Burocracia e herança patrimonialista: a Secretaria de Educação do Estado de São Paulo entre 1995 e 2010

Mandel, Lúcia Mara

doi:10.11606/t.48.2015.tde-17122015-113038

Cited by 4 publications

(14 citation statements)

References 3 publications

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“…Owing to the strong dependence of mass-loss rates with mass, even systems that avoid contact altogether evolve towards q = 1 at high masses. Mandel & de Mink (2016) modelled this channel without contact systems and found that many binaries form double BHs from progenitors below the PISN gap, with final mass ratios in the range of 0.6 to 1, reflecting just a small shift from the initial mass ratio distribution as a result of mass loss. However, Mandel & de Mink (2016) did not perform detailed stellar evolution calculations.…”

Section: Mass Distribution and Mass Ratiosmentioning

confidence: 99%

“…This is most likely due to the increase of their luminosity-to-mass ratio and the related approach to the Eddington limit (Sanyal et al 2015). As a result, the vast majority of the binaries considered by Mandel & de Mink (2016) enter contact when computed in detail. Therefore, our final mass ratio distribution is much more strongly biased towards q = 1.…”

Section: Mass Distribution and Mass Ratiosmentioning

confidence: 99%

“…de Mink et al (2009) therefore suggested that massive close binaries, where rapid rotation and thus chemically homogeneous evolution can be enforced through the tidal interaction of both stars, could evolve towards black holes without ever encountering contact or mass transfer (see also Mandel & de Mink 2016;Song et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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A new route towards merging massive black holes

Marchant

Langer

Podsiadlowski

et al. 2016

A&A

571

748

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With recent advances in gravitational-wave astronomy, the direct detection of gravitational waves from the merger of two stellarmass compact objects has become a realistic prospect. Evolutionary scenarios towards mergers of various double compact objects generally invoke so-called common-envelope evolution, which is poorly understood and leads to large uncertainties in the predicted merger rates. Here we explore, as an alternative, the scenario of massive overcontact binary (MOB) evolution, which involves two very massive stars in a very tight binary that remain fully mixed as a result of their tidally induced high spin. While many of these systems merge early on, we find many MOBs that swap mass several times, but survive as a close binary until the stars collapse. The simplicity of the MOB scenario allows us to use the efficient public stellar-evolution code MESA to explore it systematically by means of detailed numerical calculations. We find that, at low metallicity, MOBs produce double-black-hole (BH+BH) systems that will merge within a Hubble time with mass-ratios close to one, in two mass ranges, about 25 . . . 60 M and > ∼ 130 M , with pairinstability supernovae (PISNe) being produced at intermediate masses. Our models are also able to reproduce counterparts of various stages in the MOB scenario in the local Universe, providing direct support for the scenario. We map the initial binary parameter space that produces BH+BH mergers, determine the expected chirp mass distribution, merger times, and expected Kerr parameters, and predict event rates. We find typically one BH+BH merger event for ∼1000 core-collapse supernovae for Z < ∼ Z /10 . The advanced LIGO (aLIGO) detection rate is more uncertain and depends on the cosmic metallicity evolution. From deriving upper and lower limits from a local and a global approximation for the metallicity distribution of massive stars, we estimate aLIGO detection rates (at the aLIGO design limit) of ∼19−550 yr −1 for BH-BH mergers below the PISN gap and of ∼2.1−370 yr −1 above the PISN gap. Even with conservative assumptions, we find that aLIGO will probably soon detect BH+BH mergers from the MOB scenario. These could be the dominant source for aLIGO detections.

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Section: Mass Distribution and Mass Ratiosmentioning

confidence: 99%

Section: Mass Distribution and Mass Ratiosmentioning

confidence: 99%

See 1 more Smart Citation

A new route towards merging massive black holes

Marchant

Langer

Podsiadlowski

et al. 2016

A&A

571

748

View full text Add to dashboard Cite

show abstract

“…Although the common envelope phase is considered essential in the standard picture of evolution from isolated massive binary to black hole binary merger, it has been pointed out that other processes could operate if the stars rotate rapidly, or if they have a strong tidal interaction with a close companion [121,122]. The point is that the core-envelope structure develops because once a fused nucleus (say, helium on the main sequence, or carbon or heavier nuclei later on) is produced, it stays in the core and is not replaced by fresh fuel.…”

Section: Isolated Binariesmentioning

confidence: 99%

“…This would lead to a constant resupply of fuel. [121,122] suggest that this could mean that there would never be a giant phase, which could in turn mean that the stars never come into contact with each other. This might also lead to the formation of extra-massive black holes, because the cores that collapse would be large.…”

Section: Isolated Binariesmentioning

confidence: 99%

Implications of the gravitational wave event GW150914

Miller

2016

Gen Relativ Gravit

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The era of gravitational-wave astronomy began on 14 September 2015, when the LIGO Scientific Collaboration detected the merger of two ∼ 30 M ⊙ black holes at a distance of ∼ 400 Mpc. This event has facilitated qualitatively new tests of gravitational theories, and has also produced exciting information about the astrophysical origin of black hole binaries. In this review we discuss the implications of this event for gravitational physics and astrophysics, as well as the expectations for future detections. In brief: (1) because the spins of the black holes could not be measured accurately and because mergers are not well calculated for modified theories of gravity, the current analysis of GW150914 does not place strong constraints on gravity variants that change only the generation of gravitational waves, but (2) it does strongly constrain alterations of the propagation of gravitational waves and alternatives to black holes. Finally, (3) many astrophysical models for the origin of heavy black hole binaries such as the GW150914 system are in play, but a reasonably robust conclusion that was reached even prior to the detection is that the environment of such systems needs to have a relatively low abundance of elements heavier than helium.

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Gravitational wave background from Population III binary black holes consistent with cosmic reionization

Inayoshi

Kashiyama

Visbal

et al. 2016

Mon. Not. R. Astron. Soc.

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The recent discovery of the gravitational wave source GW150914 has revealed a coalescing binary black hole (BBH) with masses of ∼ 30 M ⊙ . Previous proposals for the origin of such a massive binary include Population III (PopIII) stars. PopIII stars are efficient producers of BBHs and of a gravitational wave background (GWB) in the 10 − 100 Hz band, and also of ionizing radiation in the early Universe. We quantify the relation between the amplitude of the GWB (Ω gw ) and the electron scattering optical depth (τ e ), produced by PopIII stars, assuming that f esc ≈ 10% of their ionizing radiation escapes into the intergalactic medium. We find that PopIII stars would produce a GWB that is detectable by the future O5 LIGO/Virgo if τ e 0.07, consistent with the recent Planck measurement of τ e = 0.055 ± 0.09. Moreover, the spectral index of the background from PopIII BBHs becomes as small as d ln Ω gw /d ln f 0.3 at f 30 Hz, which is significantly flatter than the value ∼ 2/3 generically produced by lower-redshift and less-massive BBHs. A detection of the unique flattening at such low frequencies by the O5 LIGO/Virgo will indicate the existence of a high-chirp mass, high-redshift BBH population, which is consistent with the PopIII origin. A precise characterization of the spectral shape near 30 − 50 Hz by the Einstein Telescope could also constrain the PopIII initial mass function and star formation rate.

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Burocracia e herança patrimonialista: a Secretaria de Educação do Estado de São Paulo entre 1995 e 2010

Cited by 4 publications

References 3 publications

A new route towards merging massive black holes

A new route towards merging massive black holes

Implications of the gravitational wave event GW150914

Gravitational wave background from Population III binary black holes consistent with cosmic reionization

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