8 research outputs found
Evidence for a 304-day Orbital Period for GX 1+4
In this paper we report strong evidence for a ~304-day periodicity in the
spin history of the accretion-powered pulsar GX 1+4 that is very likely to be a
signature of the orbital period of the system. Using BATSE public-domain data,
we show a highly-significant periodic modulation of the pulsar frequency from
1991 to date which is in excellent agreement with the ephemeris proposed by
Cutler, Dennis & Dolan in 1986, which were based on a few events of enhanced
spin-up that occurred during the pulsar's spin-up era in the 1970s. Our results
indicate that the orbital period of GX 1+4 is 303.8+-1.1 days, making it by far
the widest low-mass X-ray binary system known. A likely scenario for this
system is an elliptical orbit in which the neutron star decreases its spin-down
rate (or even exhibits a momentary spin-up behavior) at periastron passages due
to the higher torque exerted by the accretion disk onto the magnetosphere of
the neutron star.Comment: 5 pages, 2 figures, 1 single PS file, to appear in "Proceedings of
the 5th Compton Symposium on Gamma-Ray Astrophysics", AI
EXPERIMENTOS DE FÍSICA: uma abordagem não formal para a popularização da ciência e tecnologia
O atual ambiente socioeconômico caracteriza-se por seu dinamismo e complexidade que, tão cheio de dificuldades, necessitam cada vez mais de indivíduos com uma consciência cidadã e atitudes mais objetivas em suas ações, pois sendo capazes de interpretar e agir diante dos desafios da vida moderna, poderão assim transformá-la
Discovery of optical pulsations in V2116 Ophiuchi/GX 1+4
We report the detection of pulsations with s period in V2116 Oph,
the optical counterpart of the low-mass X-ray binary GX 1+4. The pulsations are
sinusoidal with modulation amplitude of up to 4% in blue light and were
observed in ten different observing sessions during 1996 April-August using a
CCD photometer at the 1.6-m and 0.6-m telescopes of Laborat\'orio Nacional de
Astrof\'{\i}sica, in Brazil. The pulsations were also observed with the
fast photometer. With only one exception the observed optical periods are
consistent with those observed by the BATSE instrument on board the Compton
Gamma Ray Observatory at the same epoch. There is a definite correlation
between the observability of pulsations and the optical brightness of the
system: V2116~Oph had magnitude in the range when the pulsed
signal was detected, and when no pulsations were present. The
discovery makes GX 1+4 only the third of accretion-powered X-ray
pulsars to be firmly detected as a pulsating source in the optical. The
presence of flickering and pulsations in V2116 Oph adds strong evidence for an
accretion disk scenario in this system. The absolute magnitude of the pulsed
component on 1996 May 27 is estimated to be . The implied
dimensions for the emitting region are 1.1 R_{\sun}, 3.2 R_{\sun}, and 7.0
R_{\sun}, for black-body spectral distributions with K, K, and K, respectively.Comment: 9 pages, 3 figures in PostScript, latex, accepted for publication on
the Astrophysical Journal Letter
PLANETÁRIO ITINERANTE COMO FERRAMENTA DE POPULARIZAÇÃO DE CIÊNCIAS NAS ESCOLAS DA BAHIA
O projeto Planetário Itinerante é um programa de extensão destinado a divulgação científica com sede na Universidade Estadual de Feira de Santana. Ligado ao Observatório Astronômico Antares e Departamento de Física da UEFS