Physical Sciences and Mathematics Commons^™

A Multiparameter Degeneracy In Microlensing Events With Extreme Finite Source Effects, Samson A. Johnson, Matthew T. Penny, B. Scott Gaudi

Faculty Publications

For microlenses with sufficiently low mass, the angular radius of the source star can be much larger than the angular Einstein ring radius of the lens. For such extreme finite source effect (EFSE) events, finite source effects dominate throughout the duration of the event. Here, we demonstrate and explore a continuous degeneracy between multiple parameters of such EFSE events. The first component in the degeneracy arises from the fact that the directly observable peak change of the flux depends on both the ratio of the angular source radius to the angular Einstein ring radius and the fraction of the baseline …

Gaia Gral: Gaia Dr2 Gravitational Lens Systems. Vii. Xmm-Newton Observations Of Lensed Quasars, Thomas Connor, Daniel Stern, Alberto Krone-Martins, S. G. Djorgovski, Matthew J. Graham

Faculty Publications

We present XMM-Newton X-ray observations of nine confirmed lensed quasars at 1 less than or similar to z less than or similar to 3 identified by the Gaia Gravitational Lens program. Eight systems are strongly detected, with 0.3-8.0 keV fluxes F (0.3-8.0) greater than or similar to 5 x10(-14) erg cm(-2) s(-1). Modeling the X-ray spectra with an absorbed power law, we derive power-law photon indices and 2-10 keV luminosities for the eight detected quasars. In addition to presenting sample properties for larger quasar population studies and for use in planning for future caustic-crossing events, we also identify three quasars …

Search Full Text Options Here 2 Of 4 Kmt-2021-Blg-0912lb: A Microlensing Super Earth Around A K-Type Star, Cheongho Han, Ian A. Bond, Jennifer C. Yee, Weicheng Zang, Michael D. Albrow

Faculty Publications

Aims. The light curve of the microlensing event KMT-2021-BLG-0912 exhibits a very short anomaly relative to a single-lens single-source form. We investigate the light curve for the purpose of identifying the origin of the anomaly.

Methods. We model the light curve under various interpretations. From this, we find four solutions, in which three solutions are found under the assumption that the lens is composed of two masses (2L1S models), and the other solution is found under the assumption that the source is comprised of binary stars (1L2S model). The 1L2S model is ruled out based on the contradiction that the …

Search For Continuous Gravitational Waves From 20 Accreting Millisecond X-Ray Pulsars In O3 Ligo Data, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams

Faculty Publications

Results are presented of searches for continuous gravitational waves from 20 accreting millisecond x-ray pulsars with accurately measured spin frequencies and orbital parameters, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. The search algorithm uses a hidden Markov model, where the transition probabilities allow the frequency to wander according to an unbiased random walk, while the J-statistic maximum-likelihood matched filter tracks the binary orbital phase. Three narrow subbands are searched for each target, centered on harmonics of the measured spin frequency. The search yields 16 candidates, consistent with a false alarm probability of …

Towards A Quantum Notion Of Covariance In Spherically Symmetric Loop Quantum Gravity, Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Faculty Publications

The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way-they preserve the quantum line element-for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints, and the recovery of standard general relativity in the classical …

Towards A Quantum Notion Of Covariance In Spherically Symmetric Loop Quantum Gravity, Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Faculty Publications

The covariance of loop quantum gravity studies of spherically symmetric space-times has recently been questioned. This is a reasonable worry, given that they are formulated in terms of slicing-dependent variables. We show explicitly that the resulting space-times, obtained from Dirac observables of the quantum theory, are covariant in the usual sense of the way-they preserve the quantum line element-for any gauge that is stationary (in the exterior, if there is a horizon). The construction depends crucially on the details of the Abelianized quantization considered, the satisfaction of the quantum constraints, and the recovery of standard general relativity in the classical …

Testing Effects Of Lorentz Invariance Violation In The Propagation Of Astroparticles With The Pierre Auger Observatory, P. Abreu, M. Aglietta, J. M. Albury, I. Allekotte, K. Almeida Cheminant

Faculty Publications

Lorentz invariance violation (LIV) is often described by dispersion relations of the form E-i(2) = m(i)(2) + p(i)(2) + delta E-i,n(2+ n) with delta different based on particle type i, with energy E, momentum p and rest mass m. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients delta(i,n) tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological …

Search For Lensing Signatures In The Gravitational-Wave Observations From The First Half Of Ligo-Virgo's Third Observing Run, R. Abbott, T. D. Abbott

Faculty Publications

We search for signatures of gravitational lensing in the gravitational-wave signals from compact binary coalescences detected by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) and Advanced Virgo during O3a, the first half of their third observing run. We study: (1) the expected rate of lensing at current detector sensitivity and the implications of a non-observation of strong lensing or a stochastic gravitational-wave background on the merger-rate density at high redshift; (2) how the interpretation of individual high-mass events would change if they were found to be lensed; (3) the possibility of multiple images due to strong lensing by galaxies or galaxy …

A Gravitational-Wave Measurement Of The Hubble Constant Following The Second Observing Run Of Advanced Ligo And Virgo (Vol 908, 218, 2021), B. P. Abbott, R. Abbott, T. D. Abbott

Faculty Publications

No abstract provided.

Multi-Scale Feedback And Feeding In The Closest Radio Galaxy Centaurus A, B. Mckinley, S. J. Tingay, M. Gaspari, R. P. Kraft, C. Matherne, A. R. Offringa, M. Mcdonald, M. S. Calzadilla, S Veilleux, S. S. Shabala, S. D. J. Gwyn, J. Bland-Hawthorn, D. Crnojevic, B. M. Gaensler, M. Johnston-Hollitt

Faculty Publications

Supermassive black holes and supernova explosions at the centres of active galaxies power cycles of outflowing and inflowing gas that affect galactic evolution and the overall structure of the Universe(1,2). While simulations and observations show that this must be the case, the range of physical scales (over ten orders of magnitude) and paucity of available tracers make both the simulation and observation of these effects difficult(3,4). By serendipity, there lies an active galaxy, Centaurus A (NGC 5128)(5,6), at such a close proximity as to allow its observation over this entire range of scales and across the entire electromagnetic spectrum. In …

Diving Beneath The Sea Of Stellar Activity: Chromatic Radial Velocities Of The Young Au Mic Planetary System, Bryson Cale, Michael Reefe, Peter Plavchan, Angelle Tanner, Eric Gaidos, Jonathan Gagne, Peter Gao, Stephen R. Kane, Victor J. S. Bejar, Nicolas Lodieu, Guillem Anglada-Escude, Ignasi Ribas, Enric Palle, Andreas Quirrenbach, Pedro Amado, Ansgar Reiners, Jose A. Caballero, Maria Rosa Zapatero Osorio, Stefan Dreizler, Andrew W. Howard, Benjamin J. Fulton, Sharon Xuesong Wang, Kevin I. Collins, Mohammed El Mufti, Justin Wittrock, Emily A. Gilbert, Thomas Barclay, Baptiste Klein, Eder Martioli, Robert Wittenmyer, Duncan Wright, Brett Addison, Teruyuki Hirano, Motohide Tamura, Takayuki Kotani, Norio Narita, David Vermilion, Rena A. Lee, Claire Geneser, Johanna Teske, Samuel N. Quinn, David W. Latham, Gilbert A. Esquerdo, Michael L. Calkins, Perry Berlind, Farzaneh Zohrabi, Caitlin Stibbards, Srihan Kotnana, Jon Jenkins, Joseph D. Twicken, Christopher Henze, Richard Kidwell, Jr., Christopher Burke, Joel Villasenor, Patricia Boyd

Faculty Publications

We present updated radial-velocity (RV) analyses of the AU Mic system. AU Mic is a young (22 Myr) early-M dwarf known to host two transiting planets-P-b similar to 8.46 days, R-b = 4.381(-0.18)(+0.18) R-circle plus, P-c similar to 18.86 days, R-c = 3.5(-0.16)(+0.16) R-circle plus. With visible RVs from Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical echelle Spectrographs (CARMENES)-VIS, CHIRON, HARPS, HIRES, MINERVA-Australis, and Tillinghast Reflector Echelle Spectrograph, as well as near-infrared (NIR) RVs from CARMENES-NIR, CSHELL, IRD, iSHELL, NIRSPEC, and SPIRou, we provide a 5 sigma upper limit to the mass of AU …

Nonsingular Quantum Gravitational Dynamics Of An Lemaitre-Tolman-Bondi Dust Shell Model: The Role Of Quantization Prescriptions, Kristina Giesel, Bao-Fei Li, Parampreet Singh

Faculty Publications

We study some consequences of the loop quantization of the outermost dust shell in the LemaitreTolman-Bondi spacetime with a homogeneous dust density using different quantization strategies motivated by loop quantum gravity. Prior work has dealt with loop quantizing this model by employing holonomies and the triads, following the procedure in standard loop quantum cosmology. In this work we compare this quantization with the one in which holonomies and gauge-covariant fluxes are used. While both of the quantization schemes resolve the central singularity, they lead to different mass gaps at which a trapped surface forms. This trapped surface which is matched …

Search Full Text Options Here 1 Of 1 Constraints From Ligo O3 Data On Gravitational-Wave Emission Due To R-Modes In The Glitching Pulsar Psr J0537-6910, R. Abbott, T. D. Abbott

Faculty Publications

We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537-6910 using data from the LIGO-Virgo Collaboration observing run O3. PSR J0537-6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochs between …

Directly Determined Properties Of Hd 97658 From Interferometric Observations, Tyler G. Ellis, Tabetha Boyajian, Kaspar Von Braun, Roxanne Ligi, Denis Mourard, Diana Dragomir, Gail H. Schaefer, Christopher D. Farrington

Faculty Publications

We conducted interferometric observations with the CHARA Array of transiting super-Earth host HD 97658 and measured its limb-darkened angular diameter to be theta(LD) = 0.314 +/- 0.004 mas. The combination of the angular diameter with the Gaia EDR3 parallax value with zero-point correction (pi = 46.412 +/- 0.022 mas, d =21.546 +/- 0.011 pc) yields a physical radius of R-star = 0.728 +/- 0.008 R-circle dot. We also measured the bolometric flux of the star to be F-bol = 2.42 +/- 0.05 x 10(-8) erg s(-1) cm(-2), which, together with angular size, allows a measurement of the effective temperature T-eff …

Dirac-Born-Infeld Warm Inflation Realization In The Strong Dissipation Regime, Meysam Motaharfar, Rudnei O. Ramos

Faculty Publications

We consider warm inflation with a Dirac-Born-Infeld (DBI) kinetic term in which both the non-equilibrium dissipative particle production and the sound speed parameter slow the motion of the inflaton field. We find that a low sound speed parameter removes, or at least strongly suppresses, the growing function appearing in the scalar of curvature power spectrum of warm inflation, which appears due to the temperature dependence in the dissipation coefficient. As a consequence of that, a low sound speed helps to push warm inflation into the strong dissipation regime, which is an attractive regime from a model building and phenomenological perspective. …

Spatiotemporal Trends And Variability In The Centroid Of The Northern Hemisphere's Circumpolar Vortex, Nazla Bushra, Robert V. Rohli

Faculty Publications

Recent previous research has established the "sharpest gradient" approach to defining the circumpolar vortex and has identified correlations of the area and circularity of the Northern Hemisphere's circumpolar vortex (NHCPV) to important atmospheric-oceanic teleconnections. However, because geographical shifts in the NHCPV, independent of area or circularity changes, could affect surface environmental conditions, this research addresses the question of the extent to which the NHCPV centroid undergoes such shifts, both intra- and inter-annually. Results show that during the 1979-2017 period, the centroid has moved less on a daily basis in more recent years, perhaps indicative of a stabilization in circulation, with …

"Super Gzk" Particles In A Classic Kramers' Diffusion-Over-A-Barrier Model. I. The Case Of Protons, S. T. Alnussirat, A. F. Barghouty, G. M. Webb, P. L. Biermann

Faculty Publications

In interactions of ultra-high-energy cosmic ray (UHECR) protons with cosmic microwave background photons, we focus in this work on photopion production reactions and the effects of the measured, broad, energy-loss distributions in these reactions on the evolution of the protons' density functions in energy space. We rely on a Fokker-Planck transport equation in energy space whose transport coefficients are calculated using laboratory measurements. We also derive a Fokker-Planck potential that accounts for both systematic (drift) and stochastic (dispersive) energy losses due to photopion production reactions. Our results show that dispersive energy losses have significant effects on estimating the protons' horizon …

Relating Dust Reference Models To Conventional Systems In Manifestly Gauge Invariant Perturbation Theory, Kristina Giesel, Bao-Fei Li, Parampreet Singh

Faculty Publications

Models with dust reference fields in relational formalism have proved useful in understanding the construction of gauge invariant perturbation theory to arbitrary orders in the canonical framework. These reference fields modify the dynamical equations for perturbation equations. However, important questions remain open on the relation with conventional perturbation theories of inflaton coupled to gravity and of multifluid systems, and on understanding modifications in terms of physical degrees of freedom. These gaps are filled in this manuscript for Brown-Kuchar and Gaussian dust models, both of which involve three scalar physical degrees of freedom. We establish a relationship of these models with …

Octo-Tiger: A New, 3d Hydrodynamic Code For Stellar Mergers That Uses Hpx Parallelization, Dominic C. Marcello, Sagiv Shiber, Orsola De Marco, Juhan Frank, Geoffrey C. Clayton, Patrick M. Motl, Patrick Diehl, Hartmut Kaiser

Faculty Publications

OCTO-TIGER is an astrophysics code to simulate the evolution of self-gravitating and rotating systems of arbitrary geometry based on the fast multipole method, using adaptive mesh refinement. OCTO-TIGER is currently optimized to simulate the merger of well-resolved stars that can be approximated by barotropic structures, such as white dwarfs (WDs) or main-sequence stars. The gravity solver conserves angular momentum to machine precision, thanks to a 'correction' algorithm. This code uses firx parallelization, allowing the overlap of work and communication and leading to excellent scaling properties, allowing for the computation of large problems in reasonable wall-clock times. In this paper, we …

Loop Quantum Black Hole Extensions Within The Improved Dynamics, Rodolfo Gambini, Javier Olmedo, Jorge Pullin

Faculty Publications

We continue our investigation of an improved quantization scheme for spherically symmetric loop quantum gravity. We find that in the region where the black hole singularity appears in the classical theory, the quantum theory contains semi-classical states that approximate general relativity coupled to an effective anisotropic fluid. The singularity is eliminated and the space-time can be continued into a white hole space-time. This is similar to previously considered scenarios based on a loop quantum gravity quantization.

Sphincs_Bssn: A General Relativistic Smooth Particle Hydrodynamics Code For Dynamical Spacetimes, S. Rosswog, P. Diener

Faculty Publications

We present a new methodology for simulating self-gravitating general-relativistic fluids. In our approach the fluid is modelled by means of Lagrangian particles in the framework of a general-relativistic (GR) smoothed particle hydrodynamics (SPH) formulation, while the spacetime is evolved on a mesh according to the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation that is also frequently used in Eulerian GR-hydrodynamics. To the best of our knowledge this is the first Lagrangian fully general relativistic hydrodynamics code (all previous SPH approaches used approximations to GR-gravity). A core ingredient of our particle-mesh approach is the coupling between the gas (represented by particles) and the spacetime (represented …

The Fermi-Gbm Gamma-Ray Burst Spectral Catalog: 10 Yr Of Data, S. Poolakkil, R. Preece, C. Fletcher, A. Goldstein, P. N. Bhat, E. Bissaldi, M. S. Briggs, E. Burns, W. H. Cleveland, M. M. Giles, C. M. Hui, D. Kocevski, S. Lesage, B. Mailyan, C. Malacaria, W. S. Paciesas, O. J. Roberts, P. Veres, A. Von Kienlin, C. A. Wilson-Hodge

Faculty Publications

We present the systematic spectral analyses of gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor during its first ten years of operation. This catalog contains two types of spectra: time-integrated spectral fits and spectral fits at the brightest time bin, from 2297 GRBs, resulting in a compendium of over 18,000 spectra. The four different spectral models used for fitting the spectra were selected based on their empirical importance to the shape of many GRBs. We describe in detail our procedure and criteria for the analyses, and present the bulk results in the form of parameter distributions both in …

R Coronae Borealis Star Evolution: Simulating 3d Merger Events To 1d Stellar Evolution Including Large-Scale Nucleosynthesis, Bradley Munson, Emmanouil Chatzopoulos, Juhan Frank, Geoffrey Clayton, Courtney Crawford, Pavel A. Denissenkov, Falk Herwig

Faculty Publications

R Coronae Borealis (RCB) stars are rare hydrogen-deficient carbon-rich variable supergiants thought to be the result of dynamically unstable white dwarf mergers. We attempt to model RCB stars through all the relevant timescales by simulating a merger event in Octo-tiger, a 3D adaptive mesh refinement (AMR) hydrodynamics code, and mapping the post-merger object into MESA, a 1D stellar evolution code. We then post-process the nucleosynthesis on a much larger nuclear reaction network to study the enhancement of s-process elements. We present models that match observations or previous studies in most surface abundances, isotopic ratios, early evolution, and lifetimes. We also …

Primordial Power Spectrum From A Matter-Ekpyrotic Bounce Scenario In Loop Quantum Cosmology, Bao-Fei Li, Sahil Saini, Parampreet Singh

Faculty Publications

A union of matter bounce and ekpyrotic scenarios is often studied in an attempt to combine the most promising features of these two models. Since nonperturbative quantum geometric effects in loop quantum cosmology (LQC) result in natural bouncing scenarios without any violation of energy conditions or fine tuning, an investigation of matter-ekpyrotic bounce scenario is interesting to explore in this quantum gravitational setting. In this work, we explore this unified phenomenological model for a spatially flat Friedmann-Lemaistre-Robertson-Walker (FLRW) universe in LQC filled with dust and a scalar field in an ekpyrotic scenario like negative potential. Background dynamics and the power …

Updated Miniboone Neutrino Oscillation Results With Increased Data And New Background Studies, A. A. Aguilar-Arevalo, B. C. Brown, J. M. Conrad, R. Dharmapalan, A. Diaz, Z. Djurcic, D. A. Finley, R. Ford, G. T. Garvey, S. Gollapinni, A. Hourlier, E-C Huang, N. W. Kamp, G. Karagiorgi, T. Katori, T. Kobilarcik, K. Lin, W. C. Louis, C. Mariani, W. Marsh, G. B. Mills, J. Mirabal-Martinez, C. D. Moore, R. H. Nelson, J. Nowak, I Parmaksiz, Z. Pavlovic, H. Ray, B. P. Roe, A. D. Russell, A. Schneider, M. H. Shaevitz, H. Siegel, J. Spitz, I. Stancu, R. Tayloe, R. T. Thornton, M. Tzanov, R. G. Van De Water, D. H. White, E. D. Zimmerman

Faculty Publications

The MiniBooNE experiment at Fermilab reports a total excess of 638.0 +/- 52.1(stat) +/- 122.2(syst) electronlike events from a data sample corresponding to 18.75 x 10(20) protons-on-target in neutrino mode, which is a 46% increase in the data sample with respect to previously published results and 11.27 x 10(20) protons-on-target in antineutrino mode. The overall significance of the excess, 4.8 sigma, is limited by systematic uncertainties, assumed to be Gaussian, as the statistical significance of the excess is 12.2 sigma. The additional statistics allow several studies to address questions on the source of the excess. First, we provide two-dimensional plots …

Planet Hunters Tess Ii: Findings From The First Two Years Of Tess, N. L. Eisner, O. Barragan, C. Lintott, S. Aigrain, B. Nicholson, T. S. Boyajian, S. Howell, C. Johnston, B. Lakeland, G. Miller, A. Mcmaster, H. Parviainen, E. J. Safron, M. E. Schwamb, L. Trouille, S. Vaughan, N. Zicher, C. Allen, S. Allen, M. Bouslog, C. Johnson, M. N. Simon, Z. Wolfenbarger, E. M. L. Baeten, D. M. Bundy, T. Hoffman

Faculty Publications

We present the results from the first two years of the Planet Hunters TESS (PHT) citizen science project, which identifies planet candidates in the TESS (Transiting Exoplanet Survey Satellite) data by engaging members of the general public. Over 22000 citizen scientists from around the world visually inspected the first 26 sectors of TESS data in order to help identify transit-like signals. We use a clustering algorithm to combine these classifications into a ranked list of events for each sector, the top 500 of which are then visually vetted by the science team. We assess the detection efficiency of this methodology …

Dynamical Modelling Of Cxogbs J175553.2-281633: A 10 H Long Orbital Period Cataclysmic Variable, Sebastian Gomez, Manuel A. P. Torres, Peter G. Jonker, Zuzanna Kostrzewa-Rutkowska, Theo F. J. Van Grunsven, Andrzej Udalski, Robert I. Hynes, Craig O. Heinke, Thomas J. Maccarone, Ricardo Salinas, Jay Strader

Faculty Publications

We present modelling of the long-term optical light and radial velocity curves of the binary stellar system CXOGBS J175553.2-281633, first detected in X-rays in the Chandra Galactic Bulge Survey. We analysed 7 yr of optical I-band photometry from Optical Gravitational Lensing Experiment and found long-term variations from year to year. These long-term variations can most likely be explained with by either variations in the luminosity of the accretion disc or a spotted secondary star. The phased light curve has a sinusoidal shape, which we interpret as being due to ellipsoidal modulations. We improve the orbital period to be P = …

Quasinormal Modes And Their Overtones At The Common Horizon In A Binary Black Hole Merger, Pierre Mourier, Xisco Jimenez Forteza, Daniel Pook-Kolb, Dadri Krishnan, Erik Schnetter

Faculty Publications

It is expected that all astrophysical black holes in equilibrium are well described by the Kerr solution. Moreover, any black hole far away from equilibrium, such as one initially formed in a compact binary merger or by the collapse of a massive star, will eventually reach a final equilibrium Kerr state. At sufficiently late times in this process of reaching equilibrium, we expect that the black hole is modeled as a perturbation around the final state. The emitted gravitational waves will then be damped sinusoids with frequencies and damping times given by the quasinormal mode spectrum of the final Kerr …

Identification Of A Local Sample Of Gamma-Ray Bursts Consistent With A Magnetar Giant Flare Origin, E. Burns, D. Svinkin, K Hurley, Z. Wadiasingh, M. Negro, G. Younes, R. Hamburg, A. Ridnaia, D. Cook, S. B. Cenko, R. Aloisi, G. Ashton, M. Baring, M. S. Briggs, N. Christensen, D. Frederiks, A. Goldstein, C. M. Hui, D. L. Kaplan, M. M. Kasliwal, D. Kocevski, O. J. Roberts, V. Savchenko, A. Tohuvavohu, P. Veres, C. A. Wilson-Hodge

Faculty Publications

Cosmological gamma-ray bursts (GRBs) are known to arise from distinct progenitor channels: short GRBs mostly from neutron star mergers and long GRBs from a rare type of core-collapse supernova (CCSN) called collapsars. Highly magnetized neutron stars called magnetars also generate energetic, short-duration gamma-ray transients called magnetar giant flares (MGFs). Three have been observed from the Milky Way and its satellite galaxies, and they have long been suspected to constitute a third class of extragalactic GRBs. We report the unambiguous identification of a distinct population of four local (<5 Mpc) short GRBs, adding GRB 070222 to previously discussed events. While identified solely based on alignment with nearby star-forming galaxies, their rise time and isotropic energy release are independently inconsistent with the larger short GRB population at >99.9% confidence. These properties, the host galaxies, and nondetection in gravitational waves …

Demonstration Of Dynamic Thermal Compensation For Parametric Instability Suppression In Advanced Ligo, T. Hardwick, V. J. Hamedan, C. Blair, A. C. Green, D. Vander-Hyde

Faculty Publications

Advanced LIGO and other ground-based interferometric gravitational-wave detectors use high laser power to minimize shot noise and suspended optics to reduce seismic noise coupling. This can result in an opto-mechanical coupling which can become unstable and saturate the interferometer control systems. The severity of these parametric instabilities scales with circulating laser power and first hindered LIGO operations in 2014. Static thermal tuning and active electrostatic damping have previously been used to control parametric instabilities at lower powers but are insufficient as power is increased. Here we report the first demonstration of dynamic thermal compensation to avoid parametric instability in an …