J/ApJ/952/151 MSPES. VI. Analysis of the AP and SP polarization (Mitra+, 2023)
Meterwavelength Single Pulse Polarimetric Emission Survey.
VI. Toward understanding the phenomenon of pulsar polarization in partially
screened vacuum gap model.
Mitra D., Melikidze G.I., Basu R.
<Astrophys. J., 952, 151 (2023)>
=2023ApJ...952..151M 2023ApJ...952..151M
ADC_Keywords: Pulsars; Radio lines; Polarization; Surveys
Keywords: Radio pulsars
Abstract:
We have observed 123 pulsars with periods longer than 0.1s in the
Meterwavelength Single Pulse Polarimetric Emission Survey. In this
work, a detailed study of the polarization behavior of these pulsars
has been carried out. We were able to fit the rotating vector model to
the polarization position angle sweeps in 68 pulsars, and in
34 pulsars the emission heights could be measured. In all cases the
radio emission was constrained to arise below 10% of the light
cylinder radius. In pulsars with low spin-down energy loss,
dE/dt<1034erg/s, we found the mean fractional linear polarization of
the individual time samples in single pulses to be around 0.57 (57%),
which is significantly larger than the fractional linear polarization
of 0.29 (29%) obtained from the average profiles. On the other hand,
the mean fractional circular polarization of the individual time
samples in single pulses is around 0.08 (8%), similar to the
measurements from the average profiles. To explain the observed
polarization features, we invoke the partially screened vacuum gap
model of pulsars, where dense spark-associated plasma clouds exist
with high pair plasma multiplicity, with significant decrease of
density in the regions between the clouds that are dominated by iron
ions. The coherent radio emission is excited by curvature radiation
from charge bunches in these dense plasma clouds and escape as
linearly polarized waves near cloud boundaries. We suggest that the
circular polarization arises due to propagation of waves in the
low-pair-multiplicity, ion-dominated inter-cloud regions.
Description:
The Meterwavelength single-pulse Polarimetric Emission Survey (MSPES)
was conducted using the Giant Meterwave Radio Telescope (GMRT)
primarily to increase the available sample for average profile/single
pulse (AP/SP) studies (Mitra+ 2016ApJ...833...28M 2016ApJ...833...28M, Paper I). The GMRT
consists of a Y-shaped array of 30 antennas of 45m diameter, with
14 antennas located within a central 1km2 area, and the remaining
16 antennas placed along the three arms, which have a maximum distance
of 27km. The MSPES observations were carried out at two different
frequencies centered around 325 and 610MHz with a bandwidth of
16.67MHz at each frequency.
In this paper we use the MSPES observations to measure the radio
emission heights in pulsars using APs, and further compare the SP
polarization properties with AP.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 115 The measurements of 68 pulsars from the Meterwavelength
single-pulse Polarimetric Emission Survey (MSPES)
sample where it was possible to obtain suitable
rotating vector model (RVM) fits to the polarization
position angle (PPA) traverse
table2.dat 64 105 The measurements of the average fractional single
pulse (SP) polarization --updated version of the table
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See also:
B/psr : ATNF Pulsar Catalogue (Manchester+, 2005)
J/MNRAS/301/235 : Multifrequency polarimetry of 300 pulsars (Gould+, 1998)
J/A+A/445/243 : Pulsar subpulse modulation data at 21cm (Weltevrede+, 2006)
J/MNRAS/391/1210 : Characteristics of energetic pulsars (Weltevrede+, 2008)
J/MNRAS/474/4629 : Polarimetry of pulsars from 1.4GHz obs. (Johnston+, 2018)
J/MNRAS/489/1543 : Arecibo polarimetric single-pulse survey (Olszanski+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- ID [1/68] Index number
4- 6 I3 MHz Freq [333/618] Frequency
8- 17 A10 --- PSR Pulsar identifier (JHHMM-DDMM)
19- 23 F5.3 s Per [0.1/8.51] Period
25- 30 F6.2 --- chi2 [0.6/273.7] Minimum χ2 fit value
32- 37 F6.1 deg phil [-172/-1.1] Phase of leading edge
39- 41 F3.1 deg e_phil [0.1/0.8] Uncertainty in phil
43- 47 F5.1 deg phit [1.2/103.7] Phase of trailing edge
49- 51 F3.1 deg e_phit [0.1/0.8] Uncertainty in phit
53- 57 F5.1 deg phideg [-31.3/58.5] Phase of the steepest gradiant point
59- 62 F4.1 deg e_phideg [0.1/70] Uncertainty in phideg (1)
64- 69 F6.2 deg Delphi [-18/48]? Shift between profile midpoint and
steepest gradiant (SG) point
71- 74 F4.1 deg e_Delphi [0.1/15]? Uncertainty in Delphi (1)
76- 79 I4 km h [47/2530]? Emission height estimate
81- 84 I4 km e_h [23/1200]? Uncertainty in h (1)
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Note (1): Note that generally errors in phideg are asymmetric, however here
only the average value is quoted, which is further used to find
the error in delphi and h.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- PSR Pulsar identifier (JHHMM-DDMM)
12- 14 I3 MHz Freq [333/618] Frequency
16- 26 F11.5 10-24W Edot [0.003/14300]? Spindown energy loss;
1031erg/s
28- 33 I6 --- Nsamp [91/114821] Number of SP samples (1)
35- 38 F4.2 --- L/I [0.2/0.81] Mean fractional linear
polarization
40- 43 F4.2 --- e_L/I [0.09/0.3] Uncertainty in L/I
45- 49 F5.2 --- V/I [-0.4/0.3] Mean circular polarization
51- 54 F4.2 --- e_V/I [0.1/0.4] Uncertainty in V/I
56- 59 F4.2 --- abs(V/I) [0.09/0.4] Mean absolute circular
polarization, |V|/I
61- 64 F4.2 --- e_abs(V/I) [0.07/0.2] Uncertainty in abs(V/I)
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Note (1): That were above the detection threshold and used for the
polarization estimates.
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Acknowledgements:
Dipanjan Mitra [dmitra at ncra.tifr.res.in]
History:
From electronic version of the journal
* Table 2 sent by the author to correct abs(V/I) values;
see erratum (submitted)
References:
Mitra et al. Paper I. 2016ApJ...833...28M 2016ApJ...833...28M
Basu et al. Paper II. 2016ApJ...833...29B 2016ApJ...833...29B
Basu et al. Paper III. 2017ApJ...846..109B 2017ApJ...846..109B
Skrzypczak et al. Paper IV. 2018ApJ...854..162S 2018ApJ...854..162S
Basu et al. Paper V. 2021ApJ...917...48B 2021ApJ...917...48B
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Sep-2025