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Spectroscopic Orbits of Subsystems in Multiple Stars. IX
Tokovinin, Andrei
New spectroscopic orbits of inner subsystems in 14 hierarchies are determined from long-term monitoring with the optical echelle spectrometer, CHIRON. Their main components are nearby solar-type stars belonging to nine triple systems (HIP 3645, 14307, 36165, 79980, 103735, 103814, 104440, 105879, 109443) and five quadruples of 2 + 2 hierarchy (HIP…
The intensity ratio variation of the Si IV 1394/1403 Å lines during solar flares. Resonance scattering and opacity effects
Ding, M. D.; Hong, J.; Yu, H. C.
Context. The Si IV lines at 1394 Å and 1403 Å form in the solar atmosphere at a temperature of ∼104.8 K. They are usually considered optically thin, but their opacity can be enhanced during solar flares. Traditionally, the intensity ratio of these lines are used as an indicator of the optical thickness. However, observations have shown …
Long-Term Density Trend in the Mesosphere and Lower Thermosphere From Occultations of the Crab Nebula With X-Ray Astronomy Satellites
Katsuda, Satoru; Enoto, Teruaki; Sato, Kosuke +9 more
We present long-term density trends of the Earth's upper atmosphere at altitudes between 71 and 116 km, based on atmospheric occultations of the Crab Nebula observed with X-ray astronomy satellites, ASCA, RXTE, Suzaku, NuSTAR, and Hitomi. The combination of the five satellites provides a time period of 28 years from 1994 to 2022. To suppress seaso…
The MOSDEF survey: probing resolved stellar populations at z 2 Using a new bayesian-defined morphology metric called patchiness
Siana, Brian; Shapley, Alice E.; Reddy, Naveen A. +12 more
We define a new morphology metric called 'patchiness' (P) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy centre to be defined, and can be used on the spatially resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its uti…
Mercury's Exosphere as Seen by BepiColombo/PHEBUS Visible Channels During the First Two Flybys
Reberac, A.; Korablev, O.; Leblanc, F. +10 more
BepiColombo, the ESA/JAXA joint mission performed its first flyby of Mercury on 1 October 2021 and its second on 23 June 2022. PHEBUS observed the exosphere of Mercury during these flybys notably with its visible channels c404 (centered on the potassium emission line at 404 nm) and c422 (centered on the calcium emission line at 422 nm). The c422 s…
Trigonometric parallax discrepancies in space telescopes measurements I: The case of the stellar binary system Hip 84976
Al-Wardat, Mashhoor A.; Hussein, Abdallah M.; Widyan, Hatem +1 more
In addition to the complete set of fundamental parameters of its individual components, we present the solution for the discrepancy between the two main astrometric space telescopes Gaia and Hipparcos, in their measurements of the trigonometric parallax for the stellar binary system Hip 84976. In our analysis of the system, we followed Al-Wardat's…
Astrometry via close approach events: applications to main-belt asteroid (702) Alauda
Vienne, A.; Peng, Q. Y.; Guo, B. F. +1 more
The release of Gaia catalogue is revolutionary to the astronomy of Solar system objects. After some effects such as atmospheric refraction and CCD geometric distortion have been taken into account, the astrometric precision for ground-based telescopes can reach the level of tens of milli-arcseconds (mas). If an object approaches a reference star i…
The magnetic field clock angle departure in the Venusian magnetosheath and its response to IMF rotation
Xu, Qi; Zhang, Tielong; Rong, Zhaojin +4 more
We investigate the characteristics of interplanetary magnetic field (IMF) draping in the Venusian magnetosheath using both Venus Express (VEX) observations and magnetohydrodynamics simulations. The distributions of magnetosheath field clock angle illustrate the nearly symmetric morphology of draped magnetic field with respect to the solar wind ele…
Search for Dormant Black Holes in the OGLE Data
Mróz, P.; Kapusta, M.
Light curves of ellipsoidal variables collected by the Optical Gravitational Lensing Experiment (OGLE) were analyzed, in order to search for dormant black hole candidates. After the preselection based on the amplitude of ellipsoidal modulation, each object was investigated by means of the spectral energy distribution fit, which allowed us to selec…
The first evidence of tidally induced activity in a brown dwarf-M dwarf pair: a Chandra study of the NLTT 41135/41136 system
Stelzer, Beate; Poppenhaeger, Katja; Wolk, Scott J. +3 more
The magnetic activity of low-mass stars changes as they age. The primary process decreasing the stellar activity level is the angular momentum loss via magnetized stellar wind. However, processes like tidal interactions between stars and their close companions may slow down the braking effect and the subsequent decrease of the activity level. Unti…