ULTRASAT: Exoplanets Working Group - S. Ben-Ami and Y. Shvartzvald - Weizmann Institute of ...
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
ULTRASAT: Exoplanets Working Group S. Ben-Ami and Y. Shvartzvald
Science Cases - Characterization • Activity / Habitability. o UV flares amplitude and frequency for various stellar types to infer planet habitability. And atmosphere evolution • Atmospheres. o Comparative transit depth: NUV vs. Visible. - For any detected planet during the mission lifetime. • Stellar-Planet Interaction o Stellar activity correlation to the presence of a planet in a short orbit period. 7/9/2020 2
Science Cases - Transit Detection • Main Sequence Transits: o Cool stars: FGK dwarf transits (O. Aharonson and A. Ofir) o OBA main sequence. • Post Main Sequence: o FGK giants through Chromosphere/Corona occultation. o White Dwarf transits. • Detection through Transit Timing Variations (known hosts, etc.). 7/9/2020 3
Field Content 130,000 exposures per objects! 7/9/2020 4
Number of stellar targets 2 76% fill factor • We examine 200 centered at RA = 210°, DEC = 60°. • GALEX AIS catalogue complete to 22 . • We identify 67,297 targets. • 62,078 with SDSS cross match. o 43,953 classified as stars. • 43,290 with GAIA cross match. • With APSIS fits: 36,465 7/9/2020 5
Activity and Habitability 7/9/2020 6
Stellar Activity and its effect on planetary atmospheres • Strong host activity can have severe impact on exoplanet atmospheres • ULTRASAT unprecedented data in time domain and wavelength NUV flare frequency and luminosity distribution for host stars as functions of both spectral subclass, and stellar rotation period. The MUSCLES survey (France et al. 2016, Loyd et al. 2018) indicates correlation between NUV emission and Ca II is not statistically significant. 7/9/2020 7
The UV Habitable Zone: Focus on M-Dwarfs • M-Dwarfs are the ideal hosts of exoplanets candidates for transmission spectroscopy studies. • Study the UV environment around M-dwarfs the implications for the emergence of life: o Stressors. o Eustressors – prebiotic origin of the pyrimidine RNA monomer on the young earth. • Identify the best habitable planet candidates for expensive spectroscopic bio-marker searches with JWST / ELTs. Dose Rate – Ranjan et al. 2017 7/9/2020 8
White Dwarf Transits 7/9/2020 9
Field Content - WDs • From GAIA WD Catalogue we identify ~202 WDs (Jimenez-Esteban 2018). • Completion level to 250pc is 44% : 460 WDs. • Identified GAIA-GALEX X-match (complete to 21mag): 95 targets. • We expect 400 WDs above limit magnitude in a single FoV.
Detection Capability
Current Limits (K2 – 1148 WDs) Roche Limit for ℎ : 0.005AU
Other Exotic Transits 7/9/2020 13
Sample characteristics: Hot dwarfs • 110 stars with 7,500 < < 10,000 and 1 < < 3 ⨀ o Expected from population models for A- and B- type stars: ~200 stars in each field. 7/9/2020 14
Sample characteristics: Red Giants • 2695 giants stars with > 2.5 ⨀ and < 7,000 • A subset are candidates for chromosphere / corona occultations. Consistent with zero detections. Assef, Gaudi, and Stanek (2011) 7/9/2020 15
Transiting Exoplanets orbiting MS dwarfs Aviv Ofir Oded Aharonson Exoplanet WG 7/9/2020 16
Transiting Exoplanets orbiting MS dwarfs Gaia catalog: • Select objects in N1 field with high Teff • Use BB to estimate flux @ ULTRASAT band → “U” mag estimate • ULTRASAT requirement: SNR of 5 at U=23 → scaled SNR to U mag Obtain per-star, per-point SNR estimate. 7/9/2020 17
Transiting Exoplanets orbiting MS dwarfs Simulated survey • Apply constraints: geom. probability, Roche limit, 95% duty cycle, multiple-visit scaling → Per-star sensitivity-map • Apply real planet population (Fulton+2017) → Yield-map • O(40) planets in N1, all HJs, some around A dwarfs 7/9/2020 18
You can also read
