arXiv subjects

Banshi Lal

Publications and source records attributed to Banshi Lal.

3 recordsLinked to original sources

arXiv2026

Long-term monitoring of repeating FRB 20220912A with the uGMRT at low radio frequencies

Some repeating FRBs exhibit occasional extreme repetition rates, but very few show a sustained high activity level. One such hyperactive repeater is FRB 20220912A, which was discovered by CHIME/FRB Collaboration on 2022 September 12. Here, we present results from a long-term monitoring campaign of FRB 20220912A using the upgraded Giant Metrewave Radio Telescope (uGMRT) in the frequency range from 300 to 750 MHz. Over the course of nearly two years, we detected a total of 643 bursts in this frequency range. The source exhibited extreme activity for a few months after its discovery and sustained its active phase for more than 1.5 years, with unsystematic modulations in the activity during this phase. The cumulative energy distributions in both bands show a break, consistent with other active repeaters like FRB 20121102A, FRB 202011124A, etc., suggesting common underlying emission mechanisms. Moreover, we show that the energy distribution shape for FRB 20220912A remains broadly same across a large range of frequencies and over time. Overall, the extended high activity, estimated total energy output, persistent power-law tails in the energy distributions, and the lack of detectable short timescale periodicity favor progenitor models invoking young dynamic magnetars, potentially emitting pulses across large rotation phase ranges.

astro-ph.HE↗

arXiv2026

Survey of compact sources for pulsars and exotic objects -- I. Overview and initial discoveries

Targeted searches for pulsars based on their counterparts in radio images have resulted in the discovery of interesting pulsars including the first ever discovered millisecond pulsar (MSP). Here, we report the first results from our image-based survey of compact sources for pulsars and exotic objects (SCOPE). SCOPE utilizes interferometric as well as time-domain observations to search for radio pulsations as well as characterize the sources in the image-domain to identify their true nature. In the first stage of the SCOPE survey, we have used the Giant Metrewave Radio Telescope (GMRT) and the Green Bank Telescope (GBT) to follow up a sample of 31 compact and steep-spectrum sources. We provide an overview of the survey, the sample selection, the search procedures, and present discoveries of two MSPs -- PSR J1840+1102 and PSR J1827-0849. PSR J1840+1102 is a 1.6 ms pulsar at the edge of the Scutum-Centaurus arm, while PSR J1827-0849 is the radio counterpart of a gamma-ray pulsar that was earlier thought to be radio-quiet, and both the sources have very steep radio spectra. Using the interferometric data, we also provide a morphological classification of all the sources, model and characterize their spectra and identify the resolved, extragalactic sources in our sample. We discuss these results in the context of future image-based pulsar surveys.

astro-ph.HE↗

arXiv2025

Low-energy Radio Bursts from Magnetar XTE J1810$-$197: Implications for Fast Radio Bursts

Magnetars are the leading candidate sources of fast radio bursts (FRBs). However, the observational probes of the connections between magnetars and FRBs are severely limited by the paucity of detection of highly energetic radio events from magnetars -- to date, only one radio burst as energetic as FRBs has been detected from a Galactic magnetar. Here, we present a detailed analysis of a large sample of low-energy bursts detected from the magnetar XTE J1810$-$197, and probe their implications for FRB emission from magnetars. We report detection of over 97000 bright radio pulses from 242 observations of the magnetar XTE J1810$-$197 over 4.5 years and two decades in frequency (300 MHz to 6.15 GHz), using the Giant Meterwave Radio Telescope and the Green Bank Telescope, after its recent outburst onset in December 2018. We present detailed analysis of the burst fluence distributions and their trends with time as well as frequency, and the waiting time distribution. We show that XTE J1810$-$197 rapidly switches between pulsar-like and giant-pulse-like emission states, and magnetars like XTE J1810$-$197 remain viable and likely emitters of FRBs, in the form of giant-pulses with energies comparable to FRBs. We also demonstrate that the lack of the detection of an underlying periodicity in the bursts from repeating FRBs might be caused by emission across a wide range of spin phases.

astro-ph.HE↗