The NANOGrav 15-Year Data Set

The NANOGrav 15-Year Data Set
Public release "v2" 2023/10/09

OVERVIEW
--------

  This file contains "narrowband" and "wideband" TOAs and timing
solutions for the NANOGrav 15-year data set, covering data taken from
2004 to mid-2020 using Arecibo, the Green Bank Telescope (GBT), and the
Very Large Array (VLA) with ASP/GASP and PUPPI/GUPPI/YUPPI backend
instrumentation.  The observations, data reduction, and analysis
procedures used to produce these data are described in detail in the
accompanying paper, "The NANOGrav 15-year Data Set: Observations and
Timing of 68 Millisecond Pulsars" (Agazie et al., 2023, ApJL 951 L9,
DOI 10.3847/2041-8213/acda9a, arXiv:2306.16217).

  This release is available at Zenodo (DOI 10.5281/zenodo.8423265).

  All *.par and *.tim files are ASCII and are formatted for use with 
standard pulsar timing packages such as tempo2 and PINT, except for 
profile template files which are FITS format (narrowband) or python 
pickle files (wideband).

  Correlation matrix files are available in three formats (*.txt, *.npz,
and *.hdf5). See "description.txt" in both the narrowband and wideband 
./correlations subdirectories for more details about these files.

  Questions about the contents of this data set can be addressed to Joe
Swiggum (swiggumj@gmail.com) or comments@nanograv.org.


DIRECTORY AND FILE STRUCTURE (FURTHER DETAILS BELOW)
---------------------------------------------------

    ./README
        This file.
    ./clock
        Files for tracing observatory-measured TOAs to clock standards.
    ./narrowband
        Directory containing the narrowband data set.
	    Details are provided in README.narrowband in that directory.
    ./wideband
        Directory containing the wideband data set.
	    Details are provided in README.wideband in that directory.
    ./correlations
        Directory containing the correlation matrix files for both the 
            narrowband and wideband data. Details are provided in the 
            /wideband/ and /narrowband/ subdirectories' description.txt 
            files. 


SOFTWARE
--------

  This data set requires up-to-date installations of PINT or tempo2.
Our original analysis used PINT v0.9.1 and tempo2 v2022.01.1.  Up to date
versions of these packages, as well as usage information and
documentation can be found at the following repositories:

  PINT    https://github.com/nanograv/PINT
  tempo2  https://bitbucket.org/psrsoft/tempo2

  Note that we do not guarantee complete/correct functionality of these
timing models in the older original tempo software package.

  Please also ensure that the clock files you are using cover the full
range of the data set. Using the provided clock files (see below)
will ensure this.

  All models included here are based on a generalized least squares
(GLS) fit that includes a noise model with covariance between TOAs
(ECORR/jitter parameters, if narrowband; RNAMP/RNIDX red noise
parameters, if significant), as well as "traditional" EQUAD and EFAC
parameters.  Additional EFAC parameters for the wideband DM measurements
are also included.  All noise model parameters are included in the par
files.


CLOCK FILES
-----------

  The clock files used for our analysis are provided in the clock/
subdirectory.  While the standard files distributed with tempo and
tempo2 should be consistent with the clock files provided in the current
release at the time of writing, this may be a source of inconsistent
results in the future.  Please see ./clock/README.clock directory for 
installation instructions.


PLANNED REVISIONS
-----------------

  The initial release of the data set contained all fundamental data
products needed for pulsar timing analysis:  Times of arrival (.tim
files), timing models (.par files), standard template profiles,
clock correction files, and noise modeling MCMC chains. In v2,
parameter correlation matrices were added, as well as alternate versions
of timing model parameter files ("NoRedNoise" and "predictive"). A 
future release will add a number of other useful derived products as 
mentioned in the paper, including post-fit timing residuals and dispersion
measure time series.


CHANGE LOG
----------
2023/09/19
    Addition of "NoRedNoise" and "predictive" par files, correlation
    matrices, noise modeling chains (v2).
2023/07/01
    Correction to tar.gz directory structure (v1.0.1).
2023/06/28
    Initial public release (v1).