Pushchino Multibeam Pulsar Search. IX. Detection of a minute-long transient on the LPA antenna

TL;DR

This study reports the discovery of a minute-long transient, LPA J0108+13, detected near the radio galaxy 3C 33 with the Pushchino LPA-3 at 110.4 MHz. Six powerful bursts (tens to hundreds of Jy, lasting 1–4 minutes) were found across ~200 hours of archival data, analyzed via aperture-like beam modeling and sky-map verification to separate the transient from 3C 33. The authors derive coordinates consistent with 3C 33 but acknowledge potential galactic-origin scenarios; no dispersion-based distance could be measured, leaving the source’s nature open. They propose a new class of strong minute transients and call for continued archival studies to establish their prevalence and physical mechanism, highlighting the significance for transient radio astronomy at low frequencies.

Abstract

A transient (LPA J0108+13) with repeated bursts was detected on the Large Phased Array (LPA) radio telescope at a central frequency of 110.4 MHz in the direction of the radio galaxy 3C 33. The flux density of bursts ranges from tens to hundreds of Jy, and the duration of the bursts is \approx 1^m - 4^m. In daily observations, the total duration of which at the location of the transient exceeds 200 hours in the observation interval 2013-2025, 6 bursts were found. The nature of the source could not be determined. We believe that a new type of transients has been discovered.

Figures (5)

• Figure 1: Sky map for September 22, 2024 based on observations at LPA-3. Declinations are marked on the vertical axis, and UTC time is shown on the horizontal axis. Some bright radio sources have been signed. The flux density scale (the panel to the right of the panoramic image) is given in units of the calibration step. The colors from dark blue to burgundy show brightness temperatures from about 450 K to more than 3000 K. In the right part of the figure, source 3C 48 is marked (a powerful quasar clearly visible on the maps is a landmark for identifying weaker sources), as well as radio galaxies such as FRII 3C 47 and 3C 33, which fall on map fragments containing the studied transient for different dates and are presented in the following sections.
• Figure 2: The figure shows the recording of the 3C 33 source for August 13, 2024 in two adjacent beams the day before the observed flare. The data contains the source model, the sum of the base signal level and the function $[sin(x)/x]^2$ (see equations \ref{['eq:model']} and \ref{['eq:psf']}). Strong ionospheric scintillations lasting tens of seconds is visible on the source. During calm ionospheric conditions, the source signal repeats the model almost exactly. The source record in the main beam is shown in orange, the red dotted line is the inscribed source model, the green and blue lines are the entry in the neighboring beam and the inscribed model.
• Figure 3: The transient is LPA J0108+13 after subtracting 3C 33. The horizontal axis shows the time in seconds. A segment showing the flux density is shown along the vertical axis. The transient pulse in the main beam is shown in blue, and the adjacent beam is shown in orange. From the ratio of the amplitudes and based on the energy distribution between the beams according to the dependence $[sin(x)/x]^2$, the coordinate LPA J0108+13 in declination was calculated. The transient profile sometimes becomes negative due to the contribution of the ionosphere to the amplification and attenuation of the 3C 33 flux before subtracting its transmission curve model.
• Figure 4: Fragments of sky maps. 3C 33 is centered, the coordinates are close to the coordinates of the ICRS system. The maximum pixel value corresponds to the height of the calibration step. Six series of map fragments are laid out along the horizontal axis for each found event with a transient. The series consists of three consecutive days, from top to bottom: a fragment of the map the day before the burst, the day with the burst, and the next day. The data for November 11 and 13, 2016 are of poor observation quality, and the gaps in the data are filled in with black. The arrows mark the sources 3C 33 and 3C 47.
• Figure 5: The transient LPA J0108+13 in the luminosity diagram is the duration of the signal relative to known types of sources. The basis of the drawing is taken from the paper Pietka2015, Pietka2015.