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Context. A defining characteristic of active galactic nuclei (AGN) that distinguishes them from other astronomical sources is their stochastic variability, which is observable across the entire electromagnetic spectrum. Upcoming optical…

The galactic bulge is a significant part of our galaxy, but it is hard to observe, being both distant and covered by dust in the disk. Therefore there do not exist many hi-res optical spectra of bulge stars with large wavelength coverage,…

Astrophysics of Galaxies · Physics 2017-02-08 H. Jönsson , N. Ryde , T. Nordlander , A. Pehlivan , H. Hartman , P. Jönsson , K. Eriksson

The determination of photospheric abundances in late-type stars from spectroscopic observations is a well-established field, built on solid theoretical foundations. Improving those foundations to refine the accuracy of the inferred…

Solar and Stellar Astrophysics · Physics 2016-07-27 Carlos Allende Prieto

The application of artificial neural networks (ANNs) for the estimation of HI gas mass fraction (\fgas) is investigated, based on a sample of 13,674 galaxies in the Sloan Digital Sky Survey (SDSS) with HI detections or upper limits from the…

Astrophysics of Galaxies · Physics 2016-12-07 Hossen Teimoorinia , Sara L. Ellison , David R. Patton

[Abbreviated] Context. Given their high luminosities (L>~10^4Lsun), red supergiants (RSGs) are good tracers of the chemical abundances of the young stellar population in the Milky Way and nearby galaxies. However, previous abundance…

We combine Sloan Digital Sky Survey spectra of 22,000 luminous, red, bulge-dominated galaxies to get high S/N average spectra in the rest-frame optical and ultraviolet (2600A to 7000A). The average spectra of these massive, quiescent…

Aims: We describe our newly developed approach to detailed abundance analysis from integrated-light high-dispersion spectra of star clusters. As a pilot project, we measure abundances of several elements for three globular clusters (GCs) in…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-11 S. S. Larsen , J. P. Brodie , J. Strader

Analysis of x-ray absorption spectroscopy (XAS) data often involves the removal of artifacts or glitches from the acquired signal, a process commonly known as deglitching. Glitches result either from specific orientations of monochromator…

Data Analysis, Statistics and Probability · Physics 2020-12-01 Samuel M. Wallace , Marco A. Alsina , Jean-François Gaillard

A number of large spectroscopic surveys of stars in the Milky Way are under way or are being planned. In this context it is important to discuss the extent to which elemental abundances can be used as discriminators between different (known…

Astrophysics of Galaxies · Physics 2015-06-15 Lennart Lindegren , Sofia Feltzing

Time domain astronomy and the increasing number of exoplanet candidates call for reliable, robust, and automatic wavelength calibration. We present an algorithm for wavelength calibrating \'echelle spectrographs that uses order-by-order…

Instrumentation and Methods for Astrophysics · Physics 2020-06-24 G. M. Brandt , T. D. Brandt , C. McCully

With the availability of multi-object spectrometers and the designing \& running of some large scale sky surveys, we are obtaining massive spectra. Therefore, it becomes more and more important to deal with the massive spectral data…

Instrumentation and Methods for Astrophysics · Physics 2023-12-27 Xiangru Li , Yangtao Lin , Kaibin Qiu

We analyze existing measurements of [Fe/H] and [$\alpha$/Fe] for individual red giant branch (RGB) stars in the Giant Stellar Stream (GSS) of M31 to determine whether spatial abundance gradients are present. These measurements were obtained…

Astrophysics of Galaxies · Physics 2021-07-14 Ivanna Escala , Karoline M. Gilbert , Jennifer Wojno , Evan N. Kirby , Puragra Guhathakurta

Optimal extraction is a key step in processing the raw images of spectra as registered by two-dimensional detector arrays to a one-dimensional format. Previously reported algorithms reconstruct models for a mean one-dimensional spatial…

Instrumentation and Methods for Astrophysics · Physics 2015-06-18 M. Zechmeister , G. Anglada-Escudé , A. Reiners

In 2006 ESO Council authorized a Phase B study of a European AO-telescope with a 42 m segmented primary with a 5-mirror design, the E-ELT. Several reports and working groups have already presented science cases for an E-ELT, specifically…

Astrophysics of Galaxies · Physics 2015-05-18 Nils Ryde

High-resolution spectrographs open a detailed window onto the atmospheres of stars and planets. As the number of systems observed with different instruments grows, it is crucial to develop a standard in analyzing spectral time series of…

The X-shooter Spectral Library (XSL) is a large empirical stellar library used as a benchmark for the development of stellar population models. The inclusion of $\alpha$-elements abundances is crucial to disentangling the chemical evolution…

Astrophysics of Galaxies · Physics 2023-04-19 Pablo Santos-Peral , Patricia Sánchez-Blázquez , Alexandre Vazdekis , Pedro A. Palicio

The VLT-FLAMES Survey of Massive Stars was an ESO Large Programme to understand rotational mixing and stellar mass-loss in different metallicity environments, in order to better constrain massive star evolution. We gathered high-quality…

The 8m class telescopes allow for the first time to study stars of external galaxies with the same resolution and S/N ratio which has been so far used for Galactic stars. It is quite likely that this study will shake some of our current…

Astrophysics · Physics 2016-11-03 P. Bonifacio , P. Molaro

We propose a line list that may be useful for the abundance analysis of G-type stars in the wavelength range 4080 -- 6780 A. It is expected that the line list will be useful for surveys/libraries with overlapping spectral regions (e.g.…

Solar and Stellar Astrophysics · Physics 2023-10-09 T. Sahin , M. Marismak , N. Cinar , S. Bilir