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Multiwavelength classification of X-ray selected galaxy cluster candidates using convolutional neural networks
Kendrew, Sarah; Valtchanov, Ivan; Werner, Norbert +15 more
Galaxy clusters appear as extended sources in XMM-Newton images, but not all extended sources are clusters. So, their proper classification requires visual inspection with optical images, which is a slow process with biases that are almost impossible to model. We tackle this problem with a novel approach, using convolutional neural networks (CNNs)…
Fundamental parameters of Ap-star HD 108662
Romanovskaya, A. M.; Ryabchikova, T. A.; Shulyak, D. V.
We present the results of self-consistent spectroscopic analysis of the atmosphere of Ap-star HD 108662 based on high resolution spectrum and spectrophotometric observations in a wide wavelength range. Magnetic field effects were taking into account. Abundances of 24 chemical elements were derived, and stratification of Fe which lines make the mai…
HD 93795: a late-B supergiant star with a square circumstellar nebula
Katkov, I. Y.; Gvaramadze, V. V.; Castro, N. +1 more
We report the discovery of a square axisymmetric circumstellar nebula around the emission-line star HD 93795 in the archival Spitzer Space Telescope 24 {µ m} data. We classify HD 93795 as a B9 Ia star using optical spectra obtained with the Southern African Large Telescope (SALT). A spectral analysis carried out with the stellar atmosphere c…
Investigation of the coronal heating through phase relation of solar activity indexes
Li, K. J.; Xu, J. C.; Yin, Z. Q. +2 more
The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total…
Photochemistry of Methane and Ethane in the Martian Atmosphere
Taysum, Benjamin M.; Palmer, Paul I.
We develop an existing 1-D photochemistry model to include a comprehensive description of organic chemistry on Mars that includes the oxidation products of methane (CH4) and ethane (C2H6),a longer-chain hydrocarbon that can be used to differentiate between abiotic and biotic surface releases of CH4. We f…
ALMA reveals the coherence of the magnetic field geometry in OH 231.8+4.2
Sahai, R.; Zijlstra, A. A.; Sabin, L. +7 more
In a continuing effort to investigate the role of magnetic fields in evolved low- and intermediate-mass stars (principally regarding the shaping of their envelopes), we present new Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution polarization data obtained for the nebula OH 231.8+4.2. We found that the polarized emission likely …
On the metallicity gradient in the Galactic disk
Loktin, Alexander; Popova, Maria
The problem of the chemical composition gradient in the Galactic disk is studied based on a sample of metallicity estimates of open star clusters, using Gaia DR2-improved distance estimates. A clearly non-monotonic variation was observed in the average metallicity of clusters with increasing Galactocentric distance. One can clearly see the metalli…
Exhaustive study of three-time periods of solar activity due to single active regions: sunspot, flare, CME, and geo-effectiveness characteristics
Soni, Shirsh Lata; Yadav, Manohar Lal; Gupta, Radhe Syam +1 more
In this paper, we present the multi-wavelength study of a high level of solar activity during which a single active region produced multiple flares/CMEs. According to the sunspot observations, the current solar cycle 24 manifest to be less intense in comparison with the previous recent sunspot cycles. In the course of the current sunspot cycle 24,…
The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder - II. Estimating radial velocity of SPIRE spectral observation sources
Valtchanov, Ivan; Scott, Jeremy P.; Spencer, Locke D. +3 more
The Herschel SPIRE FTS Spectral Feature Finder (FF) detects significant spectral features within SPIRE spectra and employs two routines, and external references, to estimate source radial velocity. The first routine is based on the identification of rotational 12CO emission, the second cross-correlates detected features with a line temp…
Identification of a new ultraluminous X-ray source in NGC 1316
Ozdogan Ela, M.; Akyuz, A.; Aksaker, N. +3 more
In this study, we report identification of a new ultraluminous X-ray source (ULX) named as X-7 in NGC 1316, with an unabsorbed luminosity of 2.1 × 1039 erg s-1 using the two recent Chandra archival observations. The X-7 was detected in the Chandra 2001 observation and was included in the source list of the NGC 1316 as CXOUJ03…