Gaiaphotometry for white dwarfs

Abstract

Context. White dwarfs can be used to study the structure and evolution of the Galaxy by analysing their luminosity function and initial mass function. Among them, the very cool white dwarfs provide the information for the early ages of each population. Because white dwarfs are intrinsically faint only the nearby (∼20 pc) sample is reasonably complete. The Gaia space mission will drastically increase the sample of known white dwarfs through its 5-6 years survey of the whole sky up to magnitude V = 20-25. Aims. We provide a characterisation of Gaia photometry for white dwarfs to better prepare for the analysis of the scientific output of the mission. Transformations between some of the most common photometric systems and Gaia passbands are derived. We also give estimates of the number of white dwarfs of the different galactic populations that will be observed. Methods. Using synthetic spectral energy distributions and the most recent Gaia transmission curves, we computed colours of three different types of white dwarfs (pure hydrogen, pure helium, and mixed composition with H/He = 0.1). With these colours we derived transformations to other common photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, and 2MASS). We also present numbers of white dwarfs predicted to be observed by Gaia. Results. We provide relationships and colour-colour diagrams among different photometric systems to allow the prediction and/or study of the Gaia white dwarf colours. We also include estimates of the number of sources expected in every galactic population and with a maximum parallax error. Gaia will increase the sample of known white dwarfs tenfold to about 200 000. Gaia will be able to observe thousands of very cool white dwarfs for the first time, which will greatly improve our understanding of these stars and early phases of star formation in our Galaxy.

Prospects for detection of detached double white dwarf binaries with Gaia, LSST and LISA

“…Amaro-Seoane et al 2012). All three instruments will be sensitive to short period (P < a few days) binaries (e.g., Prša et al 2011;Eyer et al 2012;Nelemans 2013;Carrasco et al 2014) and will provide a large sample of new ultra-compact DWDs that are interesting for several reasons. First, compact DWDs are systems that experienced at least two phases of mass transfer, and thus provide a good test for binary evolution models, and, in particular, for our understanding of mass transfer and the common envelope (CE) phase.…”

The binarity of the local white dwarf population

“…The selection effects for the Gaia samples are clean and homogeneous, and therefore the samples will be very suitable for statistical investigations such as BPS studies. Regarding WDs, Gaia is expected to increase the known sample significantly; from the current ∼ 2 · 10 4 objects (Kleinman et al 2013;Kepler et al 2016) to a few 10 5 WDs (Torres et al 2005;Robin et al 2012;Carrasco et al 2014). In particular, the large sample size provides us with the opportunity to study rare WDs, for example WDs that are pulsating, magnetic, cool, part of the halo population, or possible supernova Type Ia progenitors.…”

“…The advantage of the Solar neighbourhood is that even the coolest WDs can be identified with relative ease at these short distances from us (e.g. Carrasco et al 2014). The level of completeness that has been achieved for the WD sample within 20 pc is exceptional, and is estimated to be 80-90% Sion et al 2009;Giammichele et al 2012;Holberg et al 2016).…”

Constraints on the Initial-Final Mass Relation From Wide Double White Dwarfs

“…With precision astrometry from the Gaia space telescope, identifying WDs and matching them with common proper motion companions will be significantly easier. Furthermore, as pointed out by Carrasco et al (2014), data from the BP and RP spectrophotometers, combined with distance measurements and a mass-radius relation, will provide T eff and M WD for every WD identified. These authors estimate Gaia will find some 250,000 to 500,000 WDs.…”