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  1. Free, publicly-accessible full text available March 1, 2023
  2. Context. The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30 m radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. Aims. We aim to introduce to the international community the upgrades performed and to show that the IAR observatory has become suitable for investigations in numerous areas of pulsar radio astronomy, such as pulsar timing arrays, targeted searches of continuous gravitational waves sources, monitoring of magnetars and glitching pulsars, and studies of a short time scale interstellar scintillation. Methods. We refurbished the two antennas at IARmore »to achieve high-quality timing observations. We gathered more than 1000 h of observations with both antennas in order to study the timing precision and sensitivity they can achieve. Results. We introduce the new developments for both radio telescopes at IAR. We present daily observations of the millisecond pulsar J0437−4715 with timing precision better than 1 μ s. We also present a follow-up of the reactivation of the magnetar XTE J1810–197 and the measurement and monitoring of the latest (Feb. 1, 2019) glitch of the Vela pulsar (J0835–4510). Conclusions. We show that IAR is capable of performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. This opens up the possibility of pursuing several goals in pulsar science, including coordinated multi-wavelength observations with other observatories. In particular, daily observations of the millisecond pulsar J0437−4715 would increase the sensitivity of pulsar timing arrays. We also show IAR’s great potential for studying targets of opportunity and transient phenomena, such as magnetars, glitches, and fast-radio-burst sources.« less
  3. Free, publicly-accessible full text available May 1, 2023
  4. Free, publicly-accessible full text available April 1, 2023
  5. Abstract We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds nomore »evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate.« less
    Free, publicly-accessible full text available April 1, 2023
  6. Free, publicly-accessible full text available March 1, 2023
  7. Intermediate-mass black holes (IMBHs) span the approximate mass range 100−10 5   M ⊙ , between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass ∼150  M ⊙ providing direct evidencemore »of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200  M ⊙ and effective aligned spin 0.8 at 0.056 Gpc −3 yr −1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpc −3 yr −1 .« less
    Free, publicly-accessible full text available March 1, 2023