17 research outputs found
Evidence for profile changes in PSR J1713+0747 using the uGMRT
PSR 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
High Precision Measurements of Interstellar Dispersion Measure with the upgraded GMRT
Pulsar radio emission undergoes dispersion due to the presence of free
electrons in the interstellar medium (ISM). The dispersive delay in the arrival
time of pulsar signal changes over time due to the varying ISM electron column
density along the line of sight. Correcting for this delay accurately is
crucial for the detection of nanohertz gravitational waves using Pulsar Timing
Arrays. In this work, we present in-band and inter-band DM estimates of four
pulsars observed with uGMRT over the timescale of a year using two different
template alignment methods. The DMs obtained using both these methods show only
subtle differences for PSR 1713+0747 and J19093744. A considerable offset is
seen in the DM of PSR J1939+2134 and J21450750 between the two methods. This
could be due to the presence of scattering in the former and profile evolution
in the latter. We find that both methods are useful but could have a systematic
offset between the DMs obtained. Irrespective of the template alignment methods
followed, the precision on the DMs obtained is about pc cm
using only BAND3 and pc cm after combining data from BAND3 and
BAND5 of the uGMRT. In a particular result, we have detected a DM excess of
about pc cm on 24 February 2019 for PSR J21450750.
This excess appears to be due to the interaction region created by fast solar
wind from a coronal hole and a coronal mass ejection (CME) observed from the
Sun on that epoch. A detailed analysis of this interesting event is presented.Comment: 11 pages, 6 figures, 2 tables. Accepted by A&
Noise analysis of the Indian Pulsar Timing Array data release I
The Indian Pulsar Timing Array (InPTA) collaboration has recently made its
first official data release (DR1) for a sample of 14 pulsars using 3.5 years of
uGMRT observations. We present the results of single-pulsar noise analysis for
each of these 14 pulsars using the InPTA DR1. For this purpose, we consider
white noise, achromatic red noise, dispersion measure (DM) variations, and
scattering variations in our analysis. We apply Bayesian model selection to
obtain the preferred noise models among these for each pulsar. For PSR
J16003053, we find no evidence of DM and scattering variations, while for
PSR J19093744, we find no significant scattering variations. Properties vary
dramatically among pulsars. For example, we find a strong chromatic noise with
chromatic index 2.9 for PSR J1939+2134, indicating the possibility of a
scattering index that doesn't agree with that expected for a Kolmogorov
scattering medium consistent with similar results for millisecond pulsars in
past studies. Despite the relatively short time baseline, the noise models
broadly agree with the other PTAs and provide, at the same time,
well-constrained DM and scattering variations.Comment: Accepted for publication in PRD, 30 pages, 17 figures, 4 table
Multi-band Extension of the Wideband Timing Technique
The wideband timing technique enables the high-precision simultaneous
estimation of Times of Arrival (ToAs) and Dispersion Measures (DMs) while
effectively modeling frequency-dependent profile evolution. We present two
novel independent methods that extend the standard wideband technique to handle
simultaneous multi-band pulsar data incorporating profile evolution over a
larger frequency span to estimate DMs and ToAs with enhanced precision. We
implement the wideband likelihood using the libstempo python interface to
perform wideband timing in the tempo2 framework. We present the application of
these techniques to the dataset of fourteen millisecond pulsars observed
simultaneously in Band 3 (300 - 500 MHz) and Band 5 (1260 - 1460 MHz) of the
upgraded Giant Metrewave Radio Telescope (uGMRT) as a part of the Indian Pulsar
Timing Array (InPTA) campaign. We achieve increased ToA and DM precision and
sub-microsecond root mean square post-fit timing residuals by combining
simultaneous multi-band pulsar observations done in non-contiguous bands for
the first time using our novel techniques.Comment: Submitted to MNRA
Personalpolitische Funktionen, betriebspolitische und soziale Folgen befristeter Arbeitsvertraege eine empirische Untersuchung und ihre Verwendung in der politischen Diskussion um das Beschaeftigungsfoerderungsgesetz 1990
UuStB Koeln(38)-11Y4661 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman
Follow-up Timing of Three GMRT Pulsars
Surnis MP, Joshi BC, McLaughlin MA, Moochickal Ambalappat K, Manoharan PK, Naidu A. Follow-up Timing of Three GMRT Pulsars. The Astrophysical Journal. 2019;870(1): 8.We report on the results of multi-frequency follow-up observations of three pulsars (PSRs J0026+6320, J2208+5500, and J2217+5733) discovered with the Giant Metrewave Radio Telescope (GMRT). These observations were carried out with the GMRT and the Ooty Radio Telescope (ORT). We report improved timing solutions for all three pulsars. For PSR J2208+5500, we estimate the nulling fraction to be 53(3)%. The steep spectrum of this pulsar, its single component profile, and narrow pulse width suggest its single component to be a core component. If so, this significant cessation of emission in a core component is inconsistent with a geometric origin of nulls, such as those due to "empty" sightline traverses, and more likely due to intrinsic changes in the pulsar magnetosphere. We have measured scatter-broadening timescales at 325 and 610 MHz for PSRs J0026+6320 and J2217+5733. The implied scatter-broadening frequency scaling index of −2.9 for both pulsars is different from that expected assuming Kolmogorov turbulence in the interstellar medium. We also report spectral indices, obtained from imaging observations, for all three pulsars for the first time. The spectra for two of these pulsars indicate a possible spectral turnover between 100 and 300 MHz. Multi-frequency timing analyses carried out for these pulsars have enabled us to determine dispersion measures with accuracies of 0.01 pc cm−3. This demonstrates the usefulness of quasi-simultaneous multi-frequency multi-epoch timing observations with the GMRT and the ORT for studying variations in DM for millisecond pulsars