147 research outputs found
Decade-long timing of four GMRT discovered millisecond pulsars
The discovery and timing follow-up of millisecond pulsars (MSPs) are
necessary not just for their usefulness in Pulsar Timing Arrays (PTAs) but also
for investigating their own intriguing properties. In this work, we provide the
findings of the decade-long timing of the four MSPs discovered by the Giant
Metre-wave Radio Telescope (GMRT), including their timing precision, model
parameters, and newly detected proper motions. We compare the timing results
for these MSPs before and after the GMRT upgrade in 2017, characterise the
improvement in timing precision due to the bandwidth upgrade. We discuss the
suitability of these four GMRT MSPs as well as the usefulness of their
decade-long timing data for the PTA {experiments. It may aid} in the global
effort to improve the signal-to-noise (S/N) of recently detected signature of
gravitational waves in cross-correlation statistics of residuals of MSPs.Comment: Accepted in Astrophysical Journal (APJ) on October 31, 202
A fast radio burst with a low dispersion measure
Fast radio bursts (FRBs) are millisecond pulses of radio emission of
seemingly extragalactic origin. More than 50 FRBs have now been detected, with
only one seen to repeat. Here we present a new FRB discovery, FRB 110214, which
was detected in the high latitude portion of the High Time Resolution Universe
South survey at the Parkes telescope. FRB 110214 has one of the lowest
dispersion measures of any known FRB (DM = 168.90.5 pc cm), and was
detected in two beams of the Parkes multi-beam receiver. A triangulation of the
burst origin on the sky identified three possible regions in the beam pattern
where it may have originated, all in sidelobes of the primary detection beam.
Depending on the true location of the burst the intrinsic fluence is estimated
to fall in the range of 50 -- 2000 Jy ms, making FRB 110214 one of the
highest-fluence FRBs detected with the Parkes telescope. No repeating pulses
were seen in almost 100 hours of follow-up observations with the Parkes
telescope down to a limiting fluence of 0.3 Jy ms for a 2-ms pulse. Similar
low-DM, ultra-bright FRBs may be detected in telescope sidelobes in the future,
making careful modeling of multi-beam instrument beam patterns of utmost
importance for upcoming FRB surveys.Comment: 8 pages, 3 figures, accepted for publication in MNRA
The Green Bank North Celestial Cap Pulsar Survey. IV: Four New Timing Solutions
We present timing solutions for four pulsars discovered in the Green Bank
Northern Celestial Cap (GBNCC) survey. All four pulsars are isolated with spin
periods between 0.26s and 1.84s. PSR J00382501 has a 0.26s
period and a period derivative of ,
which is unusually low for isolated pulsars with similar periods. This low
period derivative may be simply an extreme value for an isolated pulsar or it
could indicate an unusual evolution path for PSR J00382501, such as a
disrupted recycled pulsar (DRP) from a binary system or an orphaned central
compact object (CCO). Correcting the observed spin-down rate for the Shklovskii
effect suggests that this pulsar may have an unusually low space velocity,
which is consistent with expectations for DRPs. There is no X-ray emission
detected from PSR J00382501 in an archival swift observation, which suggests
that it is not a young orphaned CCO. The high dispersion measure of PSR
J1949+3426 suggests a distance of 12.3kpc. This distance indicates that PSR
J1949+3426 is among the most distant 7% of Galactic field pulsars, and is one
of the most luminous pulsars.Comment: 7 pages, 5 figure
Multi-Messenger Gravitational Wave Searches with Pulsar Timing Arrays: Application to 3C66B Using the NANOGrav 11-year Data Set
When galaxies merge, the supermassive black holes in their centers may form
binaries and, during the process of merger, emit low-frequency gravitational
radiation in the process. In this paper we consider the galaxy 3C66B, which was
used as the target of the first multi-messenger search for gravitational waves.
Due to the observed periodicities present in the photometric and astrometric
data of the source of the source, it has been theorized to contain a
supermassive black hole binary. Its apparent 1.05-year orbital period would
place the gravitational wave emission directly in the pulsar timing band. Since
the first pulsar timing array study of 3C66B, revised models of the source have
been published, and timing array sensitivities and techniques have improved
dramatically. With these advances, we further constrain the chirp mass of the
potential supermassive black hole binary in 3C66B to less than using data from the NANOGrav 11-year data set. This
upper limit provides a factor of 1.6 improvement over previous limits, and a
factor of 4.3 over the first search done. Nevertheless, the most recent orbital
model for the source is still consistent with our limit from pulsar timing
array data. In addition, we are able to quantify the improvement made by the
inclusion of source properties gleaned from electromagnetic data to `blind'
pulsar timing array searches. With these methods, it is apparent that it is not
necessary to obtain exact a priori knowledge of the period of a binary to gain
meaningful astrophysical inferences.Comment: 14 pages, 6 figures. Accepted by Ap
Recommended from our members
Enhanced methods for unbiased deep sequencing of Lassa and Ebola RNA viruses from clinical and biological samples
We have developed a robust RNA sequencing method for generating complete de novo assemblies with intra-host variant calls of Lassa and Ebola virus genomes in clinical and biological samples. Our method uses targeted RNase H-based digestion to remove contaminating poly(rA) carrier and ribosomal RNA. This depletion step improves both the quality of data and quantity of informative reads in unbiased total RNA sequencing libraries. We have also developed a hybrid-selection protocol to further enrich the viral content of sequencing libraries. These protocols have enabled rapid deep sequencing of both Lassa and Ebola virus and are broadly applicable to other viral genomics studies. Electronic supplementary material The online version of this article (doi:10.1186/s13059-014-0519-7) contains supplementary material, which is available to authorized users
Using Cognitive Interviewing for the Semantic Enhancement of Multi-Lingual Versions of Personality Questionnaires
We discuss the use of cognitive interviewing with bilinguals as an integral part of cross-cultural adaptation of personality questionnaires. The aim is to maximize semantic equivalence to increase the likelihood of items maintaining the intended structure and meaning in the target language. We refer to this part of adaptation as semantic enhancement, and integrate cognitive interviewing within it as a tool for scrutinizing translations, the connotative meaning, and the psychological impact of items across languages. During the adaptation of a work-based personality questionnaire from English to Arabic, Chinese (Mandarin), and Spanish, we cognitively interviewed 12 bilingual participants about 136 items in different languages (17% of all items), of which 67 were changed. A content analysis categorizing the reasons for amending items elicited eleven errors that affect two identified forms of semantic equivalence. We provide the resultant coding scheme as a framework for designing cognitive interviewing protocols and propose a procedure for implementing them. We discuss implications for theory and practic
Bayesian Solar Wind Modeling with Pulsar Timing Arrays
Using Bayesian analyses we study the solar electron density with the NANOGrav
11-year pulsar timing array (PTA) dataset. Our model of the solar wind is
incorporated into a global fit starting from pulse times-of-arrival. We
introduce new tools developed for this global fit, including analytic
expressions for solar electron column densities and open source models for the
solar wind that port into existing PTA software. We perform an ab initio
recovery of various solar wind model parameters. We then demonstrate the
richness of information about the solar electron density, , that can be
gleaned from PTA data, including higher order corrections to the simple
model associated with a free-streaming wind (which are informative probes of
coronal acceleration physics), quarterly binned measurements of and a
continuous time-varying model for spanning approximately one solar cycle
period. Finally, we discuss the importance of our model for chromatic noise
mitigation in gravitational-wave analyses of pulsar timing data and the
potential of developing synergies between sophisticated PTA solar electron
density models and those developed by the solar physics community.Comment: 22 pages, 7 figures, Submitted to Ap
The NANOGrav 11-Year Data Set: Arecibo Observatory Polarimetry And Pulse Microcomponents
We present the polarization pulse profiles for 28 pulsars observed with the
Arecibo Observatory by the North American Nanohertz Observatory for
Gravitational Waves (NANOGrav) timing project at 2.1 GHz, 1.4 GHz, and 430 MHz.
These profiles represent some of the most sensitive polarimetric millisecond
pulsar profiles to date, revealing the existence of microcomponents (that is,
pulse components with peak intensities much lower than the total pulse peak
intensity). Although microcomponents have been detected in some pulsars
previously, we present microcomponents for PSRs B1937+21, J1713+0747, and
J2234+0944 for the first time. These microcomponents can have an impact on
pulsar timing, geometry, and flux density determination. We present rotation
measures for all 28 pulsars, determined independently at different observation
frequencies and epochs, and find the Galactic magnetic fields derived from
these rotation measures to be consistent with current models. These
polarization profiles were made using measurement equation template matching,
which allows us to generate the polarimetric response of the Arecibo
Observatory on an epoch-by-epoch basis. We use this method to describe its time
variability, and find that the polarimetric responses of the Arecibo
Observatory's 1.4 and 2.1 GHz receivers vary significantly with time.Comment: 41 pages, 20 figure
The Green Bank North Celestial Cap Pulsar Survey. III. 45 New Pulsar Timing Solutions
We provide timing solutions for 45 radio pulsars discovered by the Robert C. Byrd Green Bank Telescope. These pulsars were found in the Green Bank North Celestial Cap pulsar survey, an all-GBT-sky survey being carried out at a frequency of 350 MHz. We include pulsar timing data from the Green Bank Telescope and Low Frequency Array. Our sample includes five fully recycled millisecond pulsars (MSPs, three of which are in a binary system), a new relativistic double neutron star system, an intermediate-mass binary pulsar, a mode-changing pulsar, a 138 ms pulsar with a very low magnetic field, and several nulling pulsars. We have measured two post-Keplerian parameters and thus the masses of both objects in the double neutron star system. We also report a tentative companion mass measurement via Shapiro delay in a binary MSP. Two of the MSPs can be timed with high precision and have been included in pulsar timing arrays being used to search for low-frequency gravitational waves, while a third MSP is a member of the black widow class of binaries. Proper motion is measurable in five pulsars, and we provide an estimate of their space velocity. We report on an optical counterpart to a new black widow system and provide constraints on the optical counterparts to other binary MSPs. We also present a preliminary analysis of nulling pulsars in our sample. These results demonstrate the scientific return of long timing campaigns on pulsars of all types
- …