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473 research outputs found

A new method for short duration transient detection in radio images: Searching for transient sources in MeerKAT data of NGC 5068

Author: Andersson A.
Chastain S.
de Blok W. J. G.
de Ruiter I.
Fender R.
Fijma S.
Healy J.
Maccagni F. M.
Meyers Z. S.
Rowlinson A.
van der Horst A. J.
van der Meulen K.
Wijers R. A. M. J.
Woudt P. A.
Zijlstra A.
Publication venue
Publication date: 28/06/2023
Field of study

Transient surveys are a vital tool in exploring the dynamic universe, with radio transients acting as beacons for explosive and highly energetic astrophysical phenomena. However, performing commensal transient surveys using radio imaging can require a significant amount of computing power, data storage and time. With the instrumentation available to us, and with new and exciting radio interferometers in development, it is essential that we develop efficient methods to probe the radio transient sky. In this paper, we present results from an commensal short duration transient survey, on time scales of 8 seconds, 128 seconds and 1 hour, using data from the MeerKAT radio telescope. The dataset used was obtained as part of a galaxy observing campaign, and we focus on the field of NGC 5068. We present a quick, wide field imaging strategy to enable fast imaging of large datasets, and develop methods to efficiently filter detected transient candidates. No transient candidates were identified on the time scales of 8 seconds, 128 seconds and 1 hour, leading to competitive limits on the transient surface densities of

6.7{\times}10^{-5}

deg

^{-1}

1.1{\times}10^{-3}

deg

^{-1}

, and

3.2{\times}10^{-2}

deg

^{-1}

at sensitivities of 56.4 mJy, 19.2 mJy, and 3.9 mJy for the respective time scales. We find one possible candidate that could be associated with a stellar flare, that was rejected due to strict image quality control. Further short time-scale radio observations of this candidate could give definite results to its origin.Comment: 11 pages (9 main, 2 appendix), 8 figures, 2 tables. Submitted to MNRA

arXiv.org e-Print Archive

Search and identification of transient and variable radio sources using MeerKAT observations: a case study on the MAXI J1820+070 field

Author: Andersson A.
Bright J.
Chastain S.
Driessen L. N.
Fender R.
Fijma S.
Heywood I.
Meijn J.
Rowlinson A.
Sivakoff G. R.
Tremou E.
van der Horst A. J.
Wijers R. A. M. J.
Woudt P. A.
Publication venue
Publication date: 31/03/2022
Field of study

Many transient and variable sources detected at multiple wavelengths are also observed to vary at radio frequencies. However, these samples are typically biased towards sources that are initially detected in wide-field optical, X-ray or gamma-ray surveys. Many sources that are insufficiently bright at higher frequencies are therefore missed, leading to potential gaps in our knowledge of these sources and missing populations that are not detectable in optical, X-rays or gamma-rays. Taking advantage of new state-of-the-art radio facilities that provide high quality wide-field images with fast survey speeds, we can now conduct unbiased surveys for transient and variable sources at radio frequencies. In this paper, we present an unbiased survey using observations obtained by MeerKAT, a mid-frequency (

\sim

1.4 GHz) radio array in South Africa's Karoo Desert. The observations used were obtained as part of a weekly monitoring campaign for X-ray binaries (XRBs) and we focus on the field of MAXI J1820+070. We develop methods to optimally filter transient and variable candidates that can be directly applied to other datasets. In addition to MAXI J1820+070, we identify four likely active galactic nuclei, one source that could be a Galactic source (pulsar or quiescent X-ray binary) or an AGN, and one variable pulsar. No transient sources, defined as being undetected in deep images, were identified leading to a transient surface density of