Day 1365

Tuesday.

1802.00817
Gravitational lensing of a star by a rotating black hole
Dokuchaev, Nazarova

The gravitational lensing of a finite star moving around a rotating Kerr black hole has been numerically calculated. Calculations for the direct image of the star and for the first and second light echos have been performed for the star moving with an orbital period of 3.22 h around the supermassive BH SgrA* at the Galactic Center.  Time dependencies for the observed star position on the celestial sphere, radiation flux from the star, frequency of detected radiation, major and minor semi axes of the lensed star image have been calculated and plotted.  The detailed observation of such lensing requires a space interferometer such as the Russian Millimetron project.  
[video: https://youtu.be/P6DneV0vk7U]


1802.01188
Where is Population II?
Mould, Bianchini, Forbes, Reichart

The concept of a pristine generation of stars, followed by a protogalactic era, and finally the mainstream stellar population is a plausible starting point for testing the physical understanding of early star formation.  This will be observationally driven as never before in the coming decade.  In this paper, search out observational tests of an idealized coeval and homogeneous distribution of population II stars.  Examine the spatial distribution of quasars, globular clusters, and they integrated free electron density of the IGM, in order to test the assumption of homogeneity.  Any real inhomogeneity implies a population II that is not coeval.


1802.01212
Non-Gaussian information from weak lensing data via deep learning
Gupta, Matilla, Hsu, Haiman

WL maps contain information beyond 2pt statistics on small scales.  Much recent work has tried to extract this information through a range of different observables or via nonlinear transformations of the lensing field.  Train and apply a 2D convolutional neural network to simulated noiseless lensing maps coving 96 different cosmological models over a range of Omega_m, sigma_8.  Using the area of the confidence contour in the Omega_m, sigma_8 plane as a figure-of-merit, derived from simulated convergence maps smoothed on a scale of 1.0 arcmin, show that the neural network yields ~5x tighter constraints than the power spectrum, and ~4 x tighter than the lensing peaks.  Such gains illustrate the extent to which WL data encode cosmological information not accessible to the power spectrum or even non-Gaussian statistics such as lensing peaks.


1802.01440
A robotic "Social Media" controlled observatory for education and research
Lane

The world's first robotic observatory to interact with its observers entirely using the social media platforms Facebook or Twitter.  The telescope "tweets" what it's doing, points live images, and responds to observer commands through a comprehensive command set.  Observation requests are queued and observed by a responsive queue engine.  Its architecture, social media based image processing capability and several usage examples are also described.