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

Konar, Sushan; Bagchi, Manjari; Bandyopadhyay, Debades; Banik, Sarmistha; Bhattacharya, Dipankar; Bhattacharyya, Sudip; Gangadhara, R. T.; Gopakumar, A.; Gupta, Yashwant; Joshi, B. C.; Maan, Yogesh; Maitra, Chandreyee; Mukherjee, Dipanjan; Paul, Biswajit; Ray, Alak; Sutaria, Firoza

doi:10.1007/s12036-016-9409-6

Cited by 19 publications

(17 citation statements)

References 183 publications

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“…Recently, the GMRT has been upgraded with the wider bandwidth of 200 MHz (Kumar 2014;Konar et al 2016) which is much broader than 32 MHz used for our observations. Observations using such wider bandwidth will improve single pulse S/N by orders of magnitude and will allow us to robustly model both the components.…”

Section: On the Origin Of Pulsar Nullsmentioning

confidence: 99%

On Nulling, Drifting, and Their Interactions in PSRs J1741–0840 and J1840–0840

Gajjar

Yuan

Yuen

et al. 2017

ApJ

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We report detailed investigation of nulling and drifting behavior of two pulsars PSRs J1741−0840 and J1840−0840 observed from the Giant Meterwave Radio Telescope at 625 MHz. PSR J1741−0840 was found to show nulling fraction (NF) of around 30±5% while PSR J1840−0840 was shown to have NF of around 50±6%. We measured drifting behavior from different profile components in PSR J1840−0840 for the first time with the leading component showing drifting with 13.5±0.7 periods while the weak trailing component showed drifting of around 18±1 periods. Large nulling do hamper accuracy of these quantities derived using standard Fourier techniques. A more accurate comparison was drawn from driftband slopes, measured after sub-pulse modeling. These measurements revealed interesting sporadic and irregular drifting behavior in both pulsars. We conclude that the previously reported different drifting periodicities in the trailing component of PSR J1741−0840 is likely due to the spread in these driftband slopes. We also find that both components of PSR J1840−0840 show similar driftband slopes within the uncertainties. Unique nulling-drifting interaction is identified in PSR J1840−0840 where, in most occasions, the pulsar tends to start nulling after what appears to be an end of a driftband. Similarly, when the pulsar switches back to an emission phase, in most occasions it starts at the beginning of a new driftband in both components. Such behaviors have not been detected in any other pulsars to our knowledge. We also found that PSR J1741−0840 seems to have no memory of its previous burst phase while PSR J1840−0840 clearly exhibits memory of its previous state even after longer nulls for both components. We discuss possible explanations for these intriguing nulling-drifting interactions seen in both pulsars based on various pulsar nulling models.

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Section: On the Origin Of Pulsar Nullsmentioning

confidence: 99%

On Nulling, Drifting, and Their Interactions in PSRs J1741–0840 and J1840–0840

Gajjar

Yuan

Yuen

et al. 2017

ApJ

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“…Fifty years of observations have yielded ∼3000 neutron stars, with diverse characteristic properties, which fall into three major categories, namely -a) the rotation powered, b) the accretion powered, and c) the internal-energy powered neutron stars; according to their mechanisms of energy generation (Kaspi 2010;Konar 2013;Konar et al 2016;Konar 2017). Radio pulsars, which belong to the category of rotation powered pulsars (RPP), are strongly magnetized rotating neutron stars (mostly isolated or in non-interacting binaries) characterized by their short spin periods (P ∼ 10 −3 − 10 2 s) and large inferred surface magnetic fields (B ∼ 10 8 − 10 15 G).…”

Section: Introductionmentioning

confidence: 99%

Radio pulsar sub-populations (I): The curious case of nulling pulsars

Konar

Deka

2019

J Astrophys Astron

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About ∼200 radio pulsars have been observed to exhibit nulling episodes -short and long. We find that the nulling fraction of a pulsar does not have any obvious correlation with any of the intrinsic pulsar parameters. It also appears that the phenomenon of nulling may be preferentially experienced by pulsars with emission coming predominantly from the polar cap region, and also having extremely curved magnetic fields.

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“…2 Importantly, this kinetic heating may be within reach of forthcoming infrared telescopes [18,19]. Provided NSs are nearby, faint and sufficiently isolated, they are likely to be discovered by existing radio telescopes such as the Fivehundred-meter Aperture Spherical radio Telescope (FAST) [37], or the future Square Kilometer Array (SKA) [38]. Their thermal emission can then be measured by infrared telescopes such as the James Webb Space Telescope (JWST), the Thirty Meter Telescope (TMT), or the European Extremely Large Telescope (E-ELT) [18].The projected NS kinetic heating limits on the DM-nucleon interaction strength were recently calculated in [18,19,21], where they were found to be comparable to, or in many cases much stronger than, existing or projected limits from direct detection experiments.…”

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confidence: 99%

Capture of leptophilic dark matter in neutron stars

Bell

Busoni

Robles

2019

J. Cosmol. Astropart. Phys.

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Dark matter particles will be captured in neutron stars if they undergo scattering interactions with nucleons or leptons. These collisions transfer the dark matter kinetic energy to the star, resulting in appreciable heating that is potentially observable by forthcoming infrared telescopes. While previous work considered scattering only on nucleons, neutron stars contain small abundances of other particle species, including electrons and muons. We perform a detailed analysis of the neutron star kinetic heating constraints on leptophilic dark matter. We also estimate the size of loop induced couplings to quarks, arising from the exchange of photons and Z bosons. Despite having relatively small lepton abundances, we find that an observation of an old, cold, neutron star would provide very strong limits on dark matter interactions with leptons, with the greatest reach arising from scattering off muons. The projected sensitivity is orders of magnitude more powerful than current dark matter-electron scattering bounds from terrestrial direct detection experiments.Neutron stars provide particularly powerful DM constraints, because their high density leads to efficient capture. Indeed, for DM-nucleon cross sections above a threshold value of order 10 −45 cm 2 , the capture probably saturates at the geometric limit, σ ∼ πR 2 * m n /M * , such that all dark matter incident on the star is captured. This conclusion holds irrespective of whether DM scattering interactions are spin independent (SI) or spin dependent (SD). Given that conventional direct detection experiments currently have sensitivity to DM-nucleon cross sections below 10 −45 cm 2 only in a limited DM mass range, and only for SI interactions, NS techniques are clearly very useful. Moreover, velocity or momentum dependent interactions are completely inaccessible to terrestrial direct detection experiments, being severely suppressed in the non-relativistic regime applicable for scattering on Earth. In comparison, DM particles are accelerated to quasi-relativistic velocities upon NS infall, effectively erasing such kinematic suppression.When dark matter is gravitationally captured by a NS, the kinetic energy transferred in the collisions heat up the star. The captured dark matter will then undergo a series of further collisions, eventually transferring almost all of its initial kinetic energy, to reach a state of thermal equilibrium with the star. As shown in Refs. [18,19] this can heat neutron stars up to 1700K. 1 Because old isolated neutron stars can cool to temperatures below 1000K, such heating (or its absence) can be used to place limits on the strength of dark matter interactions. 2 Importantly, this kinetic heating may be within reach of forthcoming infrared telescopes [18,19]. Provided NSs are nearby, faint and sufficiently isolated, they are likely to be discovered by existing radio telescopes such as the Fivehundred-meter Aperture Spherical radio Telescope (FAST) [37], or the future Square Kilometer Array (SKA) [38]. Their thermal emission can then be m...

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

Cited by 19 publications

References 183 publications

On Nulling, Drifting, and Their Interactions in PSRs J1741–0840 and J1840–0840

On Nulling, Drifting, and Their Interactions in PSRs J1741–0840 and J1840–0840

Radio pulsar sub-populations (I): The curious case of nulling pulsars

Capture of leptophilic dark matter in neutron stars

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