scholarly journals The Structure and Evolution of Thorne-Żytkow Objects

1996 ◽  
Vol 165 ◽  
pp. 29-41
Author(s):  
Philipp Podsiadlowski
Keyword(s):  
Neutron Star ◽  
High Mass ◽  
Mass Star ◽  
X Ray ◽  
The Core ◽  
Rp Process ◽  
The Galaxy ◽  
Red Supergiants ◽  
Nuclear Burning ◽  
Low Mass

Thorne-Żytkow objects (TŻOs) are red supergiants with neutron cores. The energy source in TŻOs with low-mass envelopes (≲8 M⊙) is accretion onto the neutron core, while for TŻOs with massive envelopes (≲14 M⊙) it is nuclear burning via the exotic rp process. TŻOs are expected to form as a result of unstable mass transfer in high-mass X-ray binaries, the direct collision of a neutron star with a massive companion after a supernova or the collision of a neutron star with a low-mass star in a globular cluster. We estimate a birth rate of massive TŻOs in the Galaxy of ∼2 10−4 yr−1. Thus, for a characteristic TŻO lifetime of 105–106 yr there should be 20–200 TŻOs in the Galaxy at present. These can be distinguished from ordinary red supergiants because of anomalously high surface abundances of lithium and rp-process elements, produced in the TŻO interior. The TŻO phase ends when either the star has exhausted its rp-process seed elements or the envelope mass decreases below a critical mass (∼14 M⊙). Then nuclear burning becomes inefficient and a neutrino runaway ensues, leading to the dynamical accretion of matter near the core onto the neutron star and its spin up to spin frequencies of up to ∼100 Hz. The fate of the massive envelope is not entirely clear. If a significant fraction can be accreted onto the core, the formation of a black hole becomes likely. Part of the envelope may collapse into a massive disk which may ultimately become gravitationally unstable and lead to the formation of planets or even low-mass stars. We discuss the various possible outcomes and suggest a possible link between massive TŻOs and soft X-ray transients.

scholarly journals The Galactic Pulsar Population and Neutron Star Birth

1987 ◽  
Vol 125 ◽  
pp. 67-78
Author(s):  
Ramesh Narayan
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Binary Systems ◽  
Magnetic Coupling ◽  
Scale Height ◽  
High Magnetic Fields ◽  
Radio Pulsars ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

scholarly journals The O stars: optical review

1979 ◽  
Vol 83 ◽  
pp. 1-22
Author(s):  
J. B. Hutchings
Keyword(s):  
Neutron Star ◽  
Interstellar Medium ◽  
Mass Loss ◽  
Large Fraction ◽  
Significant Fraction ◽  
High Mass ◽  
X Ray ◽  
The Galaxy ◽  
High Mass Loss ◽  
Rough Outline

I would like to start with a quick overview of the O stars - their significance and role in the galaxy and in astrophysics - just to remind ourselves of why we are here and what we hope to talk about. In Table 1 I show a rough outline of the contribution of O stars to what happens in the galaxy as a whole. Because of their extreme luminosity, they contribute a large fraction of the radiation of the galaxy, while forming a very tiny group of objects and mass. Because of their short lifetime they are a population that has gone through 104 generations in the life of the galaxy. Their high mass loss rates may account for a large fraction of the new matter injected into the interstellar medium, and they probably power some significant fraction of the hard X-ray sources in the galaxy, by virtue of the fact that a companion can become a neutron star a) without disrupting the binary and b) while the companion is still a mass losing O star.

scholarly journals A Survey of X-ray Point Sources in the Magellanic Clouds

1999 ◽  
Vol 192 ◽  
pp. 100-103
Author(s):  
A. P. Cowley ◽  
P. C. Schmidtke ◽  
V. A. Taylor ◽  
T.K. McGrath ◽  
J. B. Hutchings ◽  
...  
Keyword(s):  
Stellar Population ◽  
Population Based ◽  
Magellanic Clouds ◽  
Point Sources ◽  
High Mass ◽  
Be Stars ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass ◽  
X Ray Binaries

In this study we compare the global populations of stellar X-ray sources in the LMC, SMC, and the Galaxy. After removing foreground stars and background AGN from the samples, the relative numbers of the various types of X-ray point sources within the LMC and SMC are similar, but differ markedly from those in the Galaxy. The Magellanic Clouds are rich in high-mass X-ray binaries (HMXB), especially those containing rapidly rotating Be stars. However, the LMC and SMC both lack the large number of low-mass X-ray binaries (LMXB) found in the Milky Way, which are known to represent a very old stellar population based on their kinematics, chemical composition, and spatial distribution.

scholarly journals The first galactic stars and chemical enrichment in the halo

2009 ◽  
Vol 5 (S265) ◽  
pp. 81-89
Author(s):  
Piercarlo Bonifacio
Keyword(s):  
Chemical Composition ◽  
High Mass ◽  
Mass Star ◽  
Low Mass Stars ◽  
Chemical Enrichment ◽  
The Galaxy ◽  
Low Metallicity ◽  
Low Mass ◽  
Indirect Information ◽  
The Universe

AbstractThe cosmic microwave background and the cosmic expansion can be interpreted as evidence that the Universe underwent an extremely hot and dense phase about 14 Gyr ago. The nucleosynthesis computations tell us that the Universe emerged from this state with a very simple chemical composition: H, 2H, 3He, 4He, and traces of 7Li. All other nuclei where synthesised at later times. Our stellar evolution models tell us that, if a low-mass star with this composition had been created (a “zero-metal” star) at that time, it would still be shining on the Main Sequence today. Over the last 40 years there have been many efforts to detect such primordial stars but none has so-far been found. The lowest metallicity stars known have a metal content, Z, which is of the order of 10−4Z⊙. These are also the lowest metallicity objects known in the Universe. This seems to support the theories of star formation which predict that only high mass stars could form with a primordial composition and require a minimum metallicity to allow the formation of low-mass stars. Yet, since absence of evidence is not evidence of absence, we cannot exclude the existence of such low-mass zero-metal stars, at present. If we have not found the first Galactic stars, as a by product of our searches we have found their direct descendants, stars of extremely low metallicity (Z ≤ 10−3Z⊙). The chemical composition of such stars contains indirect information on the nature of the stars responsible for the nucleosynthesis of the metals. Such a fossil record allows us a glimpse of the Galaxy at a look-back time equivalent to redshift z = 10, or larger. The last ten years have been full of exciting discoveries in this field, which I will try to review in this contribution.

scholarly journals The XXL Survey

2020 ◽  
Vol 642 ◽  
pp. A126 ◽  
Author(s):  
M. Ricci ◽  
R. Adam ◽  
D. Eckert ◽  
P. Ade ◽  
P. André ◽  
...  
Keyword(s):  
High Redshift ◽  
High Mass ◽  
Optical Data ◽  
Local Pressure ◽  
Mass System ◽  
Cluster Galaxy ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass ◽  
The Impact

High-mass clusters at low redshifts have been intensively studied at various wavelengths. However, while more distant objects at lower masses constitute the bulk population of future surveys, their physical state remain poorly explored to date. In this paper, we present resolved observations of the Sunyaev-Zel’dovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC 102, a relatively low-mass system (M500 ∼ 2 × 1014 M⊙) at z = 0.97 detected from the XXL survey. We combine NIKA2 SZ data, XMM-Newton X-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC 102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC 102, obtaining relatively tight constraints up to about ∼r500, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC 102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters at z ∼ 1, especially with low signal-to-noise ratio data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data. This is promising for the study of high redshift clusters from the combination of eROSITA and high resolution SZ instruments and will complement the new generation of optical surveys from facilities such as LSST and Euclid.

scholarly journals The Formation and Evolution of Black-Hole Binaries

1996 ◽  
Vol 165 ◽  
pp. 93-103
Author(s):  
Roger W. Romani
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
High Mass ◽  
X Ray ◽  
Black Hole Binaries ◽  
Low Mass ◽  
Formation And Evolution ◽  
X Ray Binaries ◽  
Black Hole Candidates

The presence of accreting black holes (BH) among the X-ray binaries has been recognized for many years. Traditionally, Cyg X-1 and the handful of other candidates have been thought of as cousins of the HMXB neutron star systems. Recent studies of the soft X-ray transients such as A 0620-00 have, however, shown that the dynamical evidence makes these low-mass systems very strong black-hole candidates. Further, analysis of the eventual end-states of various high-mass X-ray binaries suggest that some could end as observable BH-pulsar binaries, although the first such system is yet to be discovered.

scholarly journals A strange star scenario for the formation of isolated millisecond pulsars

2020 ◽  
Vol 633 ◽  
pp. A45 ◽  
Author(s):  
Long Jiang ◽  
Na Wang ◽  
Wen-Cong Chen ◽  
Xiang-Dong Li ◽  
Wei-Min Liu ◽  
...  
Keyword(s):  
Neutron Star ◽  
Galactic Plane ◽  
Critical Mass ◽  
Strange Star ◽  
Millisecond Pulsars ◽  
X Ray ◽  
Mass Distributions ◽  
The Galaxy ◽  
Low Mass ◽  
X Ray Binaries

According to the recycling model, neutron stars in low-mass X-ray binaries were spun up to millisecond pulsars (MSPs), which indicates that all MSPs in the Galactic plane ought to be harbored in binaries. However, about 20% Galactic field MSPs are found to be solitary. To interpret this problem, we assume that the accreting neutron star in binaries may collapse and become a strange star when it reaches some critical mass limit. Mass loss and a weak kick induced by asymmetric collapse during the phase transition (PT) from neutron star to strange star can result in isolated MSPs. In this work, we use a population-synthesis code to examine the PT model. The simulated results show that a kick velocity of ∼60 km s−1 can produce ∼6 × 103 isolated MSPs and birth rate of ∼6.6 × 10−7 yr−1 in the Galaxy, which is approximately in agreement with predictions from observations. For the purpose of comparisons with future observation, we also give the mass distributions of radio and X-ray binary MSPs, along with the delay time distribution.

scholarly journals GAMA/XXL: X-ray point sources in low-luminosity galaxies in the GAMA G02/XXL-N field

2021 ◽  
Vol 502 (2) ◽  
pp. 3101-3112
Author(s):  
E Nwaokoro ◽  
S Phillipps ◽  
A J Young ◽  
I Baldry ◽  
A Bongiorno ◽  
...  
Keyword(s):  
Positional Information ◽  
Point Sources ◽  
High Mass ◽  
X Ray ◽  
Star Forming ◽  
Flux Limit ◽  
The Galaxy ◽  
Low Mass ◽  
Mass Assembly ◽  
X Ray Binaries

ABSTRACT Relatively few X-ray sources are known that have low-mass galaxies as hosts. This is an important restriction on studies of active galactic nuclei (AGNs), hence black holes, and of X-ray binaries (XRBs) in low-mass galaxies; addressing it requires very large samples of both galaxies and X-ray sources. Here, we have matched the X-ray point sources found in the XXL-N field of the XXL survey (with an X-ray flux limit of ∼6 × 10−15 erg s−1 cm−2 in the [0.5–2] keV band) to galaxies with redshifts from the Galaxy And Mass Assembly (GAMA) G02 survey field (down to a magnitude limit r = 19.8) in order to search for AGNs and XRBs in GAMA galaxies, particularly those of low optical luminosity or stellar mass (fainter than Mr = −19 or $M_* \lesssim 10^{9.5}\, \mathrm{M}_{\odot }$). Out of a total of 1200 low-mass galaxies in the overlap region, we find a total of 28 potential X-ray source hosts, though this includes possible background contaminants. From a combination of photometry (optical and infrared colours), positional information, and optical spectra, we deduce that most of the ≃20 X-ray sources genuinely in low-mass galaxies are high-mass X-ray binaries in star-forming galaxies. None of the matched sources in a low-mass galaxy has a BPT classification as an AGN, and even ignoring this requirement, none passes both criteria of close match between the X-ray source position and optical galaxy centre (separation ≤3 arcsec) and high [O iii] line luminosity (above 1040.3 erg s−1).

scholarly journals Supernovae — Birthplace of Pulsars?

1981 ◽  
Vol 95 ◽  
pp. 403-416
Author(s):  
Roger A. Chevalier
Keyword(s):  
Neutron Star ◽  
Supernova Remnants ◽  
Massive Star ◽  
Type I ◽  
Type Ii ◽  
X Ray ◽  
The Core ◽  
The Galaxy ◽  
Recent Developments ◽  
Available Information

Recent developments in the theory of the light from supernovae indicate that while Type II supernovae probably involve the explosion of a massive star with an extended envelope, Type I supernovae may involve the total thermonuclear disruption of a white dwarf. The energy release in a Type II supernova is presumably related to the contraction of the core to a neutron star and pulsar formation is likely. The hypothesis that Type II supernovae leave pulsars while Type I supernovae do not leave compact remnants is shown to be consistent with the available information on X-ray sources containing neutron stars, young supernova remnants, and the distribution of pulsars in the galaxy. Some pulsars are probably formed in the explosion of a massive star that has lost its envelope. These events may not be accompanied by a bright supernova display.

scholarly journals SS433 and the nature of ultra-luminous X-ray sources

2006 ◽  
Vol 2 (S238) ◽  
pp. 219-224
Author(s):  
P. A. Charles ◽  
A. D. Barnes ◽  
J. Casares ◽  
J. S. Clark ◽  
R. Cornelisse ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
High Resolution ◽  
Binary System ◽  
Compact Object ◽  
High Mass ◽  
X Ray ◽  
New Class ◽  
The Galaxy ◽  
X Ray Binaries

AbstractThe prototypical micro-quasar, SS433, one of the most bizarre objects in the Galaxy, is a weak X-ray source, yet the kinetic energy of its relativistic, precessing jets is vastly greater. In spite of its importance as the nearest example of directly observable relativistic phenomena, we know remarkably little about the nature of this binary system. There are ongoing arguments not only about the mass of the compact object, but even as to whether it is a black hole or a neutron star, an argument that recent high resolution optical spectroscopy has contributed to.Combined with the INTEGRAL discovery of a new class of highly obscured galactic high-mass X-ray binaries, one of which has been found to precess on a similar timescale to SS433, we suggest that these would indeed be seen by external observers as ULXs, once additional effects such as beaming (either relativistic or geometrical) are included.

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