New results for the open cluster bica 6 and its associated planetary nebula abell 8

The likely membership of the planetary nebula Abell 8 (PN G167.0-00.9) in the open cluster Bica 6 is confirmed by CCD spectra, UBV (RI) C photometry, and radial velocities for luminous cluster stars. The reddening, estimated distance, and radial velocity of the planetary nebula agree with parameters derived for Bica 6 of E B-V (mean) 1/4 0:42, d 1/4 1:60 \ub1 0:11 kpc, and V R 1/4 57 \ub1 1 km s -1, with a cluster age of 10 9 yr, a diagnostic blue hook, and a few blue stragglers, including a peculiar B1 Vnn star (HDE 277593) that may be a post-AGB star. The results identify Bica 6 as a potential calibrator of the planetary nebula distance scale. The central star of the planetary nebula has a reddening of E B-V 1/4 0:49 \ub1 0:02, with a possible circumnebular excess, and an estimated luminosity of M V = +7.44 \ub1 0.16. It is also an optical double in 2MASS images, with a likely progenitor according to evolutionary considerations being a late B-type dwarf of ~2:3 M. 99. \ua9 2011. The Astronomical Society of the Pacific. All rights reserved.Peer reviewed: YesNRC publication: Ye

DE CVn: A Bright, Eclipsing Red Dwarf - White Dwarf Binary

Contains fulltext : 35976.pdf (preprint version ) (Open Access)DE CVn is a relatively unstudied eclipsing binary where one of the components is an M dwarf. Its brightness makes it an ideal system for a detailed study in the context of common-envelope evolution of a detached white dwarf - red dwarf binary with a relatively short orbital period (~8.7 hours). We present a detailed study of the basic parameters (e.g. orbital period, components' masses, spectral type) for this system from photometric and spectroscopic studies. The eclipses observed during several photometric observing runs were used to derive the ephemeris. We have used spectroscopic data to derive the radial velocity variations of the emission lines and these are used to determine the components' masses and the orbital separation. The secondary component in DE CVn is an M3 main-sequence star and the primary star, which is not visible in the spectra, is a cool white dwarf with a temperature of ~8000 K. From the photometry and spectroscopy together, we have set a limit on the binary inclination. This system is a post-common-envelope system where the progenitor of the present day white dwarf was a low-mass star (M<2 Msun). The time before DE CVn becomes a semi-detached system is longer than the Hubble time

International Asteroid Warning Network Timing Campaign: 2019 XS

As part of the International Asteroid Warning Network's observational exercises, we conducted a campaign to observe near-Earth asteroid 2019 XS around its close approach to Earth on 2021 November 9. The goal of the campaign was to characterize errors in the observation times reported to the Minor Planet Center, which become an increasingly important consideration as astrometric accuracy improves and more fast-moving asteroids are observed. As part of the exercise, a total of 957 astrometric observations of 2019 XS during the encounter were reported and subsequently were analyzed to obtain the corresponding residuals. While the timing errors are typically smaller than 1 s, the reported times appear to be negatively biased, i.e., they are generally earlier than they should be. We also compared the observer-provided position uncertainty with the cross-track residuals, which are independent of timing errors. A large fraction of the estimated uncertainties appear to be optimistic, especially when <0 2. We compiled individual reports for each observer to help identify and remove the root cause of any possible timing error and improve the uncertainty quantification process. We suggest possible sources of timing errors and describe a simple procedure to derive reliable, conservative position uncertainties. © 2022. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]