Alexander Werner Pollak

We have discovered PSR J2108+5055, an extremely luminous but sporadic mode-changing rotating radio transient (RRAT), with a period of 0.495 s using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (FRB) instrument. We show that the brightest pulse from PSR J2108+5055 has a flux density of 3.1 ± 1.0 kJy, corresponding to a spectral luminosity of (7.5 ± 2.3) × 10 ²³ erg s ⁻¹ Hz ⁻¹ , assuming a dispersion-measure-derived distance of 1.6 ± 0.3 kpc. We place an upper limit on the duty cycle of PSR J2108+5055 at 0.002 and measure a surface magnetic field of 5.8 × 10 ¹¹ G, a characteristic age of 1.2 × 10 ⁷ yr, and a spindown luminosity of 2.2 × 10 ³² erg s ⁻¹ . Using a simple model based on the Green Bank North Celestial Cap (GBNCC) survey, we place an upper limit on the number of PSR J2108+5055–like sources with similar peak flux densities in the GBNCC survey area of ∼80 RRATs. We show that if PSR J2108+5055 were placed at the edge of the Local Group of galaxies, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) would detect its brightest pulse. The second brightest pulse has a peak flux density of 1.5 ± 0.7 kJy, and FAST would detect such a pulse out to ∼1 Mpc, covering the inner Local Group, including Andromeda.

In the search for technosignatures, it can be useful to narrow down the cosmic haystack by prioritizing time-coordinate “Schelling points” at which a beacon may be more likely to be transmitted. One such Schelling point is the antisolar point (ASP), the place and moment at which Earth would lie directly between a hypothetical transmitter in the Earth's transit zone (i.e., ecliptic) and the Sun. In this work, we describe a campaign to survey the ASP for radio technosignatures using the Allen Telescope Array, report the results of 3 initial nights of data from a pilot study in summer 2023, and discuss the future of the campaign. In the pilot study, we find no sky-localized narrowband 1–2.4 GHz technosignatures within an R.A. range of approximately 20.266–21.312 hr during the ASP, setting an upper limit flux density threshold of 115–936 Jy.

Quantifying the maximum energy of fast radio bursts (FRBs) can provide stringent constraints on their emission mechanisms and progenitor models. However, the most energetic bursts are rare, requiring a large sample of FRBs to detect them. In this work, we use the largest available such sample, 2998 one-off FRBs from the Second CHIME/FRB Catalog, to obtain a lower limit on the maximum energy ( E iso max ) of FRBs, assuming isotropic energy distribution from FRB sources. In the absence of known redshifts ( z ) for most sources, we present a framework that uses the dispersion measures (DMs) and fluences of these FRBs, together with the probability distribution of z given DM, to derive the lower limit on E iso max . We generate simulated FRB samples assuming different parameter values for a log-normal DM _host distribution and a Schechter function form of the FRB energy function to estimate how many outliers—FRBs with large DM contributions from the host galaxy or intervening galaxy halos—could artificially inflate this limit. After accounting for outliers, the lower limit on E iso max from Catalog 2 FRBs ranges between 1.1 × 10 ⁴¹ and 1.9 × 10 ⁴² erg, with best estimate 1.5 × 10 ⁴² erg. This limit is consistent with estimates of the Schechter function cutoff energy ( E iso cutoff ) derived from much smaller FRB samples. Moreover, inferred energies of hundreds of FRBs appear collectively limited around ∼10 ⁴² erg, suggesting a physical limit on the energy reservoir of FRB sources. The corresponding isotropic-equivalent FRB source energy is consistent with the total energy available in a magnetar’s external dipole magnetic field, supporting magnetars as FRB progenitors.

The LTT 3780 system hosts two known exoplanets—LTT 3780 b, a rocky super-Earth, and LTT 3780 c, a temperate sub-Neptune—orbiting a nearby M dwarf on opposite sides of the radius valley. LTT 3780 c has been proposed as a candidate Hycean world, making the system an important target for astrobiological investigation, particularly in light of recent JWST atmospheric observations. Although biosignature and technosignature searches both seek evidence of life beyond Earth, these approaches have historically been pursued independently. Well-characterized exoplanet systems provide an opportunity to combine these complementary search strategies. In this work, we conducted radio technosignature observations of the LTT 3780 system using both the Allen Telescope Array and the Karl G. Jansky Very Large Array (VLA). The two facilities provide complementary observational capabilities, with the ATA optimized for wide-band multibeam postprocessing analyses and the VLA enabling high-sensitivity real-time interferometric searches. Across ∼30 hr of total observing time, we searched for narrowband Doppler-drifting signals in the frequency range ∼1–10 GHz. After applying comprehensive radio-frequency interference mitigation and multibeam consistency tests, no candidate signals consistent with astrophysical or technosignature origins were identified. We place minimum detectable effective isotropic radiated power limits of 4.7 × 10 ¹² –3.6 × 10 ¹³ W across the observed bands and facilities. Although no technosignatures were detected, this work demonstrates how complementary observation and analysis strategies can be applied to exoplanets of astrobiological interest and serves as a pathfinder for future combined biosignature and technosignature investigations.

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.

We present the discovery and subsequent 3.2 yr monitoring campaign of the repeating fast radio burst (FRB) FRB 20220529A with CHIME/FRB. We observe a gradual decline in dispersion measure (DM) of −0.881 ± 0.001 pc cm ⁻³ yr ⁻¹ (−1.235 ± 0.001 pc cm ⁻³ yr ⁻¹ in the rest frame), implying a ≥3.5% ± 0.2% decrease in the total electron column in the source environment, and we see scattering timescale variations over weeks to years. We observe a short-lived excursion in which the DM rises by ∼1 pc cm ⁻³ , immediately preceding an increase in transient Faraday rotation measure (RM) of ∼2000 rad m ⁻² previously reported for this source, before returning to its gradual decline in DM. During this DM/RM excursion, we identify a local line-of-sight magnetic field of 3.4 ± 0.2 mG around FRB 20220529A, corresponding to one of the most strongly magnetized FRB environments. We measure a decrease in the linear polarization fraction of FRB 20220529A bursts with decreasing frequency that we attribute to depolarization from multipath propagation in the source environment. We also place a 5 σ upper limit on the spectral luminosity of an associated persistent radio source of ≤5 × 10 ²⁸ erg s ⁻¹ Hz ⁻¹ at 1.5 GHz. These observations are consistent with FRB 20220529A originating from a young (approximately years to centuries old) expanding supernova remnant, with short-lived DM and RM variability arising from interactions with the supernova remnant or with a binary companion.

Context . The South Pole Telescope third-generation camera (SPT-3G) has observed over 10 000 square degrees of sky at 95, 150, and 220 GHz (3.3, 2.0, 1.4 mm, respectively) and will significantly overlap the ongoing 14 000 square-degree Euclid Wide Survey. The Euclid collaboration recently released Euclid Deep Field South (EDF-S) observations of 23 square degrees at wide field depths in the first quick data release (Q1). Aims . With the goal of releasing complementary millimeter-wave data and encouraging legacy science, we performed dedicated observations of a 57-square-degree field overlapping the EDF-S. Methods . The observing time totaled 20 days, and we reached noise depths of 4.3, 3.8, and 13.2 μK-arcmin at 95, 150, and 220 GHz, respectively. Results . In this work we present the temperature maps and two catalogs constructed from these data. The emissive source catalog contains 601 objects (334 inside EDF-S) with 54% synchrotron-dominated sources and 46% thermal dust emission-dominated sources. The 5σ detection thresholds are 1.7, 2.0, and 6.5 mJy in the three bands. The cluster catalog contains 217 cluster candidates (121 inside EDF-S) with median mass M _500c = 2.12 × 10 ¹⁴ M _⊙ /h ₇₀ and median redshift z = 0.70, corresponding to an order-of-magnitude improvement in cluster density over previous tSZ-selected catalogs in this region (3.81 clusters per square degree). Conclusions . The overlap between SPT and Euclid data will enable a range of multiwavelength studies of the aforementioned source populations. This work serves as the first step toward joint projects between SPT and Euclid and provides a rich dataset containing information on galaxies, clusters, and their environments.