An Intermediate-age Alpha-rich Galactic Population in K2

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.

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Challenges faced by current Galactic planetary nebula surveys

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317003507 ◽

2016 ◽

Vol 12 (S323) ◽

pp. 11-19

Author(s):

David J. Frew

Keyword(s):

Planetary Nebula ◽

Time Interval ◽

Important Goal ◽

Satellite Mission ◽

Galactic Population ◽

Multi Wavelength ◽

Evolutionary Pathways ◽

Optical Surveys ◽

Central Stars ◽

Galactic Planetary Nebula

AbstractDetermining the demographics of the Galactic planetary nebula (PN) population is an important goal to further our understanding of this intriguing phase of stellar evolution. The Galactic population has more than doubled in number over the last 15 years, particularly from narrowband Hα surveys along the plane. In this review I will summarise these results, with emphasis on the time interval since the last IAU Symposium. These primarily optical surveys are not without their limitations and new surveys for PNe in the infrared similarly face a number of challenges. I will discuss the need for multi-wavelength approaches to discovery and analysis. The desire to have accurate volume-limited samples of Galactic PNe at our disposal is emphasised, which will be impacted with new data from the Gaia satellite mission. We need robust surveys of PNe and their central stars, especially volume-limited surveys, in order to clarify and quantify their evolutionary pathways.

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Pulsars as a galactic population

Symposium - International Astronomical Union ◽

10.1017/s0074180900014315 ◽

1979 ◽

Vol 84 ◽

pp. 119-123

Author(s):

Joseph H. Taylor

Keyword(s):

Carbon Monoxide ◽

Statistical Analysis ◽

Supernova Remnants ◽

Galactic Center ◽

Hii Regions ◽

The Sun ◽

Disk Thickness ◽

Galactic Population ◽

The Galaxy

Recent pulsar surveys have increased the number of known pulsars to well over 300, and many of them lie at distances of several kpc or more from the sun. The distribution of pulsars with respect to distance from the galactic center is similar to other population I material such as HII regions, supernova remnants, and carbon monoxide gas, but the disk thickness of the pulsar distribution is rather greater, with <|z|>≈350 pc. Statistical analysis suggests that the total number of active pulsars in the Galaxy is a half million or more, and because kinematic arguments require the active lifetimes of pulsars to be ≲5×106 years, it follows that the birthrate required to maintain the observed population is one pulsar every ∼10 years (or less) in the Galaxy.

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uvby β Photometric Data and Fourier Coefficients for Galactic Population I and Population II Cepheids

The Astrophysical Journal Supplement Series ◽

10.1086/313108 ◽

1998 ◽

Vol 117 (1) ◽

pp. 167-208 ◽

Cited By ~ 17

Author(s):

A. Arellano Ferro ◽

E. Rojo Arellano ◽

S. Gonzalez‐Bedolla ◽

Patricia Rosenzweig

Keyword(s):

Fourier Coefficients ◽

Photometric Data ◽

Galactic Population

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Statistical characteristics of radio sources connected with high latitude galactic population of objects

Astronomical and Astrophysical Transactions ◽

10.1080/10556799908203034 ◽

1999 ◽

Vol 18 (1) ◽

pp. 53-59

Author(s):

M. G. Larionov ◽

V. N. Sidorenkov ◽

L. N. Larionova ◽

L. S. Ugol'kova

Keyword(s):

High Latitude ◽

Statistical Characteristics ◽

Radio Sources ◽

Galactic Population

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A Model for the Galactic Population of Supersoft X-Ray Sources

International Astronomical Union Colloquium ◽

10.1017/s0252921100039282 ◽

1996 ◽

Vol 158 ◽

pp. 417-420

Author(s):

L. Yungelson ◽

A. Tutukov ◽

A. Fedorova ◽

M. Livio ◽

J. W. Truran

Keyword(s):

White Dwarfs ◽

Main Sequence ◽

X Ray ◽

Galactic Population ◽

Transient Sources ◽

Orbital Periods ◽

Symbiotic Binaries ◽

Detached Binaries

AbstractThree major sub-populations of Galactic supersoft X-ray sources may exist: semi-detached binaries with main sequence or subgiant donors, and symbiotic binaries (~550, ~460, and ~600 objects, respectively). Each group contains both permanent and transient sources. The intrinsic and interstellar absorptions reduce the number of observable sources to ~25. We derive the distributions of the sources over orbital periods, masses of the components, and ‘on’-times. The rate at which white dwarfs in Galactic binaries reach MCh is ~ 3 10−5 yr−1. The rate of He-shell detonations which may lead to supernovae may be up to 3 10−4 yr−1.

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Metallicity Structures of the Milky Way

Symposium - International Astronomical Union ◽

10.1017/s0074180900230040 ◽

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.

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Concluding Remarks (I)

Symposium - International Astronomical Union ◽

10.1017/s0074180900227575 ◽

1991 ◽

Vol 145 ◽

pp. 447-450

Author(s):

B. Baschek

Keyword(s):

Stellar Evolution ◽

Magellanic Cloud ◽

Alphabetical Order ◽

Oxygen Abundance ◽

B Stars ◽

Galactic Population ◽

Stellar Models

After a week of highly interesting discussions on ‘stellar evolution and the photospheric abundance connection’ we now come to resume the contributions to this Symposium. This task has been divided up among three of us, arranged according to the course of stellar evolution, and in alphabetical order of the speakers (Baschek, Lambert, van Horn). I begin with the essentially unevolved stars, recalling some results and problems, not systematically but rather selected from my own interests.First I should like to briefly reconsider the accuracy of abundance determinations in view of the contributions following my review. Then some comments on stellar models are given, followed by a few remarks about peculiar A stars. Finally, the similarity of the oxygen abundance in Magellanic Cloud B stars and galactic population II stars is pointed out.

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Local Stellar Kinematics from RAVE Data: IV. Solar Neighbourhood Age–Metallicity Relation

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2013.21 ◽

2013 ◽

Vol 30 ◽

Cited By ~ 8

Author(s):

Ş. Duran ◽

S. Ak ◽

S. Bilir ◽

S. Karaali ◽

T. Ak ◽

...

Keyword(s):

Radial Velocity ◽

Spectral Type ◽

Stellar Kinematics ◽

Bayesian Procedure ◽

Experiment Data ◽

Data Release ◽

Galactic Population ◽

Effective Temperatures ◽

Metallicity Distribution ◽

Total Velocity

AbstractWe investigated the age–metallicity relation using a sample of 5691 F- and G-type dwarfs from RAdial Velocity Experiment Data Release 3 (RAVE DR3) by applying several constraints. (i) We selected stars with surface gravities log g(cm s−2) ≥ 3.8 and effective temperatures in the $5310\le T_{\text{eff}}\text{(K)}\le 7300$ range and obtained a dwarf sample. (ii) We plotted the dwarfs in metallicity sub-samples in the $T_{\text{eff}}\text{--}(J-K_s)_0$ plane to compare with the corresponding data of González Hernández & Bonifacio (2009) and identified the ones in agreement. (iii) We fitted the reduced dwarf sample obtained from constraints (i) and (ii) to the Padova isochrones and re-identified those which occupy the plane defined by isochrones with ages t ≤ 13 Gyr. (iv) Finally, we omitted dwarfs with total velocity errors larger than 10.63 km s−1. We estimated the ages using the Bayesian procedure of Jørgensen & Lindegren (2005). The largest age–metallicity slope was found for early F-type dwarfs. We found steeper slopes when we plotted the data as a function of spectral type rather than Galactic population. We noticed a substantial scatter in metallicity distribution at all ages. The metal-rich old dwarfs turned out to be G-type stars which can be interpreted as they migrated from the inner disc or bulge.

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