Sagnick Mukherjee
A5003901153- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Spectroscopy and Laser Applications
- Gamma-ray bursts and supernovae
- Atmospheric and Environmental Gas Dynamics
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Atmospheric chemistry and aerosols
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- High-pressure geophysics and materials
- Adsorption, diffusion, and thermodynamic properties of materials
- Solar and Space Plasma Dynamics
- Advanced Thermodynamics and Statistical Mechanics
- Planetary Science and Exploration
- Spacecraft and Cryogenic Technologies
- Catalysis and Oxidation Reactions
- Zeolite Catalysis and Synthesis
- Plant Water Relations and Carbon Dynamics
- Spacecraft Design and Technology
- Space Exploration and Technology
University of California, Santa Cruz
2020-2025
Presidency University
2019-2021
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking formation evolution exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based high-resolution ground-based facilities. Here we report medium-resolution (R$\sim$600) transmission spectrum atmosphere between 3-5 $\mu$m covering multiple absorption...
Abstract Carbon dioxide (CO 2 ) is a key chemical species that found in wide range of planetary atmospheres. In the context exoplanets, CO an indicator metal enrichment (that is, elements heavier than helium, also called ‘metallicity’) 1–3 , and thus formation processes primary atmospheres hot gas giants 4–6 . It one most promising to detect secondary terrestrial exoplanets 7–9 Previous photometric measurements transiting planets with Spitzer Space Telescope have given hints presence but not...
Transmission spectroscopy provides insight into the atmospheric properties and consequently formation history, physics, chemistry of transiting exoplanets. However, obtaining precise inferences from transmission spectra requires simultaneously measuring strength shape multiple spectral absorption features a wide range chemical species. This has been challenging given precision wavelength coverage previous observatories. Here, we present spectrum Saturn-mass exoplanet WASP-39b obtained using...
Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability. However, no unambiguous photochemical products have been detected in exoplanet to date. Recent observations from JWST Transiting Exoplanet Early Release Science Program found spectral absorption feature at 4.05 $\mu$m arising SO$_2$ atmosphere WASP-39b. WASP-39b 1.27-Jupiter-radii, Saturn-mass (0.28 M$_J$) gas giant orbiting Sun-like star with an equilibrium temperature...
Abstract Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining dominant chemical processes at work and, if equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. 1,2 ) provides necessary means by abundances of oxygen- carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution high precision, which, together, are not achievable with...
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is $<$20 M$_\mathrm{Jup}$ widely separated ($\sim$8\arcsec, = 150 au), young, companion that shares photometric colors and spectroscopic features with directly imaged exoplanets HR 8799 c, d, e. As an L-to-T transition object, exists along region color-magnitude diagram where substellar atmospheres from cloudy clear. observed 1256~b \textit{JWST}'s NIRSpec IFU MIRI MRS modes for coverage 1 $\mu$m 20 at...
Abstract Upcoming James Webb Space Telescope observations will allow us to study exoplanet and brown dwarf atmospheres in great detail. The physical interpretation of these upcoming high signal-to-noise requires precise atmospheric models exoplanets dwarfs. While several 1D 3D have been developed the past three decades, often relied on simplified assumptions like chemical equilibrium are also not open-source, which limits their usage development by wider community. We present a Python-based...
Abstract We present a sample of 88 candidate z ∼ 8.5–14.5 galaxies selected from the completed NIRCam imaging Cosmic Evolution Early Release Science survey. These data cover ∼90 arcmin 2 (10 pointings) in six broadband filters and one medium-band filter. With this we confirm at higher confidence early JWST conclusions that bright epoch are more abundant than predicted by most theoretical models. construct rest-frame ultraviolet luminosity functions 9, 11, 14 show space density ( M UV = −20)...
We present JWST Early Release Science (ERS) coronagraphic observations of the super-Jupiter exoplanet, HIP 65426 b, with Near-Infrared Camera (NIRCam) from 2-5 $\mu$m, and Mid-Infrared Instrument (MIRI) 11-16 $\mu$m. At a separation $\sim$0.82" (86$^{+116}_{-31}$ au), b is clearly detected in all seven our observational filters, representing first images an exoplanet to be obtained by JWST, ever direct detection beyond 5 These demonstrate that exceeding its nominal predicted performance up...
Abstract Disequilibrium chemistry due to vertical mixing in the atmospheres of many brown dwarfs and giant exoplanets is well established. Atmosphere models for these objects typically parameterize with highly uncertain K zz diffusion parameter. The role altering abundances C-N-O-bearing molecules has mostly been explored a solar composition. However, atmospheric metallicity C/O ratio also impact chemistry. Therefore, we present Sonora Elf Owl grid self-consistent cloud-free 1D...
The recent inference of sulfur dioxide (SO2) in the atmosphere hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations1-3 suggests that photochemistry is a key process high-temperature atmospheres4. This because low (<1 ppb) abundance SO2 under thermochemical equilibrium compared with produced H2O and H2S (1-10 ppm)4-9. However, was made single, small molecular feature transmission spectrum at 4.05 μm and, therefore, detection other absorption bands...
Abstract We present a new grid of cloudy atmosphere and evolution models for substellar objects. These include the effect refractory cloud species, including silicate clouds, on spectra evolution. effective temperatures from 900 to 2400 K surface gravities log g = 3.5 5.5, appropriate broad range objects with masses between 1 84 M J . Model pressure–temperature structures are calculated assuming radiative–convective chemical equilibrium. consider both clouds metallicity atmospheric...
Direct imaging studies have mainly used low-resolution spectroscopy ($R\sim20-100$) to study the atmospheres of giant exoplanets and brown dwarf companions, but presence clouds has often led degeneracies in retrieved atmospheric abundances (e.g. C/O, metallicity). This precludes clear insights into formation mechanisms these companions. The Keck Planet Imager Characterizer (KPIC) uses adaptive optics single-mode fibers transport light NIRSPEC ($R\sim35,000$ $K$ band), aims address challenges...
The future is now - after its long-awaited launch in December 2021, JWST began science operations July 2022 and already revolutionizing exoplanet astronomy. Early Release Observations (ERO) program was designed to provide the first images spectra from JWST, covering a multitude of cases using multiple modes each on-board instrument. Here, we present transmission spectroscopy observations hot-Saturn WASP-96b with Single Object Slitless Spectroscopy (SOSS) mode Near Infrared Imager...
Abstract We present the first JWST spectral energy distribution of a Y dwarf. This Y0 dwarf WISE J035934.06−540154.6 consists low-resolution ( λ /Δ ∼100) spectroscopy from 1–12 μ m and three photometric points at 15, 18, 21 m. The spectrum exhibits numerous fundamental, overtone, combination rotational–vibrational bands H 2 O, CH 4 , CO, CO NH 3 including previously unidentified ν band Using Rayleigh–Jeans tail to account for flux emerging wavelengths greater than m, we measure bolometric...
Abstract The unprecedented medium-resolution ( R λ ∼ 1500–3500) near- and mid-infrared (1–18 μ m) spectrum provided by JWST for the young (140 ± 20 Myr) low-mass (12–20 M Jup ) L–T transition (L7) companion VHS 1256 b gives access to a catalog of molecular absorptions. In this study, we present comprehensive analysis data set utilizing forward-modeling approach applying our Bayesian framework, ForMoSA . We explore five distinct atmospheric models assess their performance in estimating key...
Abstract WASP-69 b is a hot, inflated, Saturn-mass planet (0.26 M Jup ) with zero-albedo equilibrium temperature of 963 K. Here, we report the JWST 2–12 μ m emission spectrum consisting two eclipses observed NIRCam grism time series and one eclipse MIRI low-resolution spectrometer (LRS). The shows absorption features water vapor, carbon dioxide, monoxide, but no strong evidence for methane. b’s poorly fit by cloud-free homogeneous models. We find three possible model scenarios planet: (1)...
Abstract Evidence of disequilibrium chemistry due to vertical mixing in the atmospheres many T- and Y-dwarfs has been inferred enhanced ratios CO reduced NH 3 . Atmospheric models planets brown dwarfs typically parameterize this phenomenon with eddy diffusion coefficient, K zz While can perhaps be approximated convective regions atmosphere length theory, radiative regions, strength is uncertain by orders magnitude. With a new grid self-consistent 1D model from T eff 400–1000 K, computed...
Abstract We report observations of the atmospheric transmission spectrum sub-Neptune exoplanet GJ 3470 b taken using Near-Infrared Camera on JWST. Combined with two archival Hubble Space Telescope/Wide-Field 3 transit and 15 Spitzer observations, we detect water, methane, sulfur dioxide, carbon dioxide in atmosphere b, each a significance >3 σ . is lowest-mass—and coldest—exoplanet known to show substantial feature its spectrum, at M p = 11.2 ⊕ T eq 600 K. This indicates that...
Abstract The sensitivity and spectral coverage of JWST are enabling us to test our assumptions ultracool dwarf atmospheric chemistry, especially with regards the abundances phosphine (PH 3 ) carbon dioxide (CO 2 ). In this paper, we use Near Infrared Spectrograph PRISM spectra (∼0.8−5.5 μ m, R ∼ 100) four late T Y dwarfs show that standard substellar atmosphere models have difficulty replicating 4.1−4.4 m wavelength range, as they predict an overabundance underabundance dioxide. To help...
Abstract We present infrared spectral energy distributions of 23 late-type T and Y dwarfs obtained with the James Webb Space Telescope. The consist NIRSpec PRISM MIRI low-resolution spectrometer spectra covering ∼1–12 μ m wavelength range at λ /Δ ≈ 100 broadband photometry 15, 18, 21 m. exhibit absorption features common to these objects including H 2 O, CH 4 , CO, CO NH 3 . Interestingly, while morphology changes relatively smoothly type < > 8 m, it shows no clear trend in 5 region...
Abstract We observed HD 19467 B with JWST’s NIRCam in six filters spanning 2.5–4.6 μ m the long-wavelength bar coronagraph. The brown dwarf was initially identified through a long-period trend radial velocity of G3V star 19467. subsequently detected via coronagraphic imaging and spectroscopy, characterized as late-T type an approximate temperature ∼1000 K. part GTO science program, demonstrating first use Long Wavelength Bar mask. object all (contrast levels 2 × 10 −4 to −5 ) at separation...
Abstract We present a performance analysis for the aperture masking interferometry (AMI) mode on board James Webb Space Telescope Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables, AMI accesses inner working angles down even within classical diffraction limit. The scientific potential of this has recently been demonstrated by Early Release Science (ERS) 1386 program with deep search close-in companions in HIP 65426 exoplanetary system. As...