A5006605151- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Video Analysis and Summarization
- Spectroscopy and Chemometric Analyses
- Multimedia Communication and Technology
- Galaxies: Formation, Evolution, Phenomena
- Semiconductor Lasers and Optical Devices
- Power Transformer Diagnostics and Insulation
- Bee Products Chemical Analysis
- Adaptive optics and wavefront sensing
- Analytical Chemistry and Chromatography
- Spacecraft and Cryogenic Technologies
- Advanced Chemical Physics Studies
- Mass Spectrometry Techniques and Applications
- High voltage insulation and dielectric phenomena
- Digital Games and Media
- Atmospheric Ozone and Climate
University of Kansas
2022-2024
Georgia State University
2020-2023
York University
2015
Abstract Using Keck Planet Imager and Characterizer high-resolution ( R ∼ 35,000) spectroscopy from 2.29 to 2.49 μ m, we present uniform atmospheric retrievals for eight young substellar companions with masses of ∼10–30 M Jup , orbital separations spanning ∼50–360 au, T eff between ∼1500 2600 K. We find that all have solar C/O ratios metallicities within the 1 σ –2 level, measurements clustered around composition. Stars in same stellar associations as our systems near-solar abundances, so...
Abstract We present the first elemental abundance measurements of K dwarf (K7V) exoplanet-host star WASP-107 using high-resolution ( R ≃45,000), near-infrared H - and -band) spectra taken from Gemini-S/IGRINS. use previously determined physical parameters literature infer abundances 15 elements—C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Ni, all with precision < 0.1 dex—based on model fitting MARCS atmospheres Turbospectrum spectral synthesis code. Our results show near-solar a...
Abstract We present an in-depth, high-resolution spectroscopic analysis of the M dwarf K2-18, which hosts a sub-Neptune exoplanet in its habitable zone. show our technique to accurately normalize observed spectrum, is crucial for proper spectral fitting. also introduce new automatic, line-by-line, model-fitting code, AutoSpecFit, performs iterative χ 2 minimization process measure individual elemental abundances cool dwarfs. apply this code star and abundance 10 elements: C, O, Na, Mg, Al,...
Abstract Exoplanets hosting M dwarfs are the best targets to characterize Earth-like or super-Earth planetary atmospheres with James Webb Space Telescope (JWST). We determine detailed stellar parameters ( T eff , log g and ξ ) individual abundances of 12 elements for four cool exoplanets TOI-1685, GJ 436, 3470, TOI-2445, scheduled future observations by JWST. The analysis utilizes high-resolution near-infrared spectra from Sloan Digital Sky Survey IV APOGEE survey between 1.51 1.69 μ m....
Abstract Due to their ubiquity and very long main-sequence lifetimes, M dwarfs provide an excellent tool study the formation chemical enrichment history of our Galaxy. However, owing intrinsic faintness, acquisition high-resolution, high signal-to-noise spectra low-mass stars has been limited small numbers nearby stars, mostly from Galactic disk population. On other hand, large low- medium-resolution M-type dwarf both local halo are available various surveys. In order fully exploit these...
Based on a carefully constructed sample of dwarf stars, new optical-near infrared photometric calibration to estimate the metallicity late-type K and early-to-mid-type M dwarfs is presented. The has two parts; first part includes 18 with metallicities determined by high-resolution spectroscopy second contains 49 obtained through moderate-resolution spectra. By applying this large around 1.3 million from Sloan Digital Sky Survey Two-Micron All Survey, distribution compared those previous...
Abstract We present a model-fit pipeline to determine the stellar parameters of M-type dwarfs, which is an improvement on our previous work described in Hejazi et al. apply this analyze low-resolution ( R ∼ 2000) spectra 3745 M dwarfs/subdwarfs, collected at MDM Observatory, Lick Kitt Peak National and Cerro Tololo Inter-American Observatory. examine variation inferred parameter values H-R diagram constructed from their Gaia Early Data Release 3 (EDR3) parallaxes optical magnitudes. also...
Using Keck Planet Imager and Characterizer (KPIC) high-resolution ($R$~35000) spectroscopy from 2.29-2.49 $\mu$m, we present uniform atmospheric retrievals for eight young substellar companions with masses of ~10-30 $M_\textrm{Jup}$, orbital separations spanning ~50-360 au, $T_\textrm{eff}$ between ~1500-2600 K. We find that all have solar C/O ratios, metallicities, to within the 1-2$\sigma$ level, measurements clustered around composition. Stars in same stellar associations as our systems...
The elemental and isotopic abundances of volatiles like carbon, oxygen, nitrogen may trace a planet's formation location relative to H$_2$O, CO$_2$, CO, NH$_3$, N$_2$ "snowlines", or the distance from star at which these volatile elements sublimate. By comparing C/O $^{12}$C/$^{13}$C ratios measured in giant exoplanet atmospheres complementary measurements their host stars, we can determine whether planet inherited stellar inside snowlines, non-stellar $^{13}$C enrichment characteristic...
Abstract To understand the parameter degeneracy of M subdwarf spectra at low resolution, we assemble a large number spectral features in wavelength range 0.6–2.5 μ m with band strength quantified by narrowband indices. Based on index trends BT-Settl model sequences, illustrate how main atmospheric parameters ( T eff , log g [M/H], and [ α /Fe]) affect each feature differently. Furthermore, propose four-step process to determine four sequentially, which extends basic idea proposed Jao et al....
In this research note, we present linemake, an open-source atomic and molecular line list generator. Rather than a replacement for number of well-established spectral databases, linemake aims to be lightweight, easy-to-use tool generate formatted curated lists suitable synthesis work. We encourage users understand the sources their transition data cite them as appropriate in published provide code, database, extensive literature references GitHub repository...
Exoplanets hosting M dwarfs are the best targets to characterize Earth-like or super-Earth planetary atmospheres with James Webb Space Telescope (JWST). We determine detailed stellar parameters ($T_{\rm eff}$, log$g$, and $\xi$) individual abundances of twelve elements for four cool exoplanets TOI-1685, GJ 436, 3470, TOI-2445, scheduled future observations by JWST. The analysis utilizes high-resolution near-infrared spectra from SDSS-IV APOGEE survey between 1.51-1.69$\mu$. Based on 1D-LTE...
We present an in-depth, high-resolution spectroscopic analysis of the M dwarf K2-18 that hosts a sub-Neptune exoplanet in its habitable zone. show our technique to accurately normalize observed spectrum, which is crucial for proper spectral fitting. also introduce new automatic, line-by-line model-fitting code, AutoSpecFit, performs iterative ${\chi}^{2}$ minimization process measure individual elemental abundances cool dwarfs. apply this code star K2-18, and abundance 10 elements - C, O,...
The chemical abundance measurements of host stars and their substellar companions provide a powerful tool to trace the formation mechanism planetary systems. We present detailed high-resolution spectroscopic analysis young M-type star, DH Tau A, which is located in Taurus molecular cloud belonging Taurus-Auriga star-forming region. This star low-mass companion, b, both companion are still accreting phase. apply our technique (Hejazi et al. 2024) measure abundances carbon oxygen using carbon-...
Abstract The chemical abundance measurements of host stars and their substellar companions provide a powerful tool to trace the formation mechanism planetary systems. We present detailed high-resolution spectroscopic analysis young M-type star, DH Tau A, which is located in Taurus molecular cloud belonging Taurus-Auriga star-forming region. This star low-mass companion, b, both companion are still accreting phase. apply our technique measure abundances carbon oxygen using carbon-...
We present a summary of the splinter session on "touchstone stars" -- stars with directly measured parameters that was organized as part Cool Stars 18 conference. discuss several methods to precisely determine cool star properties such masses and radii from eclipsing binaries, effective temperatures interferometry. highlight recent results in identifying measuring for touchstone stars, ongoing efforts use other stars. conclude by comparing models, noting some unusual patterns differences.
We present the first elemental abundance measurements of K dwarf (K7V) exoplanet-host star WASP-107 using high-resolution (R = 45,000), near-infrared (H- and K-band) spectra taken from Gemini-S/IGRINS. use previously determined physical parameters literature infer abundances 15 elements: C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Ni, all with precision < 0.1 dex, based on model fitting MARCS atmospheres spectral synthesis code Turbospectrum. Our results show near-solar a...