Search Publications
New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55
Negueruela, I.; Roche, P.; Tabernero, H. M. +3 more
As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55, and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation period…
Period Analysis of Seven Field ab-type RR Lyrae Stars Based on O - C Diagrams: Cyclic Variations and Long-term Period Changes
Qian, S. -B.; Zhu, L. -Y.; Li, L. -J.
Using the times of light maximum collected from the GEOS RR Lyrae database and determined from sky surveys, we utilize the O - C method to study the period variations of seven field ab-type RR Lyrae stars. The time coverage of data for most stars is more than 100 years, allowing us to investigate period changes over a large time span. We find that…
Optical/X-ray correlations during the V404 Cygni June 2015 outburst
Mas-Hesse, J. M.; Charles, P. A.; Gandhi, P. +6 more
Context. We present a multiwavelength analysis of the simultaneous optical and X-ray light curves of the microquasar V404 Cyg during the June 2015 outburst.
Aims: We have performed a comprehensive analysis of all the INTEGRAL/IBIS, JEM-X, and OMC observations during the brightest epoch of the outburst, along with complementary NuSTAR, AAVSO, …
Ground-based x-ray calibration of the Astro-H/Hitomi soft x-ray telescopes
Maeda, Yoshitomo; Ishida, Manabu; Okajima, Takashi +10 more
We present the summary of the on-ground calibration of two soft x-ray telescopes (SXT-I and SXT-S), developed by NASA's Goddard Space Flight Center (GSFC), onboard Astro-H/Hitomi. After the initial x-ray measurements with a diverging beam at the GSFC 100-m beamline, we performed the full calibration of the x-ray performance, using the 30-m x-ray b…
Modelling the structure of star clusters with fractional Brownian motion
Whitworth, A. P.; Lomax, O.; Bates, M. L.
The degree of fractal substructure in molecular clouds can be quantified by comparing them with fractional Brownian motion (FBM) surfaces or volumes. These fields are self-similar over all length-scales and characterized by a drift exponent H, which describes the structural roughness. Given that the structure of molecular clouds and the initial st…
Measurement Process and Inversions Using Helioseismic Normal-mode Coupling
Hanasoge, Shravan
Normal modes are coupled by the presence of perturbations in the Sun, providing a novel and underappreciated helioseismic technique with which to image the solar interior. The process of measuring coupling between normal modes is straightforward, much more so when compared with other prevalent helioseismic techniques. The theoretical framework to …
An Empirical Study of Contamination in Deep, Rapid, and Wide-field Optical Follow-up of Gravitational Wave Events
Berger, E.; Rest, A.; Foley, R. J. +10 more
We present an empirical study of contamination in wide-field optical follow-up searches of gravitational wave sources from Advanced LIGO/Virgo using dedicated observations with the Dark Energy Camera. Our search covered ∼56 deg2, with two visits per night, in the i and z bands, followed by an additional set of griz images three weeks la…
Made-to-measure modelling of observed galaxy dynamics
Bovy, Jo; Kawata, Daisuke; Hunt, Jason A. S.
Amongst dynamical modelling techniques, the made-to-measure (M2M) method for modelling steady-state systems is amongst the most flexible, allowing non-parametric distribution functions in complex gravitational potentials to be modelled efficiently using N-body particles. Here, we propose and test various improvements to the standard M2M method for…
EPIC 246851721 b: A Tropical Jupiter Transiting a Rapidly Rotating Star in a Well-aligned Orbit
Vanderburg, Andrew; Bieryla, Allyson; Latham, David W. +15 more
We report the discovery of EPIC 246851721 b, a “tropical” Jupiter in a 6.18-day orbit around the bright (V = 11.439) star EPIC 246851721 (TYC 1283-739-1). We present a detailed analysis of the system using K2 and ground-based photometry, radial velocities, Doppler tomography, and adaptive optics imaging. From our global models, we infer that the h…
Geology of Hebes Chasma, Mars: 1. Structure, Stratigraphy, and Mineralogy of the Interior Layered Deposits
Flahaut, Jessica; Hauber, Ernst; Fueten, Frank +2 more
Hebes Chasma is an 8-km deep, 126 by 314 km, isolated basin that is partially filled with massive deposits of water-altered strata called interior layered deposits (ILDs). By analyzing the ILD's structure, stratigraphy, and mineralogy, a depositional history of Hebes Chasma is interpreted. Three distinct ILD units were found and are informally ref…