88 research outputs found
A hadronic scenario for HESS J1818-154
No full textAims: G15.4+0.1 is a faint supernova remnant (SNR) that has recently been associated with the γ-ray source HESS J1818-154. We investigate a hadronic scenario for the production of the γ-ray emission. Methods: Molecular 13 CO (J = 1-0) taken from the Galactic Ring Survey (GRS) and neutral hydrogen (HI) data from the Southern Galactic Plane Survey (SGPS) have been used in combination with new 1420 MHz radio continuum observations carried out with the Giant Metrewave Radio Telescope (GMRT). Results: From the new observations and analysis of archival data we provided for the first time a reliable estimate for the distance to the SNR G15.4+0.1 and discovered molecular clouds located at the same distance. On the basis of HI absorption features, we estimate the distance to G15.4+0.1 in 4.8 ± 1.0 kpc. The 13 CO observations clearly show a molecular cloud about 5´ in size with two bright clumps, labeled A and B, clump A positionally associated with the location of HESS J1818-154 and clump B in coincidence with the brightest northern border of the radio SNR shell. The HI absorption and the 13 CO emission study indicates a possible interaction between the molecular material and the remnant. We estimate the masses and densities of the molecular gas as (1.2 ± 0.5) × 10 3 M⊙ and (1.5 ± 0.4) × 10 3 cm -3 for clump A and (3.0 ± 0.7)× 10 3 M⊙ and (1.1 ± 0.3) × 10 3 cm -3 for clump B. Calculations show that the average density of the molecular clump A is sufficient to produce the detected γ-ray flux, thus favoring a hadronic origin for the high-energy emission.Fil: Castelletti, Gabriela Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); Argentina;Fil: Supán, Jorge Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); Argentina;Fil: Dubner, Gloria Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio(i); Argentina;Fil: Joshi, B.C.. National Centre for Radio Astrophysics (NCRA); India;Fil: Surnis, M.P.. National Centre for Radio Astrophysics (NCRA); India
A complete radio study of SNR G15.4+0.1 from new GMRT observations
No full textAims. The supernova remnant (SNR) G15.4+0.1 is considered to be the possible counterpart of the γ-ray source HESS J1818−154. With the goal of getting a complete view of this remnant and understanding the nature of the gamma-ray flux, we conducted a detailed radio study that includes the search for pulsations and a model of the broadband emission for the SNR G15.4+0.1/HESS J1818−154 system. Methods. Low-frequency imaging at 624 MHz and pulsar observations at 624 and 1404 MHz towards G15.4+0.1 were carried out with the Giant Metrewave Radio Telescope (GMRT). We correlated the new radio data with observations of the source at X-ray and infrared wavelengths from XMM-Newton and Herschel observatories, respectively. To characterize the neutral hydrogen (HI) medium towards G15.4+0.1, we used data from the Southern Galactic Plane Survey. We modelled the spectral energy distribution (SED) using both hadronic and leptonic scenarios. Results. From the combination of the new GMRT observations with existing data, we derived a continuum spectral index alpha = -0.62 +- 0.03 for the whole remnant. The local synchrotron spectra of G15.4+0.1, calculated from the combination of the GMRT data with 330 MHz observations from the Very Large Array, tends to be flatter in the central part of the remnant, accompanying the region where the blast wave is impinging molecular gas. No spectral index trace was found indicating the radio counterpart to the pulsar wind nebula proposed from X-ray observations. In addition, the search for radio pulsations yielded negative results. Emission at far-infrared wavelengths is observed in the region where the SNR shock is interacting with dense molecular clumps. We also identified HI features forming a shell that wraps most of the outer border of G15.4+0.1. Characteristic parameters were estimated for the shocked HI gas. We found that either a purely hadronic or leptonic model is compatible with the broadband emission known so far.Fil: Supán, Jorge Leonardo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Castelletti, Gabriela Marta. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Joshi, B. C.. National Centre for Radio Astrophysics; IndiaFil: Surnis, M. P.. National Centre for Radio Astrophysics; IndiaFil: Supanitsky, Alberto Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin
GMRT Galactic Plane Pulsar and Transient Survey and the discovery of PSR J1838+1523
No full textSurnis MP, Joshi BC, McLaughlin MA, et al. GMRT Galactic Plane Pulsar and Transient Survey and the discovery of PSR J1838+1523. Monthly Notices of the Royal Astronomical Society. 2018;478(4):4433-4441.We report the results of a blind pulsar survey carried out with the Giant Metrewave Radio Telescope (GMRT) at 325 MHz. The survey covered about 10 per cent of the region between Galactic longitude 45° < l < 135° and Galactic latitude 1° < |b| < 10° with a dwell time of 1800 s, resulting in the detection of 28 pulsars. One of these, PSR J1838+1523, was previously unknown and has a period of 549 ms and a dispersion measure of 68 pc cm−3. We also present the timing solution of this pulsar obtained from multifrequency timing observations carried out with the GMRT and the Ooty Radio Telescope. The measured flux density of this pulsar is 4.3±1.8 and 1.2±0.7 mJy at 325 and 610 MHz, respectively. This implies a spectral index of −2 ±0.8, thus making the expected flux density at 1.4 GHz to be about 0.2 mJy, which would be just detectable in the high-frequency pulsar surveys like the Northern High Time Resolution Universe pulsar survey. This discovery underlines the importance of low-frequency pulsar surveys in detecting steep spectrum pulsars, thus providing complementary coverage of the pulsar population
Evidence for profile changes in PSR J1713+0747 using the uGMRT
No full textPSR J1713+0747 is one of the most precisely timed pulsars in the international pulsar timing array experiment. This pulsar showed an abrupt profile shape change between 2021 April 16, (MJD 59320) and 2021 April 17 (MJD 59321). In this paper, we report the results from multi-frequency observations of this pulsar carried out with the upgraded Giant Metrewave Radio Telescope (uGMRT) before and after the event. We demonstrate the profile change seen in Band 5 (1260 MHz-1460 MHz) and Band 3 (300 MHz-500 MHz). The timing analysis of this pulsar shows a disturbance accompanying this profile change followed by a recovery with a time-scale of ∼159 days. Our data suggest that a model with chromatic index as a free parameter is preferred over models with combinations of achromaticity with DM bump or scattering bump. We determine the frequency dependence to be ∼ν+1.34. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
The evolution of nulling in pulsars
No full textNulling is a phenomenon where the emission from a pulsar becomes undetectable (or significantly weaker) for a relatively short period of time, followed by a return to a normal emission state. The time-scale of nulling ranges from a few pulse periods to many hours or even days. The fraction of time a nulling pulsar spends in a null state varies across the population of canonical pulsars, from 0 to 95 per cent. The long-term behaviour of a pulsar’s nulling fraction, however, is currently unknown, as published values have typically been obtained through single observations. Here, we present the first long-term analysis of nulling behaviour in eight pulsars observed in the Parkes Multibeam Pulsar Survey over the course of eight to ten years. We also apply a new Bayesian method for pulse-energy analysis, yielding posterior estimates of the nulling fraction per observation. In several cases, the nulling affects only specific components of the pulse profile, rather than the entirety of the emission. Our analysis reveals that, while most pulsars show no significant trend in their nulling fraction over time, a subset exhibit some evidence for non-zero gradients in nulling fraction. In particular, PSRs J1048–3832, J1745–3040, and J1825–0935 show statistically significant trends over the span of the data. Studying the behaviour of nulling over years and decades is valuable as it can provide insights into the physical emission processes within pulsars. Studying how nulling evolves also provides valuable insights into pulsar evolution and the characterization of the broader pulsar population
Science Using Single-Pulse Exploration with Combined Telescopes (SUSPECT) I. The mode-switching, flaring, and single-pulse morphology of PSR B1822-09
No full textAims. We aim to elucidate the pulsar radio emission by studying several
single-pulse phenomena, how they relate to each other, and how they evolve with
observing frequency. We intend to inspire models for the pulsar radio emission
and fast radio bursts.
Methods. We set up an observing programme called the SUSPECT project running
at the Nancay Radio Observatory telescopes in France (10 - 85 MHz, 110 - 240
MHz, 1 - 3.5 GHz) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in
India. In this first paper, we focus on high-sensitivity data obtained of PSR
B1822-09 with the uGMRT between 550 and 750 MHz. The pulsar has precursor (PC),
main pulse (MP), and interpulse (IP) emission, and exhibits mode-switching. We
present its single-pulse stacks, investigate its mode-switching using a hidden
Markov switching model, and analyse its single-pulse morphology.
Results. PSR B1822-09's pulse profile decomposes into seven components. We
show that its mode-switching is well described using a hidden Markov switching
model. The pulsar exhibits at least three stable emission modes, one of which
is a newly discovered bright flaring mode. We confirm that the PC and MP switch
synchronously to each other, and both asynchronously to the IP, indicating
information transfer between the polar caps. Additionally, we performed a
fluctuation spectral analysis and discovered three fluctuation features in its
quiescent Q-mode emission, one of which is well known. We conclude that it is
longitude-stationary amplitude modulation. Finally, we visually classified the
single-pulses into four categories. We found extensive 0.2 - 0.4 ms
microstructure in the PC with a typical quasi-periodicity of 0.8 ms. There is
low-level PC activity during the Q-mode, indicating mode mixing. We discovered
low-intensity square-like pulses and extremely bright pulses in the MP, which
suggest bursting.Comment: 19 pages, 19 figures, 2 tables. Submitted to A&A. We appreciate
comments and question
MeerTRAP: Twelve Galactic fast transients detected in a real-time, commensal MeerKAT survey
No full textMeerTRAP is a real-time untargeted search project using the MeerKAT telescope to find single pulses from fast radio transients and pulsars. It is performed commensally with the MeerKAT large survey projects (LSPs), using data from up to 64 of MeerKAT’s 13.96 m dishes to form hundreds of coherent beams on sky, each of which is processed in real time to search for millisecondduration pulses. We present the first twelve Galactic sources discovered by MeerTRAP, with DMs in the range of 33–381 pc cm−3. One source may be Galactic or extragalactic depending on the Galactic electron density model assumed. Follow-up observations performed with the MeerKAT, Lovell, and Parkes radio telescopes have detected repeat pulses from seven of the twelve sources. Pulse periods have been determined for four sources. Another four sources could be localised to the arcsecond-level using a novel implementation of the tied-array beam localisation method
A MeerKAT, e-MERLIN, HESS, and Swift search for persistent and transient emission associated with three localized FRBs
No full textWe report on a search for persistent radio emission from the one-off fast radio burst (FRB) 20190714A, as well as from two repeating FRBs, 20190711A and 20171019A, using the MeerKAT radio telescope. For FRB 20171019A, we also conducted simultaneous observations with the High-Energy Stereoscopic System (H.E.S.S.) in very high-energy gamma rays and searched for signals in the ultraviolet, optical, and X-ray bands. For this FRB, we obtain a UV flux upper limit of 1 . 39 ×10 −16 erg cm −2 s −1 Å−1 , X-ray limit of ∼6 . 6 ×10 −14 erg cm −2 s −1 and a limit on the very high energy gamma-ray flux Φ ( E > 120 GeV ) < 1 . 7 ×10 −12 erg cm −2 s −1 . We obtain a radio upper limit of ∼15 μJy beam −1 for persistent emission at the locations of both FRBs 20190711A and 20171019A with MeerKAT. Ho we ver, we detected an almost unresolved (ratio of integrated flux to peak flux is ∼1.7 beam) radio emission, where the synthesized beam size was ∼8 arcsec size with a peak brightness of ∼53 μJy beam −1 at MeerKAT and ∼86 μJy beam −1 at e-MERLIN, possibly associated with FRB 20190714A at z = 0.2365. This represents the first detection of persistent continuum radio emission potentially associated with a (as-yet) non-repeating FRB. If the association is confirmed, one of the strongest remaining distinction between repeaters and non-repeaters would no longer be applicable. A parallel search for repeat bursts from these FRBs revealed no new detections down to a fluence of 0.08 Jy ms for a 1 ms duration burst.J. O. Chibueze, M. Caleb, L. Spitler, H. Ashkar, F. Sch, ussler, B. W. Stappers, C. Venter, I. Heywood, A. M. S. Richards, D. R. A. Williams, M. Kramer, R. Beswick, M. C. Bezuidenhout, R. P. Breton, L. N. Driessen, F. Jankowski, E. F. Keane, M. Malenta, M. Mickaliger, V. Morello, H. Qiu, K. Rajwade, S. Sanidas, M. Surnis, T. W. Scragg, C. R. H. Walker, N. Wrigley, H.E.S.S. Collaboration, F. Aharonian, F. Ait Benkhali, E. O. Ang, uner, M. Backes, V. Baghmanyan, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, M. B, ottcher, C. Boisson, J. Bolmont, M. de Bony de Lavergne, M. Breuhaus, R. Brose, F. Brun, T. Bulik, F. Cangemi, S. Caroff, S. Casanova, J. Catalano, M. Cerruti, T. Chand, A. Chen, O. U. Chibueze, G. Cotter, P. Cristofari, J. Damascene Mbarubuc ye ye, J. Devin, A. Djannati-Ata, ı, A. Dmytriiev, K. Egberts, J.-P. Ernenwein, A. Fiasson, G. Fichet de Clairfontaine, G. Fontaine, S. Funk, S. Gabici, S. Ghafourizadeh, G. Giavitto, D. Glawion, M.-H. Grondin, M. H, orbe, C. Hoischen, T. L. Holch, Zhiqiu Huang, M. Jamrozy, F. Jankowsky, V. Joshi, I. Jung-Richardt, E. Kasai, K. Katarzy, nski, U. Katz, B. Kh, elifi, W. Klu, zniak, Nu. Komin, K. Kosack, D. Kostunin, A. Lemi, ere, J.-P. Lenain, F. Leuschner, T. Lohse, A. Luashvili, I. Lypova, J. Mackey, D. Malyshev, V. Marandon, P. Marchegiani, A. Marcowith, G. Mart, ı-Devesa, R. Marx, A. Mitchell, R. Moderski, L. Mohrmann, E. Moulin, J. Muller, K. Nakashima, M. de Naurois, A. Nayerhoda, J. Niemiec, A. Priyana Noel, P. O, Brien, S. Ohm, L. Olivera-Nieto, E. de Ona Wilhelmi, M. Ostrowski, S. P ann y, R. D. P arsons, S. Pita, V. Poireau, D. A. Prokhorov, H. Prokoph, G. P, uhlhofer, A. Quirrenbach, P. Reichherzer, A. Reimer, O. Reimer, G. Rowell, B. Rudak, E. Ruiz-Velasco, V. Sahakian, S. Sailer, H. Salzmann, D. A. Sanchez, A. Santangelo, M. Sasaki, H. M. Schutte, U. Schw ank e, J. N. S. Shapopi, A. Specovius, S. Spencer, R. Steenkamp, S. Steinmassl, T . Takahashi, T . Tanaka, C. Thorpe-Morgan, N. Tsuji, C. van Eldik, J. Veh, J. Vink, S. J. Wagner, A. Wierzcholska, Yu Wun Wong, A. Yusafzai, M. Zacharias, D. Zargaryan, A. A. Zdziarski, A. Zech, S. J. Zhu, S. Zouari, and N., Zywuck
A complete radio study of SNR G15.4+0.1 from new GMRT observations
No full textAims. The supernova remnant (SNR) G15.4+0.1 is considered to be the possible counterpart of the γ-ray source HESS J1818−154. With the goal of getting a complete view of this remnant and understanding the nature of the γ-ray flux, we conducted a detailed radio study that includes the search for pulsations and a model of the broadband emission for the SNR G15.4+0.1/HESS J1818−154 system.
Methods. Low-frequency imaging at 624 MHz and pulsar observations at 624 and 1404 MHz towards G15.4+0.1 were carried out with the Giant Metrewave Radio Telescope (GMRT). We correlated the new radio data with observations of the source at X-ray and infrared wavelengths from XMM-Newton and Herschel observatories, respectively. To characterize the neutral hydrogen (HI) medium towards G15.4+0.1, we used data from the Southern Galactic Plane Survey. We modelled the spectral energy distribution (SED) using both hadronic and leptonic scenarios.
Results. From the combination of the new GMRT observations with existing data, we derived a continuum spectral index α = −0.62 ± 0.03 for the whole remnant. The local synchrotron spectra of G15.4+0.1, calculated from the combination of the GMRT data with 330 MHz observations from the Very Large Array, tends to be flatter in the central part of the remnant, accompanying the region where the blast wave is impinging molecular gas. No spectral index trace was found indicating the radio counterpart to the pulsar wind nebula proposed from X-ray observations. In addition, the search for radio pulsations yielded negative results. Emission at far-infrared wavelengths is observed in the region where the SNR shock is interacting with dense molecular clumps. We also identified HI features forming a shell that wraps most of the outer border of G15.4+0.1. Characteristic parameters were estimated for the shocked HI gas. We found that either a purely hadronic or leptonic model is compatible with the broadband emission known so far
Science Using Single-Pulse Exploration with Combined Telescopes (SUSPECT) I. The mode-switching, flaring, and single-pulse morphology of PSR B1822-09
No full textInternational audienceAims. We aim to elucidate the pulsar radio emission by studying several single-pulse phenomena, how they relate to each other, and how they evolve with observing frequency. We intend to inspire models for the pulsar radio emission and fast radio bursts. Methods. We set up an observing programme called the SUSPECT project running at the Nancay Radio Observatory telescopes in France (10 - 85 MHz, 110 - 240 MHz, 1 - 3.5 GHz) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in India. In this first paper, we focus on high-sensitivity data obtained of PSR B1822-09 with the uGMRT between 550 and 750 MHz. The pulsar has precursor (PC), main pulse (MP), and interpulse (IP) emission, and exhibits mode-switching. We present its single-pulse stacks, investigate its mode-switching using a hidden Markov switching model, and analyse its single-pulse morphology. Results. PSR B1822-09's pulse profile decomposes into seven components. We show that its mode-switching is well described using a hidden Markov switching model. The pulsar exhibits at least three stable emission modes, one of which is a newly discovered bright flaring mode. We confirm that the PC and MP switch synchronously to each other, and both asynchronously to the IP, indicating information transfer between the polar caps. Additionally, we performed a fluctuation spectral analysis and discovered three fluctuation features in its quiescent Q-mode emission, one of which is well known. We conclude that it is longitude-stationary amplitude modulation. Finally, we visually classified the single-pulses into four categories. We found extensive 0.2 - 0.4 ms microstructure in the PC with a typical quasi-periodicity of 0.8 ms. There is low-level PC activity during the Q-mode, indicating mode mixing. We discovered low-intensity square-like pulses and extremely bright pulses in the MP, which suggest bursting
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