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High Precision Measurements of Interstellar Dispersion Measure with the upgraded GMRT

Krishnakumar, M. A. and Manoharan, P. K. and Joshi, Bhal Chandra and Girgaonkar, Raghav and Desai, Shantanu and Bagchi, Manjari and Nobleson, K. and Dey, Lankeswar and Susobhanan, Abhimanyu and Susarla, Sai Chaitanya and Surnis, Mayuresh P. and Maan, Yogesh and Gopakumar, A. and Basu, Avishek and Dhanda Batra, Neelam and Choudhary, Arpita and De, Kishalay and Gupta, Yashwant and Naidu, Arun Kumar and Pathak, Dhruv and Singha, Jaikhomba and Prabu, T. (2021) High Precision Measurements of Interstellar Dispersion Measure with the upgraded GMRT. . (Unpublished)

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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 J1909−3744. A considerable offset is seen in the DM of PSR 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 have 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 (CME) observed from the Sun on that epoch. A detailed analysis of this interesting event is presented.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemSolar wind analysis ItemCode
Krishnakumar, M. A.0000-0003-4528-2745
Manoharan, P. K.0000-0003-4274-211X
Joshi, Bhal Chandra0000-0002-0863-7781
Bagchi, Manjari0000-0001-8640-8186
Dey, Lankeswar0000-0002-2554-0674
Susobhanan, Abhimanyu0000-0002-2820-0931
Maan, Yogesh0000-0002-0862-6062
Gopakumar, A.0000-0003-4274-4369
Basu, Avishek0000-0002-4142-7831
Dhanda Batra, Neelam0000-0003-0266-0195
Choudhary, Arpita0000-0003-2031-1183
De, Kishalay0000-0002-8989-0542
Gupta, Yashwant0000-0001-5765-0619
Pathak, Dhruv0000-0001-8129-0473
Additional Information:Attribution 4.0 International (CC BY 4.0). Data Availability. The data used in this paper will be made available on reasonable request. The SDO 171Å images used for the solar wind analysis can be found at The code used for measuring DM in this work, DMcalc is publicly available at MAK is thankful to Caterina Tiburzi and Joris Verbiest for their valuable inputs and useful discussions at various stages of this work. 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 acknowledge support from the Women’s Scientist scheme (WOSA), Department of Science & 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 acknowledge 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 data sets 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 – Gravitational Waves – Sun:coronal mass ejections
Record Number:CaltechAUTHORS:20210202-095312685
Persistent URL:
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:03 Feb 2021 21:24

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