DOI: 10.5281/zenodo.10689772
title: Rossi X-ray Timing Explorer All-Sky Monitor Count Rate Light Curve Data Release

description: This data release includes Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) data. These data consist of a table of ASM pointings, individual count rate light curves in three energy bands for each of three ASM cameras during times of fixed pointings from 1996 Jan 5 through 2009 Dec 17, and a summary of gamma-ray bursts found by the RXTE ASM team within the ASM data.

Full Details:

RXTE comprised three instruments, the ASM, and two pointed instruments, the Proportional Counter Array (PCA) and the High Energy X-ray Timing Experiment (HEXTE). The ASM (see [1]) had three cameras, each with a long-by-short field of view (FOV): 90x6 deg FWHM and 105x12 deg FWZI. They were known as scanning shadow cameras (SSC) with SSC1 and SSC2 aligned in the pointing direction with the long axes tilted with respect to one another. SSC3 pointed 90 deg away, along the instrument spin axis.  The detector plane contained an array of carbon-coated quartz anodes, embedded in a Xe gas mixture. X-ray event positions along the anodes were determined with the charge-division method, and position histograms of recorded events are imprinted by the shadow of the camera's mask, with patterns shifted by the two offset angles, i.e., the short-axis offset and long-axis offset of a given X-ray source, compared to the camera pointing direction. The coded mask was a metal plate perforated with patterns of open slits that were narrow along the short axis, providing a ~1 arcmin position in that dimension.  Six such slit patterns, separated by solid support bands, were stacked along the camera's long axis, and the recognition of which mask subarray is projected on which anodes constrained the source position along the camera's long axis.  The cameras were thus considered to be 1.5 dimensional. The large FOV meant that there were usually a combination of overlapping coded mask patterns in each camera's position histogram array.

The ASM had three energy channels, roughly 1.5-3, 3-5, and 5-12 keV. The coded mask deconvolution was not solved in fine keV steps, so a response matrix was not used. Instead a rough scaling to Crab energy was used for the three ASM bands (see [2]).

Data came in a series of 90 second “dwells”, with cameras fixed on the sky, followed by a quick 6 deg rotation of the instrument. Only the camera light curves from the fixed dwells are included in this package. A dwell is defined by two numbers, the dwell sequence id, given in RXTE spacecraft time (s), for the start of the first dwell, followed by the dwell number in the particular sequence. The first dwell file available in this data set is dwell sequence number 63448692 and dwell number 04, stored in filename amts63448692.04. The prefix “amts” means that the camera light curve was delivered via ASM "multiple time series mode", which continued through March 1, 2001. On March 2, 2001, ASM data were delivered in event mode. The camera light curves were made for event mode, prefix “ev”, with 1 second resolution and three energy bands with the same format as the “amts” files. The file asm_mission_pointing.table, included in this package, includes the start time (in RXTE spacecraft time), dwell sequence, and dwell id, which can be used to identify which dwell files to input, plus additional information about the camera pointings which is not currently used. The HEASARC xTime tool can be used to convert UTC to RXTE mission elapsed time.  

Dataset Description:

Each light curve file in these tarred directories has 90 rows x 10 columns. Time (SCT) plus counts in SSC1 (energy bands A, B, C) SSC2 (A, B, C) and SSC3 3 (A, B, C).

Columns are arranged as: SCT (seconds) SSC1-A, SSC1-B, SSC1-C, SSC2-A, SSC2-B, SSC2-C, SSC3-A, SSC3-B, SSC3-C



cam_dwasc_01.tar.gz  ASM camera light curves for dwell sequence numbers 63448692 through 99999185 (1996 Jan 5-1997 Mar 3)

cam_dwasc_02.tar.gz  ASM camera light curves for dwell sequence numbers 100002126 through 159998663 (1997 Mar 3 - 1999 Jan 26)

cam_dwasc_03.tar.gz  ASM camera light curves for dwell sequence numbers 160001624 through 226104807 (1999 Jan 26 - 2001 Mar 2)

cam_evasc_01.tar.gz ASM camera light curves for dwell sequence numbers 226109232 through 299998768 (2001 Mar 2 - 2003 Jul 5).

cam_evasc_02.tar.gz ASM camera light curves for dwell sequence numbers 300002608 through 399996336 (2003 Jul 5 - 2006 Sep 4)

cam_evasc_03.tar.gz ASM camera light curves for dwell sequence numbers 400000656 through 499999792 (2006 Sep 4 - 2009 Nov 5)

cam_evasc_04.tar.gz ASM camera light curves for dwell sequence numbers 500001984 through 503710464 (2009 Sep 4 - Dec 17)


Note that these data are also available in a less accessible format 



ASM camera pointing information: https://heasarc.gsfc.nasa.gov/FTP/xte/data/archive/ASMProducts/

ASM dwell count rate information: https://heasarc.gsfc.nasa.gov/FTP/xte/data/archive/ASMData/


Note that all files, including those within the tar files, are human readable ascii text.

asm_final_grb_info.dat is a catalog table of 40 GRBs/Candidate GRBs identified in RXTE ASM. Columns are GRB/candidate name, RA, Dec, arcsec, MJD, and RXTE mission week. The early portion of this catalog is reported in detail in [3]. Light curves from this paper can be compared with the camera light curves for those times.

asm_mission_pointing.table is an index file providing start times, sequence numbers, and dwell ids for ASM camera light curves. Columns in this file correspond to the individual dwell start time in seconds, dwell sequence number, dwell id number, exposure for each of 3 SSCs, RA, Dec, and roll angle for each of 3 SSCs, Instrument rotation angle, summed counts for each of 3 SSCs.

References

[1] Levine, A. et al. 1996, ApJ, 469, L33

[2] Zhang, S.N. et al. 1997, ApJ, 477, L95

[3] Smith, D.A. et al. 2002, ApJS, 141, 415