The Upgraded GMRT:Opening New Windows on the Radio Universe

Gupta, Yashwant; Ajithkumar, B.; Kale, H. S.; Nayak, Sisir Kumar; Sabhapathy, S.; Sureshkumar, S.; Swami, R. V.; Chengalur, J. N.; Ghosh, S. K.; Ishwara‐Chandra, C. H.; Joshi, B. C.; Kanekar, Nissim; Lal, D.; Roy, Sthitadhi

doi:10.18520/cs/v113/i04/707-714

Cited by 262 publications

(191 citation statements)

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“…On the other hand, no such in-depth studies exist for J1816 -the eclipse and corresponding TOA delays are reported in Stovall et al (2014), but not deeply investigated -thus we obtained a dedicated eclipse observation at higher-frequency to complement the LOFAR data. For this, we utilised the upgraded Giant Metrewave Radio Telescope (uGMRT; Gupta et al 2017) to make a 6.5 h observation of J1816 with all available antennas in a 550-750 MHz band, pausing every ∼ 1.5 h to phase calibrate the array for ∼ 10 mins. The raw data were recorded with spectral and temporal resolutions of 48.8 kHz and 81.92 µs, respectively.…”

Section: Observationsmentioning

confidence: 99%

Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition

Polzin

Breton

Bhattacharyya

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a comparative study of the low-frequency eclipses of spider (compact, irradiating binary) PSRs B1957+20 and J1816+4510. Combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. PSRs B1957+20 and J1816+4510 have similar orbital properties, but the companions to the pulsars have masses that differ by an order of magnitude. A dedicated campaign to simultaneously observe the pulsed and imaged continuum flux densities throughout the eclipses reveals many similarities between the excess material within the two binaries, irrespective of the companion star properties. The observations show that the pulsar fluxes are removed from the line of sight throughout the main body of the eclipses. For PSR J1816+4510 we present the first direct evidence of an eclipse mechanism that transitions from one that removes the pulsar flux from the line of sight to one that merely smears out pulsations, and claim that this is a consequence of scattering in a tail of material flowing behind the companion. Inferred mass loss rates from the companion stars are found to be M C ∼ 10 −12 M yr −1 and M C ∼ 2 × 10 −13 M yr −1 for PSR B1957+20 and PSR J1816+4510, respectively; seemingly too low to evaporate the stars within Hubble time. Measurements of eclipse durations over a wide range of radio-frequencies show a significant dependence of eclipse duration on frequency for all pulsars, with wider eclipses at lower-frequencies. These results provide a marked improvement in the observational constraints available for theoretical studies of the eclipse mechanisms.

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Section: Observationsmentioning

confidence: 99%

Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition

Polzin

Breton

Bhattacharyya

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…However, in the near future it will be much easier to investigate whether more sources with the same characteristics exist. The combination of multifrequency new-generation instruments and surveys such as the LOFAR Two-metre Sky Survey (LoTSS, Shimwell et al 2019), the upgraded Giant Metrewave Radio Telescope (uGMRT, Gupta et al 2017), the APERture Tile In Focus (APERTIF, Oosterloo et al 2009), the MeerKAT International GHz Tiered Extragalactic Exploration survey (MIGHTEE, Jarvis et al 2016) now offer us unprecedented opportunities to perform statistical studies of the spatially resolved spectral properties of restarted radio galaxies, and of radio galaxies in general (Harwood & Morganti 2016, Morganti et al in prep).…”

Section: Summary and Prospectsmentioning

confidence: 99%

Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388

Brienza

Morganti

Harwood

et al. 2020

A&A

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Context. Restarted radio galaxies represent a unique tool for investigating the duty cycle of the jet activity in active galactic nuclei (AGN). The radio galaxy 3C388 has long been claimed to be a peculiar example of an AGN with multi-epoch activity because it shows a very sharp discontinuity in the GHz spectral index distribution of its lobes. Aims. We present here for the first time a spatially resolved study of the radio spectrum of 3C388 down to MHz frequencies aimed at investigating the radiative age of the source and constraining its duty cycle. Methods. We used new low-frequency observations at 144 MHz performed with the Low Frequency Array and at 350 MHz performed with the Very Large Array that we combined with archival data at higher frequencies (614, 1400, and 4850 MHz).Results. We find that the spectral indices in the lower frequency range, 144-614 MHz, have flatter values (α low ∼0.55-1.14) than those observed in the higher frequency range, 1400-4850 MHz, (α high ∼0.75-1.57), but they follow the same distribution across the lobes, with a systematic steepening towards the edges. However, the spectral shape throughout the source is not uniform and often deviates from standard models. This suggests that mixing of different particle populations occurs, although it remains difficult to understand whether this is caused by observational limitations (insufficient spatial resolution and/or projection effects) or by the intrinsic presence of multiple particle populations, which might be related to the two different outbursts.Conclusions. Using single-injection radiative models, we compute that the total source age is 80 Myr and that the duty cycle is about t on /t tot ∼ 60%, which is enough to prevent the intracluster medium from cooling, according to X-ray estimates. While to date the radio spectral distribution of 3C388 remains a rare case among radio galaxies, multi-frequency surveys performed with new-generation instruments will soon allow us to investigate whether more sources with the same characteristics exist.

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“…In this paper, we present the results of recent glitches that have been detected using the Ooty Radio Telescope (ORT: Swarup et al 1971) and the upgraded Giant Metrewave Radio Telescope (uGMRT: Swarup et al 1991;Gupta et al 2017) in a program of high cadence monitoring of high glitch rate pulsars. The ORT is a 530 m long offset parabolic cylindrical antenna in the north-south direction and 30 m wide in the east-west direction.…”

Section: Introductionmentioning

confidence: 99%

Observed glitches in 8 young pulsars

Basu

Joshi

Krishnakumar

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present eleven pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches (∆ν/ν) from our data ranges from 10 −6 to 10 −9 . Among these glitches, three are new discoveries, being reported for the first time. We also reanalyze the largest pulsar glitch in the Crab pulsar (PSR J0534+2200) by fitting the ORT data to a new phenomenological model including the slow rise in the post-glitch evolution. We measure an exponential recovery of 30 days after the Vela glitch detected on MJD 57734 with a healing factor Q = 5.8 × 10 −3 . Further, we report the largest glitch (∆ν/ν = 3147.9 × 10 −9 ) so far in PSR J1731−4744.

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The Upgraded GMRT:Opening New Windows on the Radio Universe

Cited by 262 publications

References 0 publications

Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition

Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition

Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388

Observed glitches in 8 young pulsars

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