arXiv subjects

Benetge Perera

Publications and source records attributed to Benetge Perera.

5 recordsLinked to original sources

arXiv2025

Inferring Mbh-Mbulge Evolution from the Gravitational Wave Background

We test the impact of an evolving supermassive black hole (SMBH) mass scaling relation (Mbh-Mbulge) on the predictions for the gravitational wave background (GWB). The observed GWB amplitude is 2-3 times higher than predicted by astrophysically informed models which suggests the need to revise the assumptions in those models. We compare a semi-analytic model's ability to reproduce the observed GWB spectrum with a static versus evolving-amplitude Mbh-Mbulge relation. We additionally consider the influence of the choice of galaxy stellar mass function on the modeled GWB spectra. Our models are able to reproduce the GWB amplitude with either a large number density of massive galaxies or a positively evolving Mbh-Mbulge amplitude (i.e., the Mbh / Mbulge ratio was higher in the past). If we assume that the Mbh-Mbulge amplitude does not evolve, our models require a galaxy stellar mass function that implies an undetected population of massive galaxies (Mstellar > 10^11 Msun at z > 1). When the Mbh-Mbulge amplitude is allowed to evolve, we can model the GWB spectrum with all fiducial values and an Mbh-Mbulge amplitude that evolves as alpha(z) = alpha_0 (1 + z)^(1.04 +/- 0.5).

astro-ph.HE↗

arXiv2023

A Cryogenic Wideband (2.5-14 GHz) Receiver system for the Arecibo 12m Telescope

In this paper we present details of the construction of a wideband, cryogenic receiver and its successful commissioning on the Arecibo 12m telescope. The cryogenic receiver works in the 2.5-14 GHz frequency range. The telescope is operated by the Arecibo Observatory, and is located within the premises of the Observatory. We upgraded the current narrow band, room temperature receivers of the telescope with the new wideband receiver. The current receiver is built around a Quadruple-Ridged Flared Horn (QRHF) developed by Akgiray et al. (2013). To mitigate strong radio frequency interference (RFI) below 2.7 GHz, we installed a highpass filter before the first stage low noise amplifier (LNA). The QRHF, highpass filter, noise coupler and LNA are located inside a cryostat and are cooled to 15 K. The measured receiver temperature is 25 K (median value) over 2.5 GHz to 14 GHz. The system temperature measured at zenith is about 40 K near 3.1 and 8.6 GHz and the zenith antenna gains are 0.025 and 0.018 K/Jy at the two frequencies respectively. In the next stage of the development, we plan to upgrade the highpass filter in order to achieve better RFI rejection near 2.5 GHz, improve the aperture efficiency at 8.6 GHz and upgrade the IF system to increase the upper frequency of operation from 12 GHz to 14 GHz.

astro-ph.IM↗

arXiv2023

The NANOGrav 15-year Data Set: Bayesian Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries

Evidence for a low-frequency stochastic gravitational wave background has recently been reported based on analyses of pulsar timing array data. The most likely source of such a background is a population of supermassive black hole binaries, the loudest of which may be individually detected in these datasets. Here we present the search for individual supermassive black hole binaries in the NANOGrav 15-year dataset. We introduce several new techniques, which enhance the efficiency and modeling accuracy of the analysis. The search uncovered weak evidence for two candidate signals, one with a gravitational-wave frequency of $\sim$4 nHz, and another at $\sim$170 nHz. The significance of the low-frequency candidate was greatly diminished when Hellings-Downs correlations were included in the background model. The high-frequency candidate was discounted due to the lack of a plausible host galaxy, the unlikely astrophysical prior odds of finding such a source, and since most of its support comes from a single pulsar with a commensurate binary period. Finding no compelling evidence for signals from individual binary systems, we place upper limits on the strain amplitude of gravitational waves emitted by such systems.

astro-ph.HE↗

arXiv2022

Regular Solar Radio Imaging at Arecibo: Space Weather Perspective of Evolution of Active Regions

The sudden release of magnetic energy on the Sun drives powerful solar flares and coronal mass ejections. The key issue is the difficulty in predicting the occurrence time and location of strong solar eruptions, i.e., those leading to the high impact space weather disturbances at the near-Earth environment. Solar radio imaging helps identify the magnetic field characteristics of active regions susceptible to intense flares and energetic coronal mass ejections. Mapping of the Sun at X-band (8.1 -- 9.3 GHz) with the 12-m radio telescope at the Arecibo Observatory allows monitoring of the evolution of the brightness temperature of active regions in association with the development of magnetic complexity, which can lead to strong eruptions. For a better forecasting strategy in the future, such ground-based radio observations of high-spatial and temporal resolution, along with a full polarization capability, would have tremendous potential not only to understand the magnetic activity of solar eruptions, but also for revealing the particle acceleration mechanism and additional exciting science.

astro-ph.IM↗

arXiv2010

The Evolution of PSR J0737-3039B and a Model for Relativistic Spin Precession

We present the evolution of the radio emission from the 2.8-s pulsar of the double pulsar system PSR J0737-3039A/B. We provide an update on the Burgay et al. (2005) analysis by describing the changes in the pulse profile and flux density over five years of observations, culminating in the B pulsar's radio disappearance in 2008 March. Over this time, the flux density decreases by 0.177 mJy/yr at the brightest orbital phases and the pulse profile evolves from a single to a double peak, with a separation rate of 2.6 deg/yr. The pulse profile changes are most likely caused by relativistic spin precession, but can not be easily explained with a circular hollow-cone beam as in the model of Clifton & Weisberg (2008). Relativistic spin precession, coupled with an elliptical beam, can model the pulse profile evolution well. This particular beam shape predicts geometrical parameters for the two bright orbital phases which are consistent and similar to those derived by Breton et al. (2008). However, the observed decrease in flux over time and B's eventual disappearance cannot be easily explained by the model and may be due to the changing influence of A on B.

astro-ph.GA↗