25 research outputs found
A MeerKAT view of the pulsars in the globular cluster NGC 6522
We present the results of observations aimed at discovering and studying
pulsars in the core-collapsed globular cluster (GC) NGC 6522 performed by the
MeerTIME and TRAPUM Large Survey Project with the MeerKAT telescope. We have
discovered two new isolated pulsars bringing the total number of known pulsars
in the cluster to six. PSR J18033002E is a mildly recycled pulsar with spin
period of 17.9 ms while pulsar PSR J18033002F is a slow pulsar with spin
period of 148.1 ms. The presence of isolated and slow pulsars is expected in
NGC 6522 and confirms the predictions of previous theories for clusters at this
stage in evolution. We further present a tentative timing solution for the
millisecond pulsar (MSP) PSR J18033002C combining older observations taken
with the Parkes 64m radio telescope, Murriyang. This solution implies a
relatively small characteristic age of the pulsar in contrast with the old age
of the GC. The presence of a slow pulsar and an apparently young MSP, both rare
in GCs, suggests that their formation might be linked to the evolutionary stage
of the cluster.Comment: 8 pages, 5 figues, 3 tables. Accepted for publication in Astronomy
and Astrophysic
The MPIfR-MeerKAT Galactic Plane Survey II. The eccentric double neutron star system PSR J1208-5936 and a neutron star merger rate update
The MMGPS-L is the most sensitive pulsar survey in the Southern Hemisphere.
We present a follow-up study of one of these new discoveries, PSR J1208-5936, a
28.71-ms recycled pulsar in a double neutron star system with an orbital period
of Pb=0.632 days and an eccentricity of e=0.348. Through timing of almost one
year of observations, we detected the relativistic advance of periastron
(0.918(1) deg/yr), resulting in a total system mass of Mt=2.586(5) Mo. We also
achieved low-significance constraints on the amplitude of the Einstein delay
and Shapiro delay, in turn yielding constraints on the pulsar mass
(Mp=1.26(+0.13/-0.25) Mo), the companion mass (Mc=1.32(+0.25/-0.13) Mo, and the
inclination angle (i=57(2) degrees). This system is highly eccentric compared
to other Galactic field double neutron stars with similar periods, possibly
hinting at a larger-than-usual supernova kick during the formation of the
second-born neutron star. The binary will merge within 7.2(2) Gyr due to the
emission of gravitational waves. With the improved sensitivity of the MMGPS-L,
we updated the Milky Way neutron star merger rate to be 25(+19/-9) Myr
within 90% credible intervals, which is lower than previous studies based on
known Galactic binaries owing to the lack of further detections despite the
highly sensitive nature of the survey. This implies a local cosmic neutron star
merger rate of 293(+222/-103} Gpc/yr, consistent with LIGO and Virgo O3
observations. With this, we predict the observation of 10(+8/-4) neutron star
merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties
on the component masses and the inclination angle will be reduced to
5x10 Mo and 0.4 degrees after two decades of timing, and that in at
least a decade from now the detection of the shift in Pb and the sky proper
motion will serve to make an independent constraint of the distance to the
system
A MeerKAT look at the polarization of 47 Tucanae pulsars: magnetic field implications
We present the polarization profiles of 22 pulsars in the globular cluster 47Tucanae using observations from the MeerKAT radio telescope at UHF-band(544-1088 MHz) and report precise values of dispersion measure (DM) androtation measure (RM). We use these measurements to investigate the presence ofturbulence in electron density and magnetic fields. The structure function ofDM shows a break at arcsec ( pc at the distance of 47Tucanae) that suggests the presence of turbulence in the gas in the clusterdriven by the motion of wind-shedding stars. On the other hand, the structurefunction of RM does not show evidence of a break. This non-detection could beexplained either by the limited number of pulsars or by the effects of theintervening gas in the Galaxy along the line of sight. Future pulsardiscoveries in the cluster could help confirm the presence and localise theturbulence.<br
A MeerKAT look at the polarization of 47 Tucanae pulsars: magnetic field implications
We present the polarization profiles of 22 pulsars in the globular cluster 47
Tucanae using observations from the MeerKAT radio telescope at UHF-band
(544-1088 MHz) and report precise values of dispersion measure (DM) and
rotation measure (RM). We use these measurements to investigate the presence of
turbulence in electron density and magnetic fields. The structure function of
DM shows a break at arcsec ( pc at the distance of 47
Tucanae) that suggests the presence of turbulence in the gas in the cluster
driven by the motion of wind-shedding stars. On the other hand, the structure
function of RM does not show evidence of a break. This non-detection could be
explained either by the limited number of pulsars or by the effects of the
intervening gas in the Galaxy along the line of sight. Future pulsar
discoveries in the cluster could help confirm the presence and localise the
turbulence.Comment: Accepted for publication in MNRAS, 14 pages, 6 figure
Four pulsar discoveries in NGC 6624 by TRAPUM using MeerKAT
We report 4 new pulsars discovered in the core-collapsed globular cluster
(GC) NGC 6624 by the TRAPUM Large Survey Project with the MeerKAT telescope.
All of the new pulsars found are isolated. PSR J18233021I and PSR
J18233021K are millisecond pulsars with period of respectively 4.319 ms and
2.768 ms. PSR J18233021J is mildly recycled with a period of 20.899 ms, and
PSR J18233022 is a long period pulsar with a period of 2.497 s. The pulsars
J18233021I, J18233021J, and J18233021K have position and dispersion
measure (DM) compatible with being members of the GC and are therefore
associated with NGC 6624. Pulsar J18233022 is the only pulsar bright enough
to be re-detected in archival observations of the cluster. This allowed the
determination of a timing solution that spans over two decades. It is not
possible at the moment to claim the association of pulsar J18233022 with the
GC given the long period and large offset in position ( arcminutes) and
DM (with a fractional difference of 11 percent compared the average of the
pulsars in NGC 6624). The discoveries made use of the beamforming capability of
the TRAPUM backend to generate multiple beams in the same field of view which
allows sensitive searches to be performed over a few half-light radii from the
cluster center and can simultaneously localise the discoveries. The discoveries
reflect the properties expected for pulsars in core-collapsed GCs.Comment: Accepted for publication on Monthly Notices of the Royal Astronomical
Society. 11 pages, 6 figure
TRAPUM discovery of thirteen new pulsars in NGC 1851 using MeerKAT
We report the discovery of 13 new pulsars in the globular cluster NGC 1851 by the TRAPUM Large Survey Project using the MeerKAT radio telescope. The discoveries consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. For all the pulsars, we present the basic kinematic, astrometric, and orbital parameters, where applicable, as well as their polarimetric properties, when these are measurable. Two of the binary MSPs (PSR J0514-4002D and PSR J0514-4002E) are in wide and extremely eccentric (e > 0.7) orbits with a heavy white dwarf and a neutron star as their companion, respectively. With these discoveries, NGC 1851 is now tied with M28 as the cluster with the third largest number of known pulsars (14). Its pulsar population shows remarkable similarities with that of M28, Terzan 5 and other clusters with comparable structural parameters. The newly-found pulsars are all located in the innermost regions of NGC 1851 and will likely enable, among other things, detailed studies of the cluster structure and dynamics
Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397
We report the discovery of a new 5.78 ms-period millisecond pulsar (MSP), PSR J1740-5340B (NGC 6397B), in an eclipsing binary system discovered with the Parkes radio telescope (now also known as Murriyang), Australia, and confirmed with the MeerKAT radio telescope in South Africa. The measured orbital period, 1.97 days, is the longest among all eclipsing binaries in globular clusters (GCs) and consistent with that of the coincident X-ray source U18, previously suggested to be a 'hidden MSP'. Our XMM-Newton observations during NGC 6397B's radio quiescent epochs detected no X-ray flares. NGC 6397B is either a transitional MSP or an eclipsing binary in its initial stage of mass transfer after the companion star left the main sequence. The discovery of NGC 6397B potentially reveals a subgroup of extremely faint and heavily obscured binary pulsars, thus providing a plausible explanation to the apparent dearth of binary neutron stars in core-collapsed GCs as well as a critical constraint on the evolution of GCs
The TRAPUM L-band survey for pulsars in Fermi-LAT gamma-ray sources
More than 100 millisecond pulsars (MSPs) have been discovered in radio
observations of gamma-ray sources detected by the Fermi Large Area Telescope
(LAT), but hundreds of pulsar-like sources remain unidentified. Here we present
the first results from the targeted survey of Fermi-LAT sources being performed
by the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. We
observed 79 sources identified as possible gamma-ray pulsar candidates by a
Random Forest classification of unassociated sources from the 4FGL catalogue.
Each source was observed for 10 minutes on two separate epochs using MeerKAT's
L-band receiver (856-1712 MHz), with typical pulsed flux density sensitivities
of 100Jy. Nine new MSPs were discovered, eight of which are in
binary systems, including two eclipsing redbacks and one system, PSR
J15262744, that appears to have a white dwarf companion in an unusually
compact 5 hr orbit. We obtained phase-connected timing solutions for two of
these MSPs, enabling the detection of gamma-ray pulsations in the Fermi-LAT
data. A follow-up search for continuous gravitational waves from PSR
J15262744 in Advanced LIGO data using the resulting Fermi-LAT timing
ephemeris yielded no detection, but sets an upper limit on the neutron star
ellipticity of . We also detected X-ray emission from the
redback PSR J18036707 in data from the first eROSITA all-sky survey, likely
due to emission from an intra-binary shock.Comment: 17 pages, 8 figures, accepted for publication in MNRA
The TRAPUM L-band survey for pulsars in Fermi-LAT gamma-ray sources
More than 100 millisecond pulsars (MSPs) have been discovered in radioobservations of gamma-ray sources detected by the Fermi Large Area Telescope(LAT), but hundreds of pulsar-like sources remain unidentified. Here we presentthe first results from the targeted survey of Fermi-LAT sources being performedby the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. Weobserved 79 sources identified as possible gamma-ray pulsar candidates by aRandom Forest classification of unassociated sources from the 4FGL catalogue.Each source was observed for 10 minutes on two separate epochs using MeerKAT'sL-band receiver (856-1712 MHz), with typical pulsed flux density sensitivitiesof 100Jy. Nine new MSPs were discovered, eight of which are inbinary systems, including two eclipsing redbacks and one system, PSRJ15262744, that appears to have a white dwarf companion in an unusuallycompact 5 hr orbit. We obtained phase-connected timing solutions for two ofthese MSPs, enabling the detection of gamma-ray pulsations in the Fermi-LATdata. A follow-up search for continuous gravitational waves from PSRJ15262744 in Advanced LIGO data using the resulting Fermi-LAT timingephemeris yielded no detection, but sets an upper limit on the neutron starellipticity of . We also detected X-ray emission from theredback PSR J18036707 in data from the first eROSITA all-sky survey, likelydue to emission from an intra-binary shock.<br
Development and performance evaluation of a coronary artery disease prediction system with transfer learned model based on single lead and multi-lead ECG & TMT-ECG signals
Coronary artery disease is one of the major cardiovascular diseases and is a cardiac condition where plaque formed in arteries leads to death worldwide. The identification of CAD in the traditional approach needs a report of ECG, TMT ECG, Pharmacological test, and echocardiogram. The confirmation of CAD leads to undergoing cardiac catheterization. An effective prediction system that can detect the existence of CAD with an initial test like ECG or TMT ECG report image will act as a good assistance to doctors and patients undergoing periodic health monitoring. The present study is focused on developing a prediction system for CAD disease based on raw and filtered, single lead and twelve lead ECG signal images. The algorithm results are compared with transfer learning algorithms. The novelty of the work is highlighted by the fact that the prediction accuracy of the developed algorithm, with single lead and twelve lead ECG or TMT ECG signals (accuracy of approximately 93.5% for single lead and 94.5% for twelve lead) is much higher compared to transfer learned algorithms. The developed model exhibited better accuracy with lesser number of layers compared to deeper pre-trained algorithms.