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MHD Modeling of the Background Solar Wind in the Inner Heliosphere From 0.1 to 5.5 AU: Comparison With In Situ Observations
Wang, C.; Li, H.; Guo, X. C. +4 more
The accurate prediction of solar wind conditions in the interplanetary space is crucial in the context of both scientific research and technical applications. In this study, we simulate the solar wind throughout the heliosphere from 0.1 to 5.5 astronomical units (AU) with our improved heliospheric magnetohydrodynamics (MHD) model during the time p…
A blazar as the likely counterpart to 4FGL J0647.7-4418 instead of a gamma-ray binary
Corbet, Robin H. D.; Luque-Escamilla, Pedro L.; Martí, Josep +3 more
The persistent gamma-ray source 4FGL J0647.7-4418 is tentatively associated in the latest Fermi catalogue with the subdwarf O-type X-ray binary HD 49798. However, an active galactic nucleus (AGN) candidate is also mentioned as an alternative identification in updated versions of the catalogue accompanying paper. If the first association were corre…
Multiwavelength Photometry and Progenitor Analysis of the Nova V906 Car
Law, Nicholas M.; Blagorodnova, Nadejda; Kupfer, Thomas +12 more
We present optical and infrared photometry of the classical nova V906 Car, also known as Nova Car 2018 and ASASSN-18fv, which was discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) on 2018 March 16.32 UT (MJD 58193.0). The nova reached its maximum on MJD 58222.56 at Vmax = 5.84 ± 0.09 mag, and had decline times of ${t}_…
Short-Term X-ray Variability during Different Activity Phases of Blazars S5 0716+714 and PKS 2155-304
Pal, Main; Kushwaha, Pankaj
We explored the statistical properties of short-term X-ray variability using long-exposure XMM-Newton data during high X-ray variability phases of blazars S5 0716+714 and PKS 2155-304. In general, the hardness ratio shows correlated variations with the source flux state (count rate), but in a few cases, mainly the bright phases, the trend is compl…
HST Survey of the Orion Nebula Cluster in the H2O 1.4 µm Absorption Band. III. The Population of Substellar Binary Companions
Gennaro, Mario; Pueyo, Laurent; Ubeda, Leonardo +4 more
We present new results concerning the substellar binary population in the Orion Nebula Cluster (ONC). Using the Karhunen-Loève Image Projection algorithm, we have reprocessed images taken with the IR channel of the Wide Field Camera 3 mounted on the Hubble Space Telescope to unveil faint, close companions in the wings of the stellar point-spread f…
Estimating the fate of oxygen ion outflow from the high-altitude cusp
Slapak, Rikard; Schillings, Audrey; Haaland, Stein +2 more
We have investigated the oxygen escape-to-capture ratio from the high-altitude cusp regions for various geomagnetic activity levels by combining EDI and CODIF measurements from the Cluster spacecraft. Using a magnetic field model, we traced the observed oxygen ions to one of three regions: plasma sheet, solar wind beyond a distant X-line or daysid…
Gravitational potential from small-scale clustering in action space: application to Gaia Data Release 2
Yang, Tianyi; Boruah, Supranta S.; Afshordi, Niayesh
Most measurements of mass in astronomy that use kinematics of stars or gas rely on assumptions of equilibrium that are often hard to verify. Instead, we develop a novel idea that uses the clustering in action space, as a probe of the underlying gravitational potential: the correct potential should maximize small-scale clustering in the action spac…
Molecular gas in the central region of NGC 7213
Pozzi, F.; Hatziminaoglou, E.; Vignali, C. +4 more
We present a multi-wavelength study (from X-ray to mm) of the nearby low-luminosity active galactic nucleus NGC 7213. We combine the information from the different bands to characterise the source in terms of contribution from the AGN and the host-galaxy interstellar medium. This approach allows us to provide a coherent picture of the role of the …
The distances to molecular clouds in the fourth Galactic quadrant
Wang, Shu; Jiang, Biwei; Chen, Bingqiu +4 more
Distance measurements to molecular clouds are essential and important. We present directly measured distances to 169 molecular clouds in the fourth quadrant of the Milky Way. Based on the near-infrared photometry from the Two Micron All Sky Survey and the Vista Variables in the Via Lactea Survey, we select red clump stars in the overlapping direct…
Spectrophotometric calibration of low-resolution spectra
Jordi, C.; Fabricius, C.; Carrasco, J. M. +1 more
Context. Low-resolution spectroscopy is a frequently used technique. Aperture prism spectroscopy in particular is an important tool for large-scale survey observations. The ongoing ESA space mission Gaia is the currently most relevant example.
Aims: In this work we analyse the fundamental limitations of the calibration of low-resolution spect…