Pixel level decorrelation in service of the Spitzer microlens parallax survey

Abstract

Microlens parallax measurements combining space-based and ground-based observatories can be used to study planetary demographics. In recent years, the Spitzer Space Telescope was used as a microlens parallax satellite. Meanwhile, Spitzer IRAC has been employed to study short-period exoplanets and their atmospheres. As these investigations require exquisite photometry, they motivated the development of numerous self-calibration techniques now widely used in the exoplanet atmosphere community. Specifically, Pixel Level Decorrelation (PLD) was developed for starring-mode observations in uncrowded fields. We adapt and extend PLD to make it suitable for observations obtained as part of the Spitzer Microlens Parallax Campaign. We apply our method to two previously published microlensing events, OGLE-2017-BLG-1140 and OGLE-2015-BLG-0448, and compare its performance to the state-of-the-art pipeline used to analyses Spitzer microlensing observation. We find that our method yields photometry 1.5–6 times as precise as previously published. In addition to being useful for Spitzer, a similar approach could improve microlensing photometry with the Nancy Grace Roman Space Telescope.

OGLE-2016-BLG-1093Lb: A Sub-Jupiter-mass Spitzer Planet Located in the Galactic Bulge

“…Systematics at the level of ∼1 flux unit have been seen in several events (e.g., Poleski et al 2016;Dang et al 2020;Gould et al 2020;Hirao et al 2020) and are confirmed in this case. The potential impact of systematics will be most pronounced in events for which the overall flux change is small (e.g., for Δf Spz  10 flux units).…”

OGLE-2016-BLG-1093Lb: A Sub-Jupiter-mass Spitzer Planet Located in Galactic Bulge

“…Systematics at the level of ∼ 1 flux unit have been seen in several events (e.g., Poleski et al 2016;Dang et al 2020;Gould et al 2020;Hirao et al 2020) and are confirmed in this case. The potential impact of systematics will be most pronounced in events for which the overall flux change is small (e.g., for ∆f Spz 10 flux units).…”

MOA-2007-BLG-400 A Super-Jupiter-mass Planet Orbiting a Galactic Bulge K-dwarf Revealed by Keck Adaptive Optics Imaging

“…Unfortunately, the orbital motion of the Earth allows π E to be determined for only a relatively small subset of events such as the ones that have very long durations (e.g., Gaudi et al 2008;Bennett et al 2010b), long duration events with bright source stars (e.g., Muraki et al 2011), and events with special lens geometries (e.g., Sumi et al 2016). The microlensing parallax program using the Spitzer space telescope at ∼1 au from Earth has recently expanded the number of events with microlensing parallax measurements (Udalski et al 2015;Street et al 2016), but recent studies indicate that systematic errors in the Spitzer photometry can affect some of the Spitzer π E measurements (Dang et al 2020;Gould et al 2020;.…”