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Extraction of HETG ONC VLP Spectra and Light Curves

Orion VLP Master Source Table Data, Flux Spectra and Light Curves from Reliably Detected Sources, Official Release 1 (October 30 2023)

1. Introduction:

This first release provides the community with a first cut of confusion cleaned X-ray spectra of the Orion Nebula Cluster observed with the HETG onboard the Chandra X-ray Observatory. The data were taken starting in 1999 until 2021.

The confusion cleaning is based on several aspects of sources for confusion, which includes cluster point sources intersecting with grating dispersions, grating arms intersecting each other in CCD space, as well as grating dispersion overlaps prohibiting proper order sorting. The latter is a major effect and resulted in sometimes severe data losses. In the first release, our automated procedure took care of the vast majority of point sources and grating arm intersections. With respect to the dispersion arm overlaps, in this release we took a statistical approach optimizing the agreement of all four grating dispersion arms in the merged data to agree within a 1 sigma statistical uncertainty over 90% of the bandpass between 2 and 15 Angstrom. For that we used the zero order flux fractions of the interfering sources as the driving parameter.

There are still many caveats and rooms for improvement, which we will address in upcoming releases, which include the treatment of the increasing background at high dispersion, improve extraction efficiency, exclude observations with non-detections before confusion cleaning, include possible new detections, investigate the 5 Angstrom excess we observe in the HEG, though at low statistics, spotcheck individual observations for any residual issues.

Release 1 provides the community with an excellent starting point for addressing our identified science projects. Out of the 46 sources that were extracted, 37 resulted in valid spectral data. 7 sources have less than 1000 counts in 1st order, some of those may not yet be very useful.

The overall data properties are summarized in the HETG Orion VLP pilot paper:

Schulz et al, AJ.... orion_vlp.pdf

2. Download all data (84 Mb gtar): all_data.tar.gz

Download of all the data that made this 1st release, which includes four (MEG +/-1st, HEG +/-1st orders) rmfs (all sources can use the same rmfs), four (MEG +/-1st, HEG +/-1st orders) arfs for each ONC source, one pha2 file containing MEG +/-1st, HEG +/-1st order spectra for each ONC source.

3. Download rmfs only (50 Mb gtar): rmfs.tar.gz

Download of the four (MEG +/-1st, HEG +/-1st orders)) rmfs separately

4. Download flux lightcurves: lctabs.tar.gz

Tarball of ascii tables to download containing the fluxes for all four (MEG +/-1st, HEG +/-1st orders) grating arms (part,order,day,flux,err, where part = 1 is HEG and part = 2 is MEG, day is the number of days past the CHandra MJD reference of 50814.0 days)

5. Source table with various individual information and downloads:

source: Source name as used in the download data

tot. counts(eff): The total number of remaining counts after cleaning. "eff." describes the cleaning efficiency which lists the percentage of the remaining counts after cleaning.

eff.exp [ks]: The effective exposure of that source that remeins after cleaning in kilo seconds.

spectrum: Thumbnail of the co-added 1st order spectrum on an MEG grid grouped by a factor 12. Click on thumbnail for full image.

lightcurve: X-ray light curve stretched for the three data periods, each data point represents an observation ID. Click on thumbnail for full image.

data: Tarball (gzipped) of individual source arfs and pha2s to download. Click on green "PHA2,ARFs". For rmfs see (3.)

spectral type: The identified spectral type as in the master source list

log T_eff: The surface temperature as in the master source list

M_sun : Stellar mass as in the master source list

log age: Stellar age as in the master source list

Lightcurves thumbnails: all_lcurve.tar.gz

Spectra thumbnails: all_spectra.tar.gz