astro-legacy-archive/rosat-rass-events

ROSAT RASS screened events

[image]

This is the scanning-mode PSPC-C STDEVT product for RASS field rs931621n00, source title RASS 3/16/21, not a derived sky cutout. It is the example field linked by HEASARC's RASS guide. That guide states verbatim: "The ROSAT All Sky Survey consists of 1378 distinct fields". This dataset contains all 74,317 screened events in source row order and the field's basic and ancillary table companions in embedded metadata.

Event columns and decoding

The source units, including pixeL and CODED, are retained verbatim. The event range is TIME 10773536.701904297--11511569.689453125 s and PI 8--300 chan. TIMESYS='scc', TIMEREF='LOCAL', MJDREFI=48043, and MJDREFF=0.879745370373712 define the time conversion. The observation header has TSTART=10485264 and TSTOP=12107004, corresponding to 1990-10-01T05:41:14 through 1990-10-20T00:10:14.

The FITS ONTIME=15025 s is the sum of accepted times over the component scans, not the exposure at any sky position. STDGTI contains 149 discontinuous intervals, with a summed duration of 12683 s, and retains its source START, STOP, and OBI_NUM columns. The pinned merged exposure map has shape 512x512 and spans 117.510735--443.96106 s. HEASARC warns that spectra extracted with XSELECT have incorrect assigned exposure because XSELECT uses the event-header ONTIME.

Source structure

The basic-products FITS file contains seven HDUs: PRIMARY (no data), STDGTI (149 rows, 3 columns), STDEVT (74,317 rows, 8 columns), REJEVT (12,374 rows, 8 columns), TSI (1,944 rows, 22 columns), STDQLM (1 row, 36 columns), and ALLQLM (1 row, 36 columns). REJEVT has the same eight source column identifiers as STDEVT.

The ancillary-products FITS file contains eight HDUs: PRIMARY (no data), OBSTABLE (1 row, 14 columns), EPHEM (0 rows, 19 columns), ASPECT (56,970 rows, 16 columns), HKP (0 rows, 9 columns), EVRATE (27,001 rows, 32 columns), HKSTA (0 rows, 12 columns), and GSTAR (0 rows, 1 column).

The Parquet schema metadata key event_list is JSON. Its fields object gives every event column's meaning, source FITS identity, type, unit, and encoding. Its auxiliary_tables array gives every other table's source index, HDU index, EXTNAME, row count, and complete per-column descriptions and values. Its fits_sources array preserves every FITS header. This is the canonical route to the numerous embedded per-column descriptions; identifiers and source values are not renamed or normalised.

Pinned sources

• —rs931621n00_bas.fits.Z: https://heasarc.gsfc.nasa.gov/FTP/rosat/data/pspc/processeddata/900000/rs931621n00/rs931621n00bas.fits.Z — 1,727,132 B compressed, 2,465,280 B uncompressed; SHA-256 ca8d7cd4f8b8a89d9801ce60a2ccd3e959dd32091a411074484768cf3d6d93aa.
• —rs931621n00_anc.fits.Z: https://heasarc.gsfc.nasa.gov/FTP/rosat/data/pspc/processeddata/900000/rs931621n00/rs931621n00anc.fits.Z — 3,742,814 B compressed, 9,302,400 B uncompressed; SHA-256 f964b7f9fff38644d9b94dcf502bbd70443bd2a3c81d7599dd1d393f94389ae2.
• —rs931621n00_mex.fits: https://heasarc.gsfc.nasa.gov/FTP/rosat/data/pspc/processeddata/900000/rs931621n00/rs931621n00mex.fits — 535,680 B; SHA-256 d56fe7ef4c3ceb99c645dd5a7569146c590c8687ce2865f649b0ece0d74e6fd5.
• —rs931621n00.public_contents: https://heasarc.gsfc.nasa.gov/FTP/rosat/data/pspc/processeddata/900000/rs931621n00/rs931621n00.publiccontents — 2,131 B; SHA-256 105dd4f48d7ce98d013b8c6c1ad001032b6ce85cf7c9f6bbf44db0e00c0d8a51.

The sources were checked on 2026-08-30. The manifest records NUMBER_OF_FILES = "10" and TOTAL_BYTES = "16159680" for the ten uncompressed FITS products; the four pins above are not claimed as the complete ten-file field.

Use and citation

The data were released to the public on 2000-03-11. HEASARC states:

HEASARC materials are all available freely for your use.

This is an express free-use statement, not a named formal licence. The survey data were processed at the Max-Planck-Institut für extraterrestrische Physik. Cite Voges et al. 1999, A&A 349, 389. HEASARC's requested acknowledgement is:

This research has made use of data and/or software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC.

Both statements are from the HEASARC data-use page, checked on 2026-08-30.

python -m venv .venv && .venv/bin/pip install datasets huggingface_hub pyarrow

from datasets import load_dataset
dataset = load_dataset("astro-legacy-archive/rosat-rass-events", "rs931621n00_bas__STDEVT", split="train[:1]")
print(dataset[0]["TIME"], dataset[0]["PI"])

10773536.701904297 23

import json
from huggingface_hub import hf_hub_download
import pyarrow.parquet as pq
path = hf_hub_download("astro-legacy-archive/rosat-rass-events", "rs931621n00_bas__STDEVT.parquet", repo_type="dataset")
print(json.loads(pq.read_metadata(path).metadata[b"event_list"])["event_count"])

74317

Errata and requests

Report corrections or dataset requests in the dataset's Community tab.