4 research outputs found
Rotation measure variations in Galactic Centre pulsars
We report the results of an observational campaign using the Effelsberg 100-m
telescope of the pulsars J17462849, J17462850, J17462856 and
J17452912 located in the Central Molecular Zone (CMZ) close to the Galactic
centre in order to study rotation measure (RM) variations. We report for the
first time the RM value of PSR J17462850 to be rad
m. This pulsar shows significant variations of RM of rad
m over the course of months to years that suggest a strongly magnetized
environment. The structure function analysis of the RM of PSR J17462850
revealed a steep power-law index of comparable to the
value expected for isotropic turbulence. This pulsar also showed large
dispersion measure (DM) variation of pc cm in an event lasting
a few months where the RM increased by rad m. The large
difference in RM between PSR J17462849 and PSR J17462850 despite the
small angular separation reveals the presence of a magnetic field of at least
70 G in the CMZ and can explain the lack of polarization in the radio
images of the region. These results contribute to our understanding of the
magnetic field in the CMZ and show similarities between the RM behaviours of
these pulsars and some fast radio bursts (FRBs).Comment: Accepted for publication on Monthly Notices of the Royal Astronomical
Society, 13 pages, 7 figure
The High Time Resolution Universe Pulsar Survey -- XVIII. The reprocessing of the HTRU-S Low Lat survey around the Galactic centre using a Fast Folding Algorithm pipeline for accelerated pulsars
The HTRU-S Low Latitude survey data within 1of the Galactic Centre
(GC) were searched for pulsars using the Fast Folding Algorithm (FFA). Unlike
traditional Fast Fourier Transform (FFT) pipelines, the FFA optimally folds the
data for all possible periods over a given range, which is particularly
advantageous for pulsars with low-duty cycle. For the first time, a search over
acceleration was included in the FFA to improve its sensitivity to binary
pulsars. The steps in dispersion measure (DM) and acceleration were optimised,
resulting in a reduction of the number of trials by 86 per cent. This was
achieved over a search period range from 0.6-s to 432-s, i.e. 10 per cent of
the observation time (4320s), with a maximum DM of 4000 pc cm and an
acceleration range of m s. The search resulted in the
re-detections of four known pulsars, including a pulsar which was missed in
previous FFT processing of this survey. This result indicates that the FFA
pipeline is more sensitive than the FFT pipeline used in the previous
processing of the survey within our parameter range. Additionally, we
discovered a 1.89-s pulsar, PSR J1746-2829, with a large DM, located~0.5 from
the GC. Follow-up observations revealed that this pulsar has a relatively flat
spectrum() and has a period derivative of
s s, implying a surface magnetic field of
G and a characteristic age of yr. While the
period, spectral index, and surface magnetic field strength are similar to many
radio magnetars, other characteristics such as high linear polarization are
absent.Comment: 12 pages, 6 figures, 4 tables, Accepted for publication on Monthly
Notices of the Royal Astronomical Societ
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A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set
In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region