Measuring the Rotational Periods of Isolated Magnetic White Dwarfs

Brinkworth, Carolyn; Burleigh, M. R.; Lawrie, Katherine; Marsh, T. R.; Knigge, Christian

doi:10.1088/0004-637x/773/1/47

Cited by 93 publications

(98 citation statements)

References 82 publications

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“…For the MWD members, the calculated data pair (ρ, P) are indicated by triangles in Figure 7, with the solid line of best fit drawn though the triangles. We have taken the period of WD1829 + 547 to be 100 years, the minimum value estimated via measurement as reported in [52]. It is rather surprising that though a huge gap is missing in the range of P (10 6 -10 9 s), the measured/deduced data point from other groups over the years follow a straight line according to our model.…”

Section: White Dwarfs (Wd) and Magnetic White Dwarfs (Mwd) With Mass mentioning

confidence: 82%

See 1 more Smart Citation

On the Origin of Mass and Angular Momentum of Stellar Objects

Fung¹,

Wong²

2015

JMP

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The consequence of the 5D projection theory [1] is extended beyond the Gell-Mann Standard Model for hadrons to cover astronomical objects and galaxies. The proof of Poincare conjecture by Perelman's differential geometrical techniques led us to the consequence that charged massless spinors reside in a 5D void of a galactic core, represented by either an open 5D core or a closed, time frozen, 3D × 1D space structure, embedded in massive structural stellar objects such as stars and planets. The open galactic core is obtained from Ricci Flow mapping. There exist in phase, in plane rotating massless spinors within these void cores, and are responsible for 1) the outward spiral motion of stars in the galaxy in the open core, and 2) self rotations of the massive stellar objects. It is noted that another set of eigen states pertaining to the massless charged spinor pairs rotating out of phase in 1D (out of the 5D manifold) also exist and will generate a relatively weak magnetic field out of the void core. For stars and planets, it forms the intrinsic dipole field. Due to the existence of a homogeneous 5D manifold from which we believe the universe evolves, the angular momentum arising from the rotation of the in-phase spinor pairs is proposed to be counter-balanced by the rotation of the matter in the surrounding Lorentz domain, so as to conserve net zero angular momentum. Explicit expression for this total angular momentum in terms of a number of convergent series is derived for the totally enclosed void case/core, forming in general the structure of a star or a planet. It is shown that the variables/parameters in the Lorentz spacetime domain for these stellar objects involve the object's mass M, the object's Radius R, period of rotation P, and the 5D void radius Ro, together with the Fermi energy E f and temperature T of the massless charged spinors residing in the void. We discovered three laws governing the relationships between R o /R, T, E f and the angular momentum Iω of such astronomical object of interest, from which we established two distinct regions, which we define as the First and Second Laws for the evolution of the stellar object. The Fermi energy E f was found to be that of the electron mass, as it is the lightest massive elementary particle that could be created from pure energy in the core. In fact the mid-temperature of the transition region between the First and Second Law regions for this E f value is 5.3 × 10 9 K, just about that of the Bethe fusion temperature. We then apply our P. C. W. Fung, K. W. Wong 2304 theory to analyse observed data of magnetars, pulsars, pre-main-sequence stars, the NGC 6819 group, a number of low-to-mid mass main sequence stars, the M35 members, the NGC 2516 group, brown dwarfs, white dwarfs, magnetic white dwarfs, and members of the solar system. The ρ = (R o /R) versus T, and ρ versus P relations for each representative object are analysed, with reference to the general process of stellar evolution. Our analysis leads us to the following age sequence of stell...

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Section: White Dwarfs (Wd) and Magnetic White Dwarfs (Mwd) With Mass mentioning

confidence: 82%

“…Similarly, we shall analyze some data of some isolated magnetic white dwarfs (MWD) [50] [52]. We list the surface magnetic induction field reported instead of effective surface T in Table 9 for MWD, together with other parameters similar to that for the WD case.…”

Section: White Dwarfs (Wd) and Magnetic White Dwarfs (Mwd) With Mass mentioning

confidence: 99%

On the Origin of Mass and Angular Momentum of Stellar Objects

Fung¹,

Wong²

2015

JMP

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“…However, planets of sub-Jupiter to Jupiter size, if they are abundant at these orbits around WDs, could explain three or four cases. Figure 8 shows the seven periods and amplitudes we have measured, along with the ground-based measurements by Brinkworth et al (2004Brinkworth et al ( , 2005Brinkworth et al ( , 2013, for 10 magnetic WDs with fairly precise rotation periods (out of 23 WDs monitored by them, 14 of them with sensitivity to periods of up to a week). Also plotted is a point for the T = 34, 000 K DA WD BOKS53856, for which Holberg & Howell (2011) have measured, using Kepler, amplitude A = 2.5% variations with a period P = 0.255 day.…”

Section: Discussionmentioning

confidence: 99%

Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

Maoz

Mazeh

McQuillan

2014

Monthly Notices of the Royal Astronomical Society

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We make use of the high photometric precision of Kepler to search for periodic modulations among 14 normal (DA-and DB-type, likely non-magnetic) hot white dwarfs (WDs). In five, and possibly up to seven of the WDs, we detect periodic, ∼ 2 hr to 10 d, variations, with semi-amplitudes of 60-2000 ppm, lower than ever seen in WDs. We consider various explanations: WD rotation combined with magnetic cool spots; rotation combined with magnetic dichroism; rotation combined with hot spots from an interstellar-medium accretion flow; transits by size ∼ 50-200 km objects; relativistic beaming due to reflex motion caused by a cool companion WD; or reflection/reradiation of the primary WD light by a brown-dwarf or giant-planet companion, undergoing illumination phases as it orbits the WD. Each mechanism could be behind some of the variable WDs, but could not be responsible for all five to seven variable cases. Alternatively, the periodicity may arise from UV metal-line opacity, associated with accretion of rocky material, a phenomenon seen in ∼ 50% of hot WDs. Nonuniform UV opacity, combined with WD rotation and fluorescent optical re-emission of the absorbed UV energy, could perhaps explain our findings. Even if reflection by a planet is the cause in only a few of the seven cases, it would imply that hot Jupiters are very common around WDs. If some of the rotation-related mechanisms are at work, then normal WDs rotate as slowly as do peculiar WDs, the only kind for which precise rotation measurements have been possible to date.

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“…It is known that the magnetic fields of Magnetic White Dwarfs are non-dipolar and distributed irregularly [40]. Thus to produce a magnetic field of (6) later.…”

Section: K T ∼mentioning

confidence: 99%

“…Taking 7 Magnetic Whit Dwarf (MWD) samples [40] [55] [56] with close mass density values, we plot the B-P graph in Figure 28, using data in Table 8 Table 8, we show the M-R graph in Figure 30 giving a slope of −1.159. Substituting therefore the following equation (Figure not shown), the slope is negative and the magnitude is rather large, within a range −58 to −62, being consistent to Equation (6.8.5), though the data points are rather scattered.…”

Section: Magnetic White Dwarfsmentioning

confidence: 99%

Origin of Magnetic Fields of Stellar Objects in the Universe Based on the 5D Projection Theory

Fung¹,

Wong²

2017

JMP

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Beginning with a 5D homogeneous universe [1], we have provided a plausible explanation of the self-rotation phenomenon of stellar objects previously with illustration of large number of star samples [2], via a 5D-4D projection. The origin of such rotation is the balance of the angular momenta of stars and that of positive and negative charged e-trino pairs, within a 3 1 ⊗ D D void of the stellar object, the existence of which is based on conservation/parity laws in physics if one starts with homogeneous 5D universe. While the in-phase e-trino pairs are proposed to be responsible for the generation of angular momentum, the anti-phase but oppositely charge pairs necessarily produce currents. In the 5D to 4D projection, one space variable in the 5D manifold was compacted to zero in most other 5D theories (including theories of [4]). We have demonstrated, using the Fermat's Last Theorem [5], that for validity of gauge invariance at the 4D-5D boundary, the 4 th space variable in the 5D manifold is mapped into two current rings at both magnetic poles as required by Perelman entropy mapping; these loops are the origin of the dipolar magnetic field. One conclusion we draw is that there is no gravitational singularity, and hence no black holes in the universe, a result strongly supported by the recent discovery of many stars with masses well greater than 100 solar mass [6] [7] [8], without trace of phenomena observed (such as strong gamma and X ray emissions), which are supposed to be associated with black holes. We analyze the properties of such loop currents on the 4D-5D boundary, where Maxwell equations are valid. We derive explicit expressions for the dipolar fields over the whole temperature range. We then compare our prediction with measured surface magnetic fields of many stars.Since there is coupling in distribution between the in-phase and anti-phase pairs of e-trinos, the generated magnetic field is directly related to the angular momentum, leading to the result that the magnetic field can be expressible in terms of only the mechanical variables (mass M, radius R, rotation period P)of a star, as if Maxwell equations are "hidden". An explanation for the occurrence of this "un-expected result" is provided in Section (7.6). Therefore we provide satisfactory answers to a number of "mysteries" of magnetism in astrophysics such as the "Magnetic Bode's Relation/Law" [9] and the experimental finding that B-P graph in the log-log plot is linear. Moreover, we have developed a new method for studying the relations among the data (M, R, P) during stellar evolution. Ten groups of stellar objects, effectively over 2000 samples are used in various parts of the analysis. We also explain the emergence of huge magnetic field in very old stars like White Dwarfs in terms of formation of 2D Semion state on stellar surface and release of magnetic flux as magnetic storms upon changing the 2D state back to 3D structure. Moreover, we provide an explanation, on the ground of the 5D theory, for the detection of extremely weak fi...

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Measuring the Rotational Periods of Isolated Magnetic White Dwarfs

Cited by 93 publications

References 82 publications

On the Origin of Mass and Angular Momentum of Stellar Objects

On the Origin of Mass and Angular Momentum of Stellar Objects

Kepler and the seven dwarfs: detection of low-level day-time-scale periodic photometric variations in white dwarfs

Origin of Magnetic Fields of Stellar Objects in the Universe Based on the 5D Projection Theory

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