Package: arts-tracking-beams
ARTS tracking beamsThe Apertif Radio Transient System (ARTS) archive contains tied-array beam (TAB) data. The TABs have a time-dependent and
frequency-dependent pointing. This tool is able to convert the TAB data to a tracking beam (TB), which tracks a fixed point
on the sky over the course of an observation. Additionally, it can convert TAB data to Synthesised Beams (SBs),
which are suitable for transient searches.Dependenciespython >= 3.6numpy >= 1.17astropytqdmInstallationTo install the latest release:pip install arts_tracking_beamsTo install the latest master branch:pip install git+https://github.com/loostrum/arts_tracking_beamsUsageBasic usage of this package is described below. Tutorials are available athttps://loostrum.github.io/arts_tracking_beams.Input dataFirst download the data set of interest from the Apertif Long-Term Archive (ALTA). Tools to find which pulsars are in the
field-of-view of a given Apertif pointing and to download the data are available as a separatepython package.A data file from the archive is identified by three parameters: the task ID, compound beam (CB) index, and TAB index.
The fileARTS200102003_CB00_TAB00.fitswould be the observation identified by task ID 200102003
(that is, the third observation on January 2nd, 2020), CB zero, TAB zero. A TB is created from the TABs of a single CB.Creating a tracking beamA tracking beam (TB) is created from the TAB data witharts_create_tracking_beam.The simplest use case is to create a tracking beam
from a folder which contains only one data set (i.e. the TABs of one CB of one observation), for a source with known
coordinates. For example, to create a tracking beam towards the Crab pulsar:arts_create_tracking_beam --input_folder /path/to/data/ --source 'PSR B0531+21'If there are multiple data sets in the input data folder, specify the task ID and/or CB index. Instead of the source name,
it is also possible to provide a RA and Dec. The name of the output FITS file is determined automatically from the input
source name or RA/Dec, but can also be specified manually. Using all of these options, an example command is:arts_create_tracking_beam --input_folder /path/to/data/ --taskid 200102003 --cb 0 --ra 05:34:32 --dec 22:00:52 --output tracking_beam.fitsThe TB creation consists of two steps:Calculate the required TABs at each frequency and timeReorder the data from the input TAB FITS files and create a new FITS file containing the TB.The results of step 1 can be saved to disk with--save_tab_indices. To only calculate the TAB indices and
disable step 2 completely, use--no_fits_output.
To generate the FITS output from a TAB indices file on disk, use--load_tab_indices /path/to/tab/index/file.txt.
The script then loads the TAB indices and immediately goes to step 2.There are a few more settings that can be customized. Runarts_create_tracking_beam -hfor an overview of all options.Creating a synthesised beamA synthesised beam (SB) is a type of beam that reorders the TABs as function of frequency, butnotas function of time.
A single CB is covered by 71 SBs. Each SB is always made out of the same TABs. The SBs are used in the real-time
transient search that ARTS runs. The brightest transients may also be detectable in the archival data, so we here include
a tool to create the synthesised beams as well.The synthesised beam tool,arts_create_synthesised_beam, works
in a very similar fashion as the tracking beam tool. An example command:arts_create_synthesised_beam --input_folder /path/to/data --sb 35Runarts_create_synthesised_beam -hfor more options.