scholarly journals The spin rates of O stars in WR+O Magellanic Cloud binaries

2020 ◽  
Vol 492 (3) ◽  
pp. 4430-4436
Author(s):  
Michael M Shara ◽  
Steven M Crawford ◽  
Dany Vanbeveren ◽  
Anthony F J Moffat ◽  
David Zurek ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Black Holes ◽  
Angular Momentum ◽  
Magnetic Fields ◽  
Gravitational Wave ◽  
Line Width ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Significant Line ◽  
Different Parts

ABSTRACT Some massive, merging black holes (BHs) may be descendants of binary O stars. The evolution and mass transfer between these O stars determine the spins of their progeny BH. These will be measurable with future gravitational wave detectors, incentivizing the measurement of the spins of O stars in binaries. We previously measured the spins of O stars in Galactic Wolf–Rayet (WR)+O binaries. Here we measure the ve sin i of four Large Magellanic Cloud (LMC) and two Small Magellanic Cloud (SMC) O stars in WR+O binaries to determine whether lower metallicity might affect the spin rates. We find that the O stars in Galactic and Magellanic WR+O binaries display average ve sin i = 258 ± 18 and 270 ± 15 km s−1, respectively. Two LMC O stars measured on successive nights show significant line width variability, possibly due to differing orbital phases exhibiting different parts of the O stars illuminated differently by their WR companions. Despite this variability, the ve sin i are highly supersynchronous but distinctly subcritical for the O stars in all these binaries; thus we conclude that an efficient mechanism for shedding angular momentum from O stars in WR+O binaries must exist. This mechanism, probably related to Roche lobe overflow (RLOF)-created dynamo magnetic fields, prevents nearly 100 per cent breakup spin rates, as expected when RLOF operates, as it must, in these stars. A Spruit–Tayler dynamo and O star wind might be that mechanism.

scholarly journals Coalescence of Kerr Black Holes—Binary Systems from GW150914 to GW170814

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 1017
Author(s):  
Bogeun Gwak
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Wave ◽  
Orbital Angular Momentum ◽  
Binary Systems ◽  
Analytical Form ◽  
Angular Momenta ◽  
Binary Black Hole ◽  
Kerr Black Holes

We investigate the energy of the gravitational wave from a binary black hole merger by the coalescence of two Kerr black holes with an orbital angular momentum. The coalescence is constructed to be consistent with particle absorption in the limit in which the primary black hole is sufficiently large compared with the secondary black hole. In this limit, we analytically obtain an effective gravitational spin–orbit interaction dependent on the alignments of the angular momenta. Then, binary systems with various parameters including equal masses are numerically analyzed. According to the numerical analysis, the energy of the gravitational wave still depends on the effective interactions, as expected from the analytical form. In particular, we ensure that the final black hole obtains a large portion of its spin angular momentum from the orbital angular momentum of the initial binary black hole. To estimate the angular momentum released by the gravitational wave in the actual binary black hole, we apply our results to observations at the Laser Interferometer Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608 and GW170814.

scholarly journals Magnetic Fields in the Irregular Galaxy LMC

1993 ◽  
Vol 157 ◽  
pp. 317-319
Author(s):  
Richard Wielebinski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radio Continuum ◽  
The South ◽  
Irregular Galaxy ◽  
New Radio ◽  
The Magnetic Field

New radio continuum surveys allowed the determination of the magnetic field in the Large Magellanic Cloud. The magnetic field is filamentary, extending to the south of the 30 Doradus nebula. Some possible explanations for this unusual morphology are discussed.

scholarly journals Black holes lessons from multipole ratios

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Iosif Bena ◽  
Daniel R. Mayerson
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
String Theory ◽  
Gravitational Wave ◽  
Scaling Limit ◽  
Kerr Black Hole ◽  
Kerr Geometry ◽  
Dimensional Black Hole ◽  
Infinite Set

Abstract We explain in detail how to calculate the gravitational mass and angular momentum multipoles of the most general non-extremal four-dimensional black hole with four magnetic and four electric charges. We also calculate these multipoles for generic supersymmetric four-dimensional microstate geometries and multi-center solutions. Both for Kerr black holes and BPS black holes many of these multipoles vanish. However, if one embeds these black holes in String Theory and slightly deforms them, one can calculate an infinite set of ratios of vanishing multipoles which remain finite as the deformation is taken away, and whose values are independent of the direction of deformation. For supersymmetric black holes, we can also compute these ratios by taking the scaling limit of multi-center solutions, and for certain black holes the ratios computed using the two methods agree spectacularly. For the Kerr black hole, these ratios pose strong constraints on the parameterization of possible deviations away from the Kerr geometry that should be tested by future gravitational wave interferometers.

scholarly journals Radio continuum study of the large Magellanic cloud: SNR J0519-6926

2008 ◽  
pp. 59-63 ◽  
Author(s):  
E.J. Crawford ◽  
M.D. Filipovic ◽  
J.L. Payne
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radio Continuum

We present the results of new high resolution ATCA observations of SNR J0519-6926. We found that this SNR exhibits a typical 'horseshoe' appearance with ?=-0.55?0.08 and D=28?1 pc. No polarization (or magnetic fields) were detected to a level of 1%. This is probably due to a relatively poor sampling of the UV plane caused be observing in 'snap-shot' mode.

Superstrong magnetic fields of neutron stars in Be X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 135-138
Author(s):  
ChangSheng Shi ◽  
ShuangNan Zhang ◽  
XiangDong Li
Keyword(s):  
Magnetic Fields ◽  
Neutron Stars ◽  
Milky Way ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Emission Lines ◽  
Disk Accretion ◽  
Superstrong Magnetic Field ◽  
X Ray ◽  
X Ray Binaries

AbstractA few Be X-ray binaries might constitute a group of special sources because the neutron stars in them may have superstrong magnetic fields. Generally, the neutron stars have long spin periods and some emission lines are shown from the B type star, which is attributed to an equatorial disc. We re-build new dimensionless torque models and obtain the superstrong magnetic fields of the neutron stars in the Be X-ray binaries in Large Magellanic Cloud, Small Magellanic Cloud and Milky Way when the compressed magnetosphere is considered. Although our conclusions are obtained when the disk accretion mode is considered, the results may be applied the Be X-ray binaries with wind accretion mode. SXP1323 and 4U 2206+54, in which the magnetic fields of the NSs may be close to the maximum ‘virial’ value, are the best objects to explore superstrong magnetic field.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Novae in the Magellanic Clouds

1979 ◽  
Vol 46 ◽  
pp. 96-101
Author(s):  
J.A. Graham
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
University Of Michigan ◽  
The Past ◽  
Spectroscopic Information ◽  
Objective Prism ◽  
The University ◽  
Small Cloud ◽  
Low Dispersion

During the past several years, a systematic search for novae in the Magellanic Clouds has been carried out at Cerro Tololo Inter-American Observatory. The Curtis Schmidt telescope, on loan to CTIO from the University of Michigan is used to obtain plates every two weeks during the observing season. An objective prism is used on the telescope. This provides additional low-dispersion spectroscopic information when a nova is discovered. The plates cover an area of 5°x5°. One plate is sufficient to cover the Small Magellanic Cloud and four are taken of the Large Magellanic Cloud with an overlap so that the central bar is included on each plate. The methods used in the search have been described by Graham and Araya (1971). In the CTIO survey, 8 novae have been discovered in the Large Cloud but none in the Small Cloud. The survey was not carried out in 1974 or 1976. During 1974, one nova was discovered in the Small Cloud by MacConnell and Sanduleak (1974).

Problems on the Gravitational Wave and the Repulsive Gravitation

2016 ◽  
pp. 4422-4429
Author(s):  
C. Y. Lo
Keyword(s):  
Black Holes ◽  
Gravitational Wave ◽  
Einstein Equation ◽  
Wave Solution ◽  
Dynamic Solution ◽  
Pure Mathematics ◽  
Non Linear

It is exciting that the gravitational wave has been confirmed, according to the announcement of LIGO. This would be the time to fix the Einstein equation for the gravitational wave and the nonexistence of the dynamic solution. As a first step, theorists should improve their pure mathematics on non-linear mathematics and related physical considerations beyond Einstein. Then, it is time to rectify the Einstein equation that has no gravitational wave solution which Einstein has recognized, and no dynamic solution that Einstein failed to see. A problem is that physicists in LIGO did not know their shortcomings. Also, in view of the far distance of the sources, it is very questionable that the physicists can determine they are from black holes. Moreover, since the repulsive gravitation can also generate a gravitational wave, the problem of gravitational wave is actually far more complicated than we have known. A useful feature of the gravitational wave based on repulsive gravitation is that it can be easily generated on earth. Thus this can be a new tool for communication because it can penetrate any medium.

Five Mature Supernova Remnants in the Large Magellanic Cloud

1998 ◽  
Vol 115 (3) ◽  
pp. 1057-1075 ◽  
Author(s):  
John R. Dickel ◽  
D. K. Milne
Keyword(s):  
Supernova Remnants ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud
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