Approximations to the radii of Roche lobes

Eggleton, P. P.

doi:10.1086/160960

Cited by 2,191 publications

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“…On the other hand, the semimajor axis of the binary is ∼22 light-days, only marginally larger than or even comparable with the BLR sizes measured from the reverberation-mapping observations (Bentz et al 2013). The Roche lobes of the binary system have a size of (Eggleton 1983) where we assume that the black holes in the pair have the same luminosity and adopt the typical mean value L 5100 =10 43 erg s −1 using a luminosity distance of 75Mpc. Considering that the 5100 Å luminosity varies by a large factor of more than six (see Figure 3), the above estimates indicate that the two BLRs are plausibly in contact during the intermediate or high states of NGC5548 (in which > R R BLR L ).…”

Section: Discussion On the Smbhb Scenariomentioning

confidence: 63%

Spectroscopic Indication of a Centi-Parsec Supermassive Black Hole Binary in the Galactic Center of Ngc 5548

Wang

et al. 2016

ApJ

111

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As a natural consequence of cosmological hierarchical structure formation, sub-parsec supermassive black hole binaries (SMBHBs) should be common in galaxies but thus far have eluded spectroscopic identification. Based on four decades of optical spectroscopic monitoring, we report that the nucleus of NGC5548, a nearby Seyfert galaxy long suspected to have experienced a major merger about 1 billion yr ago, exhibits long-term variability with a period of ∼14 yr in the optical continuum and broad Hβ emission line. Remarkably, the double-peaked profile of Hβ shows systematic velocity changes with a similar period. These pieces of observations plausibly indicate that an SMBHB resides in the center of NGC5548. The complex, secular variations in the line profiles can be explained by orbital motion of a binary with equal mass and a semimajor axis of ∼22 light-days (corresponding to ∼18 milli-parsec). At a distance of 75Mpc, NGC5548 is one of the nearest sub-parsec SMBHB candidates that offers an ideal laboratory for gravitational wave detection.

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Section: Discussion On the Smbhb Scenariomentioning

confidence: 63%

Spectroscopic Indication of a Centi-Parsec Supermassive Black Hole Binary in the Galactic Center of Ngc 5548

Wang

et al. 2016

ApJ

111

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“…It is a one-dimensional implicit Lagrangian code which solves the hydrodynamic form of the stellar structure and evolution equations (Kippenhahn & Weigert 1990;Kozyreva et al 2014). The evolution of the donor star, the mass-transfer rate, and the orbital separation are computed simultaneously through an implicit coupling scheme (see also Wellstein & Langer 1999) using the Roche approximation in the formulation of Eggleton (1983). To compute the mass-transfer rate, we use the prescription of Ritter (1988).…”

Section: Binary Stellar Evolution Code and Initial Parameter Spacementioning

confidence: 99%

Ultra-stripped supernovae: progenitors and fate

Tauris¹,

Langer²,

Podsiadlowski³

2015

Monthly Notices of the Royal Astronomical Society

415

613

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The explosion of ultra-stripped stars in close binaries can lead to ejecta masses < 0.1 M ⊙ and may explain some of the recent discoveries of weak and fast optical transients. In Tau ris et al. (2013), it was demonstrated that helium star companions to neutron stars (NSs) may experience mass transfer and evolve into naked ∼ 1.5 M ⊙ metal cores, barely above the Chandrasekhar mass limit. Here we elaborate on this work and present a systematic investigation of the progenitor evolution leading to ultra-stripped supernovae (SNe). In particular, we examine the binary parameter space leading to electron-capture (EC SNe) and iron core-collapse SNe (Fe CCSNe), respectively, and determine the amount of helium ejected with applications to their observational classification as Type Ib or Type Ic. We mainly evolve systems where the SN progenitors are helium star donors of initial mass M He = 2.5 − 3.5 M ⊙ in tight binaries with orbital periods of P orb = 0.06 − 2.0 days, and hosting an accreting NS, but we also discuss the evolution of wider systems and of both more massive and lighter -as well as single -helium stars. In some cases we are able to follow the evolution until the onset of silicon burning, just a few days prior to the SN explosion. We find that ultra-stripped SNe are possible for both EC SNe and Fe CCSNe. EC SNe only occur for M He = 2.60 − 2.95 M ⊙ depending on P orb . The general outcome, however, is an Fe CCSN above this mass interval and an ONeMg or CO white dwarf for smaller masses. For the exploding stars, the amount of helium ejected is correlated with P orb -the tightest systems even having donors being stripped down to envelopes of less than 0.01 M ⊙ . We estimate the rise time of ultra-stripped SNe to be in the range 12 hr − 8 days, and light curve decay times between 1 and 50 days. A number of fitting formulae for our models are provided with applications to population synthesis. Ultrastripped SNe may produce NSs in the mass range 1.10 − 1.80 M ⊙ and are highly relevant for LIGO/VIRGO since most (possibly all) merging double NS systems have evolved through this phase. Finally, we discuss the low-velocity kicks which might be imparted on these resulting NSs at birth.

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“…Note that the fits presented in section 6.2 never produced a secondary star mass smaller than 0.3 M . We have approximated the radius of the donor star by its Roche-lobe volume radius (Eggleton 1983). The donor radius can then be derived from its scaled value R2/a by using the binary parameters of HS 0220+0603.…”

Section: The M-type Companionmentioning

confidence: 99%

Dynamical masses of a nova-like variable on the edge of the period gap

Rodríguez‐Gil

Shahbaz

Marsh

et al. 2015

Mon. Not. R. Astron. Soc.

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We present the first dynamical determination of the binary parameters of an eclipsing SW Sextantis star in the 3-4 hour orbital period range during a low state. We obtained time-resolved optical spectroscopy and photometry of HS 0220+0603 during its 2004-2005 low brightness state, as revealed in the combined SMARTS, IAC80 and M1 Group long-term optical light curve.The optical spectra taken during primary eclipse reveal a secondary star spectral type of M5.5±0.5 as derived from molecular band-head indices. The spectra also provide the first detection of a DAB white dwarf in a cataclysmic variable. By modelling its optical spectrum we estimate a white dwarf temperature of 30 000 ± 5 000 K.By combining the results of modelling the white dwarf eclipse from ULTRA-CAM light curves with those obtained by simultaneously fitting the emission-and absorption-line radial velocity curves and I-band ellipsoidal light curves, we measure the stellar masses to be M 1 = 0.87 ± 0.09 M and M 2 = 0.47 ± 0.05 M for the white dwarf and the M dwarf, respectively, and an inclination of the orbital plane of i ≈ 79 o . A radius of 0.0103 ± 0.0007 R is obtained for the white dwarf. The secondary star in HS 0220+0603 is likely too cool and undersized for its mass.

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Approximations to the radii of Roche lobes

Cited by 2,191 publications

References 0 publications

Spectroscopic Indication of a Centi-Parsec Supermassive Black Hole Binary in the Galactic Center of Ngc 5548

Spectroscopic Indication of a Centi-Parsec Supermassive Black Hole Binary in the Galactic Center of Ngc 5548

Ultra-stripped supernovae: progenitors and fate

Dynamical masses of a nova-like variable on the edge of the period gap

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