Pulsar (lakuran dari Pulsating Radio Sources) adalah bintang neutron yang berotasi dengan cepat, yang merupakan sisa yang tertinggal dari kematian sebuah bintang masif. para astronom telah mengkatalogkan sekitar 1.800 pulsar. Kebanyakan diataranya memancarkan denyut dalam gelombang radio namun ada juga yang melepaskan energi dalam bentuk lain seperti cahaya kasatmata dan sinar-x. Pulsar bisa menangkap elektron yang terlepas ketika inti bintang runtuh. Elektron menghasilkan gelombang radio yang tersalur keluar oleh medan magnet bintang menjadi pancaran radiasi. Sejarah penemuan Pada 1967 ahli astronomi Jocelyn Bell Burnell, yang kemudian berkerja di Universitas Campbridge di Inggris, menemukan sinyal radio aneh dan berasal dari luar angkasa yang berdenyut tiap detik. Ia menamainya LGM-1 (ini adalah kependekan dari "little green man/orang hijau kecil"). Para astronom tak tahu apa penyebabnya. Saat itu belum pernah terdeteksi sinyal radio yang sedemikian teratur di Galaksi Bimasakti. Tak lama setelah itu seorang ilmuwan menghitung bahwa bintang neutron yang berputar bisa menciptakan denyut sinyal radio. ...

Pulsar (-aris, n., verbum amalgamatum ab Anglico pulsating + star, stella pulsans), est stella neutronica rapide volvens et cuius radii electromagnetici intervallis constantibus pulsant. Pulsaria arte coniunguntur magnetaribus; differunt autem vi eorum camporum magneticorum. Origo Pulsaria reperta sunt anno 1967 ab Iocelyna Bell et Antonio Hewish Cantabrigiae cum radioscopium ad scintillantem quasarum aspectum investigandum adhiberent. Signum constantissimum invenerunt, quod brevibus impulsibus post paucas secundas redientibus constitueretur. Origo terrestris signi exclusa erat nam omnis novus exortus die sideris nec die solis erat. Inaudita res tandem explicata est signo emisso stella neutronibus rapide volventi. Impulsus erant (et adhuc sunt) emissi omni 1.3373 secunda, quae autem constantia omnem aliam rem excludebat. Nexus interni Pulsar enormium radiorum Roentgenianorum Foramen nigrum Mollis radiationis gamma iteratrum Planetae pulsarium Radiatio gamma Roentgeniani radii Nexus externi...

Pulsars are neutron stars which spin rapidly and produce huge electromagnetic radiation along a narrow beam. Neutron stars are very dense, and have short, regular spins. This produces a very precise interval between pulses that range from roughly milliseconds to seconds for an individual pulsar. The pulse can only be seen if the Earth is close enough to the direction of the beam. Similar to how you can only see a lighthouse when the beam is shining at your direction. The pulses match the star's turns. The spinning causes a lighthouse effect, as the radiation is only seen at short intervals. Werner Becker of the Max Planck Institute for Extraterrestrial Physics recently said, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work. There are many models but no accepted theory". Discovery The first pulsar was discovered in 1967. It was discovered by Jocelyn Bell Burnell and Antony Hewish. They worked at the University of Cambridge. The observed emission had pulses separated by 1.33 seconds. The pulses all came from the same place in the sky. The source kept...

Pulsars are neutron stars which spin rapidly and produce huge electromagnetic radiation along a narrow beam. Neutron stars are very dense, and have short, regular spins. This produces a very precise interval between pulses that range from roughly milliseconds to seconds for an individual pulsar. The pulse can only be seen if the Earth is close enough to the direction of the beam. Similar to how you can only see a lighthouse when the beam is shining at your direction. The pulses match the star's turns. The spinning causes a lighthouse effect, as the radiation is only seen at short intervals. Werner Becker of the Max Planck Institute for Extraterrestrial Physics recently said, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work. There are many models but no accepted theory". Discovery The first pulsar was discovered in 1967. It was discovered by Jocelyn Bell Burnell and Antony Hewish. They worked at the University of Cambridge. The observed emission had pulses separated by 1.33 seconds. The pulses all came from the same place in the sky. The source kept...

The presence of superfluid phases in the interior of a neutron star affects its dynamics, as neutrons can flow relative to the non-superfluid (normal) components of the star with little or no viscosity. A probe of superfluidity comes from pulsar glitches, sudden jumps in the observed rotational period of radio pulsars. Most models of glitches build on the idea that a superfluid component of the star is decoupled from the spin-down of the normal component, and its sudden recoupling leads to a glitch. This transition in the strength of the hydrodynamic coupling is explained in terms of quantum vortices (long-lived vortices that are naturally present in the neutron superfluid at the microscopic scale). After introducing some basic ideas, we derive (as a pedagogical exercise) the formal scheme shared by many glitch studies. Then, we apply these notions to present some recent advances and discuss how observations can help us to indirectly probe the internal physics of neutron stars.

The fast rotating magnetized white dwarf, AE Aquarii, was observed with Suzaku, in October 2005 and October 2006 with exposures of 53.1 and 42.4 ks, respectively. In addition to clear spin modulation in the 0.5--10 keV band of the XIS data at the barycentric period of 33.0769 pm 0.0001 s, the 10--30 keV HXD data in the second half of the 2005 observation also showed statistically significant periodic signals at a consistent period. On that occasion, the spin-folded HXD light curve exhibited two sharp spikes separated by about 0.2 cycles in phase, in contrast to approximately sinusoidal profiles observed in energies below about 4 keV. The folded 4--10 keV XIS light curves are understood as a superposition of those two types of pulse profiles. The phase averaged 1.5--10 keV spectra can be reproduced by two thermal components with temperatures of $2.90_{-0.16}^{+0.20}$ keV and $0.53_{-0.13}^{+0.14}$ keV, but the 12-25 keV HXD data show a significant excess above the extrapolated model. This excess can be explained by either a power-law model with photon index of $1.12_{-0.62}^{+0.63}$ or a third thermal component with a temperature of $54_{-47}^{+26}$ keV. At a distance of 102 pc, the 4--30 keV luminosities of the thermal and the additional components become $1.7_{-0.6}^{+1.3}$ and $5.3_{-0.3}^{+15.3} times 10^{29}$ erg s$^{-1}$, respectively. The latter corresponds to 0.09% of the spin down energy of the object. Possible emission mechanisms of the hard pulsations are discussed, including in particular non-thermal ones.

The variable star AR Sco was recently discovered to pulse in brightness every 1.97 min from ultraviolet wavelengths into the radio regime. The system is composed of a cool, low-mass star in a tight, 3.55 hr orbit with a more massive white dwarf. Here we report new optical observations of AR Sco that show strong linear polarization (up to 40%) which varies strongly and periodically on both the spin period of the white dwarf and the beat period between the spin and orbital period, as well as low level (< a few %) circular polarization. These observations support the notion that, similar to neutron star pulsars, the pulsed luminosity of AR Sco is powered by the spin-down of the rapidly-rotating white dwarf which is highly magnetised (up to 500 MG). The morphology of the modulated linear polarization is similar to that seen in the Crab pulsar, albeit with a more complex waveform owing to the presence of two periodic signals of similar frequency. Magnetic interactions between the two component stars, coupled with synchrotron radiation from the white dwarf, power the observed polarized and non-polarized emission. AR Scorpii is therefore the first example of a white dwarf pulsar.

White dwarfs are compact stars, similar in size to Earth but ~200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf / cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a delta-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56 hr period close binary, pulsing in brightness on a period of 1.97 min. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 s, and they are detectable at radio frequencies, the first such detection for any white dwarf system. They reflect the spin of a magnetic white dwarf which we find to be slowing down on a 10^7 yr timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they originate in large part from the cool star. AR Sco's broad-band spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.

White dwarf stars are the most common stellar fossils. When in binaries, they make up the dominant form of compact object binary within the Galaxy and can offer insight into different aspects of binary formation and evolution. One of the most remarkable white dwarf binary systems identified to date is AR Scorpii (henceforth AR Sco). AR Sco is composed of an M-dwarf star and a rapidly-spinning white dwarf in a 3.56-hour orbit. It shows pulsed emission with a period of 1.97 minutes over a broad range of wavelengths, which led to it being known as a white dwarf pulsar. Both the pulse mechanism and the evolutionary origin of AR Sco provide challenges to theoretical models. Here we report the discovery of the first sibling of AR Sco, J191213.72-441045.1 (henceforth J1912-4410), which harbours a white dwarf in a 4.03-hour orbit with an M-dwarf and exhibits pulsed emission with a period of 5.30 minutes. This discovery establishes binary white dwarf pulsars as a class and provides support for proposed formation models for white dwarf pulsars.