Related papers: Two unseen massive white dwarf candidates in close…

We created the APOGEE-GALEX-\emph{Gaia} catalog to study white dwarfs binaries. This database aims to create a minimally biased sample of WD binary systems identified from a combination of GALEX, {\it Gaia}, and APOGEE data to increase the…

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system…

Hot subdwarf stars with F-K main sequence binary companions have been known for decades, but the first orbital periods for such systems were published just recently. Current observations suggest that most have long periods, on the order of…

We report photometric observations of the eclipsing close binary CSS21055 (SDSS J141126+200911) that strongly suggest that the companion to the carbon-oxygen white dwarf is a brown dwarf with a mass between 0.030 and 0.074 Msun. The…

We analyze radial velocity observations of the 12 extremely low-mass <0.25 Msol white dwarfs (WDs) in the MMT Hypervelocity Star Survey. Eleven of the 12 WDs are binaries with orbital periods shorter than 14 hours; the one non-variable WD…

We examine the statistics of main-sequence / main-sequence, main-sequence / white-dwarf and white-dwarf / white-dwarf wide binaries at 10^2.5-10^4 AU separations in Gaia data. For binaries containing a white dwarf, we find a complex…

This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark…

Eclipse time variations have been detected in a number of post common envelope binary systems consisting of a subdwarf B star or white dwarf primary star and cool M type or brown dwarf secondary. In this paper we consider circumbinary…

White dwarfs (WD) with main-sequence (MS) companions are crucial probes of stellar evolution. However, due to the significant difference in their luminosities, the WD is often outshined by the MS star. The aim of this work is to find hidden…

We report the discovery of three edge-on binaries with white dwarf companions that gravitationally magnify (instead of eclipsing) the light of their stellar primaries, as revealed by a systematic search for pulses with long periods in the…

We analyze two binary systems containing giant stars, V723 Mon ("the Unicorn") and 2M04123153+6738486 ("the Giraffe"). Both giants orbit more massive but less luminous companions, previously proposed to be mass-gap black holes. Spectral…

We present a high-contrast imaging survey of intermediate-mass (1.75--4.5 $M_\odot$) stars to search for the most extreme stellar binaries, i.e., for the lowest mass stellar companions. Using adaptive optics at the Lick and Gemini…

There is a striking and unexplained dearth of brown dwarf companions in close orbits (< 3AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively…

Planets and other low-mass binary companions to stars face a variety of potential fates as their host stars move off the main sequence and grow to subgiants and giants. Stellar mass loss tends to make orbits expand, and tidal torques tend…

We report the discovery of a nearby M5.0V dwarf at 24.6 pc, SCR 1848-6855, that is orbited by an unusual companion causing an astrometric perturbation of more than 200 milli-arcseconds. This is by far the largest perturbation found to date…

We present the discovery of 17 low mass white dwarfs (WDs) in short-period P<1 day binaries. Our sample includes four objects with remarkable log(g)~5 surface gravities and orbital solutions that require them to be double degenerate…

We report the discovery of the first likely black hole in a non-interacting binary system with a field red giant. By combining radial velocity measurements from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) with…

We present high-speed ULTRACAM and SOFI photometry and X-shooter spectroscopy of the recently discovered 94 minute orbital period eclipsing white dwarf / main-sequence binary SDSS J085746.18+034255.3 (CSS 03170) and use these observations…

In the course of our search for double degenerate binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT (ESO SN Ia Progenitor surveY - SPY) we discovered that the sdB star HE 1047-0436 is radial…

I review detached binaries consisting of white dwarfs with either other white dwarfs or low mass main-sequence stars in tight orbits around them. Orbital periods have been measured for 15 white dwarf/white dwarf systems and 22 white dwarf/M…