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High precision measurements of interstellar dispersion measure with the upgraded GMRT

Krishnakumar, M. A. and Manoharan, P. K. and Joshi, B. C. and Girgaonkar, R. and Desai, S. and Bagchi, M. and Nobleson, K. and Dey, L. and Susobhanan, A. and Susarla, S. C. and Surnis, M. P. and Maan, Y. and Gopakumar, A. and Basu, A. and Batra, N. D. and Choudhary, A. and De, K. and Gupta, Y. and Naidu, A. K. and Pathak, D. and Singha, J. and Prabu, T. (2021) High precision measurements of interstellar dispersion measure with the upgraded GMRT. Astronomy and Astrophysics, 651 . Art. No. A5. ISSN 0004-6361. doi:10.1051/0004-6361/202140340.

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Context. 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 the pulsar signal changes over time due to the varying ISM electron column density along the line of sight. Accurately correcting for this delay is crucial for the detection of nanohertz gravitational waves using pulsar timing arrays. Aims. We aim to demonstrate the precision in the measurement of the dispersion delay achieved by combining 400−500 MHz (BAND3) wide-band data with those at 1360−1460 MHz (BAND5) observed using the upgraded GMRT, employing two different template alignment methods. Methods. To estimate the high precision dispersion measure (DM), we measure high precision times-of-arrival (ToAs) of pulses using carefully generated templates and the currently available pulsar timing techniques. We use two different methods for aligning the templates across frequency to obtain ToAs over multiple sub-bands and therefrom measure the DMs. We study the effects of these two different methods on the measured DM values in detail. Results. We present in-band and inter-band DM estimates of four pulsars over the timescale of a year using two different template alignment methods. The DMs obtained using both these methods show only subtle differences for PSRs J1713+0747 and J1909−3744. A considerable offset is seen in the DM of PSRs J1939+2134 and J2145−0750 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 10⁻³ pc cm⁻³ using only BAND3 and 10⁻⁴ pc cm⁻³ after combining data from BAND3 and BAND5 of the uGMRT. In a particular result, we detected a DM excess of about 5 × 10⁻³ pc cm⁻³ on 24 February 2019 for PSR J2145−0750. This excess appears to be due to the interaction region created by fast solar wind from a coronal hole and a coronal mass ejection observed from the Sun on that epoch. A detailed analysis of this interesting event is presented.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemSolar wind analysis ItemCode
Krishnakumar, M. A.0000-0003-4528-2745
Manoharan, P. K.0000-0003-4274-211X
Joshi, B. C.0000-0002-0863-7781
Girgaonkar, R.0000-0002-4678-2939
Desai, S.0000-0002-0466-3288
Bagchi, M.0000-0001-8640-8186
Nobleson, K.0000-0003-2715-4504
Dey, L.0000-0002-2554-0674
Susobhanan, A.0000-0002-2820-0931
Susarla, S. C.0000-0003-4332-8201
Surnis, M. P.0000-0002-9507-6985
Maan, Y.0000-0002-0862-6062
Gopakumar, A.0000-0003-4274-4369
Basu, A.0000-0002-4142-7831
Batra, N. D.0000-0003-0266-0195
Choudhary, A.0000-0003-2031-1183
De, K.0000-0002-8989-0542
Gupta, Y.0000-0001-5765-0619
Naidu, A. K.0000-0002-9225-9428
Pathak, D.0000-0001-8129-0473
Singha, J.0000-0002-1636-9414
Prabu, T.0000-0003-4038-8065
Additional Information:© ESO 2021. Article published by EDP Sciences. Received 13 January 2021; Accepted 26 May 2021. Published online 06 July 2021. The data used in this paper will be made available on reasonable request. The SDO171Å images used for the solar wind analysis can be found at MAK is thankful to Caterina Tiburzi and Joris Verbiest for their valuable inputs and useful discussions at various stages of this work. We are thankful to the anonymous referee for many constructive comments on the manuscript. AS, AG, BCJ, LD, and YG acknowledge the support of the Department of Atomic Energy, Government of India, under project Identification # RTI 4002. BCJ, YG, and AB acknowledge support from the Department of Atomic Energy, Government of India, under project # 12-R&D-TFR-5.02-0700. AC acknowledges support from the Women’s Scientist scheme (WOS-A), Department of Science and Technology, India. MPS acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 694745). NDB acknowledges support from the Department of Science & Technology, Government of India, grant SR/WOS-A/PM-1031/2014. AB acknowledges the support from the UK Science and Technology Facilities Council (STFC). Pulsar research at Jodrell Bank Centre for Astrophysics and Jodrell Bank Observatory is supported by a consolidated grant from STFC. We thank the staff of the GMRT who made our observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The open data policy of STEREO and SDO teams is acknowledged. The solar wind and interplanetary datasets have been obtained from the OMNI database.
Funding AgencyGrant Number
Department of Atomic Energy (India)RTI 4002
Department of Atomic Energy (India)12-R&D-TFR-5.02-0700
European Research Council (ERC)694745
Department of Science and Technology (India)SR/WOS-A/PM-1031/2014
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords:pulsars: general – ISM: general – Sun: coronal mass ejections (CMEs) – gravitational waves
Record Number:CaltechAUTHORS:20210202-095312685
Persistent URL:
Official Citation:High precision measurements of interstellar dispersion measure with the upgraded GMRT. M. A. Krishnakumar, P. K. Manoharan, B. C. Joshi, R. Girgaonkar, S. Desai, M. Bagchi, K. Nobleson, L. Dey, A. Susobhanan, S. C. Susarla, M. P. Surnis, Y. Maan, A. Gopakumar, A. Basu, N. D. Batra, A. Choudhary, K. De, Y. Gupta, A. K. Naidu, D. Pathak, J. Singha and T. Prabu. A&A, 651 (2021) A5; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107868
Deposited By: George Porter
Deposited On:03 Feb 2021 21:24
Last Modified:26 Jul 2021 17:59

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