Profile-Based NLTE Corrections (Experimental)

Profile-Based NLTE Corrections (Experimental)#

PySME also contains an experimental profile-based NLTE correction layer. This is separate from the standard sme.nlte departure-coefficient workflow.

  • sme.nlte controls traditional NLTE calculations based on element-specific NLTE grids and departure coefficients.

  • sme.profile_nlte controls profile corrections that are applied to selected wavelength regions after synthesis.

At the moment this interface is experimental and intentionally conservative.

Current Scope#

The current implementation supports:

  • one element provider at a time

  • a provider may internally cover multiple lines / multiple wavelength windows for that element

  • a default provider for hydrogen:

    • pysme_h_3dnlte_rbf

The current hydrogen provider is treated as one bundle. It is not a per-line toggle. If the provider is enabled, it operates on its supported Balmer-line windows as one provider.

Multiple profile-NLTE element providers at the same time are currently not supported.

Enable The Feature#

Use the sme.profile_nlte object:

from pysme.sme import SME_Structure

sme = SME_Structure()
sme.profile_nlte.enabled = True
sme.profile_nlte.element = "H"

You may optionally set the provider explicitly:

sme.profile_nlte.provider = "pysme_h_3dnlte_rbf"

If provider is left as None, PySME uses the default provider for the selected element.

Current Hydrogen Provider#

The built-in hydrogen provider currently supports these air-wavelength windows:

  • 4335.0 - 4345.0 A

  • 4855.0 - 4868.0 A

  • 6550.0 - 6575.0 A

These correspond to the current bundled Balmer-line correction windows.

Runtime Summary#

After synthesis, PySME writes the provider status to:

sme.profile_nlte.summary

The summary currently includes:

  • requested

  • applied

  • element

  • provider

  • species

  • profile_kind

  • data_key

  • data_source

  • parameter_axes

  • reference_label

  • citation_info

  • supported_windows_air

  • applied_windows_air

  • fallback

  • fallback_reason

Example:

{
    "requested": True,
    "applied": True,
    "element": "H",
    "provider": "pysme_h_3dnlte_rbf",
    "species": "H 1",
    "profile_kind": "intensity_ratio",
    "data_key": "data.hlineprof",
    "data_source": "lineprof.dat",
    "parameter_axes": ["teff", "logg", "monh", "mu"],
    "reference_label": "PySME bundled hydrogen profile dataset",
    "citation_info": None,
    "supported_windows_air": [
        [4335.0, 4345.0],
        [4855.0, 4868.0],
        [6550.0, 6575.0],
    ],
    "applied_windows_air": [
        [6550.0, 6575.0],
    ],
    "fallback": False,
    "fallback_reason": None,
}

This is the recommended way to determine whether a synthesis actually used the profile-based correction.

Provider Metadata#

Each provider is described internally by a manifest-like metadata object. This provider metadata is what drives:

  • the default provider mapping for each element

  • supported wavelength windows

  • the species check

  • summary metadata shown to the user

  • future reference / citation bookkeeping

For the current hydrogen provider, PySME records:

  • the provider name

  • the element and species

  • the supported windows

  • the profile kind

  • the data location key

  • the bundled data-source name

  • a short reference label

  • an optional citation payload

For the current hydrogen provider, the scientific reference is:

  • Amarsi et al. (2018, A&A, 615, A139)
    Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation

The provider summary therefore includes both:

  • reference_label

  • citation_info

so the citation can be surfaced directly to users and downstream tooling.

Fallback Behavior#

If the provider is requested but cannot be applied, PySME leaves the synthesis on the standard path and records the reason in sme.profile_nlte.summary.

Current fallback reasons include:

  • no_wavelength_overlap

    • the current synthesis window does not overlap any provider-supported wavelength region

  • no_matching_species_in_linelist

    • the current linelist does not contain the provider species

  • outside_profile_grid

    • the stellar parameters fall outside the supported provider grid

When one of these cases occurs, PySME also emits a WARNING-level log message.

Relationship To The Legacy Flag#

The old hydrogen-only flag

sme.tdnlte_H = True

is still accepted for backward compatibility.

Internally, it now maps onto the new profile-NLTE request path and fills sme.profile_nlte.summary. New code should prefer sme.profile_nlte.

Important Limitations#

  • This is currently an experimental feature.

  • It is not a replacement for sme.nlte.

  • It is not yet a general multi-element profile-correction framework.

  • Only one profile-NLTE element provider can be active at a time.

  • The current hydrogen provider is handled as one element-level bundle, not as independently switchable individual lines.

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