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Tests of photometry: the case of the NGC 3370 ACS field
Jang, In Sung
A critical analysis and comparison of different methods for obtaining point spread function (PSF) photometry are carried out. Deep ACS observations of NGC 3370 were reduced using four distinct approaches. These reductions explore a number of methodological differences: software packages (DAOPHOT and DOLPHOT), input images (individual and stacked f…
Identifying preflare spectral features using explainable artificial intelligence
Kleint, Lucia; Panos, Brandon; Zbinden, Jonas
The prediction of solar flares is of practical and scientific interest; however, many machine learning methods used for this prediction task do not provide the physical explanations behind a model's performance. We made use of two recently developed explainable artificial intelligence techniques called gradient-weighted class activation mapping (G…
FUMES. III. Ultraviolet and Optical Variability of M-dwarf Chromospheres
France, Kevin; Youngblood, Allison; Pineda, J. Sebastian +2 more
We obtained ultraviolet and optical spectra for nine M dwarfs across a range of rotation periods to determine whether they showed stochastic intrinsic variability distinguishable from flares. The ultraviolet spectra were observed during the Far Ultraviolet M-dwarf Evolution Survey Hubble Space Telescope program using the Space Telescope Imaging Sp…
Magnetic Fields in the Horsehead Nebula
Pattle, Kate; Hwang, Jihye; Kim, Jongsoo +2 more
We present the first polarized dust emission measurements of the Horsehead Nebula, obtained using the POL-2 polarimeter on the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera on the James Clerk Maxwell Telescope. The Horsehead Nebula contains two submillimeter sources: a photodissociation region (PDR; SMM1) and a starless core (SMM2).…
CLEAR: The Morphological Evolution of Galaxies in the Green Valley
Papovich, Casey; Cleri, Nikko J.; Giavalisco, Mauro +8 more
Quiescent galaxies having more compact morphologies than star-forming galaxies has been a consistent result in the field of galaxy evolution. What is not clear is at what point this divergence happens, i.e., when do quiescent galaxies become compact, and how big of a role does the progenitor effect play in this result? Here we aim to model the mor…
Prediction of the Transit Time of Coronal Mass Ejections with an Ensemble Machine-learning Method
Yang, Y.; Feng, X. S.; Chen, P. F. +2 more
Coronal mass ejections (CMEs), a kind of violent solar eruptive activity, can exert a significant impact on space weather. When arriving at the Earth, they interact with the geomagnetic field, which can boost the energy supply to the geomagnetic field and may further result in geomagnetic storms, thus having potentially catastrophic effects on hum…
The Tilt of the Velocity Ellipsoid of Different Galactic Disk Populations
Sun, Weixiang; Shen, Han; Liu, Xiaowei
The tilt of the velocity ellipsoid is a helpful tracer of the gravitational potential of the Milky Way. In this paper, we use nearly 140,000 red clump (RC) stars selected from LAMOST and Gaia to make a detailed analysis of the tilt of the velocity ellipsoid for various populations, as defined by stellar ages and chemical information, within 4.5 ≤ …
Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method
Butler, K.; Przybilla, N.; Aschenbrenner, P.
Context. Late O-type stars at luminosities log L/L⊙ ≲ 5.2 show weak winds with mass-loss rates lower than 10−8 M⊙ yr−1. This implies that, unlike their more massive and more luminous siblings, their photospheric layers are not strongly affected by the stellar wind.
Aims: A hybrid non-local thermodyn…
WASP-131 b with ESPRESSO - I. A bloated sub-Saturn on a polar orbit around a differentially rotating solar-type star
Lafarga, M.; Lendl, M.; Allart, R. +17 more
In this paper, we present observations of two high-resolution transit data sets obtained with ESPRESSO of the bloated sub-Saturn planet WASP-131 b. We have simultaneous photometric observations with NGTS and EulerCam. In addition, we utilized photometric light curves from TESS, WASP, EulerCam, and TRAPPIST of multiple transits to fit for the plane…
Photometric study of the late-time near-infrared plateau in Type Ia supernovae
Galbany, L.; Inserra, C.; Gutiérrez, C. P. +23 more
We present an in-depth study of the late-time near-infrared plateau in Type Ia supernovae (SNe Ia), which occurs between 70 and 500 d. We double the existing sample of SNe Ia observed during the late-time near-infrared plateau with new observations taken with the Hubble Space Telescope, Gemini, New Technology Telescope, the 3.5-m Calar Alto Telesc…