THATCH

Transient Harvester for Archival Training and Classification from Hubble

Documentation | Dataset | Paper (in prep)

THATCH is an open-source pipeline for extracting ML-ready transient light curves, image cutouts, and spectra from the Hubble Space Telescope archive. It bridges the domain gap between ground-based surveys (ZTF, Rubin/LSST) and space-based missions (Roman) by providing empirical space-based training data for transient classifiers.

Features

• thatch-harvest: Query MAST for HST observations of known transients, download calibrated images
• thatch-photometry: Aperture photometry with HST-specific aperture corrections, validated to 0.02 mag RMS
• thatch-spectra: Extract STIS slit spectra and WFC3/IR grism spectra (via grizli)
• thatch-cutouts: Generate image cutouts in HDF5 format for vision transformer ingestion
• thatch-catalog: Build unified multi-format catalogs (CSV, Parquet, FITS)
• thatch-crossmatch: Cross-match transient catalogs (TNS, OSC) against the HST archive

Installation

pip install thatch

For grism extraction support:

pip install "thatch[grism]"

Quick Start

from thatch.crossmatch import check_hst_coverage
from thatch.cutouts import extract_cutouts_for_object, save_cutouts_hdf5
from thatch.catalog import build_catalog

# Check if a transient has HST data
result = check_hst_coverage({"name": "AT2017gfo", "ra": 197.45037, "dec": -23.38148})
print(f"{result['n_imaging']} imaging + {result['n_spectroscopy']} spectroscopy observations")

# Extract cutouts
cutouts = extract_cutouts_for_object("data/AT2017gfo/", ra=197.45037, dec=-23.38148)
save_cutouts_hdf5(cutouts, "AT2017gfo_cutouts.hdf5", object_name="AT2017gfo")

# Build catalog from processed data
catalog = build_catalog("data/")
catalog.to_parquet("thatch_catalog.parquet")

CLI

thatch crossmatch                          # Find HST-observed transients
thatch cutouts AT2017gfo --ra 197.45 --dec -23.38 --datadir data/AT2017gfo/
thatch catalog data/ --format all          # Build catalog in CSV/Parquet/FITS

Demonstrated Objects

Object	Type	HST Obs	Filters	Spectroscopy
SN 1987A	SN II-pec	1,937	10	STIS, COS
SN Refsdal	Lensed SN	1,430	7	WFC3 grism
SN 2005cs	SN IIP	724	15+	STIS
SN 2014J	SN Ia	611	15	STIS
SN 2011fe	SN Ia	292	10+	STIS (43 spectra)
AT2017gfo	Kilonova	229	8	STIS + WFC3 grism
SN 1993J	SN IIb	170	10+	—
ASASSN-14li	TDE	113	5+	STIS
AT2018cow	FBOT	81	5+	—

Photometric Accuracy

THATCH aperture photometry with HST-standard aperture corrections achieves 0.02 mag RMS agreement with published values, validated against Cowperthwaite+2017 and Lyman+2018 measurements of AT2017gfo.

Citation

If you use THATCH in your research, please cite:

Coughlin et al. (in prep). THATCH: Transient Harvester for Archival Training
and Classification from Hubble.

License

BSD 3-Clause. See LICENSE.