Gravitational Wave Emission from the Single-Degenerate Channel of Type Ia Supernovae

Abstract

The thermonuclear explosion of a C/O white dwarf as a Type Ia supernova (SN Ia) generates a kinetic energy comparable to that released by a massive star during a SN II event. Current observations and theoretical models have established that SNe Ia are asymmetric, and thereforelike SNe II -potential sources of gravitational wave (GW) radiation. We establish an upper-bound GW amplitude and expected frequency range based upon the energetics and nucleosynthetic yields of SNe Ia. We perform the first detailed calculations of the gravitationally-confined detonation (GCD) mechanism and first for a SN Ia of any type within the single-degenerate channel of SNe Ia. The GCD mechanism predicts a strongly-polarized GW burst from the SD channel of SNe Ia in the frequency band around 1 Hz. Third-generation spaceborne GW observatories currently in planning, including the Big Bang Observer (BBO), and the Deci-Hertz Interferometer Gravitational Wave Observatory (DECIGO), as well as earthbound instruments, including the Einstein Telescope (ET), may be able to detect the signal predicted by the GCD mechanism from galactic SNe Ia and nearby extragalactic SNe Ia at distances up to 1 Mpc. If observable, GWs may offer a direct probe into the first few seconds of SNe Ia, and yield insights into its underlying detonation mechanism not possible in the optical portion of the spectrum.

Neutrino and gravitational wave signal of a delayed-detonation model of type Ia supernovae

“…In these models, an off-center ignited deflagration bubble rises due to buoyancy forces until it reaches the surface of the WD; the deflagration does not unbind the star but triggers a subsequent detonation that ignites opposite to the point where the deflagration bubble reaches the surface. This scenario leads to asymmetric explosions and thus to relatively strong gravitational wave signals, which are discussed in detail in [63].…”

“…Dan et al [62] calculated the gravitational wave signal of a close binary system of two WDs in the ringdown phase until the start of the merger, but they did not model the following thermonuclear burning which may lead to a supernova. Pioneering work on the signal from an actual explosion has recently been performed by Falta et al [63] and Falta and Fisher [64], who calculated the gravitational wave signal of gravitationally-confined detonation (GCD) models of thermonuclear supernovae (the Y12 model discussed extensively in Sec. II falls into this category).…”

“…Gravitational waves generated by mergers of two WDs would feature the characteristic signature of the ringdown phase -according to Dan et al [62], the gravitational wave signal in the ringdown phase is of the same magnitude as the signal of the supernova in the above discussed scenarios: hD = 2 cm to 20 cm, depending on the WD masses. Finally, GCD models show a sharp single peak in the time evolution of the amplitude (figure 2 in Falta et al 63). However, the low frequency range of the signals prevents a detection by second-generation instruments comparable to advanced LIGO; but third-generation space-based detectors like BBO or DECIGO that cover a lower frequency range should be able to detect the gravitational wave signal of at least all Galactic Type Ia supernovae.…”

“…In the first ∼0.4 s after the ignition of the deflagration, no signal is visible; after that the absolute values of all amplitudes rise in a steady, monotonic way. The initiation of the first detonation at t , the signal reaches a maximum value of hD ∼ 4 cm at t ∼ 1.36 s, about a factor of 3 less than the maximum amplitude obtained by [63] in their GCD model. The smaller maximum amplitude of the N100ν delayed-detonation model is naturally explained by the greater compactness of the GCD model when the detonation is triggered.…”

“…The energy spectrum calculated by [63] for the GCD model peaked at ∼2 Hz. It is worth noting that Falta et al [63] stated that an explosion model with more "preexpansion" prior to detonation, such as the N100ν model presented here, would exhibit a characteristic gravitational wave frequency shifted downward by a factor of ∼2, a prediction that we essentially confirm.…”