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I propose a spatial-mode demultiplexing (SPADE) measurement scheme for the far-field imaging of spatially incoherent optical sources. For any object too small to be resolved by direct imaging under the diffraction limit, I show that SPADE…

Optics · Physics 2017-03-01 Mankei Tsang

We make use of new subgrid model of turbulent mixing to accurately follow the cosmological evolution of the first stars, the mixing of their supernova ejecta, and the impact on the chemical composition of the Galactic Halo. Using the…

Astrophysics of Galaxies · Physics 2017-01-04 Richard Sarmento , Evan Scannapieco , Liubin Pan

We introduce and publicly release a new code, ADAPTSMOOTH, which serves to smooth astronomical images in an adaptive fashion, in order to enhance the signal-to-noise ratio (S/N). The adaptive smoothing scheme allows to take full advantage…

Instrumentation and Methods for Astrophysics · Physics 2021-11-05 Stefano Zibetti

We have produced an atlas of Spitzer Infrared Spectrograph (IRS) spectra of mass-losing, evolved stars in the Large Magellanic Cloud. These stars were selected to have high mass-loss rates and so contribute significantly to the return of…

In this paper, we compare the currently available evolutionary tracks for Galactic massive stars. Our main goal is to highlight the uncertainties on the predicted evolutionary paths. We compute stellar evolution models with the codes MESA…

Solar and Stellar Astrophysics · Physics 2015-06-17 F. Martins , A. Palacios

Spectroscopic surveys require fast and efficient analysis methods to maximize their scientific impact. Here we apply a deep neural network architecture to analyze both SDSS-III APOGEE DR13 and synthetic stellar spectra. When our…

Instrumentation and Methods for Astrophysics · Physics 2018-02-21 Sebastien Fabbro , Kim Venn , Teaghan O'Briain , Spencer Bialek , Collin Kielty , Farbod Jahandar , Stephanie Monty

The light emitted from the stellar photosphere serves as a unique signature for the nature of stars. The behaviour of these stellar lines depend upon the surface temperature, mass, evolutionary status and chemical composition of the star.…

Solar and Stellar Astrophysics · Physics 2016-10-25 Priyanka Chaturvedi , Abhijit Chakraborty , B. G. Anandarao

Hydrodynamical simulations of stellar interactions require stable models of stars as initial conditions. Such initial models, however, are difficult to construct for giant stars because of the wide range in spatial scales of the hydrostatic…

Solar and Stellar Astrophysics · Physics 2017-02-22 Sebastian T. Ohlmann , Friedrich K. Roepke , Rüdiger Pakmor , Volker Springel

CONTEXT: Spectral-line asymmetries and wavelength shifts are signatures of hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but observed spectra are limited by blends, too few suitable lines,…

Astrophysics · Physics 2009-11-13 Dainis Dravins

Polarization has been detected at early times for all types of supernova, indicating that such systems result from or quickly develop some form of asymmetry. In addition, the detection of strong line polarization in supernovae is suggestive…

High Energy Astrophysical Phenomena · Physics 2015-05-19 K. T. Hole , D. Kasen , K. H. Nordsieck

We briefly describe the current version of the PHOENIX code. We then present some illustrative results from the modeling of Type Ia and Type II supernovae, hot stars, and irradiated giant planets. Good fits to observations can be obtained,…

One of the most intriguing spectral features of WR binary stars is the presence of time-dependent line profiles. Long term observations of several systems revealed the periodicity of this variability, synchronized with the orbital movement.…

Astrophysics · Physics 2009-11-11 D. Falceta-Goncalves , Z. Abraham , V. Jatenco-Pereira

The spectral flux density of stars can indicate their atmospheric physical properties. A detector can obtain any band flux density at the design stage. However, the band flux density is confirmed and fixed in the process of operation…

Instrumentation and Methods for Astrophysics · Physics 2018-09-26 Chuanxin Zhang , Yuan Yuan , Zhaoyang Yu , Fuqiang Wang , Heping Tan

The Nancy Grace Roman Space Telescope will carry out a wide-field imaging and slitless spectroscopic survey of Type Ia Supernovae to improve our understanding of dark energy. Crucial to this endeavor is obtaining supernova spectra…

Optical spectra of galaxies and quasars from large cosmological surveys are used to measure redshifts and infer distances. They are also rich with information on the intrinsic properties of these astronomical objects. However, their…

We developed a code that estimates distances to stars using measured spectroscopic and photometric quantities. We employ a Bayesian approach to build the probability distribution function over stellar evolutionary models given these data,…

Realistic physical phenomena exhibit random fluctuations across many scales in the input and output processes. Models of these phenomena require stochastic PDEs. For three-dimensional coupled (vector-valued) stochastic PDEs (SPDEs), for…

Computational Engineering, Finance, and Science · Computer Science 2022-08-24 Ajit Desai , Mohammad Khalil , Chris L. Pettit , Dominique Poirel , Abhijit Sarkar

High-precision stellar analyses require hydrodynamic 3D modeling. Such models predict changes across stellar disks of spectral line shapes, asymmetries, and wavelength shifts. For testing models in stars other than the Sun, spatially…

Solar and Stellar Astrophysics · Physics 2021-04-28 Dainis Dravins , Hans-Günter Ludwig , Bernd Freytag

We reconstruct the shape of the primordial power spectrum (PPS) using a smoothing spline. Our adapted smoothing spline technique provides a complementary method to existing efforts to search for smooth features in the PPS, such as a running…

Astrophysics · Physics 2009-11-13 Carolyn Sealfon , Licia Verde , Raul Jimenez