arXiv subjects

Csanád Horváth

Publications and source records attributed to Csanád Horváth.

5 recordsLinked to original sources

arXiv2026

Evidence for the binary nature of the long-period radio transient ASKAP/DART J1832-0911

Long-period transients are a class of periodic pulsed radio source repeating on the minute to hour timescale. Recently, an increasing number of them are being identified as binary systems, specifically white dwarfs with low-mass main-sequence companions. In this work we analyse the most luminous long-period transient discovered to date, ASKAP/DART J1832-0911, with two years of radio data, and propose that it, too, may be a white dwarf system, although in a far more compact orbit than the aforementioned. The pulses are composed of quasi-periodic components which evolve in a systematic way over days and months. The source is highly linearly or elliptically polarised and its brightness enabled very high signal-to-noise measurement of the time-resolved Faraday rotation measure, which was found to vary across pulse phase. The linear polarisation position angle, circular polarised fraction, and spectral index also varied systematically in ways not typical of pulsars and magnetars. We show that an ultra-compact asynchronous polar explains much of the phenomenology of ASKAP/DART J1832-0911, in particular the evolution of the pulse morphology, rotation measure variation, and periodic X-ray emission, although we cannot conclusively prove a binary nature. However, our model makes testable predictions.

astro-ph.HE↗

arXiv2025

A binary model of long period radio transients and white dwarf pulsars

Long-period radio transients (LPTs) represent a recently uncovered class of Galactic radio sources exhibiting minute-to-hour periodicities and highly polarised pulses of second-to-minute duration. Their phenomenology does not fit exactly in any other class, although it might resemble that of radio magnetars or white dwarf (WD) radio emitting binary systems. Notably, two LPTs with confirmed multi-wavelength counterparts have been identified as WD -- M dwarf binaries. Meanwhile, systems such as AR Scorpii and J1912-44 exhibit short-period pulsations in hrs-tight orbits, with polarised radio emission proposed to be generated by the interaction of the WD magnetosphere with the low-mass companion wind. Here, we investigate the longest-lived LPT known, GPM J1839-10, demonstrating that it has a ~8.75 hr orbital period. We show that its radio pulses can be modelled in the same geometric framework as WD binary pulsars, in which radio emission is triggered when the magnetic axis of a rotating WD intersects its companion's wind in the binary orbital plane. We use a 36-year timing baseline to infer the orbital period and binary geometry from radio data alone. The model naturally predicts its intermittent emission and double-pulse structure. Crucially, we show that the beat period between the spin and the orbit matches the observed pulse substructure and polarisation signatures, providing strong support for the model. Applying it to the WD pulsar J1912-44, it successfully reproduces the emission profile and geometry as well. Our results suggest analogous emission-site geometries in these related classes of binary system -- a possibility we extend to the broader LPT / WD pulsar population.

astro-ph.HE↗

arXiv2025

A long period transient search method for the Murchison Widefield Array

We present an automated search method for radio transients on the minute timescale focused on the emerging long period transients (LPTs) in image-plane radio data. The method is tuned for use with the Murchison Widefield Array (MWA) and tested on archival observations from the GaLactic and Extragalactic All-Sky MWA Extended Survey (GLEAM-X) in the 70--300 MHz range. The images are formed from model-subtracted visibilities, before applying three filters to the time series of each pixel in an image, with each filter designed to be sensitive to a different transient behaviour. Due to the nature of radio interferometry and the refraction of the fluctuating ionosphere, the vast majority of candidates at this stage are artefacts which we identify and remove using a set of flagging measures. Of the 336 final candidates, 7 were genuine transients; 1 new LPT, 1 new pulsar, and 5 known pulsars. The performance of the method is analysed by injecting modelled transient pulses into a subset of the observations and applying the method to the result.

astro-ph.IM↗

arXiv2025

A new long period radio transient: Discovery of pulses repeating every 1.16 hours from ASKAP J175534.9-252749.1

We report the discovery of several new pulses from the source ASKAP J175534.9-252749.1 (J1755-2527), originally identified from a single 2-min long pulse, confirming it as a long period transient (LPT) with a period of ~1.16 hours. The pulses are significantly scattered, consistent with Galactic electron density models. Two of the new pulses also had measurable polarisation, but unlike the originally detected pulse, the polarisation angle does not behave as expected from the rotating vector model. We interpret historical non-detections of J1755-2527 as an intrinsic intermittency that occurs on month-long timescales, and discuss possible causes. We conjecture that, like some other LPTs with periods >~ 1 hour, J1755-2527 may host a white dwarf in a binary orbit, but note that its period is marginally shorter than the canonical orbital period minimum of cataclysmic variables. Our work highlights the importance of additional observations in establishing the nature of unusual radio-emitting objects.

astro-ph.HE↗

arXiv2025

Discovery of an RRAT-like pulsar via its single pulses in an MWA imaging survey

We report the discovery of PSR J0031$-$5726 in the GaLactic and Extragalactic All-sky MWA eXtended imaging survey at a Galactic latitude of $b \approx -60^\circ$. The pulsar exhibits both sporadic, extremely bright pulses reminiscent of rotating radio transients (RRATs) as well as a persistent, dimmer pulses. The bright pulses tend to arrive at later rotation phases than their dimmer counterparts, and have dramatically varying polarization angle curves, such that the integrated profile appears almost completely depolarized down to the system noise level. The rotation measure of individual pulses was found to sometimes vary by up to ${\sim}0.8\,$rad/m$^2$, but was otherwise generally consistent with its average (ionosphere-corrected) value of $10.0 \pm 0.1\,$rad/m$^2$. We surmise that J0031$-$5726 may represent a class of pulsar that is intermediate between normal pulsars and RRATs.

astro-ph.HE↗