scholarly journals The Galactic Population and Birth Rate of Radio Pulsars

2004 ◽  
Vol 218 ◽  
pp. 105-112 ◽  
Author(s):  
D. R. Lorimer
Keyword(s):  
Preliminary Analysis ◽  
Birth Rate ◽  
Current Understanding ◽  
Selection Effects ◽  
Radio Pulsars ◽  
Galactic Population ◽  
Review Current

We review current understanding of the underlying, as opposed to the observed, pulsar population. The observed sample is heavily biased by selection effects, so that surveys see less than 10% of all potentially observable pulsars. We compare various techniques used to correct the sample for these biases. By far the most significant recent development has been the discovery of over 700 pulsars in the Parkes Multibeam (PM) survey. This new sample is far less affected by selection effects and we use it to make a preliminary analysis of the Galactic pulsar distribution, finding further evidence for a deficit of pulsars in the inner Galaxy.

scholarly journals The Galactic population and properties of young, highly energetic pulsars

2020 ◽  
Vol 497 (2) ◽  
pp. 1957-1965
Author(s):  
Simon Johnston ◽  
D A Smith ◽  
A Karastergiou ◽  
M Kramer
Keyword(s):  
Radio Emission ◽  
Birth Rate ◽  
Selection Effect ◽  
Gap Model ◽  
Radio Pulsars ◽  
Galactic Population ◽  
Small Set ◽  
Γ Rays ◽  
Γ Ray ◽  
Partial Overlap

ABSTRACT The population of young, non-recycled pulsars with spin-down energies $\dot{E} \gt 10^{35}$ erg s−1 is sampled predominantly at γ-ray and radio wavelengths. A total of 137 such pulsars are known, with partial overlap between the sources detectable in radio and γ-rays. We use a very small set of assumptions in an attempt to test whether the observed pulsar sample can be explained by a single underlying population of neutron stars. For radio emission we assume a canonical conal beam with a fixed emission height of 300 km across all spin periods and a luminosity law which depends on $\dot{E}^{0.25}$. For γ-ray emission we assume the outer-gap model and a luminosity law which depends on $\dot{E}^{0.5}$. We synthesize a population of fast-spinning pulsars with a birth rate of one per 100 yr. We find that this simple model can reproduce most characteristics of the observed population with two caveats. The first is a deficit of γ-ray pulsars at the highest $\dot{E}$ which we surmise to be an observational selection effect due to the difficulties of finding γ-ray pulsars in the presence of glitches without prior knowledge from radio frequencies. The second is a deficit of radio pulsars with interpulse emission, which may be related to radio emission physics. We discuss the implications of these findings.

On the nature of the galactic 2CG y-ray sources

1981 ◽  
Vol 301 (1462) ◽  
pp. 495-504 ◽  
Keyword(s):  
Spatial Distribution ◽  
Power Law ◽  
Supernova Remnants ◽  
Birth Rate ◽  
Scale Height ◽  
Significant Fraction ◽  
The Sun ◽  
Radio Pulsars ◽  
The Earth

The identification of two y-ray sources of the COS-B catalogue with radio pulsars is used as an important hint for the identification of the rest of the population. The relevant distributions of y-ray pulsars visible at the Sun within the limiting sensitivity of COS-B are derived on the following assumptions: (i) the y-ray luminosity is a decreasing power law of the pulsar age, as indicated by current models; (ii) the scale height of pulsars at creation is equal to that of the supernova remnants; (iii) the pulsars’ birth rate and spatial distribution are those published by Taylor & Manchester (1977). As a preliminary result it is shown that 10 to 20 y-ray pulsars may be visible from the Earth with distributional parameters not distinguishable from those of the 2CG y-ray sources. We suggest therefore that a significant fraction of the unidentified galactic y-ray sources are pulsars.

scholarly journals Metallicity Structures of the Milky Way

1996 ◽  
Vol 169 ◽  
pp. 427-428
Author(s):  
Roland Buser ◽  
Jianxiang Rong
Keyword(s):  
High Latitude ◽  
Preliminary Analysis ◽  
Milky Way ◽  
Structural Models ◽  
Thin Disk ◽  
Thick Disk ◽  
Abundance Gradient ◽  
Galactic Population

The metallicity-sensitive (U – G) colors from the new homogeneous catalog of photographic RGU data in seven high-latitude fields have been used to determine the larger-scale metallicity distributions of the Galactic population components. For the thick disk, preliminary analysis based on our best structural models provides a mean metallicity 〈[M/H]〉 = −0.6 ± 0.3dex and a marginal vertical metallicity gradient ≈ −0.1dex/kpc. The observed color distributions are further consistent with the (old) thin disk having mean abundance 〈[M/H]〉 = −0.3 ± 0.2dex and abundance gradient ∂[M/H]/∂z = −0.6dex/kpc.

scholarly journals Gasotransmitter Regulation of Ion Channels: A Key Step in O2 Sensing By the Carotid Body

Physiology ◽  
2014 ◽  
Vol 29 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Nanduri R. Prabhakar ◽  
Chris Peers
Keyword(s):  
Ion Channels ◽  
Carotid Body ◽  
Physiological Responses ◽  
Current Understanding ◽  
Body Function ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Review Current ◽  
O2 Sensing

Carotid bodies detect hypoxia in arterial blood, translating this stimulus into physiological responses via the CNS. It is long established that ion channels are critical to this process. More recent evidence indicates that gasotransmitters exert powerful influences on O2 sensing by the carotid body. Here, we review current understanding of hypoxia-dependent production of gasotransmitters, how they regulate ion channels in the carotid body, and how this impacts carotid body function.

scholarly journals The Pulsar Birth Rate from the Parkes Multibeam Survey

2004 ◽  
Vol 218 ◽  
pp. 121-122
Author(s):  
N. Vranesevic
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Birth Rate ◽  
Selection Effects ◽  
Total Birth ◽  
Current Accounting ◽  
Dipole Magnetic Field ◽  
Total Birth Rate ◽  
Surface Dipole

We report on calculations of the pulsar birth rate based on the results of the Parkes multibeam survey. Prom the observed sample of more than 800 pulsars, we compute the pulsar current, accounting as accurately as possible for all known selection effects. The main goal of this work is to understand the pulsar birth rate as a function of the surface dipole magnetic field strength. We show that pulsars with magnetic fields greater than 1012.5 G account for about half of the total birth rate.

Magnetoconvection and the Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 307-313
Author(s):  
Å. Nordlund ◽  
S. B. F. Dorch ◽  
R. F. Stein
Keyword(s):  
Magnetic Fields ◽  
Numerical Simulations ◽  
Convection Zone ◽  
Current Understanding ◽  
Solar Dynamo ◽  
Stable Layer ◽  
Strong Magnetic Fields ◽  
Stellar Convection ◽  
Convective Motions ◽  
Review Current

AbstractWe review current understanding of the interaction of magnetic fields with convective motions in stellar convection zones. Among the most exciting recent results is the discovery that magnetic fields need not primarily be confined to the stable layer below the convection zone; numerical simulations have shown that surprisingly, strong magnetic fields can be maintained in the interior of the convection zone.

scholarly journals The APM QSO Survey: Description and Status Report

1989 ◽  
Vol 134 ◽  
pp. 25-30
Author(s):  
Craig B. Foltz ◽  
Frederic H. Chaffee ◽  
Paul C. Hewett ◽  
Brenda Frye ◽  
Ray J. Weymann ◽  
...  
Keyword(s):  
Preliminary Analysis ◽  
Selection Criteria ◽  
Status Report ◽  
Selection Effects ◽  
Schmidt Telescope ◽  
Large Sample ◽  
Quantitative Survey ◽  
Objective Prism

The APM QSO survey is a quantitative survey aimed at finding a large sample (∼ 1000) of QSOs using broadly-based selection criteria applied to machine-scanned UK Schmidt Telescope direct and objective-prism plates. The survey is currently entering its third year and, as of August 1988, the sample consists of ∼ 700 QSOs with mJ ≥ 18.75 in the range 0.2 ≤ z ≤ 3.3. Preliminary analysis suggests that the sample is relatively free of the selection effects endemic to most QSO surveys based on slitless spectroscopy.

scholarly journals Neutron Star Populations at the Millenium

2000 ◽  
Vol 177 ◽  
pp. 573-578
Author(s):  
James Cordes
Keyword(s):  
Neutron Star ◽  
Birth Rate ◽  
Core Collapse ◽  
Radio Pulsars ◽  
X Ray ◽  
Yield Information ◽  
Relationship Of ◽  
The Relationship ◽  
Careful Comparison ◽  
Shed Light

AbstractIdentified neutron star (NS) classes evidently are determined by several intertwined features: kinematics of NS at their formation (spin and translational); magnetic field strength; and binary membership. I discuss the well-known classes of isolated and accreting NS while keeping in mind recent discoveries of magnetars, anomalous X-ray pulsars, and long-period radio pulsars. I summarize the results of several likelihood analyses on radio pulsars, which yield information on the velocity distribution, luminosity function, and birth rate of high-field radio pulsars. I review the evidence for the occurrence of momentum kicks at the time of NS birth. Discerning the relationship of the classic radio pulsars to the more exotic classes probably requires careful comparison of magnetic fields, kinematics and birthrates, a program for the next millenium. Exciting discoveries of classic pulsars will also be made: sub-millisecond pulsars, massive binaries in fast orbits and truly hyper-velocity pulsars that shed light on core-collapse processes in supernovae.

scholarly journals Probing fundamental physics with pulsars

2009 ◽  
Vol 5 (H15) ◽  
pp. 131-136
Author(s):  
Duncan R. Lorimer ◽  
Maura A. McLaughlin
Keyword(s):  
Large Scale ◽  
Radio Pulsars ◽  
Fundamental Physics ◽  
Superdense Matter ◽  
Pulsar Timing ◽  
Binary Evolution ◽  
Radio Transients ◽  
Pulsar Timing Array ◽  
Review Current ◽  
Pulsar Evolution

AbstractPulsars provide a wealth of information about General Relativity, the equation of state of superdense matter, relativistic particle acceleration in high magnetic fields, the Galaxy's interstellar medium and magnetic field, stellar and binary evolution, celestial mechanics, planetary physics and even cosmology. The wide variety of physical applications currently being investigated through studies of radio pulsars rely on: (i) finding interesting objects to study via large-scale and targeted surveys; (ii) high-precision timing measurements which exploit their remarkable clock-like stability. We review current surveys and the principles of pulsar timing and highlight progress made in the rotating radio transients, intermittent pulsars, tests of relativity, understanding pulsar evolution, measuring neutron star masses and the pulsar timing array

scholarly journals Mass Distribution and Birth Rate of Central Stars of Planetary Nebulae: Comparison with White Dwarfs, and Influence of Selection Effects

1989 ◽  
Vol 131 ◽  
pp. 540-540
Author(s):  
V. Weidemann
Keyword(s):  
Recent Work ◽  
Mass Distribution ◽  
White Dwarfs ◽  
Birth Rate ◽  
Planetary Nebulae ◽  
Magellanic Cloud ◽  
Selection Effects ◽  
The One ◽  
Central Stars

The mass distribution of central stars (CPN) as derived by the Schönberner method (1981) M⊙ vs. age, v(exp) = const, for an enlarged local ensemble, as presented at the London Symposium, 1983, appears to be much narrower and more strongly peaked towards smaller masses than the one recently derived by Heap and Augensen (1987) (HA) using the same method, but IUE data and M⊙ (λ 1300) vs. age, corrected for individual v(exp). Whereas according to Schönberner 65% of all CPN have M < 0.64 M⊙, HA find only 44% below the same limit. We demonstrate that this discrepancy is entirely due to the fact, that HA use Daub and 0.9 × Cahn/Kaler distances, whereas Schönberner used 1.3 × CK. We list a number of arguments which favor the larger distances, especially the recent work by Méndez et al. (preprint, 1987) (Teff/g determinations) and investigations of Magellanic Cloud PN by Aller et al. (1987), Wood et al. (1987) and Barlow (1987) which all indicate a scale ≥. 1.4 × CK. If one uses Barlow's recalibration formula for optically thick PN, the distances for those - which mainly contribute to the massive CPN in the HA analysis - are increased so much as to remove most of them from the local ensemble. We thus obtain for the revised IUE ensemble 84% CPN with M < 0.64 M⊙, in better agreement with results for white dwarfs (70%) (cf. Weidemann, 1987).

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