarzschild radii. We perform simulations of gas-rich disc galaxy mergers with different types of AGN feedback and find that the feedback implementation plays a critical role in the merger time-scales and the resulting stellar profiles.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
K. Alabarta, D. Altamirano, M. Mendez, V. A. Cuneo, F. M. Vincentelli, N. Castro-Segura, F. Garcia, B. Luff, A. Veledina
Summary: Black hole low-mass X-ray binaries (BH LMXBs) undergo evolution during outbursts, with common events being 'failed-transition outbursts' (FT outbursts) where the source never reaches the high/soft state. Both FT and full outbursts are driven by the same physical process and initial X-ray data do not distinguish between the two types.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Mudit Garg, Andrea Derdzinski, Lorenz Zwick, Pedro R. Capelo, Lucio Mayer
Summary: This study investigates the effects of torques on the circular inspirals of intermediate-mass black hole binaries (IMBHBs) embedded in gas discs. The impact of torques on the detected gravitational wave (GW) waveform in the LISA frequency band is explored. The results suggest that torques can cause dephasing in the IMBHB's GW signal, and the measurable dephasing depends on various factors such as black hole masses, redshift, and accretion rates. These findings are important for understanding accretion discs and galactic nuclei astrophysics.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Samik Mitra, Debaprasad Maity, Indu Kalpa Dihingia, Santabrata Das
Summary: We present a novel approach to study the global structure of steady, axisymmetric, advective, magnetohydrodynamic (MHD) accretion flow around black holes in full general relativity (GR). Considering ideal MHD conditions and relativistic equation of state (REoS), we solve the governing equations to obtain all possible smooth global accretion solutions. We examine the dynamical and thermodynamical properties of accreting matter in terms of the flow parameters, namely energy (epsilon), angular momentum (L), and local magnetic fields. We observe that toroidal component of the magnetic fields generally dominates over radial component at the disc equatorial plane, suggesting the importance of toroidal magnetic field in regulating the disc dynamics. The disc remains mostly gas pressure dominated except at the near horizon region where magnetic fields become indispensable. We calculate the viscosity parameter and examine the scaling relation between alpha and beta, distinguishing two domains along the radial extent of the disc. We discuss the utility of the present formalism in GRMHD simulation studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Prashant Kocherlakota, Luciano Rezzolla
Summary: Imaging a supermassive black hole and extracting physical information requires understanding of both gravitational and astrophysical conditions. Uncertainties in geometry and emission lead to degeneracies in interpretation. Modeling the imaging of a spherically accreting black hole, we show how degenerate regions can be constrained by combining multiple pieces of information. Degeneracies can potentially be eliminated with increased angular resolution and flux sensitivity measurements.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Roberto Soria, Ruican Ma, Lian Tao, Shuang-Nan Zhang
Summary: By revisiting the published results of X-ray and optical studies on the black hole candidate MAXI J0637-430, we have improved the understanding of its system parameters. This black hole is the farthest known from the Galactic Center and has the shortest period among all Galactic black hole X-ray binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Kaushik Chatterjee, Dipak Debnath, Riya Bhowmick, Sujoy Kumar Nath, Debjit Chatterjee
Summary: The Galactic black hole candidate 4U 1630-472 has experienced multiple outbursts of different types, leading researchers to suspect that it may have two companion stars. Through studying the characteristics of its outbursts and quiescent periods, researchers are trying to understand the nature of this unique source.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Malyali, Z. Liu, A. Rau, I Grotova, A. Merloni, A. J. Goodwin, G. E. Anderson, J. C. A. Miller-Jones, A. Kawka, R. Arcodia, J. Buchner, K. Nandra, D. Homan, M. Krumpe
Summary: The ROSAT-selected tidal disruption event (TDE) candidate RX J133157.6-324319.7 (J1331) was detected as a bright and ultra-soft X-ray flare in 1993 from a quiescent galaxy. During the recent eRASS5, J1331 exhibited repeated flaring with similar spectral properties to the previous flare, suggesting two partial TDEs involving a star on an elliptical orbit around a black hole.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
R. Taverna, L. Marra, S. Bianchi, M. Dovciak, R. Goosmann, F. Marin, G. Matt, W. Zhang
Summary: Studying the radiation emitted from black hole accretion discs is crucial in understanding the physical properties of black holes, particularly their spin. In addition to spectral analysis, polarimetry is becoming increasingly important and can provide estimates of black hole spin. Absorption effects have a significant impact on the polarization properties of the emitted radiation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Ruth A. Daly
Summary: The study investigates mass accretion rates, radiant luminosity, and efficiency factors in black hole systems with outflows. It explores the relationships between different types and sub-types of sources. Comparisons with independently obtained values show similar results.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Enrico Ragusa, Richard Alexander, Josh Calcino, Kieran Hirsh, Daniel J. Price
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
Rebecca Nealon, Nicolas Cuello, Jean-Francois Gonzalez, Gerrit van der Plas, Christophe Pinte, Richard Alexander, Francois Menard, Daniel J. Price
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
G. Ballabio, R. Nealon, R. D. Alexander, N. Cuello, C. Pinte, D. J. Price
Summary: Misalignments within protoplanetary discs are commonly observed, with shadows, rings, and gaps present in the disc of HD 143006. New hydrodynamic simulations suggest a configuration with both a strongly inclined binary and an outer planetary companion, which could explain the observed morphological features.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Andrew J. Winter, Richard Alexander
Summary: Observations suggest that some planetary systems may have been dynamically perturbed. Isolating planets that have evolved without any perturbation can help constrain formation processes. Revisiting simple models for planet growth during the formation stage is worth considering.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Alison K. Young, Richard Alexander, Catherine Walsh, Rebecca Nealon, Alice Booth, Christophe Pinte
Summary: Circumstellar discs may become warped or broken into distinct planes due to misalignment with a stellar or planetary companion, impacting temperature and chemistry which in turn affects the possibility of planet formation. Observational evidence shows misaligned inner discs and warps caused by interactions with undetected companions, indicating potential planet formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
C. C. Espaillat, G. J. Herczeg, T. Thanathibodee, C. Pittman, N. Calvet, N. Arulanantham, K. France, Javier Serna, J. Hernandez, A. Kospal, F. M. Walter, A. Frasca, W. J. Fischer, C. M. Johns-Krull, P. C. Schneider, C. Robinson, Suzan Edwards, P. Abraham, Min Fang, J. Erkal, C. F. Manara, J. M. Alcala, E. Alecian, R. D. Alexander, J. Alonso-Santiago, Simone Antoniucci, David R. Ardila, Andrea Banzatti, M. Benisty, Edwin A. Bergin, Katia Biazzo, Cesar Briceno, Justyn Campbell-White, L. Ilsedore Cleeves, Deirdre Coffey, Jochen Eisloffel, Stefano Facchini, D. Fedele, Eleonora Fiorellino, Dirk Froebrich, Manuele Gangi, Teresa Giannini, K. Grankin, Hans Moritz Gunther, Zhen Guo, Lee Hartmann, Lynne A. Hillenbrand, P. C. Hinton, Joel H. Kastner, Chris Koen, K. Mauco, I Mendigutia, B. Nisini, Neelam Panwar, D. A. Principe, Massimo Robberto, A. Sicilia-Aguilar, Jeff A. Valenti, J. Wendeborn, Jonathan P. Williams, Ziyan Xu, R. K. Yadav
Summary: The Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program and the ODYSSEUS survey will greatly advance our understanding of the relationship between young stars and their protoplanetary disks. By analyzing the ULLYSES spectral database, ODYSSEUS will investigate key physical processes such as mass accretion, mass outflow, and disk structure, and provide comprehensive multi-wavelength observations.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Alison K. Young, Richard Alexander, Giovanni Rosotti, Christophe Pinte
Summary: Many circumstellar discs have misaligned central regions, causing shadows in scattered light observations. Small disc warps are difficult to detect but can be identified using CO emission characteristics. Radial profiles reveal the warp structure and the twist of the disc, which can be detected at moderate inclinations. However, the observed twist does not directly measure the warp structure due to its dependency on optical depth. The warp causes broad asymmetries in channel maps, distinct from features caused by embedded planets and gravitational instabilities.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Chiara E. Scardoni, Cathie J. Clarke, Giovanni P. Rosotti, Richard A. Booth, Richard D. Alexander, Enrico Ragusa
Summary: Recent studies have shown that in the planet-dominated regime, the torques acting on planets are correlated with the depth of the gap carved by the planet in the disc. Live-planet simulations demonstrate that the excitation of planet eccentricity can break the direct dependence between migration rate and torques, an effect not captured by fixed-planet simulations. Furthermore, a torque reversal at a certain critical value of the gap depth parameter K may shape the planetary system architecture and impede the formation of hot Jupiters through Type II migration.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Colette Salyk, Klaus M. Pontoppidan, Andrea Banzatti, Ulrich Kaufl, Cassandra Hall, Ilaria Pascucci, Andres Carmona, Geoffrey A. Blake, Richard Alexander, Inga Kamp
Summary: An analysis of water vapor emission from the young binary system VV CrA reveals an unusual spectrum in one of its components, possibly indicating the presence of a high-temperature water reservoir. Further observations and modeling are needed to determine the origin of this peculiar spectral pattern.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Simon R. G. Joyce, John P. Pye, Jonathan D. Nichols, Richard Alexander, Manuel Guedel, David Barrado
Summary: English summary: "PDS 70 is the first directly imaged planetary system. Observations with X-ray and UV radiation show that the protoplanetary disc surrounding PDS 70 is undergoing dispersal due to stellar radiation and will completely evaporate in the next million years, bringing an end to the primary planet formation process."
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Review
Physics, Multidisciplinary
F. Zagaria, G. P. Rosotti, R. D. Alexander, C. J. Clarke
Summary: In multiple stellar systems, interactions among companion stars and their discs have significant impacts on planet formation. Tidal truncation in circumstellar cases leads to smaller, fainter and shorter-lived protoplanetary discs, resulting in a reduced availability of material for forming planetary embryos. Conversely, in circumbinary cases, reduced accretion can increase the lifetime of discs, which has positive effects on planet formation. This chapter provides a review of observational results on discs in multiple stellar systems, discussing possible explanations, particularly focusing on recent numerical simulations of dust dynamics and disc evolution. Finally, open issues and future research directions are examined.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
John Debes, Rebecca Nealon, Richard Alexander, Alycia J. Weinberger, Schuyler Grace Wolff, Dean Hines, Joel Kastner, Hannah Jang-Condell, Christophe Pinte, Peter Plavchan, Laurent Pueyo
Summary: We present new visible-light imaging of the TW Hya disk using the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. The images show two separate shadows, indicating a change in behavior of the occulting structure. Based on radiative-transfer models, we suggest that the change is due to two misaligned components of the inner disk. More observations are needed to understand the nature of TW Hya's inner-disk architecture.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Richard Alexander, Giovanni Rosotti, Philip J. Armitage, Gregory J. Herczeg, Carlo F. Manara, Benoit Tabone
Summary: We find that the distribution of observed accretion rates is a powerful tool to distinguish between two mechanisms of disc accretion, namely turbulent transport of angular momentum and magnetized disc winds. A sample of 300 observed accretion rates would be sufficient to confidently differentiate between the two mechanisms, even with conservative assumptions. Current observations of T Tauri star accretion rates are too small and heterogeneous to provide a clear answer, making both viscous and wind-driven models valid.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
E. T. Whelan, I. Pascucci, U. Gorti, S. Edwards, R. D. Alexander, M. F. Sterzik, C. Melo
Summary: Spectroastrometry is used to study the low-velocity component (LVC) of optical forbidden emission from T Tauri stars RU Lupi and AS 205 N. It is found that the LVC of RU Lupi may trace a wide-angled MHD disk wind, while AS 205 N exhibits a complex outflow system.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
C. Hall, R. Dong, R. Teague, J. Terry, C. Pinte, T. Paneque-Carreno, B. Veronesi, R. D. Alexander, G. Lodato
ASTROPHYSICAL JOURNAL
(2020)
