1507.03010
ASASSN-15lh: the most luminous supernova ever discovered
Dong et al
As the title says: at z=0.2326, reached absolute magnitude of M_u,AB~23.5 and bolometric luminosity L_bol~2.2e45 erg/s, which is >~2x more luminous than any previously known supernova. Its spectra match the H-poor sub-class of super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are poorly understood. In contrast to known SLSNe-I, most of which reside in star-forming, dwarf galaxies, its host appears to be a luminous galaxy (M_V~-22; M_K~-25.1) with little star formation. In the two months since its first detection, ASASSN-15lh has radiated ~7.5e51 ergs, challenging the popular magnetar model for the engine of SLSNe-I.
1507.03086
RCSLenS: Testing gravitational physics through the cross-correlation of weak lensing and large-scale structure
Blake, Joudaki, Heymans, Choi, Erben, Harnois-Deraps, Hildebrandt, Joachimi, Nakajima, van Waerbeke, Viola
The unknown nature of DE motivates continued cosmological tests of large-scale gravitational physics. Present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxy-galaxy lensing. Take advantage of the latest generation of deep, overlapping imaging and spectroscopic datasets, combining RCSLenS CFHTLenS, WiggleZ Dark Energy survey and BOSS. Quantify the results using the "gravitational slip" statistic E_G, which is estimated at 0.48±0.10 at z=0.32 and 0.30±0.07 at z=0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of GR, for perturbed FRW metric in a universe dominated by a cosmological constant, which are E_G=0.41 and 0.36 at these respective redshifts. The combination of z-space distortion and gravitational lensing data from current and future galaxy surveys will offer increasingly stringent tests of fundamental cosmology.
1507.03212
Nearby stars as gravitational wave detectors
Lopes, Silk
Sun-like stellar oscillations are excited by turbulent convection and have been discovered in some 500 main sequence and sub-giant stars and in more than 12k red giant stars. When such stars are near gravitational wave sources, low-order quadrupole acoustic modes are also excited above the experimental threshold of detectability, and they can be observed, n principle, in the acoustic spectra of these stars. Such stars form a set of natural detectors to search for gravitational waves over a large spectra frequency range, from 1e-7 Hz to 1e-2 Hz. In particular, these stars can probe the 1e-6Hz-13-4 Hz spectral window which cannot be probed by current conventional gravitational wave detectors, such as SKA and eLISA. The PLATO stellar seismic mission will achieve photospheric velocity amplitude accuracy of cm/s. For a gravitational wave search,l need to achieve accuracies of the order of 1e-2 cm/s, i.e., at least one generation beyond PLATO. However, found that multi-body stellar systems have the ideal setup for this type of gravitational wave search. This is the case for triple stellar systems formed by a compact binary and an oscillating star. Continuous monitoring of the oscillation spectra of these stars to a distance of up to a kpc could lead to the discovery of gravitational waves originating in the galaxy or even elsewhere in the universe. Moreover, unlike experimental detectors, this observational network of stars will allow studies of progression of gravitational waves throughout space.
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