Bright Pulsars Research Articles

The broad band spectral properties of binary X-ray pulsars

The X-ray telescopes on board BeppoSAX are an optimal set of instruments to observe bright galactic binary pulsars. These sources emit very hard and quite complex X-ray spectra that can be accurately measured with BeppoSAX between 0.1 and 200 keV. A prototype of this complexity, the source Her X−1, shows at least seven different components in its spectrum. A broad band measure is therefore of paramount importance to have a thorough insight into the physics of the emitting region. Moreover the detection of cyclotron features, when present, allows a direct and highly significant measure of the magnetic field intensity in the emission region. In this paper we briefly report the results obtained with BeppoSAX on this class of sources, with emphasis on the detection and on the measured properties of the cyclotron lines.

Parameters of microstructure and noiselike intensity fluctuation in pulsar radio emission measured with submicrosecond time resolution provided by the S2 VLBI recording/playback system

AbstractThree bright pulsars (B0950+08, B1133+16, and B1929+10) were observed with the 70-m radio telescope in Tidbinbilla at a frequency of 1650 MHz using the S2 Data Acquisition System which provided continuous recording of pulsar signals in two conjugate bands of B=16 MHz each. Parameters of microstructure have been analyzed using the predetection dispersion removal technique.

Chaos may make black holes bright

Black holes cannot be seen directly since they absorb light and emit none, the very quality which earned them their name. We suggest that black holes may be seen indirectly through a chaotic defocusing of light. A black hole can capture light from a luminous companion in chaotic orbits before scattering the light in random directions. To a distant observer, the black hole would appear to light up. If the companion were a bright radio pulsar, this estimate suggests the black hole echo could be detectable.

Deep radio observations of the rich globular clusters Terzan 5 and Liller 1

We have obtained deep 6, 20 and 90 cm observation of two of the richest globular clusters in the galaxy, Terzan 5 and Liller 1. In addition to the well known eclipsing pulsar, PSR1744-24A, our 20 cm image of Terzan 5 displays numerous point sources within 30″, or 4 core radii of the cluster center. The density of these objects rises rapidly toward the core, where an elongated region of emission is found. This feature may be due to the presence of a higher density of point sources than can be resolved by the 1″ resolution of our data. Observations at 6 and 90 cm show that the brightest individual sources, as well as the extended emission, possess the steep spectra expected of pulsars. Furthermore, we find that the strength of the sources in the 20 cm image agrees well with the standard pulsar luminosity function. The total luminosity and number of objects observed in Terzan 5 suggest that this cluster may contain 100 pulsars — probably more than any other Galactic cluster. Although we do not resolve individual sources in Liller 1, comparison of our images with other observations suggests that we are again observing the sum of emission from a number of objects. The 90 cm flux densities of Terzan 5 and Liller 1 are 35 and 9 mJy, respectively, implying that a number of bright pulsars in these clusters have been hidden from pulsed searches, perhaps by a combination of dispersion smearing, scattering and doppler broadening.

Frequency dependence of the main pulse to interpulse separation for seven pulsars

In the course of a study of pulsar interpulses 43 bright pulsars were searched for interpulse emission. A previously undetected interpulse in PSR 1944 + 17 was found and improved upper limits were set on the others. The separation Delta-phi (MP-IP) between the main pulse (MP) and interpulse (IP) and the IP to MP amplitude ratio S(IP)/S(MP) for seven of the pulsars known to have interpulses was measured. Delta-phi (MP-IP) is found to be frequency independent except for PSR 1944 + 17 where Delta-phi (MP-IP) varies from 183 deg at 318 MHz to 167 deg at 2380 MHz. The ratio S(IP)/S(MP) decreases with frequency for all seven objects, although for the Crab and millisecond pulsar the IP is distinctly different from the others in that the ratio is much larger and less strongly frequency dependent. The polarization signature of these two pulsars and possibly PSR 1929 + 10 is consistent with a two-pole perpendicular rotator model, whereas the others are more readily explained by single-pole models. 43 references.