Deep searches for decametre-wavelength pulsed emission from radio-quiet gamma-ray pulsars

Maan, Yogesh; Aswathappa, H. A.

doi:10.1093/mnras/stu1902

Cited by 18 publications

(22 citation statements)

References 29 publications

(32 reference statements)

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“…The noise is determined in an area around the burst visually confirmed to be free of interference. We used the modified radiometer equation (Cordes & McLaughlin 2003;Maan & Aswathappa 2014) to convert the obtained S/N to All 30 bursts from R1 detected with Apertif. Each burst was dedispersed to a DM of 560.5 pc cm −3 .…”

Section: Flux Calibrationmentioning

confidence: 99%

Repeating fast radio bursts with WSRT/Apertif

Oostrum

Maan

Leeuwen

et al. 2020

A&A

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Context. Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments, as well as decipher the underlying emission mechanism. Detailed studies of repeating FRBs might also hold clues to the origin of FRBs as a population. Aims. We aim to detect bursts from the first two repeating FRBs: FRB 121102 (R1) and FRB 180814.J0422+73 (R2), and characterise their repeat statistics. We also want to significantly improve the sky localisation of R2 and identify its host galaxy. Methods. We use the Westerbork Synthesis Radio Telescope to conduct extensive follow-up of these two repeating FRBs. The new phased-array feed system, Apertif, allows covering the entire sky position uncertainty of R2 with fine spatial resolution in a single pointing. The data were searched for bursts around the known dispersion measures of the two sources. We characterise the energy distribution and the clustering of detected R1 bursts. Results. We detected 30 bursts from R1. The non-Poissonian nature is clearly evident from the burst arrival times, consistent with earlier claims. Our measurements indicate a dispersion measure of 563.5(2) pc cm −3 , suggesting a significant increase in DM over the past few years. Assuming a constant position angle across the burst, we place an upper limit of 8% on the linear polarisation fraction for the brightest burst in our sample. We did not detect any bursts from R2. Conclusions. A single power-law might not fit the R1 burst energy distribution across the full energy range or widely separated detections. Our observations provide improved constraints on the clustering of R1 bursts. Our stringent upper limits on the linear polarisation fraction imply a significant depolarisation, either intrinsic to the emission mechanism or caused by the intervening medium, at 1400 MHz that is not observed at higher frequencies. The non-detection of any bursts from R2, despite nearly 300 hrs of observations, implies either a highly clustered nature of the bursts, a steep spectral index, or a combination of both assuming the source is still active. Another possibility is that R2 has turned off completely, either permanently or for an extended period of time.

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Section: Flux Calibrationmentioning

confidence: 99%

Repeating fast radio bursts with WSRT/Apertif

Oostrum

Maan

Leeuwen

et al. 2020

A&A

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“…Search for transient events in these blank sky observations (nearly 250 individual sessions of 30 minutes each) also did not result in detection of any significant dispersed pulse (Maan & Aswathappa 2014).…”

Section: Search For Transients Toward Control Sources Andmentioning

confidence: 75%

“…Results of deep searches for the periodic radio signals from both the pulsars, using these 45 observing sessions, were reported in Maan & Aswathappa (2014). Observations towards several radio-quiet gamma-ray pulsars were also reported by Maan & Aswathappa (2014), which serve as blank sky observations for the findings presented below. Additionally, at least one of the two control pulsars -B0834+06 and B1919+21 -was observed on the days when the target source observations were conducted.…”

Section: Observations and Search Proceduresmentioning

confidence: 93%

“…For an optimum detection, a search across the pulsewidth is also conducted in each of the dedispersed time series. For more details of the search procedure as well as those of the acquisition setup, the Gauribidanur radio telescope, and the pre-search data processing, we refer the reader to Maan et al (2012) and Maan (2014); Maan & Aswathappa (2014).…”

Section: Observations and Search Proceduresmentioning

confidence: 99%

“…Although three research groups from the Pushchino radio astronomy observatory claimed low significance (< 10σ) detections of pulsed radio emission from this pulsar (with flux densities in the range 30-100 mJy at 102.5 MHz; Malofeev & Malov 1997;Kuz'min & Losovskii 1997;Shitov & Pugachev 1998) at a DM of about 3 pc cm −3 , several other sensitive searches, before as well as after the above claimed detections, have remained unsuccessful (e.g., Seiradakis 1992;Ramachandran et al 1998;Ershov 2007;Coenen 2013;Maan & Aswathappa 2014). A possible detection of the pulsar was also reported using the Rajkot radio telescope (India) at 103 MHz (Vats et al 1999).…”

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confidence: 99%

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Discovery of Low Dm Fast Radio Transients: Geminga Pulsar Caught in the Act

Maan

2015

ApJ

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We report discovery of several energetic radio bursts at 34 MHz, using the Gauribidanur radio telescope. The radio bursts exhibit two important properties associated with the propagation of astronomical signals through the interstellar medium: (i) frequency dependent dispersive delays across the observing bandwidth, and (ii) Faraday rotation of the plane of linear polarization. These bursts sample a range of dispersion measures (DM; 1.4-3.6 pc cm −3 ), and show DM-variation at timescales of the order of a minute. Using groups of bursts having a consistent DM, we show that the bursts have originated from the radio-quiet gamma-ray pulsar Geminga. Detection of these bursts supports the existence of occasional radio emission from Geminga. The rare occurrence of these bursts, and the short timescale variation in their DM (if really caused by the intervening medium or the pulsar magnetosphere), might provide clues as to why the pulsar has not been detected in earlier sensitive searches. We present details of the observations and search procedure used to discover these bursts, a detailed analysis of their properties, and evidences of these bursts being associated with Geminga pulsar, and discuss briefly the possible emission mechanism of these bursts.

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Neutron Star Physics in the Square Kilometre Array Era: An Indian Perspective

Konar¹,

Bagchi²,

Bandyopadhyay³

et al. 2016

J Astrophys Astron

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It is an exceptionally opportune time for Astrophysics when a number of next-generation mega-instruments are poised to observe the universe across the entire electromagnetic spectrum with unprecedented data quality. The Square Kilometre Array (SKA) is undoubtedly one of the major components of this scenario. In particular, the SKA is expected to discover tens of thousands of new neutron stars giving a major fillip to a wide range of scientific investigations. India has a sizeable community of scientists working on different aspects of neutron star physics with immediate access to both the uGMRT (an SKA pathfinder) and the recently launched X-ray observatory Astrosat. The current interests of the community largely centre around studies of -a) the generation of neutron stars and the SNe connection, b) the neutron star population and evolutionary pathways, c) the evolution of neutron stars in binaries and the magnetic fields, d) the neutron star equation of state, e) the radio pulsar emission mechanism, and, f) the radio pulsars as probes of gravitational physics. Most of these studies are the main goals of the SKA first phase, which is likely to be operational in the next four years. This article summarises the science goals of the Indian neutron star community in the SKA era, with significant focus on coordinated efforts among the SKA and other existing/upcoming instruments.

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Deep searches for decametre-wavelength pulsed emission from radio-quiet gamma-ray pulsars

Cited by 18 publications

References 29 publications

Repeating fast radio bursts with WSRT/Apertif

Repeating fast radio bursts with WSRT/Apertif

Discovery of Low Dm Fast Radio Transients: Geminga Pulsar Caught in the Act

Neutron Star Physics in the Square Kilometre Array Era: An Indian Perspective

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