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Exploring the Sun's upper atmosphere with neural networks: Reversed patterns and the hot wall effect
Asensio Ramos, A.; Socas-Navarro, H.
We have developed an inversion procedure designed for high-resolution solar spectro-polarimeters, such as those of Hinode and the DKIST. The procedure is based on artificial neural networks trained with profiles generated from random atmospheric stratifications for a high generalization capability. When applied to Hinode data, we find a hot fine-s…
AT 2019qyl in NGC 300: Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary
Boyer, Martha L.; Kilpatrick, Charles D.; Coulter, David A. +39 more
Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered astrophysical transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in the nearby Sculptor Group galaxy NGC 300. T…
Fitting procedure for estimating interstellar extinction at high galactic latitudes
Malkov, Oleg; Kovaleva, Dana; Avdeeva, Aleksandra +1 more
We determine the interstellar extinction in the selected high-latitude areas of the sky based on Gaia EDR3 astrometry and photometry and spectroscopic data from RAVE survey. We approximate the results with the cosecant law in each area thus deriving the parameters of the barometric formula for different lines of sight. The distribution of the para…
Variability in Protoplanetary Nebulae. VIII. A New Sample of Southern Hemisphere Objects
Lu, Wenxian; Hrivnak, Bruce J.; Henson, Gary +5 more
As part of our continuing study of light variability in protoplanetary nebulae (PPNe), we present the results from a long-term study of nine southern hemisphere objects. We have monitored their light variations over a nine-year interval from 2010 to 2018. These were supplemented by data from the ASAS-SN and ASAS-3 surveys, leading to combined ligh…
An HST/STIS view of protoplanetary discs in Upper Scorpius: observations of three young M stars
Kalas, Paul; Carpenter, John; Ren, Bin +2 more
We present observations of three protoplanetary discs in visible scattered light around M-type stars in the Upper Scorpius OB association using the Space Telescope Imaging Spectrograph (STIS) instrument on the Hubble Space Telescope (HST). The discs around stars 2MASS J16090075-1908526, 2MASS J16142029-1906481, and 2MASS J16123916-1859284 have all…
Star formation around three co-moving HAeBe stars in the Cepheus Flare
Saha, P.; Maheswar, G.; Kamath, U. S. +1 more
Context. The presence of three more Herbig Ae/Be (HAeBe) candidates in the Cepheus Flare within a 1.5° radius centered on HD 200775 suggests that star formation is prevalent in a wider region of the LDN 1147/1158, LDN 1172/1174, and LDN 1177 clouds. A number of young stellar objects (YSOs) are found to be distributed toward these cloud complexes a…
Evaluation of Stellar Parameters and Calibrating the Surface Gravity log g for LAMOST-II Median Resolution Survey
Luo, A. -Li; Li, Yin-Bi; Zhang, Shuo +8 more
The LAMOST II survey began in the fall of 2018, and LAMOST formally released the obtained medium-resolution spectra (MRS) as well as catalogs of stellar parameters and radial velocities (RV) derived from the MRS in the seventh LAMOST data release (DR7). Compared with the RVs and parameters from high-resolution SDSS14/APOGEE spectra, nearly no RV d…
The angular-momentum flux in the solar wind observed during Solar Orbiter's first orbit
Verscharen, Daniel; Bruno, Roberto; Maksimovic, Milan +20 more
Aims: We present the first measurements of the angular-momentum flux in the solar wind recorded by the Solar Orbiter spacecraft. Our aim is to validate these measurements to support future studies of the Sun's angular-momentum loss.
Methods: We combined 60-min averages of the proton bulk moments and the magnetic field measured by the Sol…
A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P
Rubin, M.; Vigren, E.; Eriksson, A. I. +3 more
A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number d…
Investigating variable stars in the open cluster NGC 1912 and its surrounding field
Zhang, Yu; Esamdin, Ali; Chen, Li +6 more
In this work, we studied the variable stars in the open cluster NGC 1912 based on the photometric observations and Gaia DR2 data. More than 3600 CCD frames in B, V, R filters were reduced, and we obtained the light curves that span about 63 hours. By analyzing these light curves, we detected 24 variable stars, including 16 periodic variable stars,…