PoS(GOLDEN2019)046 model 6 https://pos.sissa.it/ model may be inconsistent 6 model can be also progenitors of peculiar SNe Ia. 6 ) models by numerical simulations. We have concluded that the violent 6 ∗ [email protected] Double-Detonation (D Recently, many sub-Chandrasekhar mass explosions in the double-degenerate scenario have been explosions of carbon-oxygen (CO) white dwarfs (WDs) in binary systems. Nevertheless, it is the brightest and common transients in the universe, a standard candle for a cosmic distance, and Speaker. merger model may not explainthan normal the SNe size of Ia, SN since 2011fe, their andby their circum-binary an event matter rate order is is of much much smaller magnitude. larger than the However, SN it Ia rate can in be our progenitors Galaxy of peculiar SNe Ia. The D suggested. We have assessed the violent merger and Dynamically-Driven Double-Degenerate yet unclear what the companion stars are, and what the masses of the exploding CO WDs are. a dominant origin of iron group elements. It is widely accepted that SNe Ia are thermodynamical Type Ia supernovae (SNe Ia) are important objects in astronomy and astrophysics. They are one of has roughly consistent features withwith normal an SNe asymmetric shape Ia. and low-velocity However, carbon-oxygensurviving the component companion model due CO. to has the If supernova presence these ejecta ofwith features the normal can SNe be Ia. observed, In this the case, D the D ∗ Copyright owned by the author(s) under the terms of the Creative Commons c ⃝ Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). The Golden Age of Cataclysmic Variables2-7 and September Related 2019 Objects V (GOLDEN2019) Palermo, Italy Ataru Tanikawa Department of Earth Science and Astronomy,Tokyo, College 3-8-1 of Komaba, Arts Meguro-ku, Tokyo and 153-8902, Sciences, Japan TheE-mail: University of Progenitor and explosion models of typesupernovae Ia PoS(GOLDEN2019)046 ⊙ M 0 . ], and 1 ) model 21 6 and 1 . Ataru Tanikawa ], the collision 1 models. 14 ]. ], and collapses to 6 8 , 12 7 , we investigate the violent merger ], and can be degenerate stars, i.e. 3 3 , 2 ]. There is no main-sequence star in a and ], the spiral instability model [ ]. The progenitor problem of SNe Ia gets 2 10 6 20 , , 9 19 , 1 18 , we summarize this paper. 4 ]. Theoretical studies have pointed out the difficulty of near- ]. The second point is the mass of exploding WDs. It can be near- ]. In response to this situation, many sub-Chandrasekhar mass 11 5 , 13 4 ]. In this paper, we discuss the violent merger and the D ], and sub-Chandrasekhar mass [ 2 22 ], the Dynamically-Driven Double-Degenerate Double-Detonation (D 17 , ]. ]. The second point is whether the event rate of this model is sufficient for the normal 16 25 ]. However, their progenitors have been controversial with respect to two points. The , 23 , 1 15 24 models, respectively. In section 6 Recent observations have greatly narrowed the allowed range of the SD scenario, although In order to assess the first point, we have thoroughly investigated a binary with We briefly explain the violent merger model. Let’s consider a close binary system consisting We have assessed this model from two points of view by numerical simulation. The first point The structure of this paper is as follows. In sections Type Ia supernovae (SNe Ia) play important roles in astronomy and astrophysics. They are they cannot completely rule outpre-explosion the images SD of scenario. SN 2011fe They and have SN not 2014J found [ no red-giant stars in the (or the helium-ignited violentdetached merger DD model) model [ [ and D Ia rate [ CO WDs. We expectbecause this these CO binary WDs succeeds have in nearlymore the the drastic maximum violent with mass the of merger CO mass explosion WDs, ratio most and approaching mass easily. to accretion unity. becomes This We is have performed four SPH simulations of two CO WDs. Theythe lose lighter CO an WD orbital is energy tidallyCO due disrupted to WD by gravitational gravity rapidly wave of falls radiation. thesurface heavier into of At CO the some the WD. heavier The time, CO heavier debris WD.two CO of From CO the the WD. WDs. lighter hot Finally, The spot, the CO rapid system detonation is accretion is observed generated, as forms and an a SN incinerates Ia. the is hot whether spot this near model can the succeeds really [ succeed, and whether this model is observed as a normal Ia if it Chandrasekhar mass explosion inresults the in DD an scenario. oxygen neon A magnesium WD merger with remnant super-Chandrasekhar of massexplosions two [ in CO the WDs DD finally scenario have been suggested: the violent merger model [ 2. The violent merger model another WDs, (DD scenario) [ more complex due to the presencenormal of Ia), not but only also SNe SNe Ia Ia deviating used from as normal a Ia cosmic (hereafter, standard peculiar candle Ia) (hereafter, [ Chandrasekhar mass [ 1. Introduction one of the brightest and mostcandle, common and transients can in be the a universe,are are dominant powered utilized source by as of thermonuclear a iron cosmic explosionssystems group standard of [ elements. carbon There oxygen is (CO)first wide white point consensus dwarfs is that (WDs) the they in nature binary such of the as companion red-giant stars. and The main-sequence companion stars stars (SD can scenario) be [ non-degenerate stars, Type Ia supernovae supernova remnant LMC SNR [ a neutron star or black hole [ model [ PoS(GOLDEN2019)046 ]. . This is ⊙ 28 , M 8 . Ataru Tanikawa 27 [ 0 million particles, ⊙ 1 R 1 , and response of the . ]. The CO detonation 0 . Its size is too large to ⊙ ⊙ 29 M ≲ R % of the normal Ia rate in , 0 . 1 6 . 1 model may not be consistent 0 10 . For each mass combination, 6 ⊙ ≳ M 1 . 1 to ⊙ M 5 model becomes one of promising progenitor . 0 6 2 ], the D 20 model can be observed as normal Ia. In particular, we have 6 ]. The SPH simulations are couple with nuclear reaction networks, 30 [ ⊙ million particles. All the simulations have more than M 6 . 11 0 ]. In each simulation, we have found a hot and dense spot enough to generate CO , and model, the pathway to SN Ia explosion is as follows. There is a binary system 5 26 . 6 5 , model 8 6 . 2 , 4 . 1 We have assessed whether the D In the D We have also performed SPH simulations for binary systems of two CO WDs with various In summary, we have concluded that the violent merger model cannot explain normal Ia for explodes the heavier WD, and thesuddenly explosion free is from observed the as gravity anhypervelocity of WDs SN the have Ia. heavier been discovered WD, The [ lighter and WD results survives, in is a hypervelocity WD. Since such since the violent merger explosionthan a does million not [ become successful if the number of particles is less focused on interaction of the heavierSPH WD explosion simulation with to the follow lighter the WD. First, explosion we of have the performed heavierand CO WD have with several tenthe million supernova particles ejecta owing has to anasymmetric shape asymmetric our survives shape, massively until since its parallel supernova the remnant simulation lighter phase, code. the WD D acts Then, as an obstacle. If this models. 3. The D consisting of a CO WDCO and WD a with WD a lighter than Heto the envelope. the CO heavier The WD. WD. binary The The system transferred WDHe matter experiences detonation can consists on be mass of the helium transfer He. surface (He) from ofcenter The WD the the of mass or lighter heavier transfer the WD, WD process heavier and finally WD subsequently ignite through trigger CO the detonation double near detonation the mechanism [ lighter CO WD with with Ia supernova remnants. However, the asymmetric shape may be erased through interaction detonation. Moreover, the spot becomesnumber hotter of and particles. more Thus, dense we have with concludedin the that the this simulation violent binary increasing merger system. explosion the becomes We successful havehot examined spot the to structure generate of CO this detonation binary appears.due system to We have at tidal found the disruption circum-binary moment of matter when the (CSM) a lighter is formed CO WD. The CSM spreads to with mass combinations. The CO WD masses range from Type Ia supernovae explain a normal Ia, such as SN 2011fe in which CSM size is inferred as we have adopted different numbersmass of combinations particles cannot for ignite convergence the check.becomes violent merger successful We explosion. have only confirmed We when have what the foundbecause the mass lighter violent accretion CO merger is WDs not havemeans drastic that more enough the than to event or rate form of equal a the to hot violent spot merger to explosion is generate less CO than detonation. This two reasons. The first reason isIa. that the The CSM second of the reasonIa violent is rate merger that model by is the an too event order largepeculiar rate for of Ia. a of magnitude. normal the Nevertheless, violent the merger violent model merger is model less may than be the progenitors normal of our Galaxy. PoS(GOLDEN2019)046 ]. In all (1960) 31 132 He outer shell Ataru Tanikawa ⊙ M model may not be model may disagree 6 6 054 . 0 model can be progenitors of peculiar Ni. However, such explosion occurs in total and The Astrophysical Journal 6 , 56 ⊙ ⊙ M 9 M . model as normal Ia progenitors. 8 0 . 6 models. We have concluded that the violent 0 6 ∼ for the heavier WDs. We have adopted different 3 model, focusing on the interaction of the heavier ⊙ 6 M model has supernova ejecta with an asymmetric shape 0 . model as normal Ia progenitors, since explosions of two 6 1 6 , the double detonation mechanism in the lighter WD does ⊙ M 009 . Nucleosynthesis in Supernovae. 0 explodes through He detonation starting at the surface ignited by the ⊙ Ni for normal Ia. M 56 45 . 0 Ni. Although this explosion is quite interesting, the He shell is unrealistically 56 ⊙ M 0 . 1 ∼ . F. Hoyle and W. A. Fowler, 565 SNe Ia are important transients, and however their progenitors have been unclear. Recently, We have also investigated whether the explosions of the heavier WDs induce the explosions In summary, we have investigated the D [1] merger cannot explain normal Ia, since itit has too can large be CSM, progenitors and too of small peculiar event Ia. rate. Nevertheless, The D and low-velocity CO component.consistent with If normal these Ia. features Inin this can near case, be future. it observed, can be the progenitors D of peculiar Ia.References We will confirm them many sub-Chandrasekhar mass explosion models inthem, the DD we scenario have have been assessed suggested. the Among violent merger and D 4. Summary with interstellar medium.ejecta We strips will materials from confirm the the thiscomponent lighter issue in WD. the The in supernova stripped ejecta. near materials If compose future. these a materials low-velocity CO can Moreover, be observed, the the supernova D of the lighter WDs by numerical simulations with various mass combinations of WDs [ Type Ia supernovae with normal Ia. Even if theseIa. features can We be will observed, the investigate D whetherin these near materials future. can be observed by radiative transfer calculations the cases, we have used a CO WD with WDs for the lighter WDs.case, a We have He found WD that with the lighter WDs explode in two cases. In the first explosion of the heavier WD. The system yields only when the separation between theWD heavier should and lighter be WDs disrupted is bya unrealistically close. the configuration. The tidal In lighter field the ofexplodes second through the case, double heavier detonation a mechanism. WD CO Note beforefrom WD that the He the with detonation double system of detonation reaches the mechanism starts He tothesizes shell such triggered by the explosion ofthick. the If heavier WD. the The He system shellnot syn- mass work. is Eventually, the explosionWD. of These the facts heavier indirectly WD support the cannotWDs D induce produce the too explosion much of the lighter WD explosions with theejecta lighter have WDs. asymmetric shapes, Dueconsistent and to with the low-velocity normal CO presence Ia. components. ofthe lighter the We WDs These will lighter cannot investigate features WDs, experiencenormal these may explosions the configurations. points triggered not supernova This by in indirectly be the supports near the explosions future. 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