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Sander Weinreb

Other affiliations: Jet Propulsion Laboratory
Bio: Sander Weinreb is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Amplifier & Monolithic microwave integrated circuit. The author has an hindex of 26, co-authored 133 publications receiving 3038 citations. Previous affiliations of Sander Weinreb include Jet Propulsion Laboratory.


Papers
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Journal ArticleDOI
TL;DR: Use of a specially built radio interferometer shows that a non-repeating fast radio burst is localized to a few-arcsecond region containing a single massive galaxy, and is perhaps derived from an old stellar population.
Abstract: Intense, millisecond-duration bursts of radio waves have been detected from beyond the Milky Way [1]. Their extragalactic origins are evidenced by their large dispersion measures, which are greater than expected for propagation through the Milky Way interstellar medium alone, and imply contributions from the intergalactic medium and potentially host galaxies [2]. Although several theories exist for the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetised plasma [3,4]. Two sources have been observed to repeat [5,6], and one repeater (FRB 121102) has been localised to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 [7, 8]. However, the host galaxies and distances of the so far non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer with sufficient spatial resolution for arcsecond localisation at the time of discovery. Here we report the localisation of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is in stark contrast to the host of FRB 121102, being a thousand times more massive, with a greater than hundred times lower specific star-formation rate. The properties of this galaxy highlight the possibility of a channel for FRB production associated with older stellar populations.

324 citations

Journal ArticleDOI
01 Aug 2019-Nature
TL;DR: In this paper, the authors reported the localization of a fast radio burst (FRB-190523) to a few-arcsecond region containing a single massive galaxy at a cosmological redshift of 0.66.
Abstract: Intense, millisecond-duration bursts of radio waves (named fast radio bursts) have been detected from beyond the Milky Way1. Their dispersion measures—which are greater than would be expected if they had propagated only through the interstellar medium of the Milky Way—indicate extragalactic origins and imply contributions from the intergalactic medium and perhaps from other galaxies2. Although several theories exist regarding the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetized plasma3,4. Two of these bursts have been observed to repeat5,6, and one repeater (FRB 121102) has been localized to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 (refs. 7–9). However, the host galaxies and distances of the hitherto non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer that has sufficient spatial resolution for arcsecond localization at the time of discovery. Here we report the localization of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is different from the host of FRB 121102, as it is a thousand times more massive, with a specific star-formation rate (the star-formation rate divided by the mass) a hundred times smaller. Use of a specially built radio interferometer shows that a non-repeating fast radio burst is localized to a few-arcsecond region containing a single massive galaxy, and is perhaps derived from an old stellar population.

246 citations

Proceedings ArticleDOI
13 Jun 1999
TL;DR: In this article, the authors presented design data in the form of dimension tables for probe transitions for microstrip substrates with 4 dielectric constants (2.2, 6.0, 10.1, and 13) in two orientations relative to the waveguide (broadside and longitudinal).
Abstract: Design data in the form of dimension tables is presented for probe transitions for microstrip substrates with 4 dielectric constants (2.2, 6.0, 10.1, and 13) in two orientations relative to the waveguide (broadside and longitudinal). These dimensions have been optimized for full waveguide bandwidth with >20 dB return loss using an electromagnetic CAD procedure. The dimensions can be applied to any size waveguide with a 2:1 width/height aspect ratio. Experimental verification for two of the designs applied to a W-band waveguide is presented.

224 citations

Journal ArticleDOI
TL;DR: In this paper, a dual polarized ultrawide-band (UWB) feed with a decade bandwidth was presented for use in both single and dual reflector antennas, which has nearly constant beam width and 11 dBi directivity.
Abstract: A novel dual polarized ultrawide-band (UWB) feed with a decade bandwidth is presented for use in both single and dual reflector antennas. The feed has nearly constant beam width and 11 dBi directivity over at least a decade bandwidth. The feed gives an aperture efficiency of the reflector of 66% or better over a decade bandwidth when the subtended angle toward the sub or main reflector is about 53/spl deg/, and an overall efficiency better than 47% including mismatch. The return loss is better than 5 dB over a decade bandwidth. The calculated results have been verified with measurements on a linearly polarized lab model. The feed has no balun as it is intended to be integrated with an active 180/spl deg/ balun and receiver. The feed is referred to as the Eleven antenna because its basic configuration is two parallel dipoles 0.5 wavelengths apart and because it can be used over more than a decade bandwidth with 11 dBi directivity. We also believe that 11 dB return loss is achievable in the near future.

169 citations

Journal ArticleDOI
14 Jul 2009
TL;DR: The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in northern California as mentioned in this paper, and the fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results are discussed.
Abstract: The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of commercial off-the-shelf components, and the cost/performance tradeoffs that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed.

165 citations


Cited by
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Journal ArticleDOI
28 Feb 2018-Nature
TL;DR: The detection of a flattened absorption profile in the sky-averaged radio spectrum that is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions.
Abstract: The 21-cm absorption profile is detected in the sky-averaged radio spectrum, but is much stronger than predicted, suggesting that the primordial gas might have been cooler than predicted. As the first stars heated hydrogen in the early Universe, the 21-cm hyperfine line—an astronomical standard that represents the spin-flip transition in the ground state of atomic hydrogen—was altered, causing the hydrogen gas to absorb photons from the microwave background. This should produce an observable absorption signal at frequencies of less than 200 megahertz (MHz). Judd Bowman and colleagues report the observation of an absorption profile centred at a frequency of 78 MHz that is about 19 MHz wide and 0.5 kelvin deep. The profile is generally in line with expectations, although it is deeper than predicted. An accompanying paper by Rennan Barkana suggests that baryons were interacting with cold dark-matter particles in the early Universe, cooling the gas more than had been expected. After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz1. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0.5 kelvin. The profile is largely consistent with expectations for the 21-centimetre signal induced by early stars; however, the best-fitting amplitude of the profile is more than a factor of two greater than the largest predictions2. This discrepancy suggests that either the primordial gas was much colder than expected or the background radiation temperature was hotter than expected. Astrophysical phenomena (such as radiation from stars and stellar remnants) are unlikely to account for this discrepancy; of the proposed extensions to the standard model of cosmology and particle physics, only cooling of the gas as a result of interactions between dark matter and baryons seems to explain the observed amplitude3. The low-frequency edge of the observed profile indicates that stars existed and had produced a background of Lyman-α photons by 180 million years after the Big Bang. The high-frequency edge indicates that the gas was heated to above the radiation temperature less than 100 million years later.

992 citations

Journal ArticleDOI
R. Appleby1, H.B. Wallace
TL;DR: The techniques and technologies currently being investigated to detect weapons and contraband concealed on persons under clothing are reviewed and the basic phenomenology of the atmosphere and materials that must be understood in order to realize such a system are discussed.
Abstract: The techniques and technologies currently being investigated to detect weapons and contraband concealed on persons under clothing are reviewed. The basic phenomenology of the atmosphere and materials that must be understood in order to realize such a system are discussed. The component issues and architectural designs needed to realize systems are outlined. Some conclusions with respect to further technology developments are presented.

575 citations

Journal ArticleDOI
TL;DR: DeBoer, David R; Parsons, Aaron R; Aguirre, James E; Alexander, Paul; Ali, Zaki S; Beardsley, Adam P; Bernardi, Gianni; Bowman, Judd D; Bradley, Richard F; Carilli, Chris L; Cheng, Carina; Acedo, Eloy de Lera; Dillon, Joshua S; Ewall-Wice, Aaron; Fadana, Gcobisa; Fagnoni, Nicolas; Fritz, Randall; Furlanetto, Steve R; Glenden
Abstract: Author(s): DeBoer, David R; Parsons, Aaron R; Aguirre, James E; Alexander, Paul; Ali, Zaki S; Beardsley, Adam P; Bernardi, Gianni; Bowman, Judd D; Bradley, Richard F; Carilli, Chris L; Cheng, Carina; Acedo, Eloy de Lera; Dillon, Joshua S; Ewall-Wice, Aaron; Fadana, Gcobisa; Fagnoni, Nicolas; Fritz, Randall; Furlanetto, Steve R; Glendenning, Brian; Greig, Bradley; Grobbelaar, Jasper; Hazelton, Bryna J; Hewitt, Jacqueline N; Hickish, Jack; Jacobs, Daniel C; Julius, Austin; Kariseb, MacCalvin; Kohn, Saul A; Lekalake, Telalo; Liu, Adrian; Loots, Anita; MacMahon, David; Malan, Lourence; Malgas, Cresshim; Maree, Matthys; Martinot, Zachary; Mathison, Nathan; Matsetela, Eunice; Mesinger, Andrei; Morales, Miguel F; Neben, Abraham R; Patra, Nipanjana; Pieterse, Samantha; Pober, Jonathan C; Razavi-Ghods, Nima; Ringuette, Jon; Robnett, James; Rosie, Kathryn; Sell, Raddwine; Smith, Craig; Syce, Angelo; Tegmark, Max; Thyagarajan, Nithyanandan; Williams, Peter K. G; Zheng, Haoxuan

460 citations

Journal ArticleDOI
14 Jul 2009
TL;DR: The Murchison Widefield Array is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range, capable of a wide range of science investigations but initially focused on three key science projects: detection and characterization of three-dimensional brightness temperature fluctuations in the 21 cm line of neutral hydrogen during the epoch of reionization.
Abstract: The Murchison Widefield Array is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It is capable of a wide range of science investigations but is initially focused on three key science projects: detection and characterization of three-dimensional brightness temperature fluctuations in the 21 cm line of neutral hydrogen during the epoch of reionization (EoR) at redshifts from six to ten; solar imaging and remote sensing of the inner heliosphere via propagation effects on signals from distant background sources; and high-sensitivity exploration of the variable radio sky. The array design features 8192 dual-polarization broadband active dipoles, arranged into 512 ldquotilesrdquo comprising 16 dipoles each. The tiles are quasi-randomly distributed over an aperture 1.5 km in diameter, with a small number of outliers extending to 3 km. All tile-tile baselines are correlated in custom field-programmable gate array based hardware, yielding a Nyquist-sampled instantaneous monochromatic uv coverage and unprecedented point spread function quality. The correlated data are calibrated in real time using novel position-dependent self-calibration algorithms. The array is located in the Murchison region of outback Western Australia. This region is characterized by extremely low population density and a superbly radio-quiet environment, allowing full exploitation of the instrumental capabilities.

438 citations

Proceedings ArticleDOI
01 Aug 2008
TL;DR: Cooperating Organizations American Astronomical Society (United States) • Netherlands Institute for Radio Astronomy (ASTRON) (Netherlands) • Ball Aerospace & Technologies Corporation (U.S. as discussed by the authors ).
Abstract: Cooperating Organizations American Astronomical Society (United States) • Netherlands Institute for Radio Astronomy (ASTRON) (Netherlands) • Ball Aerospace & Technologies Corporation (United States) Canadian Astronomical Society (CASCA) (Canada) • European Astronomical Society (Switzerland) • ESO—European Southern Observatory (Germany) • International Astronomical Union • Korea Astronomy and Space Science Institute (KASI) (Republic of Korea) • National Radio Astronomy Observatory • POPSud (France) • TNO (Netherlands)

432 citations