Astrophysics and Astronomy Commons^™

A Systematic Study Of Planetary Envelope Growth With 3d Radiation-Hydrodynamics Simulations, Avery Bailey, James M. Stone, Jeffrey Fung

Physics & Astronomy Faculty Research

In the core accretion model of planet formation, envelope cooling regulates the accretion of material and ultimately sets the time-scale to form a giant planet. Given the diversity of planet-forming environments, opacity uncertainties, and the advective transport of energy by three-dimensional (3D) recycling flows, it is unclear whether one-dimensional models can adequately describe envelope structure and accretion in all regimes. Even in 3D models, it is unclear whether approximate radiative transfer methods sufficiently model envelope cooling, particularly at the planetary photosphere. To address these uncertainties, we present a suite of 3D radiation-hydrodynamics simulations employing methods that directly solve the transfer …

Macroscale Superdurable Superlubricity Achieved In Lubricant Oil Via Operando Tribochemical Formation Of Fullerene-Like Carbon, Jingjie Pan, Xinxin Gao, Chang Liu, Kan Zhang, Weitao Zheng, Changfeng Chen

Physics & Astronomy Faculty Research

Friction and wear are ubiquitous in moving mechanical assemblies, causing energy and equipment loss and producing harmful emissions. Mitigation efforts have long relied on oil-based lubricants, but challenges remain in achieving concurrent ultralow friction and wear without oil additives. Here, we demonstrate that a dual-phase TiB2-MoS2 film lubricated by oil without additives exhibits superdurable superlubricity characterized by a vanishingly small friction coefficient (0.007) and ultralow wear rate (10−9 mm3N−1m−1) maintained in lubricants over an unprecedentedly long sliding distance without performance deterioration. We identify a tribochemical route for the decomposition of oil molecules catalytically activated by the TiB2-MoS2 film, leading to …

Long Range Correlation Of Molecular Orientation And Vibration In Liquid Cdcl3, David P. Shelton

Physics & Astronomy Faculty Research

The polarization dependence of hyper-Rayleigh second harmonic light scattering (SHS) and hyper-Raman light scattering (HRS) measured for liquid CDCl₃ show the effect of long-range correlation of molecular orientation and vibration. HRS from the ν₁, ν₄, and ν₅ vibration modes is polarized transverse to the scattering wavevector, whereas HRS from the ν₂, ν₃, and ν₆ vibration modes and SHS from the ν₀ orientation mode all show longitudinal polarization. The transverse polarized HRS is accounted for by long range vibration correlation due to dipole–dipole interaction for molecules at 20–400 nm …

Eclipse Of The V773 Tau B Circumbinary Disc, M. A. Kenworthy, D. González Picos, E. Elizondo, R. G. Martin, D. M. Van Dam, J. E. Rodriguez, G. M. Kennedy, C. Ginski, M. Mugrauer, N. Vogt, C. Adam, R. J. Oelkers

Physics & Astronomy Faculty Research

Context. Young multiple stellar systems can host both circumstellar and circumbinary discs composed of gas and dust, and the orientations of circumbinary discs can be sculpted by the orientation and eccentricity of the central binaries. Studying multiple binary systems and their associated discs enables our understanding of the size and distribution of the planetary systems that subsequently form around them.

Aims. A deep (~70%) and extended (~150 days) eclipse was seen towards the young multiple stellar system V773 Tau in 2010. We interpret it as being due to the passage of a circumbinary disc around the B components moving in …

A Wind Environment And Lorentz Factors Of Tens Explain Gamma-Ray Bursts X-Ray Plateau, Hüsne Dereli-Bégué, Asaf Pe’Er, Felix Ryde, Samantha R. Oates, Bing Zhang, Maria G. Dainotti

Physics & Astronomy Faculty Research

Gamma-ray bursts (GRBs) are known to have the most relativistic jets, with initial Lorentz factors in the order of a few hundreds. Many GRBs display an early X-ray light-curve plateau, which was not theoretically expected and therefore puzzled the community for many years. Here, we show that this observed signal is naturally obtained within the classical GRB fireball model, provided that the initial Lorentz factor is rather a few tens, and the expansion occurs into a medium-low density wind. The range of Lorentz factors in GRB jets is thus much wider than previously thought and bridges an observational gap between …

Distributions Of Gas And Small And Large Grains In The Lkh 330 Disk Trace A Young Planetary System, Paola Pinilla, Myriam Benisty, Nicolás T. Kurtovic, Jaehan Bae, Ruobing Dong, Zhaohuan Zhu, S. Andrews, J. Carpenter, C. Ginski, J. Huang, A. Isella, L. Perez, L. Ricci, G. Rosotti, M. Villenave, D. Wilner

Physics & Astronomy Faculty Research

Planets that are forming around young stars are expected to leave clear imprints in the distribution of the gas and dust of their parental protoplanetary disks. In this paper, we present new scattered light and millimeter observations of the protoplanetary disk around LkH 330, using SPHERE/VLT and ALMA, respectively. The scattered-light SPHERE observations reveal an asymmetric ring at around 45au from the star in addition to two spiral arms with similar radial launching points at around 90au. The millimeter observations from ALMA (resolution of 006 004 ) mainly show an asymmetric ring located at 110au from the star. In addition …

Improving The Conductivity Of Graphite-Based Films By Rapid Laser Annealing, Gulsum Ersu, Sruthi Kuriakose, Stuart J. Goldie, Abdullah M. Al-Enizi, Ayman Nafady, Carmen Munuera, Claudia Backes, Joshua O. Island, Andres Castellanos-Gomez

Physics & Astronomy Faculty Research

We present a method to anneal devices based on graphite films on paper and polycarbonate substrates. The devices are created using four different methods: spray-on films, graphite pencil-drawn films, liquid-phase exfoliated graphite films, and graphite powder abrasion-applied films. We characterize the optical properties of the films before and after laser annealing and report the two-terminal resistance of the devices for increased laser power density. We find the greatest improvement (16× reduction) in the resistance of spray-on film devices starting from 25.0 kΩ and reaching 1.6 kΩ at the highest annealing power densities. These improvements are attributed to local laser ablation …

An Automated System For Strain Engineering And Straintronics Of 2d Materials, Onur Çakıroğlu, Joshua O. Island, Yong Xie, Riccardo Frisenda, Andres Castellanos-Gomez

Physics & Astronomy Faculty Research

This work presents an automated three-point bending apparatus that can be used to study strain engineering and straintronics in 2D materials. This work benchmarks the system by reporting reproducible strain tuned micro-reflectance, Raman, and photoluminescence spectra for monolayer molybdenum disulfide (MoS2). These results are in good agreement with reported literature using conventional bending apparatus. This work further utilizes the system to automate strain investigations of straintronic devices by measuring the piezoresistive effect and the strain effect on photoresponse in an MoS2 electrical device. The details of the construction of the straightforward system are given and it is anticipated that it …

The Disk Of Fu Orionis Viewed With Matisse/Vlti: First Interferometric Observations In L And M Bands, Foteini Lykou, P. Ábrahám, L. Chen, J. Varga, Á. Kóspál, A. Matter, M. Siwak, Zs. M. Szabo, Z. Zhu, H. B. Liu, B. Lopez, F. Allouche, J.-C. Augereau, P. Berio, P. Cruzalebes, C. Dominik, Th Henning, K.-H. Hofmann, M. Hogerheijde, W. J. Jaffe, E. Kokulina, S. Lagarde, A. Meilland, F. Millour, E. Pantin, R. Petrov, S. Robbe-Dubois, D. Schertl, M. Scheuck, R. Van Boekel, L. B. F. M. Waters, G. Weigelt, S. Wolf

Physics & Astronomy Faculty Research

Aims. We studied the accretion disk of the archetypal eruptive young star FU Orionis with the use of mid-infrared interferometry, which enabled us to resolve the innermost regions of the disk down to a spatial resolution of 3 milliarcseconds (mas) in the L band, that is, within 1 au of the protostar. Methods. We used the interferometric instrument MATISSE/VLTI to obtain observations of FU Ori’s disk in the L, M, and N bands with multiple baseline configurations. We also obtained contemporaneous photometry in the optical (UBVRIri ; SAAO and Konkoly Observatory) and near-infrared (JHKs; NOT). Our results were compared with …

A Repeating Fast Radio Burst Associated With A Persistent Radio Source, C.-H. Niu, K. Aggarwal, D. Li, X. Zhang, S. Chatterjee, C.-W. Tsai, W. Yu, C. J. Law, S. Burke-Spolaor, J. M. Cordes, Y.-K. Zhang, S. K. Ocker, J.-M. Yao, P. Wang, Y. Feng, Y. Niino, C. Bochenek, M. Cruces, L. Connor, J.-A. Jiang, S. Dai, R. Luo, G.-D. Li, C.-C. Miao, J.-R. Niu, R. Anna-Thomas, J. Sydnor, D. Stern, W.-Y. Wang, M Yuan, Y.-L. Yue, D.-J. Zhou, Z Yan, W.-W. Zhu, B. Zhang

Physics & Astronomy Faculty Research

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift …

Validation Of Accelerometry As A Digital Phenotyping Measure Of Negative Symptoms In Schizophrenia, Gregory P. Strauss, Ian M. Raugh, Luyu Zhang, Lauren Luther, Hannah C. Chapman, Daniel N. Allen, Brian Kirkpatrick, Alex S. Cohen

Physics & Astronomy Faculty Research

Negative symptoms are commonly assessed via clinical rating scales; however, these measures have several inherent limitations that impact validity and utility for their use in clinical trials. Objective digital phenotyping measures that overcome some of these limitations are now available. The current study evaluated the validity of accelerometry (ACL), a passive digital phenotyping method that involves collecting data on the presence, vigor, and variability of movement. Outpatients with schizophrenia (SZ: n = 50) and demographically matched healthy controls (CN: n = 70) had ACL continuously recorded from a smartphone and smartband for 6 days. Active digital phenotyping assessments, including surveys …

Temporal Scattering, Depolarization, And Persistent Radio Emission From Magnetized Inhomogeneous Environments Near Repeating Fast Radio Burst Sources, Yuan-Pei Yang, Wenbin Lu, Yi Feng, Bing Zhang, Di Li

Physics & Astronomy Faculty Research

Some repeating fast radio burst (FRB) sources exhibit complex polarization behaviors, including frequencydependent depolarization, variation of rotation measure (RM), and oscillating spectral structures of polarized components. Very recently, Feng et al. reported that active repeaters exhibit conspicuous frequency-dependent depolarization and a strong correlation between RM scatter (σRM) and the temporal scattering time (τs), s s 1.0 0.2, both of which can be well described by multipath propagation through a magnetized inhomogeneous plasma screen. This observation strongly suggests that the temporal scattering and RM scatter originate from the same region. Besides, a particular finding of note in Feng et al. is …

Investigating The Future Potential Of An Upgraded Alma To Image Planet-Forming Disks At Sub-Astronomical-Unit Scales, Benjamin P. Burrill, Luca Ricci, Sarah K. Harter, Shangjia Zhang, Zhaohuan Zhu

Physics & Astronomy Faculty Research

In recent years, ALMA has been able to observe large-scale substructures within protoplanetary disks. Comparison with the predictions from models of planet–disk interactions has indicated that most of these disk substructures can be explained by the presence of planets with the mass of Neptune or larger at orbital radii of ≈5–100 au. Better resolution is needed to observe structures closer to the star, where terrestrial planets are expected to form, as well as structures opened by planets with masses lower than Neptune. We investigate the capabilities of a possible extension to ALMA that would double the longest baseline lengths in …

Dark Fluxes From Accreting Black Holes Through Several Mechanisms, Rong-Gen Cai, Sichun Sun, Bing Zhang, Yun-Long Zhang

Physics & Astronomy Faculty Research

We discuss the possibility that accreting black hole systems can be sources for dark matter flux through several different mechanisms. We firstly discuss two types of systems‘: coronal thermal plasmas around supermassive black holes in active galactic nuclei (AGNs), and accretion disks of stellar-mass X-ray black hole binaries (BHBs). We explore how these black hole systems may produce keV light dark matter fluxes and find that the dark fluxes from those sources might be too weak to account for the current XENON1T excess. On the other hand, black holes can be good accelerators to accrete and boost heavy dark matter …

Circumbinary Disk Evolution In The Presence Of An Outer Companion Star, Rebecca G. Marin, Stephen Lepp, Stephen H. Lubow, Matthew A. Kenworthy, Grant M. Kennedy, David Vallet

Physics & Astronomy Faculty Research

We consider a hierarchical triple system consisting of an inner eccentric binary with an outer companion. A highly misaligned circumbinary disk around the inner binary is subject to two competing effects: (i) nodal precession about the inner binary eccentricity vector that leads to an increase in misalignment (polar alignment) and (ii) Kozai–Lidov (KL) oscillations of eccentricity and inclination driven by the outer companion that leads to a reduction in the misalignment. The outcome depends upon the ratio of the timescales of these effects. If the inner binary torque dominates, then the disk aligns to a polar orientation. If the outer …

Macroscale Robust Superlubricity On Metallic Nbb2, Jia Wang, Chang Liu, Kaifei Miao, Kan Zhang, Weitao Zheng, Changfeng Chen

Physics & Astronomy Faculty Research

Robust superlubricity (RSL), defined by concurrent superlow friction and wear, holds great promise for reducing material and energy loss in vast industrial and technological operations. Despite recent advances, challenges remain in finding materials that exhibit RSL on macrolength and time scales and possess vigorous electrical conduction ability. Here, the discovery of RSL is reported on hydrated NbB2 films that exhibit vanishingly small coefficient of friction (0.001–0.006) and superlow wear rate (≈10−17 m3 N−1 m−1) on large length scales reaching millimeter range and prolonged time scales lasting through extensive loading durations. Moreover, the measured low resistivity (≈10−6 Ω m) of the …

Misalignment Of Terrestrial Circumbinary Planets As An Indicator Of Their Formation Mechanism, Anna C. Childs, Rebecca G. Martin

Physics & Astronomy Faculty Research

Circumbinary gas disks are often observed to be misaligned with the binary orbit, suggesting that planet formation may proceed in a misaligned disk. With n-body simulations, we consider the formation of circumbinary terrestrial planets from a particle disk that is initially misaligned. We find that if terrestrial planets form in this way, in the absence of gas, they can only form close to coplanar or close to polar to the binary orbit. Planets around a circular binary form coplanar while planets around an eccentric binary can form coplanar or polar depending on the initial disk misalignment and the binary eccentricity. …

Asteroids And Life: How Special Is The Solar System?, Rebecca G. Martin, Mario Livio

Physics & Astronomy Faculty Research

Asteroid impacts with Earth may have played an essential role in the emergence of life on Earth through their creation of favorable niches for life, changes to the atmosphere, and delivery of water. Consequently, we suggest two potential requirements for life in an exoplanetary system: first, that the system has an asteroid belt, and second, that there is a mechanism to drive asteroids to impact the terrestrial habitable planet. Since in the solar system the ν6 secular resonance has been shown to have been important in driving these impacts, we explore how the masses and locations of two giant planets …

Eccentric Dust-Ring Formation In Kozai-Lidov Gas Disks, Rebecca G. Martin, Stephen H. Lubow

Physics & Astronomy Faculty Research

A highly misaligned gas disk around one component of a binary star system can undergo global Kozai-Lidov (KL) oscillations for which the disk inclination and eccentricity are exchanged. With hydrodynamical simulations of a gas and dust disk we explore the effects of these oscillations on the dust density distribution. For dust that is marginally coupled to the gas (St ≈ 1), we find that the dust undergoes dynamical behavior similar to that of the gas disk but the radial distribution of dust may be very different from that of the gas. The inward radial drift of the dust is faster …

Stability And Mechanical Properties Of W1-X Mox B4.2 (X=0.0-1.0) From First Principles, Weiguang Gong, Rui Xu, Xuecheng Shao, Quan Li, Changfeng Chen

Physics & Astronomy Faculty Research

Heavy transition-metal tetraborides (e.g., tungsten tetraboride, molybdenum tetraboride, and molybdenum-doped tungsten tetraboride) exhibit superior mechanical properties, but solving their complex crystal structures has been a long-standing challenge. Recent experimental x-ray and neutron diffraction measurements combined with first-principles structural searches have identified a complex structure model for tungsten tetraboride that contains a boron trimer as an unusual structural unit with a stoichiometry of 1:4.2. In this paper, we expand the study to binary MoB4.2 and ternary W1-xMoxB4.2 (x=0.0-1.0) compounds to assess their thermodynamic stability and mechanical properties using a tailor-designed crystal structure search method in conjunction with first-principles energetic calculations. Our …

Eccentric Neutron Star Disk Driven Type Ii Outburst Pairs In Be/X-Ray Binaries, Alessia Franchini, Rebecca G. Martin

Physics & Astronomy Faculty Research

Be star X-ray binaries are transient systems that show two different types of outbursts. Type I outbursts occur each orbital period while type II outbursts have a period and duration that are not related to any periodicity of the binary system. Type II outbursts may be caused by mass transfer to the neutron star from a highly eccentric Be star disk. A sufficiently misaligned Be star decretion disk undergoes secular Von Zeipel-Lidov-Kozai (ZLK) oscillations of eccentricity and inclination. Observations show that in some systems the type II outbursts come in pairs with the second being of lower luminosity. We use …

Nonperiodic Type I Be/X-Ray Binary Outbursts, Rebecca G. Martin, Alessia Franchini

Physics & Astronomy Faculty Research

Type I Be/X-ray binary outbursts are driven by mass transfer from a Be star decretion disk to a neutron star companion during each orbital period. Treiber et al. recently observed nonperiodic type I outbursts in RX J0529.8-6556 that has unknown binary orbital properties. We show that nonperiodic type I outbursts may be temporarily driven in a low eccentricity binary with a disk that is inclined sufficiently to be mildly unstable to Kozai-Lidov oscillations. The inclined disk becomes eccentric and material is transferred to the neutron star at up to three locations in each orbit: when the neutron star passes the …

Global 3d Radiation Hydrodynamic Simulations Of Proto-Jupiter’S Convective Envelope, Zhaohuan Zhu, Yan-Fei Jiang, Hans Baehr, Andrew N. Youdin, Philip J. Armitage, Rebecca G. Martin

Physics & Astronomy Faculty Research

The core accretion model of giant planet formation has been challenged by the discovery of recycling flows between the planetary envelope and the disc that can slow or stall envelope accretion. We carry out 3D radiation hydrodynamic simulations with an updated opacity compilation to model the proto-Jupiter’s envelope. To isolate the 3D effects of convection and recycling, we simulate both isolated spherical envelopes and envelopes embedded in discs. The envelopes are heated at given rates to achieve steady states, enabling comparisons with 1D models. We vary envelope properties to obtain both radiative and convective solutions. Using a passive scalar, we …

Multi-Messenger Astrophysics With Theseus In The 2030s, Bing Zhang, Numerous Authors, See Full List Below

Physics & Astronomy Faculty Research

Multi-messenger astrophysics is becoming a major avenue to explore the Universe, with the potential to span a vast range of redshifts. The growing synergies between different probes is opening new frontiers, which promise profound insights into several aspects of fundamental physics and cosmology. In this context, THESEUS will play a central role during the 2030s in detecting and localizing the electromagnetic counterparts of gravitational wave and neutrino sources that the unprecedented sensitivity of next generation detectors will discover at much higher rates than the present. Here, we review the most important target signals from multi-messenger sources that THESEUS will be …

Gw Ori: Circumtriple Rings And Planets, Jeremy L. Smallwood, Rebecca Nealon, Cheng Chen, Rebecca G. Martin, Jiaqing Bi, Ruobing Dong, Christophe Pinte

Physics & Astronomy Faculty Research

GW Ori is a hierarchical triple star system with a misaligned circumtriple protoplanetary disc. Recent Atacama Large Millimeter/submillimeter Array observations have identified three dust rings with a prominent gap at 100 au and misalignments between each of the rings. A break in the gas disc may be driven by the torque from either the triple star system or a planet that is massive enough to carve a gap in the disc. Once the disc is broken, the rings nodally precess on different time-scales and become misaligned. We investigate the origins of the dust rings by means of N-body integrations and …

Direct H-He Chemical Association In Superionic Feo2H2He At Deep-Earth Conditions, Jurong Zhang, Hanyu Liu, Yanming Ma, Changfeng Chen

Physics & Astronomy Faculty Research

Hydrogen and helium are known to play crucial roles in geological and astrophysical environments; however, they are inert toward each other across wide pressure-temperature (P-T) conditions. Given their prominent presence and influence on the formation and evolution of celestial bodies, it is of fundamental interest to explore the nature of interactions between hydrogen and helium. Using an advanced crystal structure search method, we have identified a quaternary compound FeO₂H₂He stabilized in a wide range of P-T conditions. Ab initio molecular dynamics simulations further reveal a novel superionic state of FeO₂H₂He hosting liquid-like …

Terrestrial Planet Formation In A Circumbinary Disc Around A Coplanar Binary, Anna C. Childs, Rebecca G. Martin

Physics & Astronomy Faculty Research

With N-body simulations, we model terrestrial circumbinary planet (CBP) formation with an initial surface density profile motivated by hydrodynamic circumbinary gas disc simulations. The binary plays an important role in shaping the initial distribution of bodies. After the gas disc has dissipated, the torque from the binary speeds up the planet formation process by promoting body-body interactions but also drives the ejection of planet building material from the system at an early time. Fewer but more massive planets form around a close binary compared to a single star system. A sufficiently wide or eccentric binary can prohibit terrestrial planet formation. …

The Large Area Burst Polarimeter (Leap) A Nasa Mission Of Opportunity For The Iss, Bing Zhang, Numerous Authors, See Full List Below

Physics & Astronomy Faculty Research

The LargE Area Burst Polarimeter (LEAP) will radically improve our understanding of some of the most energetic phenomena in our Universe by exposing the underlying physics that governs astrophysical jets and the extreme environment surrounding newborn compact objects. LEAP will do this by making the highest fidelity polarization measurements to date of the prompt gamma-ray emission from a large sample of Gamma-Ray Bursts (GRBs). The science objectives are met with a single instrument deployed as an external payload on the ISS-a wide FOV Compton polarimeter that measures GRB polarization from 50-500 keV and GRB spectra from ∼10 keV to 5 …

Free-Free Absorption In Hot Relativistic Flows: Application To Fast Radio Bursts, Esha Kundu, Bing Zhang

Physics & Astronomy Faculty Research

Magnetic flares create hot relativistic shocks outside the light cylinder radius of a magnetized star. Radio emission produced in such a shock or at a radius smaller than the shock undergoes free–free absorption while passing through the shocked medium. In this work, we demonstrate that this free–free absorption can lead to a negative drift in the frequency-time spectra. Whether it is related to the downward drift pattern observed in fast radio bursts (FRBs) is unclear. However, if the FRB down-drifting is due to this mechanism then it will be pronounced in those shocks that have isotropic kinetic energies ≳1044 erg. …

A Mechanical Model For Magnetized Relativistic Blastwaves, Shunke Ai, Bing Zhang

Physics & Astronomy Faculty Research

The evolution of a relativistic blastwave is usually delineated under the assumption of pressure balance between forward- and reverse-shocked regions. However, such a treatment usually violates the energy conservation law, and is inconsistent with existing magnetohydrodynamic numerical simulation results. A mechanical model of non-magnetized blastwaves was proposed in previous work to solve the problem. In this paper, we generalize the mechanical model to the case of a blastwave driven by an ejecta with an arbitrary magnetization parameter $\sigma_{\rm ej}$. We test our modified mechanical model by considering a long-lasting magnetized ejecta and found that it is much better than the …