Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Effects of Coronal Mass Ejection on PSR J1022+1001 and Possible Mode Change of PSR J2145-0750 in the InPTA DR2

Shaswata Chowdhury, M. A. Krishnakumar, Manjari Bagchi, Bhal Chandra Joshi, Nobleson K., Jibin Jose, Shantanu Desai, Manpreet Singh, Vaishnavi Vyasraj, Kuldeep Meena, Amarnath, Manoneeta Chakraborty, Shubham Kala, Debabrata Deb, Zenia Zuraiq, Arul Pandian B, Neelam Dhanda Batra, Churchil Dwivedi, Sushovan Mondal, Avinash Kumar Paladi, Kaustubh Rai, Abhimanyu Susobhanan, Adya Shukla, Aman Srivastava, Mayuresh Surnis, Hemanga Tahbildar, Keitaro Takahashi, Pratik Tarafdar, Prabu Thiagaraj, Kunjal Vara

TL;DR

The paper addresses outliers in dispersion-measure time series from InPTA-DR2, seeking whether some events reflect solar coronal mass ejections or intrinsic pulsar magnetospheric mode changes. It proposes a physics-guided, separation-based approach: identify outliers using solar elongation and DM-model comparisons for J1022+1001, and use frequency-resolved profile diagnostics for J2145-0750. The key findings are that the 2022 DM excursion for J1022+1001 is consistent with a CME intersecting the LOS, with DM_excess about $2.9\times10^{-3}$ pc cm$^{-3}$, corroborated by DONKI, STEREO-A in situ data, and LASCO/C3 imagery; while J2145-0750 shows evidence for a potential mode change evidenced by a significant peak-ratio deviation and frequency-dependent profile broadening, indicative of magnetospheric changes. This work demonstrates how combining DM, solar-event data, and profile analyses can enhance DM modelling and PTA timing, and lays out a path to extend these diagnostics across the full InPTA-DR2 sample to improve GW background studies.

Abstract

The Indian Pulsar Timing Array (InPTA) has recently published its second data release (DR2), comprising the timing analysis of seven years of data on 27 millisecond pulsars (MSPs), observed simultaneously in the 300-500 MHz (band 3) and 1260-1460 MHz (band 5), using the upgraded Giant Metrewave Radio Telescope (uGMRT). The low-frequency data, particularly in band 3, is highly sensitive to propagation effects such as dispersion measure (DM) fluctuations, which can be imprints of some astrophysical phenomena (scientific outliers). Here, we analyze the two outliers of possible astrophysical origin coming from the band 3 DM time series of two pulsars: PSR J1022+1001, with an ecliptic latitude of -0.06 degree, and PSR J2145-0750, one of the brightest MSPs, with multi-component profile morphology. Our study reveals compelling evidence for a coronal mass ejection (CME) event traced in the data of PSR J1022+1001, and reports evidence for a potential mode-changing event in PSR J2145-0750. By contrasting these two cases, we show that DM fluctuations due to CME interacions and intrinsic mode-changing events produce distinct observational signatures, enabling a physically informed classification of scientific outliers in PTA datasets. Extending the analyses presented here to the full sample of InPTA-DR2 pulsars is expected to reveal additional CME events, and possible mode-changing events. Such detections will not only improve our understanding of solar and pulsar magnetospheric plasma interactions but will also enable more accurate modelling of DM variations, leading to improved pulsar timing solutions, which are crucial for high-precision Pulsar Timing Array (PTA) science.

Effects of Coronal Mass Ejection on PSR J1022+1001 and Possible Mode Change of PSR J2145-0750 in the InPTA DR2

TL;DR

The paper addresses outliers in dispersion-measure time series from InPTA-DR2, seeking whether some events reflect solar coronal mass ejections or intrinsic pulsar magnetospheric mode changes. It proposes a physics-guided, separation-based approach: identify outliers using solar elongation and DM-model comparisons for J1022+1001, and use frequency-resolved profile diagnostics for J2145-0750. The key findings are that the 2022 DM excursion for J1022+1001 is consistent with a CME intersecting the LOS, with DM_excess about pc cm, corroborated by DONKI, STEREO-A in situ data, and LASCO/C3 imagery; while J2145-0750 shows evidence for a potential mode change evidenced by a significant peak-ratio deviation and frequency-dependent profile broadening, indicative of magnetospheric changes. This work demonstrates how combining DM, solar-event data, and profile analyses can enhance DM modelling and PTA timing, and lays out a path to extend these diagnostics across the full InPTA-DR2 sample to improve GW background studies.

Abstract

The Indian Pulsar Timing Array (InPTA) has recently published its second data release (DR2), comprising the timing analysis of seven years of data on 27 millisecond pulsars (MSPs), observed simultaneously in the 300-500 MHz (band 3) and 1260-1460 MHz (band 5), using the upgraded Giant Metrewave Radio Telescope (uGMRT). The low-frequency data, particularly in band 3, is highly sensitive to propagation effects such as dispersion measure (DM) fluctuations, which can be imprints of some astrophysical phenomena (scientific outliers). Here, we analyze the two outliers of possible astrophysical origin coming from the band 3 DM time series of two pulsars: PSR J1022+1001, with an ecliptic latitude of -0.06 degree, and PSR J2145-0750, one of the brightest MSPs, with multi-component profile morphology. Our study reveals compelling evidence for a coronal mass ejection (CME) event traced in the data of PSR J1022+1001, and reports evidence for a potential mode-changing event in PSR J2145-0750. By contrasting these two cases, we show that DM fluctuations due to CME interacions and intrinsic mode-changing events produce distinct observational signatures, enabling a physically informed classification of scientific outliers in PTA datasets. Extending the analyses presented here to the full sample of InPTA-DR2 pulsars is expected to reveal additional CME events, and possible mode-changing events. Such detections will not only improve our understanding of solar and pulsar magnetospheric plasma interactions but will also enable more accurate modelling of DM variations, leading to improved pulsar timing solutions, which are crucial for high-precision Pulsar Timing Array (PTA) science.

Paper Structure

This paper contains 14 sections, 2 equations, 10 figures, 1 table.

Table of Contents

  1. Introduction
  2. Observations and Analysis
  3. Investigating the effect of CMEs on PSR J1022+1001
  4. Identifying the possible CME affected observations
  5. CME responsible for the DM outlier
  6. In situ data
  7. DM excess estimate
  8. Analyzing a possible mode change epoch of PSR J2145$-$0750
  9. Peak-ratio distribution
  10. Profile evolution with frequency
  11. Eliminating systematics degenerate with mode change
  12. Indication of potential intrinsic magnetospheric changes
  13. Distinguishing CME-induced and mode-change-induced outliers
  14. Conclusions

Figures (10)

  • Figure 1: 'Observational' DM and 'modelled' DM vs separation angle (with respect to Sun) for PSR J1022+1001, with the outlier of interest being marked with red circle. The black points with vertical bars represent 'observational' DM with its uncertainty, while the blue curve denotes the 'modelled' DM from the spherically symmetric solar wind model.
  • Figure 2: PSR J1022+1001's LOS (yellow line) overlaid on the MHD simulation snapshot taken at 06:00:00 (UTC), around the pulsar observation time on 09 August 2022. Locations of various planets and satellites are shown with different symbols as explained in the legends. The dashed spirals are the Parker spirals ParkerSpiral1958, the colour code represent the density as per the colorbar. The two CMEs -- cme1, and cme2 are also labelled. These snapshots are taken from the MHD simulations in DONKI.
  • Figure 3: LASCO/C3 coronagraph base difference image plotted from the fits file corresponding to the date of cme2, which passed through the LOS of PSR J1022+1001.
  • Figure 4: In situ data from STEREO-A for a span of 10 days around the cme2 event is shown. The left panel shows the plasma density in cm$^{-3}$, SW speed, Temperature, and the thermal speed. The right panel shows the measured magnetic field in X,Y and Z directions as well as the total value, in units of nT. These plots are generated using the CDAWeb.
  • Figure 5: Geometry of paths: (a) DM estimation and (b) impact of CME on LOS of PSR J1022+1001
  • ...and 5 more figures