Real-Time Implementation of MAD-Based RFI Excision on FPGA

Buch, Kaushal D.; Naik, Kishor; Nalawade, Swapnil; Bhatporia, Shruti; Gupta, Yashwant; Ajithkumar, B.

doi:10.1142/s2251171719400063

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…Coherent beam filterbank data at the best achievable time-frequency resolution were recorded (listed in Table 1). In some of the uGMRT observing epochs (2019 December 2, 2020 January 10, and 2020 February 15), we used a real real-time broadband radio frequency interference (RFI) removal system (Buch et al 2016(Buch et al , 2019a(Buch et al , 2019b during our observations. Our observations spanned a period of 10 yr, covering a total of 39 eclipses.…”

Section: Observations and Data Analysismentioning

confidence: 99%

First Systematic Study Reporting the Changes in Eclipse Cutoff Frequency for Pulsar J1544+4937

Kumari,

Bhattacharyya,

Sharan

et al. 2024

ApJ

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We present results from long-term monitoring of frequency-dependent eclipses of the radio emission from PSR J1544+4937, which is a black widow spider millisecond pulsar (MSP) in a compact binary system. The majority of such systems often exhibit relatively long-duration radio eclipses caused by ablated material from their companion stars. With the wide spectral bandwidth of the upgraded Giant Metrewave Radio Telescope, we present the first systematic study of temporal variation of eclipse cutoff frequency. With decade-long monitoring of 39 eclipses for PSR J1544+4937, we notice significant changes in the observed cutoff frequency ranging from 343 ± 7 to ≥740 MHz. We also monitored changes in eclipse cutoff frequency on timescales of tens of days and observed a maximum change of ≥315 MHz between observations that were separated by 22 days. In addition, we observed a change of ∼47 MHz in eclipse cutoff frequency between adjacent orbits, i.e., on timescales of ∼2.9 hr. We infer that such changes in the eclipse cutoff frequency depict an eclipse environment for the PSR J1544+4937 system that is dynamically evolving, where, along with the change in electron density, the magnetic field could also be varying. We also report a significant correlation between the eclipse cutoff frequency and the mass-loss rate of the companion. This study provides the first direct evidence of mass-loss rate affecting the frequency-dependent eclipsing in a spider MSP.

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Section: Observations and Data Analysismentioning

confidence: 99%

First Systematic Study Reporting the Changes in Eclipse Cutoff Frequency for Pulsar J1544+4937

Kumari,

Bhattacharyya,

Sharan

et al. 2024

ApJ

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“…The observations in each band were taken in two sessions, placed on consecutive days. We used real-time Radio Frequency Interference (RFI) filtering (e.g., Buch et al 2019Buch et al , 2022Buch et al , 2023 in GWB, targeted for mitigating broadband (BB) RFI. We used it in the mode where the RFI samples (those that exceeded the 3σ threshold in voltages) were replaced with digital noise.…”

Section: Ugmrtmentioning

confidence: 99%

A Deep uGMRT View of the Ultra-steep Spectrum Radio Halo in A521

Santra,

Kale,

Giacintucci

et al. 2024

ApJ

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We present the first detailed analysis of the ultra-steep spectrum radio halo in the merging galaxy cluster A521, based on upgraded Giant Metrewave Radio telescope observations. The combination of radio observations (300–850 MHz) and archival X-ray data provides a new window into the complex physics occurring in this system. When compared to all previous analyses, our sensitive radio images detected the centrally located radio halo emission to a greater extent of ∼1.3 Mpc. A faint extension of the southeastern radio relic has been discovered. We detected another relic, recently discovered by MeerKAT, and coincident with a possible shock front in the X-rays, at the northwest position of the center. We find that the integrated spectrum of the radio halo is well-fitted with a spectral index of −1.86 ± 0.12. A spatially resolved spectral index map revealed the spectral index fluctuations, as well as an outward radial steepening of the average spectral index. The radio and X-ray surface brightness is well correlated for the entire and different subparts of the halo, with sublinear correlation slopes (0.50–0.65). We also found a mild anticorrelation between the spectral index and X-ray surface brightness. Newly detected extensions of the SE relic and the counter relic are consistent with the merger in the plane of the sky.

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“…3C 48 was used as the flux and phase calibrator. The real-time radio frequency interference (RFI) filter system for the uGMRT (Buch et al 2019) was used to mitigate any broadband RFI that might be present during the observation.…”

Section: Ugmrtmentioning

confidence: 99%

A Hot Core in the Group-dominant Elliptical Galaxy NGC 777

O’Sullivan,

Rajpurohit,

Schellenberger

et al. 2024

ApJ

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NGC 777 provides an example of a phenomenon observed in some group-central ellipticals, in which the temperature profile shows a central peak, despite the short central cooling time of the intragroup medium. We use deep Chandra X-ray observations of the galaxy, supported by uGMRT 400 MHz radio imaging, to investigate the origin of this hot core. We confirm the centrally peaked temperature profile and find that the entropy and cooling time both monotonically decline to low values (2.62 − 0.18 + 0.19 keV cm2 and 71.3 − 13.1 + 12.8 Myr, respectively) in the central ∼700 pc. Faint diffuse radio emission surrounds the nuclear point source, with no clear jets or lobes but extending to ∼10 kpc on the northwest–southeast axis. This alignment and extent agree well with a previously identified filamentary Hα + [N ii] nebula. While cavities are not firmly detected, we see X-ray surface brightness decrements on the same axis at 10–20 kpc radii, which are consistent with the intragroup medium having been pushed aside by expanding radio lobes. Any such outburst must have occurred long enough ago for lobe emission to have faded below detectability. Cavities on this scale would be capable of balancing radiative cooling for at least ∼240 Myr. We consider possible causes of the centrally peaked temperature profile, including gravitational heating of gas as the halo relaxes after a period of active galactic nucleus jet activity, and heating by particles leaking from the remnant relativistic plasma of the old radio jets.

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Real-Time Implementation of MAD-Based RFI Excision on FPGA

Cited by 9 publications

References 11 publications

First Systematic Study Reporting the Changes in Eclipse Cutoff Frequency for Pulsar J1544+4937

First Systematic Study Reporting the Changes in Eclipse Cutoff Frequency for Pulsar J1544+4937

A Deep uGMRT View of the Ultra-steep Spectrum Radio Halo in A521

A Hot Core in the Group-dominant Elliptical Galaxy NGC 777

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