Red Giant Eclipsing Binaries: Exploring Non-Oscillators and Testing Asteroseismic Scalings

Thanks to advances in asteroseismology, red giants have become astrophysical laboratories for probing the Milky Way. Eclipsing binaries allow us to directly measure stellar properties independently of asteroseismology, which we use to investigate why some red giants don't oscillate and test asteroseismic scaling relations for those that do. By combining orbital solutions, high-resolution spectroscopy, and stellar evolution models for a subset of eight eclipsing red giants observed by Kepler, we find short-period binaries with strong tidal forces and systems with active red giants are less likely to exhibit solar-like oscillations. We also preview the results from Gaulme et al. 2016 (submitted). We find asteroseismic scalings overestimate red giant radii by about 6% on average and masses by about 16% in ten systems observed by Kepler. Systematic overestimation of mass leads to underestimation of stellar age, which has important implications for ensemble asteroseismology applied to galactic studies

Satellite Constellation Internet Affordability and Need

Large satellite constellations in low-Earth orbit seek to be the infrastructure for global broadband Internet and other telecommunication needs. We briefly review the impacts of satellite constellations on astronomy and show that the Internet service offered by these satellites will primarily target populations where it is unaffordable, not needed, or both. The harm done by tens to hundreds of thousands of low-Earth orbit satellites to astronomy, stargazers worldwide, and the environment is not acceptable

Refined Neutron-Star Mass Determinations for Six Eclipsing X-Ray Pulsar Binaries

We present an improved method for determining the mass of neutron stars in eclipsing X-ray pulsar binaries and apply the method to six systems, namely Vela X-1, 4U 1538-52, SMC X-1, LMC X-4, Cen X-3, and Her X-1. In previous studies to determine neutron star mass, the X-ray eclipse duration has been approximated analytically by assuming the companion star is spherical with an effective Roche lobe radius. We use a numerical code based on Roche geometry with various optimizers to analyze the published data for these systems, which we supplement with new spectroscopic and photometric data for 4U 1538-52. This allows us to model the eclipse duration more accurately and thus calculate an improved value for the neutron star mass. The derived neutron star mass also depends on the assumed Roche lobe filling factor beta of the companion star, where beta = 1 indicates a completely filled Roche lobe. In previous work a range of beta between 0.9 and 1.0 was usually adopted. We use optical ellipsoidal lightcurve data to constrain beta. We find neutron star masses of 1.77 +/- 0.08 M_{sun} for Vela X-1, 0.87 +/- 0.07 M_{sun} for 4U 1538-52 (eccentric orbit), 1.00 +/- 0.10 M_{sun} for 4U 1538-52 (circular orbit), 1.04 +/- 0.09 M_{sun} for SMC X-1, 1.29 +/- 0.05 M_{sun} for LMC X-4, 1.49 +/- 0.08 M_{sun} for Cen X-3, and 1.07 +/- 0.36 M_{sun} for Her X-1. We discuss the limits of the approximations that were used to derive the earlier mass determinations, and we comment on the implications our new masses have for observationally refining the upper and lower bounds of the neutron star mass distribution.Comment: 10 figures, accepted for publication in The Astrophysical Journa

The Astropy Problem

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software

Kic 9246715: The Double Red Giant Eclipsing Binary with Odd Oscillations

International audienceWe combine Kepler photometry with ground-based spectra to present a comprehensive dynamical model of the double red giant eclipsing binary KIC 9246715. While the two stars are very similar in mass (${M}_{1}={2.171}_{-0.008}^{+0.006}\ {M}_{\odot }$, ${M}_{2}={2.149}_{-0.008}^{+0.006}\ {M}_{\odot }$) and radius (${R}_{1}={8.37}_{-0.07}^{+0.03}\ {R}_{\odot }$, ${R}_{2}={8.30}_{-0.03}^{+0.04}\ {R}_{\odot }$), an asteroseismic analysis finds one main set of solar-like oscillations with unusually low-amplitude, wide modes. A second set of oscillations from the other star may exist, but this marginal detection is extremely faint. Because the two stars are nearly twins, KIC 9246715 is a difficult target for a precise test of the asteroseismic scaling relations, which yield M = 2.17 ± 0.14 M⊙ and R = 8.26 ± 0.18 R⊙. Both stars are consistent with the inferred asteroseismic properties, but we suspect the main oscillator is Star 2 because it is less active than Star 1. We find evidence for stellar activity and modest tidal forces acting over the 171 day eccentric orbit, which are likely responsible for the essential lack of solar-like oscillations in one star and weak oscillations in the other. Mixed modes indicate the main oscillating star is on the secondary red clump (a core-He-burning star), and stellar evolution modeling supports this with a coeval history for a pair of red clump stars. This system is a useful case study and paves the way for a detailed analysis of more red giants in eclipsing binaries, an important benchmark for asteroseismology