Breakthrough Listen

Abstract:

Abstract We report the discovery and characterisation of MKT J032848.4–271904.6, a new radio transient identified in the LADUMA field using SARAO Science Data Processor SDP UHF-band images from approximately one year of MeerKAT observations. Using the Transient Pipeline TraP and advanced filtering techniques, we identified a number of candidate variable radio sources in the field. All but one show variability consistent with refractive interstellar scintillation, leaving MKT J032848.4–271904.6 as the sole source exhibiting intrinsic variability. In addition, MKT J032848.4–271904.6 shows intrinsic variability at 0.816 GHz, with 13 radio detections across 41 epochs and a peak flux density of 1.041 ± 0.043 mJy. We associate this emission with a low-mass M-dwarf star LP 888–63, located 23 pc from the Sun and identified as a companion to the white dwarf binary system LAWD 14 WD 0326–273. LP 888–63 displays active flaring behaviour across the electromagnetic spectrum including multi-band optical data from MeerLICHT. TESS photometry reveals a periodic modulation in the blended light curve of 5.780 ± 0.507 days, consistent with rotational variability of a mid-M dwarf. Archival ESO spectra reveal Hα emission, confirming magnetic activity. These findings highlight the capability of MeerKAT’s SDP imaging and facilities like MeerLICHT for real-time detection and characterisation of stellar transients.

Abstract:

In 2025 July, the third-ever interstellar object, 3I/ATLAS, was discovered on its ingress into the solar system. Similar to the NASA Voyager missions sent in 1977, science probes by extraterrestrial life (“artifact technosignatures”) could be sent to explore other stellar systems like our own. In this campaign, we used the SETI Institute’s Allen Telescope Array to observe 3I/ATLAS from 1–9 GHz. We detected nearly 74 million narrowband hits in 7.25 hr of data using the newly developed search pipeline bliss. We then blanked hits by frequency and drift rate to mitigate radio frequency interference in our dataset, narrowing the dataset down to ∼2 million hits. These hits were further filtered by the localization code NBeamAnalysis, and the remaining 211 hits were visually inspected in the time-frequency domain. We did not find any signals worthy of additional follow-up. Accounting for the Doppler drift correction and given the nondetection, we are able to set an effective isotropic radiated power upper limit of 10–110 W on radio technosignatures from 3I/ATLAS across the frequency and drift rate ranges covered by our survey.

Abstract:

We present late-time (δt > 3000 days) optical (Keck), X-ray (Chandra and the Nuclear Spectroscopic Telescope Array), and radio (the Very Large Area, the Atacama Large Millimeter/submillimeter Array, and the Upgraded Giant Metrewave Radio Telescope) observations of the Type Ic-BL (SN Ic-BL) SN 2012ap. Previous studies of this supernova (SN) have suggested that it stands out as a key example of a weak engine-driven explosion due to the lack of gamma-ray burst (GRB) detection and mildly relativistic ejecta. Recently, radio sky surveys revealed the rebrightening of the radio emission from this SN, highlighting the possibilities of a density enhancement at large radii or the existence of an off-axis relativistic jet. While the late-time optical spectra do not exhibit the broad emission lines seen in other interacting supernovae (SNe), our analysis of the broadband radio and X-ray emission implies that both scenarios are plausible. If a density enhancement is responsible for the radio rebrightening, it has to result from a change in the mass-loss rate and/or wind velocity, possibly due to the transition of the progenitor from a red supergiant to a Wolf–Rayet star. If the late-time radio component is a result of an off-axis relativistic jet, we find that an energetic narrow jet viewed at θobs ≥ 80° is needed. In this scenario, SN 2012ap is not a result of a weak engine-driven explosion, and instead, it is similar to other GRBs. However, radio rebrightenings of SN Ic-BL are not enough on their own to determine the existence of off-axis jets, and our planned Very Long Baseline Array observation will help reveal the true nature of this SN.

Abstract:

Abstract:

We present the discovery of radio emission from the Be/X-ray binary A0538−66 with the Australian Square Kilometre Array Pathfinder, and results from a subsequent weekly monitoring campaign with the MeerKAT radio telescope. A0538−66, located in the Large Magellanic Cloud, hosts a neutron star with a short spin period ( ms) in a highly eccentric -d orbit . Its rare episodes of super-Eddington accretion, rapid optical and X-ray flares, and other peculiar properties make it an interesting system among high-mass X-ray binaries. Our MeerKAT data reveal that it is also one of the most radio-luminous neutron star X-ray binaries observed to date, reaching (at 1.28 GHz), with radio emission that appears to be orbitally modulated. We consider several possible mechanisms for the radio emission, and place A0538−66 in context by comparing it to similar systems.