Type Ia supernovae (SNeIa), used as one of the standard candles in astrophysics, are believed to form when the mass of the white dwarf approaches Chandrasekhar mass limit. However, observations in last few decades detected some peculiar SNeIa, which are predicted to be originating from white dwarfs of mass much less than the Chandrasekhar mass limit or much higher than it. Although the unification of these two sub-classes of SNeIa was attempted earlier by our group, in this work, we, for the first time, explain this phenomenon in terms of just one property of the white dwarf which is its central density. Thereby we do not vary the fundamental parameters of the underlying gravity model in the contrary to the earlier attempt. We effectively consider higher order corrections to the Starobinsky-f (R) gravity model to reveal the unification. We show that the limiting mass of a white dwarf is ∼ M ⊙ for central density ρ c ∼ 1.4 × 10 8 g/cc, while it is ∼ 2.8M ⊙ for ρ c ∼ 1.6 × 10 10 g/cc under the same model parameters. We further confirm that these models are viable with respect to the solar system test. This perhaps enlightens very strongly the long standing puzzle lying with the predicted variation of progenitor mass in SNeIa.
Recent detection of gravitational wave from nine black hole merger events and one neutron star merger event by LIGO and VIRGO shed a new light in the field of astrophysics. On the other hand, in the past decade, a few super-Chandrasekhar white dwarf candidates have been inferred through the peak luminosity of the light curves of a few peculiar Type Ia supernovae, though there is no direct detection of these objects so far. Similarly, a number of neutron stars with mass $>\! 2\, \mathrm{M}_\odot$ have also been observed. Continuous gravitational wave can be one of the alternate ways to detect these compact objects directly. It was already argued that magnetic field is one of the prominent physics to form super-Chandrasekhar white dwarfs and massive neutron stars. If such compact objects are rotating with certain angular frequency, then they can efficiently emit gravitational radiation, provided their magnetic field and rotation axes are not aligned, and these gravitational waves can be detected by some of the upcoming detectors, e.g. LISA, BBO, DECIGO, Einstein Telescope, etc. This will certainly be a direct detection of rotating magnetized white dwarfs as well as massive neutron stars.
Over the past two decades, the inference of the violation of the Chandrasekhar mass limit of white dwarfs (WDs) from indirect observation has been a revolutionary discovery in astronomy. Various researchers have already proposed different theories to explain this interesting phenomenon. However, such massive WDs usually possess very little luminosity, hence they so far cannot be detected directly by any observations. We have already proposed that the continuous gravitational wave may be one of the probes to detect them directly, and in the future various space-based detectors, such as LISA, DECIGO, and BBO, should be able to detect many of those WDs (provided they behave like pulsars). In this paper, we address various timescales related to the emission of gravitational as well as dipole radiations. This exploration sets a timescale for the detectors to observe the massive WDs.
Chandrasekhar made the startling discovery about nine decades back that the mass of compact object white dwarf has a limiting value once nuclear fusion reactions stop therein. This is the Chandrasekhar mass-limit, which is [Formula: see text] for a nonrotating non-magnetized white dwarf. On approaching this limiting mass, a white dwarf is believed to spark off with an explosion called type Ia supernova, which is considered to be a standard candle. However, observations of several over-luminous, peculiar type Ia supernovae indicate the Chandrasekhar mass-limit to be significantly larger. By considering noncommutativity among the components of position and momentum variables, hence uncertainty in their measurements, at the quantum scales, we show that the mass of white dwarfs could be significantly super-Chandrasekhar and thereby arrive at a new mass-limit [Formula: see text], explaining a possible origin of over-luminous peculiar type Ia supernovae. The idea of noncommutativity, apart from the Heisenberg’s uncertainty principle, is there for quite sometime, without any observational proof however. Our finding offers a plausible astrophysical evidence of noncommutativity, arguing for a possible second standard candle, which has many far-reaching implications.
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