TY  - JOUR
A1  - Ilin, Ekaterina
A1  - Poppenhäger, Katja
A1  - Alvarado-Gómez, Julián David
T1  - Localizing flares to understand stellar magnetic fields and space weather in exo-systems
JF  - Astronomische Nachrichten = Astronomical notes
N2  - Stars are uniform spheres, but only to first order. The way in which stellar rotation and magnetism break this symmetry places important observational constraints on stellar magnetic fields, and factors in the assessment of the impact of stellar activity on exoplanet atmospheres. The spatial distribution of flares on the solar surface is well known to be nonuniform, but elusive on other stars. We briefly review the techniques available to recover the loci of stellar flares, and highlight a new method that enables systematic flare localization directly from optical light curves. We provide an estimate of the number of flares we may be able to localize with the Transiting Exoplanet Survey Satellite, and show that it is consistent with the results obtained from the first full sky scan of the mission. We suggest that nonuniform flare latitude distributions need to be taken into account in accurate assessments of exoplanet habitability.
KW  - stars
KW  - activity - stars
KW  - flare - stars
KW  - magnetic fields - methods
KW  - data
KW  - analysis
Y1  - 2022
U6  - https://doi.org/10.1002/asna.20210111
SN  - 1521-3994
VL  - 343
IS  - 4
PB  - Berlin
CY  - Wiley-VCH
ER  - 
TY  - JOUR
A1  - Dineva, Ekaterina Ivanova
A1  - Verma, Meetu
A1  - Gonzalez Manrique, Sergio Javier
A1  - Schwartz, Pavol
A1  - Denker, Carsten
T1  - Cloud model inversions of strong chromospheric absorption lines using principal component analysis
JF  - Astronomische Nachrichten = Astronomical notes
N2  - High-resolution spectroscopy of strong chromospheric absorption lines delivers nowadays several millions of spectra per observing day, when using fast scanning devices to cover large regions on the solar surface. Therefore, fast and robust inversion schemes are needed to explore the large data volume. Cloud model (CM) inversions of the chromospheric H alpha line are commonly employed to investigate various solar features including filaments, prominences, surges, jets, mottles, and (macro-) spicules. The choice of the CM was governed by its intuitive description of complex chromospheric structures as clouds suspended above the solar surface by magnetic fields. This study is based on observations of active region NOAA 11126 in H alpha, which were obtained November 18-23, 2010 with the echelle spectrograph of the vacuum tower telescope at the Observatorio del Teide, Spain. Principal component analysis reduces the dimensionality of spectra and conditions noise-stripped spectra for CM inversions. Modeled H alpha intensity and contrast profiles as well as CM parameters are collected in a database, which facilitates efficient processing of the observed spectra. Physical maps are computed representing the line-core and continuum intensity, absolute contrast, equivalent width, and Doppler velocities, among others. Noise-free spectra expedite the analysis of bisectors. The data processing is evaluated in the context of "big data," in particular with respect to automatic classification of spectra.
KW  - sun
KW  - activity - sun
KW  - atmosphere - sun
KW  - chromosphere - methods
KW  - data
KW  - analysis - techniques
KW  - spectroscopic - astronomical databases
KW  - miscellaneous
Y1  - 2020
U6  - https://doi.org/10.1002/asna.202013652
SN  - 0004-6337
SN  - 1521-3994
VL  - 341
IS  - 1
SP  - 64
EP  - 78
PB  - Wiley-VCH Verl.
CY  - Berlin
ER  -