SN 2011fe (Type Ia)¶

SN 2011fe in M101 is the best-studied nearby Type Ia supernova, with 292 HST observations across 25 programs spanning 11.5 years. It serves as the primary validation benchmark for THATCH's spectroscopic pipeline.

HST Spectral Sequence¶

THATCH extracted 71 STIS spectra across 4 gratings (G230LB, G430L, G750L, G140L), spanning days -14 to +3996 relative to B-maximum. After merging duplicate exposures at the same epoch/grating, this produces 12 unique spectral epochs covering UV through NIR:

SN 2011fe spectral sequence

HST/STIS spectral sequence of SN 2011fe from 14 days before to 11 years after B-band maximum. Each epoch combines UV (G230LB), optical (G430L), and red (G750L) gratings. The classic SN Ia spectral evolution is clearly visible: rising UV flux pre-maximum, prominent SiII 6150 Å and CaII H&K absorption, transition to iron-group emission in the nebular phase, and late-time COS/FUV detection at +3996 days.

Key Features Visible¶

Pre-maximum (-14d to 0d): Rising UV continuum, SiII 6150 Å absorption deepening
Post-maximum (+4d to +40d): UV fading, iron-group features emerging
Nebular (+376d, +378d): Forbidden [FeII], [FeIII], [CoIII] emission lines
Very late (+3996d): COS/FUV spectroscopy probing the SN remnant

Why This Matters¶

This 12-epoch UV-optical spectral sequence is exactly the type of training data needed for Roman's multimodal classifiers. SN 2011fe demonstrates that THATCH can automatically extract, merge, and organize complex multi-grating spectroscopic monitoring campaigns from the HST archive.

Reproducing This Example¶

# Extract all STIS spectra
python examples/demo_sn2011fe.py

# Plot the spectral sequence
python examples/plot_spectral_sequences.py