1908.03584
An optically targeted search for gravitational waves emitted by Core-collapse supernovae during the first and second observing runs of Advanced LIGO and Advanced Virgo
The LIGO scientific collaboration, the Virgo collaboration, et al
We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. For neutrino-driven explosions the distance at which we reach 50% detection efficiency is approaching 5 kpc, and for magnetorotationally-driven explosions is up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the gravitational-wave data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using \textit{ad hoc} harmonic signals windowed with Gaussian envelopes we constrained the gravitational-wave energy emitted during core-collapse at the levels of $4.27\times 10^{-4}\,M_\odot c^2$ and $1.28\times 10^{-1}\,M_\odot c^2$ for emissions at 235 Hz and 1304 Hz respectively. These constraints are two orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo and GEO~600 data.
An optically targeted search for gravitational waves emitted by Core-collapse supernovae during the first and second observing runs of Advanced LIGO and Advanced Virgo
The LIGO scientific collaboration, the Virgo collaboration, et al
We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. For neutrino-driven explosions the distance at which we reach 50% detection efficiency is approaching 5 kpc, and for magnetorotationally-driven explosions is up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the gravitational-wave data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using \textit{ad hoc} harmonic signals windowed with Gaussian envelopes we constrained the gravitational-wave energy emitted during core-collapse at the levels of $4.27\times 10^{-4}\,M_\odot c^2$ and $1.28\times 10^{-1}\,M_\odot c^2$ for emissions at 235 Hz and 1304 Hz respectively. These constraints are two orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo and GEO~600 data.
1908.03611
New Astronomy Reviews Special Issue: History of Kepler's major exoplanet "Firsts"
Lissauer, Eisberg
NASA's Kepler Mission revolutionized exoplanet science in the early part of the 2010's. Looking back from the perspective of the end of that decade, Kepler appears to have burst upon the scene ready for battle, like Athena springing forth, fully formed, from the head of Zeus. The story was not so simple. Kepler's first major exoplanet discoveries were not announced until more than a year had passed since the spacecraft started collecting scientific data, and by that time many exoplanet scientists not working on the project had become frustrated with the lack of results coming from the Kepler project. But an immense amount of work was required to develop the tools and conceptual framework needed to harvest the abundant field of data that the spacecraft was producing. This issue contains articles describing some of the research efforts, most of which took place behind the scenes, that led to the announcements/publication of several of Kepler's major exoplanet "firsts", written by the scientists who led the landmark discovery papers.
1908.03854
Wide-angle redshift-space distortions at quasi-linear scales: corss-correlation functions from Zel'dovich approximation
Taruya, et al
Redshift-space distortions (RSD) in galaxy redshift surveys generally break both the isotropy and homogeneity of galaxy distribution. While the former aspect is particularly highlighted as a probe of growth of structure induced by gravity, the latter aspect, often quoted as wide-angle RSD but ignored in most of the cases, will become important and critical to account for as increasing the statistical precision in next-generation surveys. However, the impact of wide-angle RSD has been mostly studied using linear perturbation theory. In this paper, employing the Zel'dovich approximation, i.e., first-order Lagrangian perturbation theory for gravitational evolution of matter fluctuations, we present a quasi-linear treatment of wide-angle RSD, and compute the cross-correlation function. The present formalism consistently reproduces linear theory results, and can be easily extended to incorporate relativistic corrections (e.g., gravitational redshift).
1908.03854
Wide-angle redshift-space distortions at quasi-linear scales: corss-correlation functions from Zel'dovich approximation
Taruya, et al
Redshift-space distortions (RSD) in galaxy redshift surveys generally break both the isotropy and homogeneity of galaxy distribution. While the former aspect is particularly highlighted as a probe of growth of structure induced by gravity, the latter aspect, often quoted as wide-angle RSD but ignored in most of the cases, will become important and critical to account for as increasing the statistical precision in next-generation surveys. However, the impact of wide-angle RSD has been mostly studied using linear perturbation theory. In this paper, employing the Zel'dovich approximation, i.e., first-order Lagrangian perturbation theory for gravitational evolution of matter fluctuations, we present a quasi-linear treatment of wide-angle RSD, and compute the cross-correlation function. The present formalism consistently reproduces linear theory results, and can be easily extended to incorporate relativistic corrections (e.g., gravitational redshift).
1908.04089
Biofluorescent Worlds I: Global biological fluorescence as a biosignature
O'Malley-James, Kaltenegger
In this paper, we analyze a new possible biological surface feature for habitable worlds orbiting other stars: biofluorescence. High ultraviolet (UV) and blue radiation fluxes drive the strongest biofluorescence in terrestrial fluorescent pigments and proteins. F stars emit more blue and UV radiation than the Sun, while planets and exomoons orbiting such stars remain in the habitable zone for 2-4 Gyr; a timespan that could allow a complex biosphere to develop. Therefore we propose biofluorescence as a new surface biosignature for F star planets. We investigate how the extra emission from surface fluorescence could cause observable signals at specific wavelengths in the visible spectrum. Using the absorption and emission characteristics of common coral fluorescent pigments and proteins, we simulate the increased emission at specific visible wavelengths caused by strong fluorescence, accounting for the effects of different (non-fluorescent) surface features, atmospheric absorption and cloud-cover. Our model shows that exoplanets with a fluorescent biosphere could have characteristic surface colours that allow the presence of surface life to be inferred from observations with upcoming telescopes.
1908.04283
Brownian motion of supermassive black holes in galaxy cores
Di Cintio, et al
We investigate the dynamics of supermassive black holes (SMBHs) in galactic cores by means of a semi-analytic model based on the Langevin equation, including dynamical friction and stochastic noise accounting for the gravitational interactions with stars. The model is validated against direct $N$-body simulations of intermediate-mass black holes in stellar clusters where a realistic number of particles is accessible. For the galactic case, we find that the SMBH experiences a Brownian-like motion with a typical displacement from the geometric center of the Galaxy of a few parsecs, for system parameters compatible with M87. \keywords{stellar dynamics, black hole physics, methods: n-body simulations, methods: statistical.
No comments:
Post a Comment