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The Phase Response of a Rough Rectangular Facet for Radar Sounder Simulations of Both Coherent and Incoherent Scattering
Gerekos, C.; Haynes, M. S.; Schroeder, D. M. +1 more
With radar sounders, coherent backscattering simulations from global planetary digital elevation models (DEMs) typically display a deficit in diffuse clutter, which is mainly due to the implicit assumption that roughness at scales below the resolution of the DEM is absent. Indeed, while polynomial approximations of the phase evolution across the f…
A Search for Exoplanets around Northern Circumpolar Stars. IX. A Multi-Period Analysis of the M Giant HD 135438
Lee, Byeong-Cheol; Park, Myeong-Gu; Lim, Beomdu +4 more
It is difficult to distinguish the pure signal produced by an orbiting planetary companion around giant stars from other possible sources, such as stellar spots, pulsations, or certain activities. Since 2003, we have obtained radial (RV) data from evolved stars using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) …
Astrometry with PRAIA
Assafin, M.
PRAIA - Package for the Reduction of Astronomical Images Automatically - is a suite of astrometric and photometric tasks designed to cope with huge amounts of heterogeneous observations with fast processing, no human intervention, minimum parameterization and yet maximum possible accuracy and precision. It is the main tool used to analyse astronom…
The radial profile of dust grain size in the protoplanetary disc of DS Tau
Wang, Hongchi; Ma, Yuehui; Liu, Yao +2 more
How do dust grains in protoplanetary discs overcome rapid radial drift and grow from micron size particles to planets is not well understood. The key is to search for evidence of dust accumulation and growth as a function of radius in the disc. We investigate the radial profile of grain size in the DS Tau disc by fitting multiband ALMA observation…
Chemical Compositions Of Red Giant Stars in the Old Open Cluster NGC 7789
Pilachowski, Catherine A.; Afşar, Melike; Sneden, Christopher +1 more
We have gathered optical-region spectra, derived model atmosphere parameters, and computed elemental abundances for 15 red giant stars in the open cluster NGC 7789. We focus on the light element group CNOLi that provides clues to evolutionary changes associated with internal fusion events and chemical mixing. We confirm and extend an early report …
New SB1s with Spectroscopic Orbits from LAMOST-LRS
Wang, Xiaoli; Fu, Yanning; Yuan, Ye +2 more
The LAMOST Low-Resolution Spectroscopic (LAMOST-LRS) Survey provides radial velocities of 10 million stars. These observations can be used to identify new single-lined spectroscopic binaries (SB1s) with their preliminary spectroscopic orbits. First, we perform a statistical χ 2 test on a subsample of LAMOST-LRS stars with velocity obser…
Secular light curves of comets 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1
Li, Juncen; Shi, Jianchun; Ma, Yuehua
The activity of Jupiter family comets, 60P/Tsuchinshan 2 and 62P/Tsuchinshan 1, is analysed by creating their Secular light curves (SLCs). We collected 850 observations in apparitions 1995, 2005, 2012, and 2018 for 60P/Tsuchinshan 2 and 471 observations in apparitions 1998, 2004, and 2017 for 62P/Tsuchinshan 1. We obtained the main activity parame…
X-Ray Unveiling Events in a z ≈ 1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
Trump, Jonathan R.; Brandt, W. N.; Vignali, C. +14 more
We investigate the extreme X-ray variability of a z = 1.608 active galactic nucleus in the 7 Ms Chandra Deep Field-South (XID 403), which showed two significant X-ray brightening events. In the first event, XID 403 brightened by a factor of >2.5 in ≲6.1 rest-frame days in the observed-frame 0.5-5 keV band. The event lasted for ≈5.0-7.3 days, an…
Gravitational Redshift Detection from the Magnetic White Dwarf Harbored in RX J1712.6-2414
Ishida, Manabu; Hayashi, Takayuki; Mori, Hideyuki +2 more
Gravitational redshift is a fundamental parameter that allows us to determine the mass-to-radius ratio of compact stellar objects, such as black holes, neutron stars, and white dwarfs (WDs). In the X-ray spectra of the close binary system, RX J1712.6-2414, obtained from the Chandra High Energy Transmission Grating observation, we detected signific…
Physical characterization of late-type contact binary systems observed by LAMOST: a comprehensive statistical analysis
Abdel Rahman, H. I.; Darwish, Mohamed
This paper presents a catalog of approximately 1800 Eclipsing W UMa systems (EWs) using parameters from LAMOST, VSX, ZTF and Gaia. Our detailed statistical analysis includes frequency distributions of parameters, confidence intervals, and hypothesis testing to provide deeper insights into the physical properties of this important eclipsing binary …