TY  - GEN
A1  - Finch, Nicolle L.
A1  - Braker, I. P.
A1  - Reindl, Nicole
A1  - Barstow, Martin A.
A1  - Casewell, Sarah L.
A1  - Burleigh, M.
A1  - Kupfer, Thomas
A1  - Kilkenny, D.
A1  - Geier, Stephan Alfred
A1  - Schaffenroth, Veronika
A1  - Bertolami Miller, Marcelo Miguel
A1  - Taubenberger, Stefan
A1  - Freudenthal, Joseph
T1  - Spectral Analysis of Binary Pre-white Dwarf Systems
T2  - Radiative signatures from the cosmos
N2  - Short period double degenerate white dwarf (WD) binaries with periods of less than similar to 1 day are considered to be one of the likely progenitors of type Ia supernovae. These binaries have undergone a period of common envelope evolution. If the core ignites helium before the envelope is ejected, then a hot subdwarf remains prior to contracting into a WD. Here we present a comparison of two very rare systems that contain two hot subdwarfs in short period orbits. We provide a quantitative spectroscopic analysis of the systems using synthetic spectra from state-of-the-art non-LTE models to constrain the atmospheric parameters of the stars. We also use these models to determine the radial velocities, and thus calculate dynamical masses for the stars in each system.
Y1  - 2019
SN  - 978-1-58381-925-8
SN  - 1050-3390
VL  - 519
SP  - 231
EP  - 238
PB  - Astronomical soc pacific
CY  - San Fransisco
ER  - 
TY  - BOOK
A1  - Freudenthal, Joseph
ED  - Diekmann, Irene
T1  - Chronik der Synagogengemeinde zu Luckenwalde und deren Vorgeschichte : zum 50jährigen Jubiläum der Synagogengemeinde 1919
T3  - Beiträge zur Geschichte und Kultur der Juden in Brandenburg, Mecklenburg-Vorpommern, Sachsen-Anhalt
Y1  - 1997
PB  - Verl. für Berlin-Brandenburg
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Schaffenroth, Veronika
A1  - Barlow, Brad N.
A1  - Geier, Stephan Alfred
A1  - Vuckovic, Maja
A1  - Kilkenny, D.
A1  - Wolz, M.
A1  - Kupfer, Thomas
A1  - Heber, Ulrich
A1  - Drechsel, H.
A1  - Kimeswenger, S.
A1  - Marsh, T.
A1  - Wolf, M.
A1  - Pelisoli, Ingrid Domingos
A1  - Freudenthal, Joseph
A1  - Dreizler, S.
A1  - Kreuzer, S.
A1  - Ziegerer, E.
T1  - The EREBOS project: Investigating the effect of substellar and low-mass stellar companions on late stellar evolution Survey, target selection, and atmospheric parameters
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Eclipsing post-common-envelope binaries are highly important for resolving the poorly understood, very short-lived common-envelope phase of stellar evolution. Most hot subdwarfs (sdO/Bs) are the bare helium-burning cores of red giants that have lost almost all of their hydrogen envelope. This mass loss is often triggered by common-envelope interactions with close stellar or even substellar companions. Cool companions to hot subdwarf stars such as late-type stars and brown dwarfs are detectable from characteristic light-curve variations - reflection effects and often eclipses. In the recently published catalog of eclipsing binaries in the Galactic Bulge and in the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey, we discovered 125 new eclipsing systems showing a reflection effect seen by visual inspection of the light curves and using a machine-learning algorithm, in addition to the 36 systems previously discovered by the Optical Gravitational Lesing Experiment (OGLE) team. The Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project aims at analyzing all newly discovered eclipsing binaries of the HW Vir type (hot subdwarf + close, cool companion) based on a spectroscopic and photometric follow up to derive the mass distribution of the companions, constrain the fraction of substellar companions, and determine the minimum mass needed to strip off the red-giant envelope. To constrain the nature of the primary we derived the absolute magnitude and the reduced proper motion of all our targets with the help of the parallaxes and proper motions measured by the Gaia mission and compared those to the Gaia white-dwarf candidate catalog. It was possible to derive the nature of a subset of our targets, for which observed spectra are available, by measuring the atmospheric parameter of the primary, confirming that less than 10% of our systems are not sdO/Bs with cool companions but are white dwarfs or central stars of planetary nebula. This large sample of eclipsing hot subdwarfs with cool companions allowed us to derive a significant period distribution for hot subdwarfs with cool companions for the first time showing that the period distribution is much broader than previously thought and is ideally suited to finding the lowest-mass companions to hot subdwarf stars. The comparison with related binary populations shows that the period distribution of HW Vir systems is very similar to WD+dM systems and central stars of planetary nebula with cool companions. In the future, several new photometric surveys will be carried out, which will further increase the sample of this project, providing the potential to test many aspects of common-envelope theory and binary evolution.
KW  - binaries: eclipsing
KW  - brown dwarfs
KW  - binaries: spectroscopic
KW  - binaries: close
KW  - subdwarfs
KW  - surveys
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201936019
SN  - 1432-0746
VL  - 630
PB  - EDP Sciences
CY  - Les Ulis
ER  -