Cross-Matching

The first step in THATCH is identifying which known transients have HST observations.

How It Works

For each transient, thatch.crossmatch queries the MAST archive within a configurable search radius (default 5"), filters to HST, and separates imaging from spectroscopy (STIS slit, WFC3/ACS grism, COS).

from thatch.crossmatch import check_hst_coverage

result = check_hst_coverage({
    "name": "AT2017gfo", "ra": 197.45037, "dec": -23.38148
})
print(f"{result['n_imaging']} imaging + {result['n_spectroscopy']} spectroscopy")
# 198 imaging + 31 spectroscopy

Results

A cross-match of 37 known transients finds 17 with HST data, totaling 6,133 observations (5,020 imaging + 1,109 spectroscopic):

Object	Type	Obs	Imaging	Spectroscopy	Programs
SN 1987A	SN II-pec	1,937	1,240	693	76
SN Refsdal	Lensed SN	1,430	1,289	141	61
SN 2005cs	SN IIP	724	664	60	30
SN 2014J	SN Ia	611	564	47	35
SN 2011fe	SN Ia	292	217	75	25
AT2017gfo	Kilonova	229	198	31	23
SN 1993J	SN IIb	170	170	0	22
ASASSN-14li	TDE	113	66	47	11
AT2018cow	FBOT	81	81	0	5

Output

The cross-match produces a Parquet table with name, ra, dec, type, n_imaging, n_spectroscopy, filters_imaging, instruments, programs, mjd_min, mjd_max.