A Wideband Digital Back-End for the Upgraded GMRT

Reddy, S H; Kudale, Sanjay; Gokhale, U.; Halagalli, Irappa; Raskar, Nilesh; De, Kishalay; Gnanaraj, Shelton; Kumar, Bambam; Gupta, Yashwant

doi:10.1142/s2251171716410117

Cited by 66 publications

(44 citation statements)

References 16 publications

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“…We observed GW170817 with the uGMRT in Band 3 (effective bandwidth 550-750 MHz) (PI: Mooley). The observations were carried out with 400 MHz correlator bandwidth centered at 750 MHz using the non-polar continuum interferometric mode of the GMRT Wideband Backend (GWB; Reddy et al 2017). The epochs from 2018 May and 2018 Jun were divided into several short (∼1-3 hr) observations carried out over several days.…”

Section: Ugmrtmentioning

confidence: 99%

A Strong Jet Signature in the Late-time Light Curve of GW170817

Mooley

Frail

Dobie

et al. 2018

ApJL

158

121

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We present new 0.6-10 GHz observations of the binary neutron star merger GW170817 covering the period up to 300 days post-merger, taken with the upgraded Karl G. Jansky Very Large Array, the Australia Telescope Compact Array, the Giant Metrewave Radio Telescope and the MeerKAT telescope. We use these data to precisely characterize the decay phase of the late-time radio light curve. We find that the temporal decay is consistent with a power-law slope of t −2.2 , and that the transition between the power-law rise and decay is relatively sharp. Such a slope cannot be produced by a quasi-isotropic (cocoon-dominated) outflow, but is instead the classic signature of a relativistic jet. This provides strong observational evidence that GW170817 produced a successful jet, and directly demonstrates the link between binary neutron star mergers and short-hard GRBs. Using simple analytical arguments, we derive constraints on the geometry and the jet opening angle of GW170817. These results are consistent with those from our companion Very Long Baseline Interferometry (VLBI) paper, reporting superluminal motion in GW170817.

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Section: Ugmrtmentioning

confidence: 99%

A Strong Jet Signature in the Late-time Light Curve of GW170817

Mooley

Frail

Dobie

et al. 2018

ApJL

158

121

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“…The source was observed on 2017 July 19 (∼ 275 days after r band peak) at L band (centered at 1.2 GHz) for a total on source time of ≈ 4.5 hours. We used the GMRT Wideband Backend (GWB; Reddy et al 2017) configured in the continuum interferometric mode with 400 MHz bandwidth. 3C48 was used as the flux density and bandpass calibrator, while the source J0029+349 was used as the phase calibrator.…”

Section: Ugmrt Observationsmentioning

confidence: 99%

iPTF 16hgs: A Double-peaked Ca-rich Gap Transient in a Metal-poor, Star-forming Dwarf Galaxy

Kasliwal

Cantwell

et al. 2018

ApJ

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Calcium rich gap transients represent an intriguing new class of faint and fast evolving supernovae that exhibit strong [Ca II] emission in their nebular phase spectra. In this paper, we present the discovery and follow-up observations of iPTF 16hgs -an intermediate luminosity and fast evolving transient that exhibited a double peaked light curve. Exhibiting a typical Type Ib spectrum in the photospheric phase and an early transition to a [Ca II] dominated nebular phase, we show that iPTF 16hgs shows properties consistent with the class of Ca-rich gap transients, with two interesting exceptions. First, while the second peak of the light curve is similar to other Ca-rich gap transients (suggesting M ej ≈ 0.4 M and peak luminosity ≈ 3 × 10 41 ergs s −1 ), we show that the first blue and fast declining (over ≈ 2 days) peak is unique to this source. Second, with Integral Field Unit observations of the host galaxy, we find that iPTF 16hgs occurred in the outskirts (projected offset of ≈ 6 kpc ≈ 1.9 R eff ) of a low metallicity (≈ 0.4 Z ), star forming, dwarf spiral galaxy. Using deep late-time VLA and uGMRT observations, we place stringent limits on the local environment of the source, ruling out a large parameter space of circumstellar densities and mass loss environments of the progenitor. If iPTF 16hgs shares explosion physics with the class of Ca-rich gap transients, we suggest that the presence of the first peak can be explained by enhanced mixing of 0.01 M of 56 Ni into the outer layers the ejecta, reminiscent of some models of He-shell detonations on WDs. On the other hand, if iPTF 16hgs is physically unrelated to the class, the first peak is consistent with shock cooling emission (of an envelope with a mass of ≈ 0.08 M and radius of ≈ 13 R ) associated with a core-collapse explosion of a highly stripped massive star in a close binary system.

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“…The more general time evolutions for the LL parameters can have observational implications due to the following reasons. These days it is indeed possible to measure TOAs with ∼100 ns uncertainties due to the advent of real-time coherent de-dispersion (Hankins & Rajkowski 1987) and availability of large collecting area telescopes like the Giant Metrewave Radio Telescope equipped with 400 MHz wide-band receivers (Reddy et al 2017). The TOA precision is likely to improve further with the advent of telescopes like the Five hundred meter Aperture Spherical Telescope (FAST; Nan et al (2011)) and the Square Kilometre Array (SKA; Combes (2015)).…”

Section: Introductionmentioning

confidence: 99%

Exploring the effect of periastron advance in small-eccentricity binary pulsars

Susobhanan

Gopakumar

Joshi

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Short-orbital period small-eccentricity binary pulsars can, in principle, experience substantial advance of periastron. We explore the possibility of measuring this effect by implementing a timing model, ELL1k, in the popular TEMPO2 pulsar timing package. True secular variations in the Laplace-Lagrange parameters, present in our ELL1k model, can lead to measurable timing residuals while pursuing decade-long timing campaigns using the existing ELL1 timing model of Lange et al. (2001), especially for binaries exhibiting significant periastron advance. We also list the main differences between our approach and various implementations of the ELL1 model present in both TEMPO and TEMPO2 packages. Detailed TEMPO2 simulations suggest the possibility of constraining the apsidal motion constant of pulsar companions in certain observed binary pulsars with minuscule eccentricities such as PSR J1719−1438. Fortunately, the ELL1k timing model does not pose any challenges to the on-going Pulsar Timing Array campaigns that routinely employ the ELL1 timing model.

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A Wideband Digital Back-End for the Upgraded GMRT

Cited by 66 publications

References 16 publications

A Strong Jet Signature in the Late-time Light Curve of GW170817

A Strong Jet Signature in the Late-time Light Curve of GW170817

iPTF 16hgs: A Double-peaked Ca-rich Gap Transient in a Metal-poor, Star-forming Dwarf Galaxy

Exploring the effect of periastron advance in small-eccentricity binary pulsars

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