109 research outputs found
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
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
The MPIfR-MeerKAT Galactic Plane Survey - I. System set-up and early results
Galactic plane radio surveys play a key role in improving our understanding of a wide range of astrophysical phenomena. Performing such a survey using the latest interferometric telescopes produces large data rates necessitating a shift towards fully or quasi-real-time data analysis with data being stored for only the time required to process them. We present here the overview and set-up for the 3000-h Max-Planck-Institut für Radioastronomie (MPIfR)-MeerKAT Galactic Plane Survey (MMGPS). The survey is unique by operating in a commensal mode, addressing key science objectives of the survey including the discovery of new pulsars and transients and studies of Galactic magnetism, the interstellar medium and star formation rates. We explain the strategy coupled with the necessary hardware and software infrastructure needed for data reduction in the imaging, spectral, and time domains. We have so far discovered 78 new pulsars including 17 confirmed binary systems of which two are potential double neutron star systems. We have also developed an imaging pipeline sensitive to the order of a few tens of micro-Jansky () with a spatial resolution of a few arcseconds. Further science operations with an in-house built S-band receiver operating between 1.7 and 3.5 GHz are about to commence. Early spectral line commissioning observations conducted at S-band, targeting transitions of the key molecular gas tracer CH at 3.3 GHz already illustrate the spectroscopic capabilities of this instrument. These results lay a strong foundation for future surveys with telescopes like the Square Kilometre Array (SKA)
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
Genome Sequence of a Mesophilic Hydrogenotrophic Methanogen Methanocella paludicola, the First Cultivated Representative of the Order Methanocellales
We report complete genome sequence of a mesophilic hydrogenotrophic methanogen Methanocella paludicola, the first cultured representative of the order Methanocellales once recognized as an uncultured key archaeal group for methane emission in rice fields. The genome sequence of M. paludicola consists of a single circular chromosome of 2,957,635 bp containing 3004 protein-coding sequences (CDS). Genes for most of the functions known in the methanogenic archaea were identified, e.g. a full complement of hydrogenases and methanogenesis enzymes. The mixotrophic growth of M. paludicola was clarified by the genomic characterization and re-examined by the subsequent growth experiments. Comparative genome analysis with the previously reported genome sequence of RC-IMRE50, which was metagenomically reconstructed, demonstrated that about 70% of M. paludicola CDSs were genetically related with RC-IMRE50 CDSs. These CDSs included the genes involved in hydrogenotrophic methane production, incomplete TCA cycle, assimilatory sulfate reduction and so on. However, the genetic components for the carbon and nitrogen fixation and antioxidant system were different between the two Methanocellales genomes. The difference is likely associated with the physiological variability between M. paludicola and RC-IMRE50, further suggesting the genomic and physiological diversity of the Methanocellales methanogens. Comparative genome analysis among the previously determined methanogen genomes points to the genome-wide relatedness of the Methanocellales methanogens to the orders Methanosarcinales and Methanomicrobiales methanogens in terms of the genetic repertoire. Meanwhile, the unique evolutionary history of the Methanocellales methanogens is also traced in an aspect by the comparative genome analysis among the methanogens
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