We report the discovery of a detached 20-min orbital period binary white dwarf (WD). WD 0931+444 (SDSS J093506.93+441106.9) was previously classified as a WD + M dwarf system based on its optical spectrum. Our time-resolved optical spectroscopy observations obtained at the 8 m Gemini and 6.5 m MMT reveal peak-to-peak radial velocity variations of

Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 1039 ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn in their spectra above about 5

We present a 3D map of extinction in the northern Galactic plane derived using photometry from the INT/WFC Photometric Hα Survey of the northern Galactic plane. The map has fine angular ( ˜ 10 arcmin) and distance (100 pc) sampling allied to a significant depth (≳5 kpc). We construct the map using a method based on a hierarchical Bayesian model

Over six years of operation, the Catalina Real-time Transient Survey (CRTS) has identified 1043 cataclysmic variable (CV) candidates - the largest sample of CVs from a single survey to date. Here, we provide spectroscopic identification of 85 systems fainter than g ≥ 19, including three AM Canum Venaticorum binaries, one helium-enriched CV, one

The study of primitive asteroids has gained much momentum in the last decade. The term "primitive" usually refers to objects with spectral characteristics similar to those of the carbonaceous chondrites, the most primitive meteorites. These meteorites contain pristine materials that have undergone very little processing since their formation, some

We present the study of the metallicity dependence of the Fourier amplitude ratios R21 and R31 for the light curves of short-period Galactic classical Cepheids in B, V, RC and IC bands. Based on the available photometric and spectroscopic data, we determined the relations between the atmospheric iron abundance, [Fe/H], and the Fourier parameters