4,307 research outputs found
Radio Timing and Optical Photometry of the Black Widow System PSR J1953+1846A in the Globular Cluster M71
We report on the determination of the astrometric, spin and orbital
parameters for PSR J1953+1846A, a "black widow" binary millisecond pulsar in
the globular cluster M71. By using the accurate position and orbital parameters
obtained from radio timing, we identified the optical companion in ACS/Hubble
Space Telescope images. It turns out to be a faint (m_F606W>=24, m_F814W>=23)
and variable star located at only ~0.06" from the pulsar timing position. The
light curve shows a maximum at the pulsar inferior conjunction and a minimum at
the pulsar superior conjunction, thus confirming the association with the
system. The shape of the optical modulation suggests that the companion star is
heated, likely by the pulsar wind. The comparison with the X-ray light curve
possibly suggests the presence of an intra-binary shock due to the interaction
between the pulsar wind and the material released by the companion. This is the
second identification (after COM-M5C) of an optical companion to a black widow
pulsar in a globular cluster. Interestingly, the two companions show a similar
light curve and share the same position in the color magnitude diagram.Comment: Accepted for publication by ApJ; 33 Pages, 10 Figures, 3 Table
Avaliação qualitativa preliminar de frutos de mangabeiras (Hancornia speciosa Gomez) em área de cerrado no Amapá.
Radio timing and optical photometry of the black widow system PSR J1518+0204C in the globular cluster M5
We report on the determination of astrometric, spin and orbital parameters
for PSR J1518+0204C, a "black widow" binary millisecond pulsar in the globular
cluster M5. The accurate position and orbital parameters obtained from radio
timing allowed us to search for the optical companion. By using WFC3/HST images
we identified a very faint variable star (m_F390W > 24.8, m_F606W > 24.3,
m_F814W > 23.1) located at only 0.25" from the pulsar's timing position. Due to
its strong variability, this star is visible only in a sub-sample of images.
However, the light curve obtained folding the available data with the orbital
parameters of the pulsar shows a maximum at the pulsar inferior conjunction and
a possible minimum at the pulsar superior conjunction. Furthermore, the shape
of the optical modulation indicates a heating process possibly due to the
pulsar wind. This is the first identification of an optical companion to a
black widow pulsar in the dense stellar environment of a globular cluster.Comment: Accepted for publication by ApJ; 24 Pages, 5 Figures, 1 Tabl
Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion
We report on timing observations of the recently discovered binary pulsar PSR
J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is
in a 9.4-hr orbit with a massive, M_WD > 0.93 M_sun, white dwarf (WD)
companion. We present, for the first time, a phase-coherent timing solution,
with precise spin, astrometric, and Keplerian orbital parameters. This shows
that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order
of magnitude than any other recycled pulsar-massive WD system. We derive an
upper limit on the true age of the system of 50 Myr. We investigate the
formation of PSR J1952+2630 using detailed modelling of the mass-transfer
process from a naked helium star on to the neutron star following a
common-envelope phase (Case BB Roche-lobe overflow). From our modelling of the
progenitor system, we constrain the accretion efficiency of the neutron star,
which suggests a value between 100 and 300% of the Eddington accretion limit.
We present numerical models of the chemical structure of a possible
oxygen-neon-magnesium WD companion. Furthermore, we calculate the past and the
future spin evolution of PSR J1952+2630, until the system merges in about 3.4
Gyr due to gravitational wave emission. Although we detect no relativistic
effects in our timing analysis we show that several such effects will become
measurable with continued observations over the next 10 years; thus PSR
J1952+2630 has potential as a testbed for gravitational theories.Comment: 12 pages, 10 figures, to be published in MNRA
Discovery of three new millisecond pulsars in Terzan 5
We report on the discovery of three new millisecond pulsars (namely
J1748-2446aj, J1748-2446ak and J1748-2446al) in the inner regions of the dense
stellar system Terzan 5. These pulsars have been discovered thanks to a method,
alternative to the classical search routines, that exploited the large set of
archival observations of Terzan 5 acquired with the Green Bank Telescope over 5
years (from 2010 to 2015). This technique allowed the analysis of stacked power
spectra obtained by combining ~206 hours of observation. J1748-2446aj has a
spin period of ~2.96 ms, J1748-2446ak of ~1.89 ms (thus it is the fourth
fastest pulsar in the cluster) and J1748-2446al of ~5.95 ms. All the three
millisecond pulsars are isolated and currently we have timing solutions only
for J1748-2446aj and J1748-2446ak. For these two systems, we evaluated the
contribution to the measured spin-down rate of the acceleration due to the
cluster potential field, thus estimating the intrinsic spin-down rates, which
are in agreement with those typically measured for millisecond pulsars in
globular clusters. Our results increase to 37 the number of pulsars known in
Terzan 5, which now hosts 25% of the entire pulsar population identified, so
far, in globular clusters.Comment: 10 pages, 6 figures. ApJ (accepted
Amapá: nova cultivar de feijão caupi para o Amapá.
Introdução; Origem; Características; Resultados experimentais; Recomendações técnicas; Comercialização; Referências bibliograficas.bitstream/CPAF-AP/4295/1/comunicado_1999_022.pd
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