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Articles 31 - 60 of 169
Full-Text Articles in Astrophysics and Astronomy
Experimental Constraint On Axionlike Particles Over Seven Orders Of Magnitude In Mass, Tanya S. Roussy, Daniel A. Palken, William B. Cairncross, Benjamin M. Brubaker, Daniel N. Gresh, Matt Grau, Kevin C. Cossel, Kia Boon Ng, Yuval Shagam, Yan Zhou, Victor V. Flambaum, Konrad W. Lehnert, Jun Ye, Eric A. Cornell
Experimental Constraint On Axionlike Particles Over Seven Orders Of Magnitude In Mass, Tanya S. Roussy, Daniel A. Palken, William B. Cairncross, Benjamin M. Brubaker, Daniel N. Gresh, Matt Grau, Kevin C. Cossel, Kia Boon Ng, Yuval Shagam, Yan Zhou, Victor V. Flambaum, Konrad W. Lehnert, Jun Ye, Eric A. Cornell
Physics & Astronomy Faculty Research
We use our recent electric dipole moment (EDM) measurement data to constrain the possibility that the HfF+ EDM oscillates in time due to interactions with candidate dark matter axionlike particles (ALPs). We employ a Bayesian analysis method which accounts for both the look-elsewhere effect and the uncertainties associated with stochastic density fluctuations in the ALP field. We find no evidence of an oscillating EDM over a range spanning from 27 nHz to 400 mHz, and we use this result to constrain the ALP-gluon coupling over the mass range 10-22-10-15 eV. This is the first laboratory constraint on the ALP-gluon coupling …
On The Role Of Resonances In Polluting White Dwarfs By Asteroids, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio, Dimitri Veras
On The Role Of Resonances In Polluting White Dwarfs By Asteroids, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio, Dimitri Veras
Physics & Astronomy Faculty Research
Pollution of white dwarf atmospheres may be caused by asteroids that originate from the locations of secular and mean-motion resonances in planetary systems. Asteroids in these locations experience increased eccentricity, leading to tidal disruption by the white dwarf. We examine how the ν6 secular resonance shifts outwards into a previously stable region of the asteroid belt, as the star evolves to a white dwarf. Analytic secular models require a planet to be engulfed in order to shift the resonance. We show with numerical simulations that as a planet gets engulfed by the evolving star, the secular resonance shifts and the …
Crafts For Fast Radio Bursts: Extending The Dispersion-Fluence Relation With New Frbs Detected By Fast, Chen Hui Niu, Di Li, Rui Luo, Wei Yang Wang, Jumei Yao, Bing Zhang, Wei Wei Zhu, Pei Wang, Haoyang Ye, Yong Kun Zhang, Jia Rui Niu, Ning Yu Tang, Ran Duan, Marko Krco, Shi Dai, Yi Feng, Chenchen Miao, Zhichen Pan, Lei Qian, Mengyao Xue, Mao Yuan, Youling Yue, Lei Zhang, Xinxin Zhang
Crafts For Fast Radio Bursts: Extending The Dispersion-Fluence Relation With New Frbs Detected By Fast, Chen Hui Niu, Di Li, Rui Luo, Wei Yang Wang, Jumei Yao, Bing Zhang, Wei Wei Zhu, Pei Wang, Haoyang Ye, Yong Kun Zhang, Jia Rui Niu, Ning Yu Tang, Ran Duan, Marko Krco, Shi Dai, Yi Feng, Chenchen Miao, Zhichen Pan, Lei Qian, Mengyao Xue, Mao Yuan, Youling Yue, Lei Zhang, Xinxin Zhang
Physics & Astronomy Faculty Research
We report three new FRBs discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), namely FRB 181017.J0036+11, FRB 181118, and FRB 181130, through the Commensal Radio Astronomy FAST Survey (CRAFTS). Together with FRB 181123, which was reported earlier, all four FAST-discovered FRBs share the same characteristics of low fluence (≤0.2 Jy ms) and high dispersion measure (DM, >1000 pc cm-3), consistent with the anticorrelation between DM and fluence of the entire FRB population. FRB 181118 and FRB 181130 exhibit band-limited features. FRB 181130 is prominently scattered (τ s ≃ 8 ms) at 1.25 GHz. FRB 181017.J0036+11 has full-bandwidth emission with …
The Pencil Code, A Modular Mpi Code For Partial Differential Equations And Particles: Multipurpose And Multiuser-Maintained, The Pencil Code Collaboration, Chao-Chin Yang
The Pencil Code, A Modular Mpi Code For Partial Differential Equations And Particles: Multipurpose And Multiuser-Maintained, The Pencil Code Collaboration, Chao-Chin Yang
Physics & Astronomy Faculty Research
The Pencil Code is a highly modular physics-oriented simulation code that can be adapted to a wide range of applications. It is primarily designed to solve partial differential equations (PDEs) of compressible hydrodynamics and has lots of add-ons ranging from astrophysical magnetohydrodynamics (MHD) (A. Brandenburg & Dobler, 2010) to meteorological cloud microphysics (Li et al., 2017) and engineering applications in combustion (Babkovskaia et al., 2011). Nevertheless, the framework is general and can also be applied to situations not related to hydrodynamics or even PDEs, for example when just the message passing interface or input/output strategies of the code are to …
Constraining Protoplanetary Disc Accretion And Young Planets Using Alma Kinematic Observations, Ian Rabago, Zhaohuan Zhu
Constraining Protoplanetary Disc Accretion And Young Planets Using Alma Kinematic Observations, Ian Rabago, Zhaohuan Zhu
Physics & Astronomy Faculty Research
Recent ALMA molecular line observations have revealed 3D gas velocity structure in protoplanetary discs, shedding light on mechanisms of disc accretion and structure formation. (1) By carrying out viscous simulations, we confirm that the disc's velocity structure differs dramatically using vertical stress profiles from different accretion mechanisms. Thus, kinematic observations tracing flows at different disc heights can potentially distinguish different accretion mechanisms. On the other hand, the disc surface density evolution is mostly determined by the vertically integrated stress. The sharp disc outer edge constrained by recent kinematic observations can be caused by a radially varying alpha in the disc. …
Kozai–Lidov Oscillations Triggered By A Tilt Instability Of Detached Circumplanetary Discs, Rebecca G. Martin, Zhaohuan Zhu, Philip J. Armitage, Chao-Chin Yang, Hans Baehr
Kozai–Lidov Oscillations Triggered By A Tilt Instability Of Detached Circumplanetary Discs, Rebecca G. Martin, Zhaohuan Zhu, Philip J. Armitage, Chao-Chin Yang, Hans Baehr
Physics & Astronomy Faculty Research
Circumplanetary discs can be linearly unstable to the growth of disc tilt in the tidal potential of the star–planet system. We use 3D hydrodynamical simulations to characterize the disc conditions needed for instability, together with its long-term evolution. Tilt growth occurs for disc aspect ratios, evaluated near the disc outer edge, of H/r ≳ 0.05, with a weak dependence on viscosity in the wave-like regime of warp propagation. Lower mass giant planets are more likely to have circumplanetary discs that satisfy the conditions for instability. We show that the tilt instability can excite the inclination to above the threshold where …
The Occurrence Of Rocky Habitable-Zone Planets Around Solar-Like Stars From Kepler Data, Steve Bryson, Michelle Kunimoto, Ravi K. Kopparapu, Jeffrey L. Coughlin, William J. Borucki, David Koch, Victor Silva Aguirre, Christopher Allen, Geert Barentsen, Natalie M. Batalha, Travis Berger, Alan Boss, Lars A. Buchhave, Christopher J. Burke, Douglas A. Caldwell, Jennifer R. Campbell, Joseph Catanzarite, Hema Chandrasekaran, William J. Chaplin, Jessie L. Christiansen, Jørgen Christensen-Dalsgaard, David R. Ciardi, Bruce D. Clarke, William D. Cochran, Jessie L. Dotson, Laurance R. Doyle, Eduardo Seperuelo Duarte, Edward W. Dunham, Andrea K. Dupree, Michael Endl, James L. Fanson
The Occurrence Of Rocky Habitable-Zone Planets Around Solar-Like Stars From Kepler Data, Steve Bryson, Michelle Kunimoto, Ravi K. Kopparapu, Jeffrey L. Coughlin, William J. Borucki, David Koch, Victor Silva Aguirre, Christopher Allen, Geert Barentsen, Natalie M. Batalha, Travis Berger, Alan Boss, Lars A. Buchhave, Christopher J. Burke, Douglas A. Caldwell, Jennifer R. Campbell, Joseph Catanzarite, Hema Chandrasekaran, William J. Chaplin, Jessie L. Christiansen, Jørgen Christensen-Dalsgaard, David R. Ciardi, Bruce D. Clarke, William D. Cochran, Jessie L. Dotson, Laurance R. Doyle, Eduardo Seperuelo Duarte, Edward W. Dunham, Andrea K. Dupree, Michael Endl, James L. Fanson
Physics & Astronomy Faculty Research
We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define η⊕ as the HZ occurrence of planets with radii between 0.5 and 1.5 R⊕ orbiting stars with effective temperatures between 4800 and 6300 K. We find that η⊕ for the conservative HZ is between... (See article for full abstract).
The Evolution Of A Circumplanetary Disc With A Dead Zone, Cheng Chen, Chao Chin Yang, Rebecca G. Martin, Zhaohuan Zhu
The Evolution Of A Circumplanetary Disc With A Dead Zone, Cheng Chen, Chao Chin Yang, Rebecca G. Martin, Zhaohuan Zhu
Physics & Astronomy Faculty Research
© 2021 Oxford University Press. All rights reserved. We investigate whether the regular Galilean satellites could have formed in the dead zone of a circumplanetary disc. A dead zone is a region of weak turbulence in which the magnetorotational instability is suppressed, potentially an ideal environment for satellite formation. With the grid-based hydrodynamic code FARGO3D, we examine the evolution of a circumplanetary disc model with a dead zone. Material accumulates in the dead zone of the disc leading to a higher total mass and but a similar temperature profile compared to a fully turbulent disc model. The tidal torque increases …
A Thousand Days After The Merger: Continued X-Ray Emission From Gw170817, E. Troja, H. Van Eerten, Bing Zhang, G. Ryan, L. Piro, R. Ricci, B. O'Connor, M. H. Wieringa, S. B. Cenko, T. Sakamoto
A Thousand Days After The Merger: Continued X-Ray Emission From Gw170817, E. Troja, H. Van Eerten, Bing Zhang, G. Ryan, L. Piro, R. Ricci, B. O'Connor, M. H. Wieringa, S. B. Cenko, T. Sakamoto
Physics & Astronomy Faculty Research
Recent observations with the Chandra X-ray telescope continue to detect X-ray emission from the transient GW170817. In a total exposure of 96.6 ks, performed between 2020 March 9 and 16 (935–942 d after the merger), a total of 8 photons are measured at the source position, corresponding to a significance of ≈5σ. Radio monitoring with the Australian Telescope Compact Array (ATCA) shows instead that the source has faded below our detection threshold... (See full abstract in article).
Space Telescope And Optical Reverberation Mapping Project. Xi. Disk-Wind Characteristics And Contributions To The Very Broad Emission Lines Of Ngc 5547, M. Dehghanian, G. J. Ferland, G. A. Kriss, B. M. Peterson, K. T. Korista, M. R. Goad, M. Chatzikos, F. Guzmán, G. D. Rosa, M. Mehdipour, J. Kaastra, S. Mathur, M. Vestergaard, Daniel Proga, Tim Waters, M. C. Bentz, S. Bisogni, W. N. Brandt, E. D. Bontà, M. M. Fausnaugh, J. M. Gelbord, Keith Horne, I. M. Mchardy, R. W. Pogge, D. A. Starkey
Space Telescope And Optical Reverberation Mapping Project. Xi. Disk-Wind Characteristics And Contributions To The Very Broad Emission Lines Of Ngc 5547, M. Dehghanian, G. J. Ferland, G. A. Kriss, B. M. Peterson, K. T. Korista, M. R. Goad, M. Chatzikos, F. Guzmán, G. D. Rosa, M. Mehdipour, J. Kaastra, S. Mathur, M. Vestergaard, Daniel Proga, Tim Waters, M. C. Bentz, S. Bisogni, W. N. Brandt, E. D. Bontà, M. M. Fausnaugh, J. M. Gelbord, Keith Horne, I. M. Mchardy, R. W. Pogge, D. A. Starkey
Physics & Astronomy Faculty Research
In 2014 the NGC 5548 Space Telescope and Optical Reverberation Mapping campaign discovered a two-month anomaly when variations in the absorption and emission lines decorrelated from continuum variations. During this time the soft X-ray part of the intrinsic spectrum had been strongly absorbed by a line-of-sight (LOS) obscurer, which was interpreted as the upper part of a disk wind. Our first paper showed that changes in the LOS obscurer produces the decorrelation between the absorption lines and the continuum. A second study showed that the base of the wind shields the broad emission-line region (BLR), leading to the emission-line decorrelation. …
Probing The Intergalactic Turbulence With Fast Radio Bursts, Siyao Xu, Bing Zhang
Probing The Intergalactic Turbulence With Fast Radio Bursts, Siyao Xu, Bing Zhang
Physics & Astronomy Faculty Research
The turbulence in the diffuse intergalactic medium (IGM) plays an important role in various astrophysical processes across cosmic time, but it is very challenging to constrain its statistical properties both observationally and numerically. Via the statistical analysis of turbulence along different sight lines toward a population of fast radio bursts (FRBs), we demonstrate that FRBs provide a unique tool to probe the intergalactic turbulence. We measure the structure function (SF) of dispersion measures (DMs) of FRBs to study the multiscale electron density fluctuations induced by the intergalactic turbulence. The SF has a large amplitude and a Kolmogorov power-law scaling with …
Requirements For Gravitational Collapse In Planetesimal Formation - The Impact Of Scales Set By Kelvin - Helmholtz And Nonlinear Streaming Instability, Konstantin Gerbig, Ruth A. Murray-Clay, Hubert Klahr, Hans Baehr
Requirements For Gravitational Collapse In Planetesimal Formation - The Impact Of Scales Set By Kelvin - Helmholtz And Nonlinear Streaming Instability, Konstantin Gerbig, Ruth A. Murray-Clay, Hubert Klahr, Hans Baehr
Physics & Astronomy Faculty Research
The formation of planetesimals is a challenging problem in planet formation theory. A prominent scenario for overcoming dust growth barriers is the gravitational collapse of locally over-dense regions, shown to robustly produce ~100 km–sized objects. Still, the conditions under which planetesimal formation occurs remain unclear. For collapse to proceed, the self-gravity of an over-density must overcome stellar tidal disruption on large scales and turbulent diffusion on small scales. Here, we relate the scales of streaming and Kelvin–Helmholtz instability (KHI), which both regulate particle densities on the scales of gravitational collapse, directly to planetesimal formation. We support our analytic findings by …
A Mildly Relativistic Outflow From The Energentic, Fast-Rising Blue Optical Transient Css161010 In A Dwarf Galaxy, Deanne L. Coppejans, R. Margutti, G. Terreran, A. J. Nayana, E. R. Coughlin, T. Laskar, K. D. Alexander, M. Bietenholz, D. Caprioli, P. Chandra, M. R. Drout, D. Frederiks, C. Frohmaier, K. H. Hurley, C. S. Kochanek, M. Macleod, A. Meisner, P. E. Nugent, A. Ridnaia, D. J. Sand, D. Svinkin, C. Ward, S. Yang, A. Baldeschi, I. V. Chilingarian, Y. Dong, C. Esquivia, W. Fong, C. Guidorzi, P. Lundqvist, D. Milisavljevic
A Mildly Relativistic Outflow From The Energentic, Fast-Rising Blue Optical Transient Css161010 In A Dwarf Galaxy, Deanne L. Coppejans, R. Margutti, G. Terreran, A. J. Nayana, E. R. Coughlin, T. Laskar, K. D. Alexander, M. Bietenholz, D. Caprioli, P. Chandra, M. R. Drout, D. Frederiks, C. Frohmaier, K. H. Hurley, C. S. Kochanek, M. Macleod, A. Meisner, P. E. Nugent, A. Ridnaia, D. J. Sand, D. Svinkin, C. Ward, S. Yang, A. Baldeschi, I. V. Chilingarian, Y. Dong, C. Esquivia, W. Fong, C. Guidorzi, P. Lundqvist, D. Milisavljevic
Physics & Astronomy Faculty Research
We present X-ray and radio observations of the Fast Blue Optical Transient CRTS-CSS161010 J045834−081803 (CSS161010 hereafter) at t = 69–531 days. CSS161010 shows luminous X-ray (L x ~ 5 × 1039 erg s−1) and radio (L ν ~ 1029 erg s−1 Hz−1) emission. The radio emission peaked at ~100 days post-transient explosion and rapidly decayed. We interpret these observations in the context of synchrotron emission from an expanding blast wave. CSS161010 launched a mildly relativistic outflow with velocity Γβc ≥ 0.55c at ~100 days. This is faster than the non-relativistic AT 2018cow (Γβc ~ 0.1c) and closer to ZTF18abvkwla (Γβc …
The Planetary Luminosity Problem: " Missing Planets" And The Observational Consequences Of Episodi Accretion, Sean D. Brittain, Joan R. Najita, Ruobing Dong, Zhaohuan Zhu
The Planetary Luminosity Problem: " Missing Planets" And The Observational Consequences Of Episodi Accretion, Sean D. Brittain, Joan R. Najita, Ruobing Dong, Zhaohuan Zhu
Physics & Astronomy Faculty Research
The high occurrence rates of spiral arms and large central clearings in protoplanetary disks, if interpreted as signposts of giant planets, indicate that gas giants commonly form as companions to young stars (Myr) at orbital separations of 10–300 au. However, attempts to directly image this giant planet population as companions to more mature stars (>10 Myr) have yielded few successes. This discrepancy could be explained if most giant planets form by "cold start," i.e., by radiating away much of their formation energy as they assemble their mass, rendering them faint enough to elude detection at later times. In that …
Gw Ori: Interactions Between A Triple-Star System And Its Circumtriple Disk In Action, Jiaquig Bi, Nienke Van Der Marel, Ruobing Dong, Takayuki Muto, Rebecca G. Martin, Jeremy L. Smallwood, Jun Hashimoto, Hauyu Baobab Liu, Hideko Nomura, Yasuhiro Hasegawa, Michihiro Takami, Mihoko Konishi, Munetake Momose, Kazuhiro D. Kanagawa, Akimasa Kataoka, Tomohiro Ono, Michael L. Sitko, Sanemichi Z. Takahashi, Kengo Tomida, Takashi Tsukagoshi
Gw Ori: Interactions Between A Triple-Star System And Its Circumtriple Disk In Action, Jiaquig Bi, Nienke Van Der Marel, Ruobing Dong, Takayuki Muto, Rebecca G. Martin, Jeremy L. Smallwood, Jun Hashimoto, Hauyu Baobab Liu, Hideko Nomura, Yasuhiro Hasegawa, Michihiro Takami, Mihoko Konishi, Munetake Momose, Kazuhiro D. Kanagawa, Akimasa Kataoka, Tomohiro Ono, Michael L. Sitko, Sanemichi Z. Takahashi, Kengo Tomida, Takashi Tsukagoshi
Physics & Astronomy Faculty Research
GW Ori is a hierarchical triple system with a rare circumtriple disk. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and 12CO J = 2 − 1 molecular gas emission of the disk. For the first time, we identify three dust rings in the GW Ori disk at ~46, 188, and 338 au, with estimated dust mass of 74, 168, and 245 Earth masses, respectively. To our knowledge, its outermost ring is the largest dust ring ever found in protoplanetary disks. We use visibility modeling of dust continuum to show that the disk has misaligned …
A Fast Radio Burst Discovered In Fast Drift Scan Survey, Weiwei Zhu, Di Li, Rui Luo, Chenchen Miao, Bing Zhang, Laura Spitler, Duncan Lorimer, Michael Kramer, David Champion, Youling Yue, Andrew Cameron, Marilyn Cruces, Ran Duan, Yi Feng, Jun Han, George Hobbs, Chenhui Niu, Jiarui Niu, Zhichen Pan, Lei Qian, Dai Shi, Ningyu Tang, Pei Wang, Hongfeng Wang, Mao Yuan, Lei Zhang, Xinxin Zhang, Shuyun Cao, Li Feng, Hengqian Gan, Long Gao
A Fast Radio Burst Discovered In Fast Drift Scan Survey, Weiwei Zhu, Di Li, Rui Luo, Chenchen Miao, Bing Zhang, Laura Spitler, Duncan Lorimer, Michael Kramer, David Champion, Youling Yue, Andrew Cameron, Marilyn Cruces, Ran Duan, Yi Feng, Jun Han, George Hobbs, Chenhui Niu, Jiarui Niu, Zhichen Pan, Lei Qian, Dai Shi, Ningyu Tang, Pei Wang, Hongfeng Wang, Mao Yuan, Lei Zhang, Xinxin Zhang, Shuyun Cao, Li Feng, Hengqian Gan, Long Gao
Physics & Astronomy Faculty Research
We report the discovery of a highly dispersed fast radio burst (FRB), FRB 181123, from an analysis of ~1500 hr of drift scan survey data taken using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulse has three distinct emission components, which vary with frequency across our 1.0–1.5 GHz observing band. We measure the peak flux density to be... (See full abstract in article).
Is Grb 110715a The Progenitor Of Frb 171209?, Xiang-Gao Wang, Long Li, Yuan-Pei Yang, Jia-Wei Luo, Bing Zhang, Da-Bin Lin, En-Wei Liang, Song-Mei Qin
Is Grb 110715a The Progenitor Of Frb 171209?, Xiang-Gao Wang, Long Li, Yuan-Pei Yang, Jia-Wei Luo, Bing Zhang, Da-Bin Lin, En-Wei Liang, Song-Mei Qin
Physics & Astronomy Faculty Research
The physical origin of fast radio bursts (FRBs) is unknown. Young magnetars born from gamma-ray bursts (GRBs) have been suggested as a possible central engine of FRBs. We test such a hypothesis by systematically searching for GRB–FRB spatial associations from 110 FRBs and 1440 GRBs. We find that one FRB event discovered by the Parkes telescope, FRB 171209, is spatially coincident with a historical long-duration GRB 110715A at z = 0.82. The afterglow of GRB 110715A is consistent with being powered by a millisecond magnetar. The extragalactic dispersion measure of FRB 171209 is in excess of that contributed by the …
Dust Condensation In Evolving Discs And The Composition Of Planetary Building Blocks, Min Li, Shichun Huang, Michail I. Petaev, Zhaohuan Zhu, Jason H. Steffen
Dust Condensation In Evolving Discs And The Composition Of Planetary Building Blocks, Min Li, Shichun Huang, Michail I. Petaev, Zhaohuan Zhu, Jason H. Steffen
Physics & Astronomy Faculty Research
Partial condensation of dust from the Solar nebula is likely responsible for the diverse chemical compositions of chondrites and rocky planets/planetesimals in the inner Solar system. We present a forward physical–chemical model of a protoplanetary disc to predict the chemical compositions of planetary building blocks that may form from such a disc. Our model includes the physical evolution of the disc and the condensation, partial advection, and decoupling of the dust within it. The chemical composition of the condensate changes with time and radius. We compare the results of two dust condensation models: one where an element condenses when the …
Swift Spectroscopy Of The Accretion Disk Wind In The Black Hole Gro J1655-40, M. Balakrishnan, J. M. Miller, N. Trueba, M. Reynolds, J. Raymond, Daniel Proga, A. C. Fabian, T. Kallman, J. Kaastra
Swift Spectroscopy Of The Accretion Disk Wind In The Black Hole Gro J1655-40, M. Balakrishnan, J. M. Miller, N. Trueba, M. Reynolds, J. Raymond, Daniel Proga, A. C. Fabian, T. Kallman, J. Kaastra
Physics & Astronomy Faculty Research
Chandra obtained two High Energy Transmission Grating spectra of the stellar-mass black hole GRO J1655−40 during its 2005 outburst, revealing a rich and complex disk wind. Soon after its launch, the Neil Gehrels Swift Observatory began monitoring the same outburst. Some X-ray Telescope (XRT) observations were obtained in a mode that makes it impossible to remove strong Mn calibration lines, so the Fe Kα line region in the spectra was previously neglected. However, these lines enable a precise calibration of the energy scale, facilitating studies of the absorption-dominated disk wind and its velocity shifts. Here we present fits to 15 …
Alma 0.88 Mm Survey Of Disks Around Planetary-Mass Companions, Ya-Lin Wu, Brendan P. Bowler, Patrick D. Sheehan, Sean M. Andrews, Gregory J. Herczeg, Adam L. Kraus, Luca Ricci, David J. Wilner, Zhaohuan Zhu
Alma 0.88 Mm Survey Of Disks Around Planetary-Mass Companions, Ya-Lin Wu, Brendan P. Bowler, Patrick D. Sheehan, Sean M. Andrews, Gregory J. Herczeg, Adam L. Kraus, Luca Ricci, David J. Wilner, Zhaohuan Zhu
Physics & Astronomy Faculty Research
Characterizing the physical properties and compositions of circumplanetary disks can provide important insights into the formation of giant planets and satellites. We report Atacama Large Millimeter/submillimeter Array 0.88 mm (Band 7) continuum observations of six planetary-mass (10–20 M Jup) companions: CT Cha b, 1RXS 1609 b, ROXs 12 b, ROXs 42B b, DH Tau b, and FU Tau b. No continuum sources are detected at the locations of the companions down to 3σ limits of 120–210 μJy. Given these nondetections, it is not clear whether disks around planetary-mass companions indeed follow the disk-flux–host-mass trend in the stellar regime. The faint …
Global 3d Radiation Magnetohydrodynamic Simulations For Fu Ori's Accretion Disc And Observational Signatures Of Magnetic Fields, Zhaohuan Zhu, Yan-Fei Jiang, James M. Stone
Global 3d Radiation Magnetohydrodynamic Simulations For Fu Ori's Accretion Disc And Observational Signatures Of Magnetic Fields, Zhaohuan Zhu, Yan-Fei Jiang, James M. Stone
Physics & Astronomy Faculty Research
FU Ori is the prototype of FU Orionis systems that are outbursting protoplanetary discs. Magnetic fields in FU Ori’s accretion discs have previously been detected using spectropolarimetry observations for Zeeman effects. We carry out global radiation ideal MHD simulations to study FU Ori’s inner accretion disc. We find that (1) when the disc is threaded by vertical magnetic fields, most accretion occurs in the magnetically dominated atmosphere at z ∼ R, similar to the ‘surface accretion’ mechanism in previous locally isothermal MHD simulations. (2) A moderate disc wind is launched in the vertical field simulations with a terminal speed of …
Fast Radio Bursts As Strong Waves Interacting With The Ambient Medium, Yuan-Pei Yang, Bing Zhang
Fast Radio Bursts As Strong Waves Interacting With The Ambient Medium, Yuan-Pei Yang, Bing Zhang
Physics & Astronomy Faculty Research
Fast radio bursts (FRBs) are mysterious radio transients whose physical origin is still unknown. Within a few astronomical units near an FRB source, the electric field of the electromagnetic wave is so large that the electron oscillation velocity becomes relativistic, which makes the classical Thomson scattering theory and the linear plasma theory invalid. We discuss FRBs as strong waves interacting with the ambient medium, in terms of both electron motion properties and plasma properties. Several novel features are identified. (1) The cross section of Thomson scattering is significantly enhanced for the scattering photons. (2) On the other hand, because of …
On The Frb Luminosity Function – – Ii. Event Rate Density, Rui Luo, Yunpeng Men, Kejia Lee, Weiyang Wang, D. R. Lorimer, Bing Zhang
On The Frb Luminosity Function – – Ii. Event Rate Density, Rui Luo, Yunpeng Men, Kejia Lee, Weiyang Wang, D. R. Lorimer, Bing Zhang
Physics & Astronomy Faculty Research
The luminosity function of Fast Radio Bursts (FRBs), defined as the event rate per unit cosmic co-moving volume per unit luminosity, may help to reveal the possible origins of FRBs and design the optimal searching strategy. With the Bayesian modelling, we measure the FRB luminosity function using 46 known FRBs. Our Bayesian framework self-consistently models the selection effects, including the survey sensitivity, the telescope beam response, and the electron distributions from Milky Way/ the host galaxy/ local environment of FRBs. Different from the previous companion paper, we pay attention to the FRB event rate density and model the event counts …
Testing The Hypothesis Of Compact-Binary-Coalescence Origin Of Fast Radio Bursts Using A Multimessenger Approach, Min-Hao Wang, Shun-Ke Ai, Zheng-Xiang Li, Nan Xing, He Gao, Bing Zhang
Testing The Hypothesis Of Compact-Binary-Coalescence Origin Of Fast Radio Bursts Using A Multimessenger Approach, Min-Hao Wang, Shun-Ke Ai, Zheng-Xiang Li, Nan Xing, He Gao, Bing Zhang
Physics & Astronomy Faculty Research
In the literature, compact binary coalescences (CBCs) have been proposed as one of the main scenarios to explain the origin of some non-repeating fast radio bursts (FRBs). The large discrepancy between the FRB and CBC event rate densities suggests that their associations, if any, should only apply at most for a small fraction of FRBs. Through a Bayesian estimation method, we show how a statistical analysis of the coincident associations of FRBs with CBC gravitational wave (GW) events may test the hypothesis of these associations. We show that during the operation period of the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), …
Fast Radio Bursts From Interacting Binary Neutron Star Systems, Bing Zhang
Fast Radio Bursts From Interacting Binary Neutron Star Systems, Bing Zhang
Physics & Astronomy Faculty Research
Recent observations of repeating fast radio bursts (FRBs) suggest that some FRBs reside in an environment consistent with that of binary neutron star (BNS) mergers. The bursting rate for repeaters could be very high and the emission site is likely from a magnetosphere. We discuss a hypothesis of producing abundant repeating FRBs in BNS systems. Decades to centuries before a BNS system coalesces, the magnetospheres of the two neutron stars start to interact relentlessly. Abrupt magnetic reconnection accelerates particles, which emit coherent radio waves in bunches via curvature radiation. FRBs are detected as these bright radiation beams point toward Earth. …
Asteroid Belt Survival Through Stellar Evolution: Dependence On The Stellar Mass, Rebecca G. Martin, Mario Livio, Jeremy L. Smallwood, Cheng Chen
Asteroid Belt Survival Through Stellar Evolution: Dependence On The Stellar Mass, Rebecca G. Martin, Mario Livio, Jeremy L. Smallwood, Cheng Chen
Physics & Astronomy Faculty Research
Polluted white dwarfs are generally accreting terrestrial-like material that may originate from a debris belt like the asteroid belt in the Solar system. ... See full text for complete abstract.
The Effects Of Disc Self-Gravity And Radiative Cooling On The Formation Of Gaps And Spirals By Young Planets, Shangjia Zhang, Zhaohuan Zhu
The Effects Of Disc Self-Gravity And Radiative Cooling On The Formation Of Gaps And Spirals By Young Planets, Shangjia Zhang, Zhaohuan Zhu
Physics & Astronomy Faculty Research
We have carried out 2D hydrodynamical simulations to study the effects of disc self-gravity and radiative cooling on the formation of gaps and spirals. (1) With disc self-gravity included, we find stronger, more tightly wound spirals and deeper gaps in more massive discs. The deeper gaps are due to the larger Angular Momentum Flux (AMF) of the waves excited in more massive discs, as expected from the linear theory. The position of the secondary gap does not change, provided that the disc is not extremely massive (Q ≳ 2). (2) With radiative cooling included, the excited spirals become monotonically more …
Effects Of Opacity Temperature Dependence On Radiatively Accelerated Clouds, Sergei Dyda, Daniel Proga, Christopher S. Reynolds
Effects Of Opacity Temperature Dependence On Radiatively Accelerated Clouds, Sergei Dyda, Daniel Proga, Christopher S. Reynolds
Physics & Astronomy Faculty Research
We study how different opacity–temperature scalings affect the dynamical evolution of irradiated gas clouds using time-dependent radiation-hydrodynamics simulations. When clouds are optically thick, the bright side heats up and expands, accelerating the cloud via the rocket effect. Clouds that become more optically thick as they heat accelerate ∼35 per cent faster than clouds that become optically thin. An enhancement of ∼85 per cent in the acceleration can be achieved by having a broken power-law opacity profile, which allows the evaporating gas driving the cloud to become optically thin and not attenuate the driving radiation flux. We find that up to …
Resolving The Fu Orionis System With Alma: Interacting Twin Disks?, Sebastian Perez, Antonio Hales, Hauyu Baobab Liu, Zhaohuan Zhu, Simon Casassus, Jonathan Williams, Alice Zurlo, Nicolas Cuello, Lucas Cieza, David Principe
Resolving The Fu Orionis System With Alma: Interacting Twin Disks?, Sebastian Perez, Antonio Hales, Hauyu Baobab Liu, Zhaohuan Zhu, Simon Casassus, Jonathan Williams, Alice Zurlo, Nicolas Cuello, Lucas Cieza, David Principe
Physics & Astronomy Faculty Research
FU Orionis objects are low-mass pre-main sequence stars characterized by dramatic outbursts several magnitudes in brightness. These outbursts are linked to episodic accretion events in which stars gain a significant portion of their mass. The physical processes behind these accretion events are not yet well understood. The archetypal FU Ori system, FU Orionis, is composed of two young stars with detected gas and dust emission. The continuum emitting regions have not been resolved until now. Here, we present 1.3 mm observations of the FU Ori binary system using the Atacama Large Millimeter/submillimeter Array. The disks are resolved at 40 mas …
Mass Determinations Of The Three Mini-Neptunes Transiting Toi-125, Louise D. Nielsen, D. Gandolfi, D. J. Armstrong, J. S. Jenkins, M. Fridlund, N. C. Santos, F. Dai, V. Adibekyan, R. Luque, Jason H. Steffen, M. Esposito, F. Meru, S. Sabotta, E. Bolmont, D. Kossakowski, J. F. Otegi, F. Murgas, M. Stalport, F. Rodler, M. R. Diaz, N. T. Kurtovic, G. Ricker, R. Vanderspek, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, R. Allart, J. M. Almenara, D. Barrado, S. C.C. Barros
Mass Determinations Of The Three Mini-Neptunes Transiting Toi-125, Louise D. Nielsen, D. Gandolfi, D. J. Armstrong, J. S. Jenkins, M. Fridlund, N. C. Santos, F. Dai, V. Adibekyan, R. Luque, Jason H. Steffen, M. Esposito, F. Meru, S. Sabotta, E. Bolmont, D. Kossakowski, J. F. Otegi, F. Murgas, M. Stalport, F. Rodler, M. R. Diaz, N. T. Kurtovic, G. Ricker, R. Vanderspek, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, R. Allart, J. M. Almenara, D. Barrado, S. C.C. Barros
Physics & Astronomy Faculty Research
The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, a steady progress was made in achieving the mission’s primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, the TESS’s observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star TOI-125, a V = 11.0 K0 dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TOI-125b, TOI-125c, and TOI-125d. TOI-125b has an orbital period …