SCLAES (Slicer Combined Lenslet Array for Exoplanet Spectroscopy)
SCALES is an instrument designed to maximize our ability at W.M. Keck Observatory to detect and characterize directly-imaged planets by combining the two most successful methods for imaging exoplanets: thermal infrared imaging, which detects exoplanets at wavelengths where they are bright, and integral-field spectroscopy, which distinguishes exoplanets from residual starlight based on the shapes of their spectral energy distributions.
SCALES cryostat at UCSC
SCALES optical design ( Renate Kupke et.al.2022)
Spectroscopic observations of exoplanet host stars
To understand how exoplanets are formed, we should understand the planet and the host star together. As the planet and the host star are formed from the same molecular cloud, their chemical properties are inter connected.
Spectroscopy is a powerful tool to resolve this mystery.
​
-
We derive the abundance of different elements in the atmosphere of the host star and try to understand how they are connected with the planet properties.​
-
Differential abundance analysis on planet host visual binaries to understand the possible planetary signature in the host star compared to the twin companion star.
-
Statistical significance of individual elements like Carbon in the planet formation process.
Occurrence rate of Carbon as a function of planet radius
LAMOST spectra of two different stars with CH band at 430 nm
Distribution of [Fe/H], [C/H], and [C/Fe] in different planet host stars.
Transit Spectroscopy
When a planet transits, a part of the light coming from the star passes through the atmosphere of the planet before it reaches the observer.
​​
Low-Resolution Transit Spectroscopy
Low resolution transit spectroscopy is important to understand the atmospheric properties of the exoplanet.
Ground-based observations are challenging mainly because of the systematic noises dominates the photon noise.
​
The first successful attempt of using a 2m Himalayan Chandra Telescope (HCT/HFOSC) for low resolution transit spectroscopy opens the possibility of using telescopes with similar instruments for the same. These observations will compliment the IR observations from HST, SPITZER, JWST, and upcoming missions.
​
Currently we are trying to implement the same technique in LICK/Kast Spectrograph and KECK/LIRIS spectrogrpah.
2D image of star and referece star (HCT/HFOSC)
Extracted spectra from the 2D image
Observed spectra & best-fit model using ATMO
lightcurve : HAT-P-1b
High-Resolution Transit Spectroscopy
The unique advantage of ground-based observations are the possibility of high spectral resolution.
​
As part of th Exo-Io team, we observed mulitple epoch of the potential exomoon candidate WASP-49b, using Keck/HIRES, VLT/ESPRESSO, and HARPS.
​
The variable amplitude Doppler shift of observed sodium indicate that, the observed sodium is unlikely from the planet atmosphere. A magnetically interactive natural satellite can be a possible reason.
​
Transit spectra at sodium doublet 589 nm
lightcurve at sodium doublet 589 nm
Importance of understanding stellar inhomogenities
Stellar inhomogenities can mimic exoplanet atmospheric signal.
​
We did some basic analysis to understand this in our most studied star: Sun using 'Sun as a star' spectra
​
Work going on ...
​
​