On the detectability of transiting planets orbiting white dwarfs using LSST

Abstract

White dwarfs are one of the few types of stellar objects for which we know almost nothing about the possible existence of companion planets. Recent evidence for metal contaminated atmospheres, circumstellar debris disks and transiting planetary debris all indicate that planets may be likely. However, white dwarf transit surveys are challenging due to the intrinsic faintness of such objects, the short timescale of the transits and the low transit probabilities due to their compact radii. The Large Synoptic Survey Telescope (LSST) offers a remedy to these problems as a deep, half-sky survey with fast exposures encompassing approximately 10 million white dwarfs with r < 24.5 apparent magnitude. We simulate LSST photometric observations of 3.5 million white dwarfs over a ten-year period and calculate the detectability of companion planets with P < 10 d via transits. We find typical detection rates in the range of 5 × 10 −6 to 4 × 10 −4 for Ceres-sized bodies to Earth-sized worlds, yielding ∼ 50 to 4 000 detections for a 100% occurrence rate of each. For terrestrial planets in the continuously habitable zone, we find detection rates of ∼ 10 −3 indicating that LSST would reveal hundreds of such worlds for occurrence rates in the range of 1% to 10%.

A Higher Cadence Subsurvey Located in the Galactic Plane

“…However, LSST's fainter magnitude range means that instead of ∼ 1000 white dwarfs monitored, LSST can observe millions and thus increase chances of observing objects in transit by orders of magnitude, an opportunity discussed in Agol (2011a,b). Recent work has expanded on this, where Cortes and Kipping (2018) use the significance of transit signals in simulated observations to highlight that tens to thousands of Ceres-sized objects could be discovered with LSST, as well as hundreds of earth-sized planets in the habitable zone of those white dwarfs. A different approach taken in Lund et al (2018) was to simulate detection of Earth-sized planets with a specialized algorithm, but similarly finds that hundreds of exoplanets can be directly discovered from simulated light curves.…”

High-resolution Spectra and Biosignatures of Earth-like Planets Transiting White Dwarfs

“…Multiple studies have addressed the possibility of WD planet detection via transits (e.g. Agol 2011;Loeb & Maoz 2013;Cortés & Kipping 2019) and several searches are already underway (e.g. Fulton et al 2014;Veras & Gänsicke 2015;Xu et al 2015;Wallach et al 2018;Bell 2019;Dame et al 2019).…”

The Search for Planet and Planetesimal Transits of White Dwarfs with the Zwicky Transient Facility

“…Still, transits of WDs can be very deep (even occulting), producing unmis- Discovering the first planets to transit WDs will require orders of magnitude larger sample sizes. Cortés, & Kipping (2019) and Lund et al (2018) have simulated the expected yield for WD transits after 10 years of Large Synoptic Survey Telescope (LSST) operations (ca. 2033), anticipating "1000 detections.…”