ترغب بنشر مسار تعليمي؟ اضغط هنا

Discovery of Three Pulsars from a Galactic Center Pulsar Population

45   0   0.0 ( 0 )
 نشر من قبل Julia Deneva
 تاريخ النشر 2009
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We report the discovery of three pulsars whose large dispersion measures and angular proximity to sgr indicate the existence of a Galactic center population of neutron stars. The relatively long periods (0.98 to 1.48 s) most likely reflect strong selection against short-period pulsars from radio-wave scattering at the observation frequency of 2 GHz used in our survey with the Green Bank Telescope. One object (PSR J1746-2850I) has a characteristic spindown age of only 13 kyr along with a high surface magnetic field $sim 4times 10^{13}$ G. It and a second object found in the same telescope pointing, PSR J1746-2850II (which has the highest known dispersion measure among pulsars), may have originated from recent star formation in the Arches or Quintuplet clusters given their angular locations. Along with a third object, PSR J1745-2910, and two similar high-dispersion, long-period pulsars reported by Johnston et al. (2006), the five objects found so far are 10 to 15 arc min from sgr, consistent with there being a large pulsar population in the Galactic center, most of whose members are undetectable in relatively low-frequency surveys because of pulse broadening from the same scattering volume that angularly broadens sgr and OH/IR masers.

قيم البحث

اقرأ أيضاً

86 - B. C. Joshi 2009
We report on the discovery of three new pulsars in the first blind survey of the north Galactic plane (45 degrees < l < 135 degrees; |b| < 1 degrees with the Giant Meterwave Radio telescope (GMRT) at an intermediate frequency of 610 MHz. The survey c overed 106 square degrees with a sensitivity of roughly 1 mJy to long-period pulsars (pulsars with period longer than 1 s). The three new pulsars have periods of 318, 933, and 1056 ms. Their timing parameters and flux densities, obtained in follow up observations with the Lovell Telescope at Jodrell Bank and the GMRT, are presented. We also report on pulse nulling behaviour in one of the newly discovered pulsars, PSR J2208+5500.
Modern pulsar surveys produce many millions of candidate pulsars, far more than can be individually inspected. Traditional methods for filtering these candidates, based upon the signal-to-noise ratio of the detection, cannot easily distinguish betwee n interference signals and pulsars. We have developed a new method of scoring candidates using a series of heuristics which test for pulsar-like properties of the signal. This significantly increases the sensitivity to weak pulsars and pulsars with periods close to interference signals. By applying this and other techniques for ranking candidates from a previous processing of the Parkes Multi-beam Pulsar Survey, 28 previously unknown pulsars have been discovered. These include an eccentric binary system and a young pulsar which is spatially coincident with a known supernova remnant.
We present the discovery and timing solutions of five new pulsars by students involved in the Pulsar Search Collaboratory (PSC), a NSF-funded joint program between the National Radio Astronomy Observatory and West Virginia University designed to exci te and engage high-school students in Science, Technology, Engineering, and Mathematics (STEM) and related fields. We encourage students to pursue STEM fields by apprenticing them within a professional scientific community doing cutting edge research, specifically by teaching them to search for pulsars. The students are analyzing 300 hours of drift-scan survey data taken with the Green Bank Telescope at 350 MHz. These data cover 2876 square degrees of the sky. Over the course of five years, more than 700 students have inspected diagnostic plots through a web-based graphical interface designed for this project. The five pulsars discovered in the data have spin periods ranging from 3.1 ms to 4.8 s. Among the new discoveries are - PSR J1926-1314, a long period, nulling pulsar; PSR J1821+0155, an isolated, partially recycled 33-ms pulsar; and PSR J1400-1438, a millisecond pulsar in a 9.5-day orbit whose companion is likely a white dwarf star.
Pulsars in the Galactic Center (GC) are important probes of General Relativity, star formation, stellar dynamics, stellar evolution, and the interstellar medium. Despite years of searching, only a handful of pulsars in the central 0.5 deg are known. The high-frequency sensitivity of ngVLA will open a new window for discovery and characterization of pulsars in the GC. A pulsar in orbit around the GC black hole, Sgr A*, will provide an unprecedented probe of black hole physics and General Relativity.
We have used millisecond pulsars (MSPs) from the southern High Time Resolution Universe (HTRU) intermediate latitude survey area to simulate the distribution and total population of MSPs in the Galaxy. Our model makes use of the scale factor method, which estimates the ratio of the total number of MSPs in the Galaxy to the known sample. Using our best fit value for the z-height, z=500 pc, we find an underlying population of MSPs of 8.3(pm 4.2)*10^4 sources down to a limiting luminosity of L_min=0.1 mJy kpc^2 and a luminosity distribution with a steep slope of dlog N/dlog L = -1.45(pm 0.14). However, at the low end of the luminosity distribution, the uncertainties introduced by small number statistics are large. By omitting very low luminosity pulsars, we find a Galactic population above L_min=0.2 mJy kpc^2 of only 3.0(pm 0.7)*10^4 MSPs. We have also simulated pulsars with periods shorter than any known MSP, and estimate the maximum number of sub-MSPs in the Galaxy to be 7.8(pm 5.0)*10^4 pulsars at L=0.1 mJy kpc^2. In addition, we estimate that the high and low latitude parts of the southern HTRU survey will detect 68 and 42 MSPs respectively, including 78 new discoveries. Pulsar luminosity, and hence flux density, is an important input parameter in the model. Some of the published flux densities for the pulsars in our sample do not agree with the observed flux densities from our data set, and we have instead calculated average luminosities from archival data from the Parkes Telescope. We found many luminosities to be very different than their catalogue values, leading to very different population estimates. Large variations in flux density highlight the importance of including scintillation effects in MSP population studies.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا