SUPERSHARP – Segmented Unfolding Primary for Exoplanet Research via Spectroscopic High Angular Resolution Photography [IMA]

We propose to search for biosignatures in the spectra of reflected light from about 100 Earth-sized planets that are already known to be orbiting in their habitable zones (HZ). For a sample of G and K type hosts, most of these planets will be between 25 and 50 milli-arcsec (mas) from their host star and 1 billion to 10 billion times fainter. To separate the planet’s image from that of its host star at the wavelength (763nm) of the oxygen biosignature we need a telescope with an aperture of 16 metres. Furthermore, the intensity of the light from the host star at the position in the image of the exoplanet must be suppressed otherwise the exoplanet will be lost in the glare.
This presents huge technical challenges. The Earth’s atmosphere is turbulent which makes it impossible to achieve the required contrast from the ground at 763nm. The telescope therefore needs to be in space and to fit the telescope in the rocket fairing it must be a factor of 4 or more times smaller when folded than when operational. To obtain spectroscopy of the planet’s biosignature at 763nm we need to use an integral field spectrometer (IFS) with a field of view (FOV) of 1000 x 1000 milli-arcsec (mas) and a spectral resolution of 100. This is a device that simultaneously takes many pictures of the exoplanet each at a slightly different wavelength which are then recorded as a data cube with two spatial dimensions and one wavelength dimension. In every data cube wavelength slice, the background light from the host star at the location of the planet image must be minimised. This is achieved via a coronagraph which blocks the light from the host star and active/adaptive optics techniques which continuously maintain very high accuracy optical alignment to make the images as sharp as possible. These are the technical challenges to be addressed in a design study.

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I. Parry, D. Queloz, G. Kennedy, et. al.
Fri, 19 Jan 18

Comments: A proposal in response to the ESA New Science Ideas call. Sept 2016. 25 pages

Neural network-based preprocessing to estimate the parameters of the X-ray emission of a single-temperature thermal plasma [IMA]

We present data preprocessing based on an artificial neural network to estimate the parameters of the X-ray emission spectra of a single-temperature thermal plasma. The method finds appropriate parameters close to the global optimum. The neural network is designed to learn the parameters of the thermal plasma (temperature, abundance, normalisation, and redshift) of the input spectra. After training using 9000 simulated X-ray spectra, the network has grown to predict all the unknown parameters with uncertainties of about a few percent. The performance dependence on the network structure has been studied. We applied the neural network to an actual high-resolution spectrum obtained with {\it Hitomi}. The predicted plasma parameters agreed with the known best-fit parameters of the Perseus cluster within $\lesssim10$\% uncertainties. The result shows a possibility that neural networks trained by simulated data can be useful to extract a feature built in the data, which would reduce human-intensive preprocessing costs before detailed spectral analysis, and help us make the best use of large quantities of spectral data coming in the next decades.

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Y. Ichinohe, S. Yamada, N. Miyazaki, et. al.
Fri, 19 Jan 18

Comments: Accepted for publication in MNRAS

IAU WG, Data-driven Astronomy Education and Public Outreach,current status and working plans [IMA]

IAU Inter-Commission B2-C1-C2 WG Data-driven Astronomy Education and Public Outreach (DAEPO) was launched officially in April 2017. With the development of many mega-science astronomical projects, for example CTA, DESI, EUCLID, FAST, GAIA, JWST, LAMOST, LSST, SDSS, SKA, and large scale simulations, astronomy has become a Big Data science. Astronomical data is not only necessary resource for scientific research, but also very valuable resource for education and public outreach (EPO), especially in the era of Internet and Cloud Computing. IAU WG Data-driven Astronomy Education and Public Outreach is hosted at the IAU Division B (Facilities, Technologies and Data Science) Commission B2 (Data and Documentation), and organized jointly with Commission C1 (Astronomy Education and Development), Commission C2 (Communicating Astronomy with the Public), Office of Astronomy for Development (OAD), Office for Astronomy Outreach (OAO) and several other non IAU communities, including IVOA Education Interest Group, American Astronomical Society Worldwide Telescope Advisory Board, Zooniverse project and International Planetarium Society. The working group has the major objectives to: Act as a forum to discuss the value of astronomy data in EPO, the advantages and benefits of data driven EPO, and the challenges facing to data driven EPO; Provide guidelines, curriculum, data resources, tools, and e-infrastructure for data driven EPO; Provide best practices of data driven EPO. In the paper, backgrounds, current status and working plans in the future are introduced. More information about the WG is available at: this http URL

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C. Cui and S. Li
Wed, 17 Jan 18

Comments: 4 pages, presented at the Astronomical Data Analysis Software and Systems (ADASS) XXVII conference, Santiago, Chile, October 2017

The Third Workshop on Extremely Precise Radial Velocities: The New Instruments [IMA]

The Third Workshop on Extremely Precise Radial Velocities was held at the Penn Stater Conference Center and Hotel in State College, Pennsylvania, USA from 2016 August 14 to 17, and featured over 120 registrants from around the world. Here we provide a brief description of the conference, its format, and its session topics and chairs. 23 instrument teams were represented in plenary talks, and we present a table containing the basic characteristics of their new precise Doppler velocimeters.

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J. Wright and P. Robertson
Wed, 17 Jan 18

Comments: Table available as PDF at this https URL

VLBI imaging of M81* at 3.4 mm with source-frequency phase-referencing [IMA]

We report on the first VLBI image of the M81 nucleus (M81) at a wavelength of 3.4 mm, obtained with the source-frequency phase-referencing (SFPR) technique. Thanks to the SFPR calibration, the coherent integration time could be eventually increased by more than an order of magnitude, which enabled the detection of fringes at the level of 45 mJy beam-1 with a dynamic range higher than 130:1. This paves the way toward future mm/sub-mm VLBI observations of weaker sources. From the analysis of the M81 visibilities, a core size of ~50 uas at 3.4 mm was estimated. This follows the power-law relationship with wavelength lambda^0.88, reported previously at lower frequencies. These results constrain the core size (at 3.4 mm) to a minimum of ~80 Schwarzschild radii of M81*.

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W. Jiang, Z. Shen, D. Jiang, et. al.
Tue, 16 Jan 18

Comments: 10 pages, 5 figures,accepted by ApJ Letter

Ten years of speckle interferometry at SOAR [IMA]

Since 2007, close binary and multiple stars are observed by speckle interferometry at the 4.1 m Southern Astrophysical Research (SOAR) telescope. The HRCam instrument, observing strategy and planning, data processing and calibration methods, developed and improved during ten years, are presented here in a concise way. Thousands of binary stars were measured with diffraction-limited resolution (29mas at 540nm wavelength) and a high accuracy reaching 1mas; two hundred new pairs or subsystems were discovered. To date, HRCam has performed over 11000 observations with a high efficiency (up to 300 stars per night). An overview of the main results delivered by this instrument is given.

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A. Tokovinin
Tue, 16 Jan 18

Comments: Accepted by PASP. 12 pages, 11 figures

Cobalt: A GPU-based correlator and beamformer for LOFAR [IMA]

For low-frequency radio astronomy, software correlation and beamforming on general purpose hardware is a viable alternative to custom designed hardware. LOFAR, a new-generation radio telescope centered in the Netherlands with international stations in Germany, France, Ireland, Latvia, Poland, Sweden and the UK, has successfully used software real-time processors based on IBM Blue Gene technology since 2004. Since then, developments in technology have allowed us to build a system based on commercial off-the-shelf components that combines the same capabilities with lower operational cost. In this paper we describe the design and implementation of a GPU-based correlator and beamformer with the same capabilities as the Blue Gene based systems. We focus on the design approach taken, and show the challenges faced in selecting an appropriate system. The design, implementation and verification of the software system shows the value of a modern test-driven development approach. Operational experience, based on three years of operations, demonstrates that a general purpose system is a good alternative to the previous supercomputer-based system or custom-designed hardware.

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P. Broekema, J. Mol, R. Nijboer, et. al.
Tue, 16 Jan 18

Comments: N/A