RELATIVISTIC SHOCK BREAKOUTS—A VARIETY OF GAMMA-RAY FLARES: FROM LOW-LUMINOSITY GAMMA-RAY BURSTS TO TYPE Ia SUPERNOVAE
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The light from a shock breakout of stellar explosions, which carries a wealth of information, strongly depends on the shock velocity at the time of the breakout. The emission from Newtonian breakouts, typical in regular core-collapse supernovae (SNe), has been explored extensively. However, a large variety of explosions result in mildly or ultrarelativistic breakouts, where the observed signature is unknown. Here we calculate the luminosity and spectrum produced by relativistic breakouts. In order to do so, we improve the analytic description of relativistic radiation-mediated shocks and follow the system from the breakout itself, through the planar phase and into the spherical phase. We limit our calculation to cases where the post-breakout acceleration of the gas ends during the planar phase (i.e., the final gas Lorentz factor ≲ 30). We find that spherical relativistic breakouts produce a flash of gamma rays with energy, Ebo, temperature, Tbo, and duration, tobsbo, that provide the breakout radius (≈5 R☉(tobsbo/10 s)(Tbo/50 keV)2) and the Lorentz factor (≈Tbo/50 keV). They also always satisfy a relativistic breakout relation (tobsbo/20 s) ∼ (Ebo/1046 erg)1/2(Tbo/50 keV)−2.68. The breakout flare is typically followed, on longer timescales, by X-rays that carry a comparable energy. We apply our model to a variety of explosions, including Type Ia and .Ia SNe, accretion-induced collapse, energetic SNe, and gamma-ray bursts (GRBs). We find that all these events produce detectable gamma-ray signals, some of which may have already been seen. Some particular examples are: (1) relativistic shock breakouts provide a natural explanation to the energy, temperature, and timescales of low-luminosity GRBs. Indeed, all observed low-luminosity GRBs satisfy the relativistic breakout relation. (2) Nearby broad-line Type Ib/c (like SN 2002ap) may produce a detectable γ-ray signal. (3) Galactic Type Ia SNe may produce detectable γ-ray flares. We conclude that relativistic shock breakouts provide a generic process for the production of gamma-ray flares.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/aa6ffaf56e5652c944122ebda7693e62a78feb90
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Citations in the corpus
- A new method for estimating the bolometric properties of Ibc supernovae (2013, unknown): “Instead, work (e.g. MacFayden et al. 2001, Bromberg et al. 2011, Bromberg et al. 2012, Nakar & Sari 2012) has suggested that XRFs are produced by “failed jets” - jets that are produced via an accreting BH, but are weak and fail to break out of their progenitor stars.”
- Observational Clues to the Progenitors of Type Ia Supernovae (2013, background): “When it emerges, it produces a ms-timescale gamma-ray flash of energy Eγ ∼ 1040−41 erg, constituting “shock breakout” (Nakar & Sari 2012).”
- The Observer's Guide to the Gamma-Ray Burst-Supernova Connection (2016, methodology): “It was shown by [60] that an SBO is likely present in all LGRB events, but for any realistic configuration the energy in the SBOpulse is lower bymany orders ofmagnitude compared to those observed in the GRB prompt emission (ESBO = 10 (44)–10(47) erg, for reasonable estimates of the ejecta mass and p”
- Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation (2015, background): “…the cocoon breaks out of the star, and feasibly leads to a different type of burst, which may resemble a low-luminosity GRB (Kulkarni et al. 1998; MacFadyen et al. 2001; Tan et al. 2001; Wang et al. 2007; Waxman et al. 2007; Katz et al. 2010; Bromberg et al. 2011; Nakar & Sari 2012; Nakar 2015).”
- A Magnetar Origin for the Kilonova Ejecta in GW170817 (2018, background): “Relativistic shock breakout (e.g., Nakar & Sari 2012) from this interaction might provide an alternative source for the gammaray emission from GW170817, which does not necessarily implicate black hole formation or the creation of an ultrarelativistic jet on this timescale.”
- EVLA OBSERVATIONS CONSTRAIN THE ENVIRONMENT AND PROGENITOR SYSTEM OF Type Ia SUPERNOVA 2011fe (2012, background): “…including (i) their compact progenitors, leading to mildly-relativistic shockwaves at the time of breakout from the star (Colgate 1970; Nakar & Sari 2012), and (ii) a common polytrope of γ = 4/3, appropriate for both massive (relativistic) WDs and the radiative envelopes of Wolf-Rayet…”
- A cocoon shock breakout as the origin of the γ-ray emission in GW170817 (2017, background): “An example of these properties can be seen in the detailed solution of a relativistic breakout from a static stellar envelope presented in Nakar & Sari (2012) and in the results of the numerical simulations that we present here.”
- The physics of gamma-ray bursts & relativistic jets (2014, background): “Physically, they may mark unsuccessful jets, and their emission is from a trans-relativistic shock breaking out from the star (e.g. Bromberg et al., 2011a; Nakar and Sari, 2012).”
- THE OBSERVABLE SIGNATURES OF GRB COCOONS (2016, background): “Since the number of pairs is exponential with the temperature, pair production behaves as a thermostat that prevents the temperature from rising above ∼ 100 keV (for an analog in the structure of relativistic radiation mediated shocks see Budnik et al. 2010; Nakar & Sari 2012). i.”