# # Program information file # PROGRAM_ID 2024B991 PROGRAM_TITLE The Youngest Known Transiting Exoplanet PROGRAM_INV1 Andrew Mann PROGRAM_INV2 PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG IRAS 04125+2902b is a Jovian-sized planet transiting a 3 Myr pre-main-sequence star in the Taurus-Auriga Molecular Cloud. This makes it, by far, the youngest transiting planet known and on par with the youngest directly-imaged planet-like companions. More interesting, the host star harbors a nearly face-on transitional disk and a wide binary companion. The discovery paper is in review in Nature. One source of complication is the parameters of the host star. The planetary radius is only known as well as the host star radius, so this can have significant implications for the interpretation of the planet. A particular problem is the issue of spot coverage on the stellar surface, which makes it hard to use traditional methods to fit the SED with empirical templates or models. The goal here is to gather SpeX spectra at long wavelengths, where extinction is low but flux from the spotted region still significant. We can fit this with a two-temperature model to better constrain the surface and spot temperatures and overall properties of the star. The target is K=9.4, W2(4.6microns) = 8.9, with a blackbody temperature of ~4000 K. We want a SNR of 100-200 in SXD using the 0.3 arcsec slit (R~2000), as we want to detect molecular and atomic lines expected from the cooler spots. This part is fast (~10 min). For LXD we can use a larger slit (0.8) as we only need R>500, which will take ~30min to get 50-100 SNR out to 4 microns. With cals and a standard I expect all proposed observations can be done in 1 hour. PROGRAM_ABSTRACT_END