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Astronomical distance scales
Mignard, François
This article is an overview of the determination of astronomical distances from a metrological standpoint. Distances are considered from the Solar System (planetary distances) to extragalactic distances, with a special emphasis on the fundamental step of the trigonometric stellar distances and the giant leap recently experienced in this field than…
Validating the C I 5052.17 Å/Mg II 4481 Å Equivalent Width Ratio as a Diagnostic for F-type Lambda Boo Stars
Cheng, Kwang-Ping; Tarbell, Erik S.; Giacinto, Anthony J. +5 more
The Lambda Boo-type stars are chemically peculiar stars with deficiencies of iron-peak elements but near-solar C, N, O, and S abundances. Since the prototype Lambda Boötis was first reported as peculiar, this group has been expanded from a small group of early A-type stars to a larger group of late B to early F-type dwarfs. Although a detailed abu…
A Hint of Three-section Halo As Seen from the APOGEE DR14
Zhao, G.; Chen, Y. Q.; Xue, X. X. +4 more
Based on the [M/H] versus [Mg/Fe] diagram and distances from APOGEE data release 14, we compare the spatial distributions, the l - V los diagram, and the abundance gradients between high-[Mg/Fe] and low-[Mg/Fe] sequences. The two sequences are clearly shown at 5< | Z| < 10 {kpc} in the metallicity range of -1.6 < [M/H] < -0.…
XMM-Newton spectrum of the magnetar CXOU J171405.7-381031
Bamba, Aya; Watanabe, Haruka; Shibata, Shinpei +1 more
We observe the magnetar CXOU J171405.7-381031 with XMM-Newton and obtain the most reliable X-ray spectral parameters for this magnetar. After removing the flux from the surrounding supernova remnant CTB 37B, the radiation of CXOU J171405.7-381031 is best described by a two-component model, consisting of a blackbody and power law. We obtain a black…
TYC 3637-1152-1 - A high amplitude δ Scuti star with peculiar pulsational properties
Meingast, Stefan; Sulzenauer, Nikolaus; Pribulla, Theodor +16 more
In some δ Scuti stars, only one or two radial modes are excited (usually the fundamental mode and/or first overtone mode) and the observed peak-to-peak amplitudes exceed 0.3 mag (V). These stars are known as High Amplitude Delta Scuti (HADS) variables.
We here present a detailed photometric and spectroscopic analysis of the HADS star TYC 3637…New Variable Stars in NGC 6652 and Its Background Sagittarius Stream
Vivas, A. Katherina; Salinas, Ricardo; Contreras Ramos, Rodrigo
We conducted a variable star search on the metal-rich Galactic globular cluster NGC 6652 using archival Gemini-S/Gemini Multiobject Spectrograph data. We report the discovery of nine new variable stars in the NGC 6652 field, of which we classify six as eclipsing binaries and one as an SX Phoenicis star, leaving two variables without classification…
Phase-curve analysis of comet 67P/Churyumov-Gerasimenko at small phase angles
Lamy, P. L.; Lara, L. M.; Bertaux, J. -L. +31 more
Aims: The Rosetta-OSIRIS images acquired at small phase angles in three wavelengths during the fly-by of the spacecraft on 9-10 April 2016 provided a unique opportunity to study the opposition effect on the surface of comet 67P/Churyumov-Gerasimenko (67P). Our goal is to study phase curves of the nucleus at small phase angles for a variety of…
Photometric study of the open cluster NGC 381
Joshi, Y. C.; Maurya, J.
We present UBVRcIc photometry of stars, down to the 20th magnitude, in the region of the intermediate- age open cluster NGC 381. The core and the cluster radii are estimated to be 2.99 +/- 0.93 and 5.6 +/- 0.1 arcmin, respectively. A total of 350 probable cluster member stars are identified by using proper motion from GAIA as the criterion of memb…
SSA Analysis and Significance Tests for Periodicity in S, RS, SU, AD, BU, KK, and PR Persei
Chaplin, G. B.
Visual observations made by experienced observers are adjusted for individual observer bias. We examine the time series using signal processing methods to identify periodicities and test for the significance of the results finding a reliable periods in S Per, and to a limited extent in RS, SU, BU, and KK Per. Recommendations for future visual and …
Estimates of the Atmospheric Escape Rates of CH4 from Titan
Ip, Wing-Huen; Hsu, Jen-Kai
The upper atmosphere of Titan is highly variable as characterized by the variations of the thermospheric and exospheric temperatures from in situ measurements by Cassini at different Titan encounters. A related question has to do with the escape flux of CH4 that might also change with the complex plasma environment and ionospheric condi…