Discovery of a bright microlensing event with planetary features towards the Taurus region: a super-Earth planet

Abstract

The transient event labeled as TCP J05074264+2447555 recently discovered towards the Taurus region was quickly recognized to be an ongoing microlensing event on a source located at distance of only 700 − 800 pc from Earth. Here, we show that observations with high sampling rate close to the time of maximum magnification revealed features that imply the presence of a binary lens system with very low mass ratio components. We present a complete description of the binary lens system which hosts an Earth-like planet with most likely mass of 9.2 ± 6.6 M ⊕ . Furthermore, the source estimated location and detailed Monte Carlo simulations allowed us to classify the event as due to the closest lens system, being at a distance of ≃ 380 pc and mass ≃ 0.25 M ⊙ .

First Resolution of Microlensed Images*

“…Therefore, we find that the two agree at the 1.5 σ level. This agreement gives added confidence to the planetary interpretation of the anomaly found by Nucita et al (2018).…”

“…We then combine this result with the measurement by Nucita et al (2018) of ρ ≡ θ * /θ E = (6.0±0.8)×10 −3 , to obtain θ E = 1.50±0.25 mas. This compares to the much more precisely derived value of θ E = 1.87 ± 0.03 mas (considering both the "no lens light" and "luminous lens" solutions) in the present work.…”

“…At this point, the detection of these events still does not strongly contradict theoretical expectations, but reconciliation of theory and experiment does require a somewhat greater efficiency of amateur observers than one might naively expect. Thus, this potential contradiction led our team (as well as many other astronomers, see, e.g., Nucita et al 2018) to undertake very aggressive observations in order to constrain the nature of this rare event. In our case, we undertook observations with the GRAVITY instrument (GRAVITY Collaboration 2017) of the Very Large Telescope Interferometer (VLTI) to obtain the first measurement of θ E by interferometric resolution of microlensed images.…”

“…Our data do not confirm or rule out the planetary deviations from the single-lens model because we did not have the necessary light-curve coverage over the reported anomaly. Nevertheless, we have conducted numerical experiments using the best-fit planetary microlensing models reported inNucita et al (2018) and found that the single-lens microlensing parameters relevant to our analysis show negligible changes if we add the reported planetary companion. We also find that the expected magnification and the positions of the major and minor images at the time of the VLTI observations are not affected, and this is because the VLTI data were taken more than 1 week after the reported planetary signals, which occurred at HJD ∼ 2458058.5.…”

“…Nucita et al (2018) reported a short-lived planetary anomaly that they modeled as a companion with planet-to-star mass ratio q = 1.1 ± 0.1 × 10 −4 . Our data do not confirm or rule out the planetary deviations from the single-lens model because we did not have the necessary light-curve coverage over the reported anomaly.…”