The origin of the highest-energy particles in nature, the ultra-high-energy (UHE) cosmic rays, is still unknown. In order to resolve this mystery, very large detectors are required to probe the low flux of these particles - or to detect the as-yet unobserved flux of UHE neutrinos predicted from their interactions. The `lunar Askaryan technique' is a method to do both. When energetic particles interact in a dense medium, the Askaryan effect produces intense coherent pulses of radiation in the MHz--GHz range. By using radio telescopes to observe the Moon and look for nanosecond pulses, the entire visible lunar surface ($20$ million km$^2$) can be used as an UHE particle detector. A large effective area over a broad bandwidth is the primary telescope requirement for lunar observations, which makes large single-aperture instruments such as the Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) well-suited to the technique. In this contribution, we describe the lunar Askaryan technique and its unique observational requirements. Estimates of the sensitivity of FAST to both the UHE cosmic ray and neutrino flux are given, and we describe the methods by which lunar observations with FAST, particularly if equipped with a broadband phased-array feed, could detect the flux of UHE cosmic rays.
KLYPVE-EUSO (K-EUSO) is a planned orbital detector of ultra-high-energy cosmic rays (UHECRs), which is to be deployed on board the International Space Station. K-EUSO is expected to have a uniform exposure over the celestial sphere and register from 120 to 500 UHECRs at energies above 57 EeV in a 2-year mission. We employed the TransportCR and CRPropa 3 packages to estimate prospects of detecting a large-scale anisotropy of ultra-high-energy cosmic rays from a nearby source with K-EUSO. Nearby active galactic nuclei Centaurus A, M82, NGC 253, M87 and Fornax A were considered as possible source…
Fast Radio Bursts (FRBs) are short duration highly energetic dispersed radio pulses. We developed a generic formalism (Bera {\em et al.}, 2016) to estimate the FRB detection rate for any radio telescope with given parameters. By using this model, we estimated the FRB detection rate for two Indian radio telescope; the Ooty Wide Field Array (OWFA) (Bhattacharyya {\em et al.}, 2017) and the upgraded Giant Metrewave Radio Telescope (uGMRT) (Bhattacharyya {\em et al.}, 2018) with three beam forming modes. In this review article, I summarize these two works. We considered the energy spectrum of FRBs…
Radio emission from Ultra-High Energy Cosmic Rays (UHECR) showers detected after specular reflection off the Antarctic ice surface has been recently demonstrated by the ANITA balloon-borne experiment. An antenna observing a large area of ice or water from a mountaintop, a balloon or a satellite may be competitive with more conventional techniques. We present an estimate of the exposure of a high altitude antenna, which provides insight on the prospects of this technique for UHECR detection. We find that a satellite antenna may reach a significantly larger exposure than existing UHECR observato…
TUS (Tracking Ultraviolet Set-up), the first orbital telescope of ultra-high energy cosmic rays (UHECRs), has demonstrated that instruments of this kind have much broader capabilities and can also detect meteors, transient luminous events, anthropogenic glow and other processes taking place in Earth atmosphere in the UV frequency range. In this short letter, we address the question if an orbital UHECR detector can also register gamma-ray bursts (GRBs) via the fluorescent glow of irradiated nocturnal atmosphere. An analysis of the Fermi GBM catalog of GRBs and properties of several active and p…
The recently observed chirping signature in the light curves of Seyfert 1 galaxy SDSSJ1430$+$2303 could be explained by a late-inspiralling supermassive binary black hole (SMBBH) system in the galactic center, which will merge in the near future (or could have merged already). For the merging SMBBH scenario, SDSSJ1430$+$2303 can be a source of nonlinear gravitational wave (GW) burst with memory (BWM), which may provide a promising target for future pulsar timing array (PTA) observations. In this work, we investigate the prospects for detecting the BWM signal from SDSSJ1430$+$2303 by the Intern…
If dark matter interactions with Standard Model particles are $CP$-violating, then dark matter annihilation/decay can produce photons with a net circular polarization. We consider the prospects for experimentally detecting evidence for such a circular polarization. We identify optimal models for dark matter interactions with the Standard Model, from the point of view of detectability of the net polarization, for the case of either symmetric or asymmetric dark matter. We find that, for symmetric dark matter, evidence for net polarization could be found by a search of the Galactic Center by an i…
One possible approach for detecting ultra-high-energy cosmic rays and neutrinos is to search for radio emission from extensive air showers created when they interact in the atmosphere of Jupiter, effectively utilizing Jupiter as a particle detector. We investigate the potential of this approach. For searches with current or planned radio telescopes we find that the effective area for detection of cosmic rays is substantial (~3*10^7 km^2), but the acceptance angle is so small that the typical geometric aperture (~10^3 km^2 sr) is less than that of existing terrestrial detectors, and cosmic rays…
Recently, Tamanini & Danielski (2019) discussed the possibility to detect circumbinary exoplanets (CBPs) orbiting double white dwarfs (DWDs) with the Laser Interferometer Space Antenna (LISA). Extending their methods and criteria, we discuss the prospects for detecting exoplanets around DWDs not only by LISA, but also by Taiji, a Chinese space-borne gravitational-wave (GW) mission which has a slightly better sensitivity at low frequencies. We first explore how different binary masses and mass ratios affect the abilities of LISA and Taiji to detect CBPs. Second, for certain known detached DWDs …
From deflections in galactic and extragalactic magnetic fields energy dependent structures in the arrival directions of ultra-high energy cosmic rays (UHECR) are expected. We propose to characterize these structures by the strength of collimation of energy along the principal axes in selected regions in the sky. While the strength of collimation are indicators of anisotropy in the arrival distribution of UHECR, the orientation of the principal system holds information about the direction of the deflections of UHECR. We discuss the method and present expected limits on the strength of deflectio…
We propose an upgrade to Advanced LIGO (aLIGO), named LIGO-LF, that focuses on improving the sensitivity in the 5-30 Hz low-frequency band, and we explore the upgrade's astrophysical applications. We present a comprehensive study of the detector's technical noises and show that with technologies currently under development, such as interferometrically sensed seismometers and balanced-homodyne readout, LIGO-LF can reach the fundamental limits set by quantum and thermal noises down to 5 Hz. These technologies are also directly applicable to the future generation of detectors. We go on to conside…
A low-amplitude periodic signal in the radial velocity (RV) time series of Barnard's Star was recently attributed to a planetary companion with a minimum mass of ${\sim}$3.2 $M_\oplus$ at an orbital period of $\sim$233 days. The relatively long orbital period and the proximity of Barnard's Star to the Sun raises the question whether the true mass of the planet can be constrained by accurate astrometric measurements. By combining the assumption of an isotropic probability distribution of the orbital orientation with the RV-analysis results, we calculated the probability density function of the …
Astrometric Methods for Detecting Exomoons Orbiting Imaged Exoplanets: Prospects for Detecting Moons Orbiting a Giant Planet in $α$ Centauri A's Habitable Zone
提出模拟框架研究通过天体测量信号探测系外卫星，发现专用空间望远镜和39m地基望远镜可在五年任务中探测到环绕 $α$ 半人马座 A 假想巨行星的地球大小卫星。
The goal of finding and characterizing nearby Earth-like planets is driving many NASA high-contrast flagship mission concepts, the latest of which is known as the Advanced Technology Large-Aperture Space Telescope (ATLAST). In this article, we calculate the optimal spectral resolution $R=λ/δλ$ and minimum signal-to-noise ratio per spectral bin (SNR), two central design requirements for a high-contrast space mission, in order to detect signatures of water, oxygen, and chlorophyll on an Earth twin. We first develop a minimally parametric model and demonstrate its ability to fit synthetic and obs…
The Lunar Ultraviolet Cosmic Imager (LUCI) is a near-ultraviolet (NUV) telescope with all-spherical mirrors, designed and built to fly as a scientific payload on a lunar mission with Team Indus - the original Indian entry to the Google Lunar X-Prize. Observations from the Moon provide a unique opportunity of a stable platform with an unobstructed view of the space at all wavelengths due to the absence of atmosphere and ionosphere. LUCI is an 80 mm aperture telescope, with a field of view of 27.6'x 20.4' and a spatial resolution of 5'', will scan the sky in the NUV (200-320 nm) domain to look f…
Space-based gravitational wave interferometers are sensitive to the galactic population of ultra-compact binaries. An important subset of the ultra-compact binary population are those stars that can be individually resolved by both gravitational wave interferometers and electromagnetic telescopes. The aim of this paper is to quantify the multi-messenger potential of space-based interferometers with arm-lengths between 1 and 5 Gm. The Fisher Information Matrix is used to estimate the number of binaries from a model of the Milky Way which are localized on the sky by the gravitational wave detect…
Over the past five years, radial-velocity and transit techniques have revealed a new population of Earth-like planets with masses of a few Earth masses. Their very close orbit around their host star requires an exquisite inner working angle to be detected in direct imaging and sets a challenge for direct imagers that work in the visible range, like SPHERE / ZIMPOL. Among all known exoplanets with less than twenty-five Earth-masses we first predict the best candidate for direct imaging. Our primary objective is then to provide the best instrument setup and observing strategy for detecting such …
The detection of satellites around extrasolar planets, so called exomoons, remains a largely unexplored territory. In this work, we study the potential of detecting these elusive objects from radial velocity monitoring of self-luminous directly imaged planets. This technique is now possible thanks to the development of dedicated instruments combining the power of high-resolution spectroscopy and high-contrast imaging. First, we demonstrate a sensitivity to satellites with a mass ratio of 1-4% at separations similar to the Galilean moons from observations of a brown-dwarf companion (HR 7672 B; …
The technique of transmission spectroscopy -- the variation of the planetary radius with wavelength due to opacity sources in the planet's terminator region -- has been to date one of the most successful in the characterization of exoplanet atmospheres, providing key insights into the composition and structure of these distant worlds. A common assumption made when using this technique, however, is that the variations are the same in the entire terminator region. In reality, the morning and evening terminators might have distinct temperature, pressure and thus compositional profiles due to the …
Prospects for gravitational wave and ultra-light dark matter detection with binary resonances beyond the secular approximation
Fermilab（费米国家加速器实验室）；Kavli Institute for Cosmological Physics, University of Chicago（芝加哥大学卡弗里宇宙物理学研究所）；Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology（巴塞罗那科技研究院高能物理研究所）；Institució Catalana de Recerca i Estudis Avançats (ICREA)（加泰罗尼亚高级研究学院）；LTE, Observatoire de Paris, Université PSL, Sorbonne Université, Université de Lille, LNE, CNRS（巴黎天文台激光技术与应用实验室（隶属于巴黎文理研究大学、索邦大学、里尔大学及法国国家科学研究中心））；Barcelona Supercomputing Center (BSC)（巴塞罗那超级计算中心）；Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；DAMTP, University of Cambridge（剑桥大学数学物理理论系）
