Recursos de colección
Caltech Authors (128.467 recursos)
Repository of works by Caltech published authors.
Type = Report or Paper
Repository of works by Caltech published authors.
Type = Report or Paper
Ingram, Adam; van der Klis, Michiel; Middleton, Matthew; Done, Chris; Altamirano, Diego; Heil, Lucy; Uttley, Phil; Axelsson, Magnus
Accreting stellar-mass black holes often show a `Type-C' quasi-periodic
oscillation (QPO) in their X-ray flux, and an iron emission line in their X-ray
spectrum. The iron line is generated through continuum photons reflecting off
the accretion disk, and its shape is distorted by relativistic motion of the
orbiting plasma and the gravitational pull of the black hole. The physical
origin of the QPO has long been debated, but is often attributed to
Lense-Thirring precession, a General Relativistic effect causing the inner flow
to precess as the spinning black hole twists up the surrounding space-time.
This predicts a characteristic rocking of the iron line between red and blue
shift as...
Rea, Nanda; Borghese, Alice; Esposito, Paolo; Zelati, Francesco Coti; Bachetti, Matteo; Israel, Gianluca; De Luca, Andrea
The 6.67 hr long periodicity and the variable X-ray flux, of the central
compact object (CCO) at the center of the SNR RCW 103, named 1E 161348-5055,
have been always difficult to interpret within the standard scenarios of an
isolated neutron star or a binary system. On 2016 June 22, the Burst Alert
Telescope (BAT) onboard Swift detected a magnetar-like short X-ray burst from
the direction of 1E 161348-5055, also coincident with a large long-term X-ray
outburst. Here we report on the properties of this magnetar-like burst, on the
Chandra, NuSTAR, and Swift (BAT and XRT) observations of this peculiar source
during its 2016 outburst peak, as well...
Doroshenko, Victor; Tsygankov, Sergey S.; Mushtukov, Alexander A.; Lutovinov, Alexander A.; Santangelo, Andrea; Suleimanov, Valery F.; Poutanen, Juri
We report on the analysis of NuSTAR observations of the Be-transient X-ray
pulsar V 0332+53 during the giant outburst in 2015. We confirm the
cyclotron-line energy - luminosity correlation previously reported in the
source, and for the first time observe a significant departure from this
correlation below L∼10^(37) erg s^(-1). We interpret this finding as first
observational evidence for the transition from super- to sub- critical
accretion associated with the disappearance of the accretion column. We also
discuss the discrepancy in cyclotron line energies corresponding to the same
luminosities in rising and declining parts of the outburst and based on the
spin evolution of the source conclude that it...
Bayliss, D.; Mawet, D.; Ngo, H.; Petigura, E.
We report the discovery of EPIC201702477b, a transiting brown dwarf in a long period (40:73691±0:00037 day) and eccentric (e=0:2281±0:0026) orbit. This system was initially reported as a planetary candidate based on two transit events seen in K2 Campaign 1 photometry and later validated as an exoplanet. We confirm the transit and refine the ephemeris with two subsequent ground-based
detections of the transit using the LCOGT1m telescope network. We rule out any transit timing variations above the level of ~30 s. Using high precision radial velocity measurements from HARPS and SOPHIE we identify the transiting companion as a brown dwarf with a...
Degenaar, N.; Altamirano, D.; Parker, M.; Miller-Jones, J. C. A.; Miller, J. M.; Heinke, C. O.; Wijnands, R.; Ludlam, R.; Parikh, A.; Hessels, J. W. T.; Gusinskaia, N.; Deller, A. T.; Fabian, A. C.
1RXS J180408.9-342058 is a transient neutron star low-mass X-ray binary that exhibited a bright accretion outburst in 2015. We present Nustar, Swift, and Chandra observations obtained around the peak of this outburst. The source was in a soft X-ray spectral state and displayed an X-ray luminosity of Lx≃(2-3)x10^(37) (D/5.8 kpc)^2 erg cm^(-2) (0.5-10 keV). The Nustar data reveal a broad Fe-K emission line that we model as relativistically broadened reflection to constrain the accretion geometry. We found that the accretion disk is viewed at an inclination of I≃27-35 degrees and extended close to the neutron star, down to R_(in)≃5-7.5 gravitational...
Gukov, Sergei; Pei, Du; Yan, Wenbin; Ye, Ke
In this paper, we show the equivalence between two seemingly distinct 2d TQFTs:
one comes from the “Coulomb branch index” of the class S theory T[Σ, G] on L(k, 1) × S^1
, the other is the LG “equivariant Verlinde formula”, or equivalently partition function of LGC
complex Chern-Simons theory on Σ×S^1. We first derive this equivalence using the M-theory
geometry and show that the gauge groups appearing on the two sides are naturally G and its
Langlands dual LG. When G is not simply-connected, we provide a recipe of computing the
index of T[Σ, G] as summation over the index of T[Σ, Ge] with non-trivial...
Rappaport, S.; Lehmann, H.; Kalomeni, B.; Borkovits, T.; Latham, D.; Bieryla, A.; Ngo, H.; Mawet, D.; Howell, S.; Horch, E.; Jacobs, T. L.; LaCourse, D.; Sodor, A.; Vanderburg, A.; Pavlovski, K.
We present a quintuple star system that contains two eclipsing binaries. The
unusual architecture includes two stellar images separated by 11" on the sky:
EPIC 212651213 and EPIC 212651234. The more easterly image (212651213) actually
hosts both eclipsing binaries which are resolved within that image at 0.09",
while the westerly image (212651234) appears to be single in adaptive optics
(AO), speckle imaging, and radial velocity (RV) studies. The 'A' binary is
circular with a 5.1-day period, while the 'B' binary is eccentric with a
13.1-day period. The gamma velocities of the A and B binaries are different by
~10 km/s. That, coupled with their resolved projected separation of...
Bryan, Marta L.; Bowler, Brendan P.; Knutson, Heather A.; Kraus, Adam L.; Hinkley, Sasha; Mawet, Dimitri; Nielsen, Eric L.; Blunt, Sarah C.
We have conducted an angular differential imaging survey with NIRC2 at Keck in search of closein
substellar companions to a sample of seven systems with confirmed planetary-mass companions
(PMCs) on wide orbits (>50 AU). These wide-separation PMCs pose significant challenges to all
three possible formation mechanisms: core accretion plus scattering, disk instability, and turbulent
fragmentation. We explore the possibility that these companions formed closer in and were scattered
out to their present-day locations by searching for other massive bodies at smaller separations. The
typical sensitivity for this survey is ∆K ∼ 12.5 at 1”. We identify eight candidate companions,
whose masses would reach as low as one...
Ngo, Henry; Knutson, Heather A.; Hinkley, Sasha; Bryan, Marta; Crepp, Justin R.; Batygin, Konstantin; Crossfield, Ian; Hansen, Brad; Howard, Andrew W.; Johnson, John A.; Mawet, Dimitri; Morton, Timothy D.; Muirhead, Philip S.; Wang, Ji
Stellar companions can influence the formation and evolution of planetary systems, but there are
currently few observational constraints on the properties of planet-hosting binary star systems. We
search for stellar companions around 77 transiting hot Jupiter systems to explore the statistical
properties of this population of companions as compared to field stars of similar spectral type. After
correcting for survey incompleteness, we find that 47% ± 7% of hot Jupiter systems have stellar
companions with semi-major axes between 50 AU-2000 AU. This is 2.9 times larger than the field star
companion fraction in this separation range, with a significance of 4.4σ. In the 1 AU-50 AU...
Bottom, Michael; Shelton, J. Chris; Wallace, James K.; Bartos, Randall; Kuhn, Jonas; Mawet, Dimitri; Mennesson, Bertrand; Burruss, Rick; Serabyn, Eugene
We present a new instrument, the "Stellar Double Coronagraph" (SDC), a
flexible coronagraphic platform. Designed for Palomar Observatory's 200" Hale
telescope, its two focal and pupil planes allow for a number of different
observing configurations, including multiple vortex coronagraphs in series for
improved contrast at small angles. We describe the motivation, design,
observing modes, wavefront control approaches, data reduction pipeline, and
early science results. We also discuss future directions for the instrument.
Pepper, Joshua; Rodriguez, Joseph E.; Collins, Karen A.; Johnson, John Asher; Fulton, Benjamin J.; Howard, Andrew W.; Beatty, Thomas; Stassun, Keivan G.; Isaacson, Howard; Colón, Knicole D.; Lund, Michael B.; Kuhn, Rudolf B.; Siverd, Robert J.; Gaudi, B. Scott; Tan, T. G.; Curtis, Ivan; Stockdale, Christopher; Mawet, Dimitri; Bottom, Michael; James, David; Zhou, George; Bayliss, Daniel; Cargile, Phillip; Bieryla, Allyson; Penev, Kaloyan; Latham, David W.; Labadie-Bartz, Jonathan; Kielkopf, John F.; Eastman, Jason D.; Oberst, Thomas E.; Jensen, Eric L. N.; Nelson, Peter; Sliski, David H.; Wittenmyer, Robert A.; McCrady, Nate; Wright, Jason T.; Relles, Howard M.
We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright (V = 8.0) subgiant HD
93396. A global analysis of the system shows that the host star is an evolved subgiant star with Teff = 5370±51
K, M∗ = 1.438+0.061
−0.052 M⊙, R∗ = 2.72+0.21
−0.17 R⊙, log g∗= 3.727+0.040
−0.046, and [Fe/H]= 0.180 ± 0.075. The
planet is a low-mass gas giant in a P = 4.736529 ± 0.00006 day orbit, with MP = 0.195 ± 0.018 MJ,
RP = 1.37+0.15
−0.12 RJ, ρP = 0.093+0.028
−0.024 g cm^(−3)
, surface gravity log gP = 2.407+0.080
−0.086, and equilibrium
temperature T_(eq) = 1712+51
−46 K. KELT-11 is the brightest known...
Gukov, Sergei; Marino, Marcos; Putrov, Pavel
We study resurgence properties of partition function of SU(2) Chern-Simons
theory (WRT invariant) on closed three-manifolds. We check explicitly that in
various examples Borel transforms of asymptotic expansions posses expected
analytic properties. In examples that we study we observe that contribution of
irreducible flat connections to the path integral can be recovered from
asymptotic expansions around abelian flat connections. We also discuss
connection to Floer instanton moduli spaces, disk instantons in 2d sigma models, and length spectra of "complex geodesics" on the A-polynomial curve.
Filippidis, Ioannis; Murray, Richard M.
This work proposes a symbolic algorithm for the construction of assume-guarantee specifications that allow multiple agents to cooperate. Each agent is assigned goals expressed in a fragment of linear temporal logic known as generalized Streett with one pair, GR(1). These goals may be unrealizable, unless each agent makes additional assumptions, about the behavior of other agents. The algorithm constructs a contract among the agents, in that only the infinite behavior of the given goals is constrained, known as liveness, not the finite one, known as safety. This defers synthesis to a later stage of refinement, modularizing the design process. We...
Artavanis, Georgios; Hsiao, Victoria; Hayes, Clarmyra A.; Murray, Richard M.
Phage integrase-based circuits are an alternative approach to relying on transcriptional and translational repression for biomolecular circuits. Previous research has shown that circuits based on integrases can perform a variety of functions, including counters, Boolean logic operators, memory modules and temporal event detectors. It is therefore essential to develop a principled theoretical and experimental framework for the design, implementation and study of such circuits. One of the fundamental questions that such a framework should address concerns the functionality limitations and temporal dynamics of the integrases as regulatory elements. Here, we test the functionality of several large serine integrases from a...
Chen, David Z.; An, Qi; Goddard, William A., III; Greer, Julia R.
The atomic-level structures of liquids and glasses are similar, obscuring any structural basis for the glass transition. To delineate structural differences between them, we characterized the atomic structures using the integrated radial distribution functions (RDF) from molecular dynamics (MD) simulations for several metallic liquids and glasses: Cu_(46)Zr_(54), Ni_(80)Al_(20),
Ni_(33.3)Zr_(66.7), and Pd_(82)Si_(18). We find that the integrated RDF leads to cumulative coordination numbers (CN) that are similar for all four metallic glasses and for all four liquids, but are consistently different between the liquid and glass phases. We find that metallic liquids have a fractal dimension of df = 2.54 ± 0.06...
Cao, ChunJun; Carroll, Sean M.
We examine how to construct a spatial manifold and its geometry from the entanglement structure of an abstract quantum state in Hilbert space. Given a decomposition of Hilbert space H into a tensor product of factors, we consider a class of "redundancy-constrained states" in H that generalize the area-law behavior for entanglement entropy usually found in condensed-matter systems with gapped local Hamiltonians. Using mutual information to define a distance measure on the graph, we employ classical multidimensional scaling to extract the best-fit spatial dimensionality of the emergent geometry. We then show that entanglement perturbations on such emergent geometries naturally give...
Ruhi, Navid Azizan; Dvijotham, Krishnamurthy; Chen, Niangjun; Wierman, Adam
Aggregators are playing an increasingly crucial role in the integration of
renewable generation in power systems. However, the intermittent nature of
renewable generation makes market interactions of aggregators difficult to
monitor and regulate, raising concerns about potential market manipulation by
aggregators. In this paper, we study this issue by quantifying the profit an
aggregator can obtain through strategic curtailment of generation in an
electricity market. We show that, while the problem of maximizing the benefit
from curtailment is hard in general, efficient algorithms exist when the
topology of the network is radial (acyclic). Further, we highlight that
significant increases in profit are possible via strategic curtailment in
practical settings.
Burnell, F. J.; Chen, Xie; Kitaev, Alexei; Metlitski, Max A.; Vishwanath, Ashvin
The boundary of a fractionalized topological phase can be gapped by condensing a proper set of bosonic quasiparticles. Interestingly, in the presence of a global symmetry, such a boundary can have different symmetry transformation properties. Here we present an explicit example of this kind, in the double semion state with time reversal symmetry. We find two distinct cases where the semionic excitations on the boundary can transform either as time reversal singlets or as time reversal (Kramers) doublets, depending on the coherent phase factor of the Bose condensate. The existence of these two possibilities are demonstrated using both field theory...
Hermele, Michael; Chen, Xie
We introduce a method, dubbed the flux-fusion anomaly test, to detect certain anomalous symmetry fractionalization patterns in two-dimensional symmetry enriched topological (SET) phases. We focus on bosonic systems with Z2 topological order, and symmetry group of the form G = U(1) ⋊ G', where G' is an arbitrary group that may include spatial symmetries and/or time reversal. The anomalous fractionalization patterns we identify cannot occur in strictly d=2 systems, but can occur at surfaces of d=3 symmetry protected topological (SPT) phases. This leads to examples of d=3 bosonic topological crystalline insulators (TCIs) that, to our knowledge, have not previously been...
Ware, Brayden; Son, Jun Ho; Cheng, Meng; Mishmash, Ryan V.; Alicea, Jason; Bauer, Bela
Dimer models have long been a fruitful playground for understanding topological physics. Here we introduce a new class - termed Majorana-dimer models - wherein bosonic dimers are decorated with pairs of Majorana modes. We find that the simplest examples of such systems realize an intriguing, intrinsically fermionic phase of matter that can be viewed as the product of a chiral Ising theory, which hosts deconfined non-Abelian quasiparticles, and a topological px−ipy superconductor. While the bulk anyons are described by a single copy of the Ising theory, the edge remains fully gapped. Consequently, this phase can arise in exactly solvable, frustration-free...