A powerful bursting radio source towards the Galactic Centre

Hyman, S. D.; Lazio, T. Joseph W.; Kassim, N. E.; Ray, Paul S.; Markwardt, C.; Yusef‐Zadeh, F.

doi:10.1038/nature03400

Cited by 162 publications

(194 citation statements)

References 23 publications

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“…Early blind searches have already uncovered multiple variable and transient radio sources (Hyman et al 2005;Lorimer et al 2007;Bower et al 2007Bower et al , 2010Burke-Spolaor & Bailes 2010). However, a majority of the observations were performed at gigahertz (cm to mm wavelength) frequencies, leaving the sub-gigahertz (meter wavelength) sky vastly unexplored.…”

Section: Introductionmentioning

confidence: 99%

Discovery of a Meter-Wavelength Radio Transient in the Swire Deep Field: 1046+59

Jaeger

Hyman

Kassim

et al. 2012

The Astronomical Journal

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We report the results of a low frequency radio variability and slow transient search using archival observations from the Very Long Array. We selected six 325 MHz radio observations from the spring of 2006, each centered on the Spitzer-Space-Telescope Wide-area Infrared Extragalactic Survey (SWIRE) Deep Field: 1046+59. Observations were spaced between one day to three months, with a typical single-epoch peak flux sensitivity below 0.2 mJy beam −1 near the field pointing center. We describe the observation parameters, data post-processing, and search methodology used to identify variable and transient emission. Our search revealed multiple variable sources and the presence of one, day-scale transient event with no apparent astronomical counterpart. This detection implies a transient rate of 1 ± 1 event per 6.5 deg 2 per 72 observing hours in the direction of 1046+59 and an isotropic transient surface density Σ = 0.12 deg −2 at 95% confidence for sources with average peak flux density higher than 2.1 mJy over 12 hr.

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Section: Introductionmentioning

confidence: 99%

Discovery of a Meter-Wavelength Radio Transient in the Swire Deep Field: 1046+59

Jaeger

Hyman

Kassim

et al. 2012

The Astronomical Journal

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“…In particular, the 77 min recurrence of the Jy level bursts was attributed to a period of rotation (Zhang & Gil 2005), revolution (Turolla et al 2005) and precession (Zhu & Xu 2006). A nulling pulsar and an "X-ray quiet, radio-loud" X-ray binary have also been suggested (Kulkarni & Phinney 2005), as well as an exoplanet and a flaring brown dwarf (Hyman et al 2005). The discovery has led to follow-up observations and re-examination of archival data at both 92 cm and other bands.…”

Section: Introductionmentioning

confidence: 99%

“…3 This is the average noise in the residual image. Hyman et al 2005). Noise levels in this image vary from 5 to 13 mJy beam −1 across the image.…”

Section: The Source On the Opposite Side Of The Supernova Remnantmentioning

confidence: 99%

“…The discovery has led to follow-up observations and re-examination of archival data at both 92 cm and other bands. Those did not reveal a source (Zhu & Xu 2006;Hyman et al 2005Hyman et al , 2006, with two exceptions (Hyman et al 2006. Both of the redetections were single bursts, possibly due to the sparse sampling of these observations.…”

Section: Introductionmentioning

confidence: 99%

“…Reports of a peculiar radio transient, GCRT J1745-3009, about 1.25 • south of the Galactic Centre (Hyman et al 2005(Hyman et al , 2006 and the suggestion that this may be the prototype of a new class of particularly bright, coherently emitting radio transients have led to speculation about its nature. In particular, the 77 min recurrence of the Jy level bursts was attributed to a period of rotation (Zhang & Gil 2005), revolution (Turolla et al 2005) and precession (Zhu & Xu 2006).…”

Section: Introductionmentioning

confidence: 99%

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A new perspective on GCRT J1745-3009

Spreeuw

Scheers

Braun

et al. 2009

A&A

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Context. Reports on a transient source about 1.25 • south of the Galactic Centre motivated these follow-up observations with the WSRT and the reinvestigation of archival VLA data. The source GCRT J1745-3009 was detected during a 2002 Galactic Centre monitoring programme with the VLA at 92 cm by five powerful 10-min bursts with a 77-min recurrence while apparently lacking any interburst emission. Aims. The WSRT observations were performed and archival VLA data reduced to detect GCRT J1745-3009 again at different epochs and frequencies, to constrain its distance, and to determine its nature. We attempted to extract a more accurate lightcurve from the discovery dataset of GCRT J1745-3009 to rule out some of the models that have been suggested. We also investigated the transient behaviour of a nearby source. Methods. The WSRT data were taken in the "maxi-short" configuration, using 10 s integrations, on 2005 March 24 at 92 cm and on 2005 May 14/15 at 21 cm. Five of the six VLA observations we reduced are the oldest of this field in this band. Results. GCRT J1745-3009 was not redetected. With the WSRT we reached an rms sensitivity of 0.21 mJy beam −1 at 21 cm and 3.7 mJy beam −1 at 92 cm. Reanalysis of the discovery observation data resulted in a more accurate and more complete lightcurve. The five bursts appear to have the same shape: a steep rise, a more gradual brightening, and a steep decay. We found variations in burst duration of order 3%. We improved the accuracy of the recurrence period of the bursts by an order of magnitude: 77.012 ± 0.021 min. We found no evidence of aperiodicity. We derived a very steep spectral index: α = −6.5 ± 3.4. We improved the 5σ upper limits for interburst emission and fractional circular polarisation to 31 mJy beam −1 and 8%, respectively. Any transient behaviour of a nearby source could not be established. Conclusions. Models that predict symmetric bursts can be ruled out, but rotating systems are favoured, because their periodicity is precise. Scattering constraints imply that GCRT J1745-3009 cannot be located far beyond the GC. If this source is an incoherent emitter and not moving at a relativistic velocity, it must be closer than 14 pc.

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Study of the effect of operative conditions on the decolourization of azo dye solutions by using hydrodynamic cavitation at the lab scale

2020

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In the present study, the potentiality of hydrodynamic cavitation (HC) for the degradation of methyl orange from synthetic aqueous solutions is presented. Hydrodynamic cavitation was set up at laboratory scale using a Venturi tube. Solutions of methyl orange (MO) were subjected to cavitation in order to investigate the efficiency and the potential of this technique for azo dye degradation. Moreover, a HC/H2O2/TiO2 hybrid system was tested with the aim to verify its potential positive impact on the decolourization process and define the best conditions, among those investigated, to remove azo dye from synthetic solutions. The results obtained in this study showed that the maximum efficiency was close to 30% using a Venturi tube at an operating pressure of 400 kPa. The presence of additives, such as titanium dioxide and hydrogen peroxide, increased the performance of the degradation process to slightly above 70%.

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A powerful bursting radio source towards the Galactic Centre

Cited by 162 publications

References 23 publications

Discovery of a Meter-Wavelength Radio Transient in the Swire Deep Field: 1046+59

Discovery of a Meter-Wavelength Radio Transient in the Swire Deep Field: 1046+59

A new perspective on GCRT J1745-3009

Study of the effect of operative conditions on the decolourization of azo dye solutions by using hydrodynamic cavitation at the lab scale

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