J/A+A/686/A144 XTE J1810-197 high-cadence monitoring (Bause+, 2024)
High-cadence monitoring of the emission properties of magnetar XTE J1810-197
with the Stockert radio telescope.
Bause M.L., Herrmann W., Spitler L.G.
<Astron. Astrophys. 686, A144 (2024)>
=2024A&A...686A.144B 2024A&A...686A.144B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, neutron ; Radio sources
Keywords: stars: magnetars - stars: neutron - stars: individual XTE J1810-197
Abstract:
Since the detection of a burst resembling a fast radio burst (FRB)
from the Galactic magnetar SGR 1935+2154, magnetars have joined the
set of favourable candidates for FRB progenitors. However, the
emission mechanism of magnetars remains poorly understood.
Observations of magnetars with a high cadence over extended timescales
have allowed for their emission properties to be determined, in
particular, their temporal variations. In this work, we present the
results of the long-term monitoring campaign of the magnetar XTE
J1810-197 since its second observed active phase from December 2018
until November 2021, with the Stockert 25m radio telescope.
We present a single pulse search method, improving on commonly used
neural network classifiers thanks to the filtering of radio frequency
interference based on its spectral variance and the magnetar's
rotation. Results. With this approach, we were able to lower the
signal to noise ratio (S/N) detection threshold from 8 to 5. This
allowed us to find over 115000 spiky single pulses - compared to
56000 from the neutral network approach. Here, we present the
temporal variation of the overall profile and single pulses. Two
distinct phases of different single pulse activity can be identified:
phase 1 from December 2018 to mid-2019, with a few single pulses per
hour, and phase 2 from September 2020 with hundreds of single pulses
per hour (with a comparable average flux density). We find that the
single pulse properties and folded profile in phase 2 exhibit a change
around mid-March 2021. Before this date, the folded profile consists
of a single peak and single pulses, with fluences of up to 1000Jy.ms
and a single-peaked width distribution at around 10 ms. After
mid-March 2021, the profile consists of a two peaks and the single
pulse population shows a bimodal width distribution with a second peak
at 1ms and fluences of up to 500Jy.ms. We also present asymmetries in
the phase-resolved single pulse width distributions beginning to
appear in 2020, where the pulses arriving earlier in the rotational
phase appear wider than those appearing later. This asymmetry persists
despite the temporal evolution of the other single pulse and emission
properties. Conclusions. We argue that a drift in the emission region
in the magnetosphere may explain this observed behaviour.
Additionally, we find that the fluence of the detected single pulses
depends on the rotational phase and the highest fluence is found in
the centre of the peaks in the profile. While the majority of the
emission can be linked to the detected single pulses, we cannot
exclude another weak mode of emission. In contrast to the pulses from
SGR 1935+2154, we have not found any spectral feature or bursts with
energies in the order of magnitude of an FRB during our observational
campaign. Therefore, the question of whether this magnetar is capable
of emitting such highly energetic bursts remains open.
Description:
Here we provide two lists. One containing the average flux density and
pulse rate measured on each day and another containing the properties
of all detected single pulses using the filtering method.
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------
18 09 51.07 -19 43 51.7 XTE J1810-197 = PSR J1809-1943
------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 128 317 Number of pulses and average flux density
per observation
tablea2.dat 100 119106 List of single pulses with the properties
discussed in the publication
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "date" Date Date of observation
11- 13 A3 --- n_Date [-S1 -S2] Note on Date
15- 30 F16.10 d MJD MJD of observation
33- 53 F21.16 --- Nsps Number of detected single pulses in
observation (nospsfiltering)
55- 71 F17.14 --- e_Nsps Uncertainty of detected single pulses in
observation
73- 84 F12.6 s tobs Duration of observation
87-107 E21.14 Jy Flux Average flux density of overall profile in
observation
109-128 E20.14 Jy e_Flux Uncertainty of Flux
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 F16.10 d MJD MJD of observation
18- 29 F12.6 s Tcand Topocentric time since start of observation
when the SP was detected (centre of pulse)
31- 46 F16.14 s Phase Rotational phase when the SP was detected
(centre of pulse)
48- 68 F21.16 Jy Fluxmean Mean flux density of the single pulse
70- 91 F22.16 Jy.ms Fluence Fluence of the single pulse
93- 98 F6.3 ms Width Duration of the single pulse
100 I1 --- Half [1/2] The half of the profile, in which the
single pulse was detected (1=left, 2=right)
--------------------------------------------------------------------------------
Acknowledgements:
Marlon Luis Bause, mbause(at)mpifr-bonn.mpg.de
(End) Marlon Luis Bause [MPIfR, Germany], Patricia Vannier [CDS] 20-Mar-2024