Overview

\(\texttt{SEDA}\) (Spectral Energy Distribution Analyzer) is an open-source Python package for forward modeling and empirical analysis of spectral energy distributions for brown dwarfs, directly imaged exoplanets, and low-mass stars.

This PDF file introduces the code and its main functionality as of January 2025, as presented at the 245th AAS meeting.

Principal Modules

For Forward Modeling

For Empirical Analysis

Code Workflow of Forward Modeling

Useful Tools

\(\texttt{SEDA}\) includes several useful functions that can be used separately:

Available Atmospheric Models

\(\texttt{SEDA}\) can use several modern and widely used atmospheric models, as indicated below. Check out tutorial_models_examination to see the parameters’ coverage and resolution of the models.

Sonora Diamondback Models

Cloudy (silicate clouds) atmospheric models assuming chemical equilibrium but considering the effect of both clouds and metallicity by Morley et al (2024). Download the Sonora Diamondback models.

Parameter coverage:

- wavelength = [0.3, 250] um
- Teff = [900, 2400] K in steps of 100 K
- logg = [3.5, 5.5] in steps of 0.5
- [M/H] = [-0.5, 0.5] (cgs) in steps of 0.5
- fsed = 1, 2, 3, 4, 8, nc

Sonora Elf Owl Models

Models with atmospheric mixing and chemical disequilibrium with varying metallicity and C/O by Mukherjee et al. (2024). Download the Sonora Elf Owl models for L-type, T-type, and Y-type.

Parameter coverage:

- wavelength = [0.6, 15] um
- Teff = [275, 2400] K in steps: 25 K for 275-600 K, 50 K for 600-1000 K, and 100 K for 1000-2400 K
- logg = [3.25, 5.50] in steps of 0.25 dex plus logg=3.0 for Teff=[275-2000], logKzz=8, [M/H]=1.0, and C/O=1.0.
- logKzz = 2, 4, 7, 8, and 9 (Kzz in cm2/s)
- [M/H] = -1.0, -0.5, +0.0, +0.5, +0.7, and +1.0 (cgs)
- C/O = 0.5, 1.0, 1.5, 2.5 (relative to solar C/O, assumed as 0.458) (these are the values in the filenames). It corresponds to C/O=[0.22, 1.12] with values of 0.22, 0.458, 0.687, and 1.12 (e.g. 0.5 in the filename means 0.5*0.458=0.22)

Lacy & Burrows (2023) Models

Cloudy (water clouds) atmospheric models with equilibrium and non-equilibrium chemistry for Y-dwarf atmospheres by Lacy & Burrows (2023). Download the LB23 models. The extended models are shared on request to the authors. The models include four grids:

  • ClearEQ: cloudless models with equilibrium chemistry

  • ClearNEQ: cloudless models with non-equilibrium chemistry

  • CloudyEQ: cloudy models with equilibrium chemistry

  • CloudyNEQ: cloudy models with non-equilibrium chemistry

Parameter coverage in common for all grids:

- wavelength = [0.5, 300] um with 30,000 frequency points evenly spaced in ln(frequency)
- R~4340 (average resolving power)

Parameter coverage for cloudless models:

- Teff = [200, 600] K in steps of 25 K
- logg = [3.50, 5.00] in steps of 0.25 (g in cgs)
- [M/H] = -0.5, 0.0, and 0.5 (Z/Z_sun = 0.316, 1.0, 3.16)
- logKzz = 6 for non-equilibrium models

Parameter coverage for cloudy models (there are some additional cloudy atmospheres extending to lower surface gravities and warmer temperatures in some combinations where convergence was easy):

- Teff = [200, 400] K (200-350 for Z/Z_sun=3.16) in steps of 25 K
- logg = [3.75, 5.00] in steps of 0.25 (g in cgs)
- [M/H] = -0.5, 0.0, and 0.5 (Z/Z_sun = 0.316, 1.0, 3.16), but some Z/Z_sun=3.16 are missing
- logKzz = 6 for non-equilibrium models

Extended models (additions to models in the paper). This grid replaces the original one (“The original spectra had an inconsistent wavelength grid and was missing CO2, so new ones are really a replacement.”)

- Teff up to 800 K
- Hmix (mixing length) = 1.0, 0.1, and 0.01

Sonora Cholla Models

Cloudless models with non-equilibrium chemistry due to different eddy diffusion parameters by Karalidi et al. (2021). Download the Sonora Cholla models.

Parameter coverage:

- wavelength = [1, 250] um for Teff>=850 K (plus some with Teff=750 K)
- wavelength = [0.3, 250] um for Teff<800 K (plus 950K_1780g_logkzz2.spec)
- Teff = [500, 1300] K in steps of 50 K
- logg = [3.00, 5.50] in steps of 0.25 (g in cgs)
- log Kzz=2, 4, and 7

Sonora Bobcat Models

Cloudless models in chemical equilibrium by Marley et al. (2021). Download the Sonora Bobcat models.

Parameter coverage:

- wavelength = [0.4, 50] um
- Teff = [200, 2400] K in steps: 25 K for 200-600 K, 50 K for 600-1000 K, and 100 K for 1000-2400 K
- logg = [3.25, 5.50] in steps of 0.25 (g in cgs)
- M/H=-0.5, 0.0, and 0.5
- C/O = 0.5, 1.0 (solar C/O), and 1.5 for solar metallicity models
- R = [6000, 200000] (the resolving power varies with wavelength but is otherwise the same for all spectra)

ATMO 2020 Models

Cloudless atmospheric models with chemical and non-chemical equilibrium by Phillips et al. (2020). Download the ATMO 2020 models. The models include three grids:

  • ATMO2020_CEQ: cloudless models with equilibrium chemistry.

  • ATMO2020_NEQ_weak: cloudless models with non-equilibrium chemistry due to weak vertical mixing (logKzz=4).

  • ATMO2020_NEQ_strong: cloudless models with non-equilibrium chemistry due to strong vertical mixing (logKzz=6).

Parameter coverage:

- wavelength = [0.2, 2000] um
- Teff = [200, 2400] K in steps varying from 25 K to 100 K
- logg = [2.5, 5.5] in steps of 0.5 (g in cgs)
- logKzz = 0 (ATMO2020_CEQ), 4 (ATMO2020_NEQ_weak), and 6 (ATMO2020_NEQ_strong)

BT-Settl Models

Cloudy models with non-equilibrium chemistry by Allard et al. (2012). Download the BT-Settl models.

Parameter coverage:

- wavelength = [1.e-4, 1000] um
- Teff = [200, 7000] K (Teff<=450 K for only logg<=3.5) in steps varying from 20 K to 100 K
- logg = [2.0, 5.5] in steps of 0.5 (g in cgs)
- R = [100000, 500000] (the resolving power varies with wavelength)

Saumon & Marley (2008) Models

Cloudy models with equilibrium chemistry by Saumon & Marley (2008). SM08 models are shared on request to the authors.

Parameter coverage:

- wavelength = [0.4, 50] um
- Teff = [800, 2400] K in steps of 100 K
- logg = [3.0, 5.5] in steps of 0.5 (g in cgs)
- fsed = 1, 2, 3, 4
- R = [100000, 700000] (the resolving power varies with wavelength)