PoS(GOLDEN 2017)066 , g , f https://pos.sissa.it/ , R. M. Wagner e University of North b , C. E. Woodward Ohio State University, Department d g , c Oak Ridge National Laboratory, Oak University of Minnesota, Minneapolis, c e , W. R. Hix b Be produced and ejected by the explosion and compare our 7 Li and C abundance. Thus, accreting Solar material results in more material 7 , C. Iliadis University Polytechnic of Catalunya, Barcelona, Catalunya, 12 h a i Li in nova V5668 Sgr. Finally, many of these simulations eject significantly less 7 , M. Bose a ∗ † University of Tennessee, Knoxville, TN; d , M. Hernanz h Institute of Space Sciences, Barcelona, Catalunya, Spain i Large Binocular Telescope Observatory, Tucson, AZ; f Speaker. This work supported by NSF and NASA grants to ASU We report on our continuing studiesthermonuclear of runaways Classical (TNRs) Nova on explosions carbon-oxygen by (CO)both following the white the mass dwarfs evolution of (WDs). the of WD We andthe have the material varied composition of has the mixed accreted from material.(multi-D) the Rather studies than beginning, of assuming mixing we that as now a consequence rely ofThe on the multi-D TNRs the in studies results WDs find that of accreted that the onlyreach Solar mixing multidimensional enrichment matter. with levels the in core agreement occurs with3 after observations studies in of the this the TNR paper. ejecta is First, abundances.1-D, well simulations fully We underway in implicit, report which and hydro on we code). accrete onlyonly Second, Solar Solar we matter use material with MESA NOVA (our and for compareinitiated similar studies the and in then results. which switch we the Third, accrete 25% composition core we and in accrete 75% the Solar Solar or accreted 50% matter layers coreproportional and until to to 50% a the the Solar. The initial mixed TNR amount composition: of is accreted either material is inversely to fuel the outburst -from much the larger beginning. than We in tabulateWe the the predict amount earlier the of studies amount ejected of where gases, mixed their materials velocities, were and used abundances. mass than accreted and, therefore, the WD is growing in mass toward the Chandrasekhar Limit. predictions to our Large Binocular Telescope (LBT) highabundance dispersion of spectra which determined the † ∗ Copyright owned by the author(s) under the terms of the Creative Commons Arizona State University- Earth and Space Exploration, Tempe, AZ,USA; c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). [email protected],[email protected],[email protected], [email protected],[email protected],[email protected],[email protected], [email protected] The Golden Age of Cataclysmic Variables11-16 and September, Related 2017 Objects IV Palermo, Italy S. Starrfield Hydrodynamic Simulations of Classical Novae: Accretion onto CO White Dwarfs asProgenitors SN Ia a J. Jóse Carolina - Physics and Astronomy, ChapelRidge, Hill, TN; NC; MN; of Astronomy, Columbus, OH; Spain; E-mail: PoS(GOLDEN 2017)066 S. Starrfield . 1 − erg s 34 10 1(4; 5). Thus, they have ∼ > z , both favor and disfavor the SD 1 in the same issue of Nature exhibit H in their spectra (e.g., 1; 2). SN Ia have light curves that can be calibrated do (11) proposed that the explosion involved a carbon-oxygen white dwarf (CO WD) which ac- In this paper we concentrate on the SD scenario. Although there is no agreement on the The SD scenario is capable of explaining most of the observed properties of the SN Ia explo- New evidence in favor of the SD scenario comes from observations of SN 2011fe in M101. Supernovae of Type Ia (SNe Ia) are typically those supernovae in which neither hydrogen Moreover, (1) claim that PTF 11kx was a SN Ia that exploded in a symbiotic nova system. In creted material from a binarycarbon companion deflagration/detonation until then its occured mass andpathway approached is produced the designated a as Chandrasekhar SN the Limit. single Iadesignated degenerate the A explosion double (SD) degenerate (12; scenario. (DD) 13; scenario, Alternatively, is a 14).(15). invoked second in mechanism, which This two CO WDs merge or collide progenitors, likely systems are theclose Cataclysmic Variables (or (CV) not and so Symbiotic close) Binariessecondary binary which star star are that systems typically which fillsLagrangian its contain point Roche both of Lobe. a the The WD binary cooler primary andabsence star a and of is fraction a losing hydrogen of larger mass this and cooler material through heliumthe is the in WDs accreted inner by the in the spectra these WD. of systems However,explode, the then are a the accreting SN accreted hydrogen- Ia envelope and may wouldin be helium-rich rule the carried material. out spectrum. along most with Nevertheless, If CV the ifduring the supernova a systems the WD ejecta sufficient since and accretion were amount be process to of seen and thethen the accreted its explosion material mass should remains can resemble on a gradually the SN grow WD Ia. close to thesion Chandrasekhar via the Limit, delayed detonation hypothesisvarious (16; proposals 17; for 18; SN 19, Ia and progenitorsin references (13), therein). (14), and (6; the Reviews 7), of implications (20), the of and their (5). explosions can Recent be reviews found of the observationsThey can imply be that found the in exploding (9) staron and was or (10). likely near a the CO WD mainhave (21) sequence ruled with (22; out a many 23). companion types that However,2011fe of was EVLA exploded, CVs. probably suggest (24) In that and the addition, optical progenitor HST (23) had studies a observations of luminosity may the less spatial than region from which SN become extremely important tools toand determine references the therein). structure and SN evolutioniron Ia of group are the elements also to Universe important the (6; because galacticIn 7, Interstellar they the Medium contribute past (ISM) a and, few major therefore, years,8; fraction to a 5; our of tremendous 9; Solar the 10). effort System. Nevertheless, has the gone progenitor(s) into of SN studies Ia of explosions their are, observed as yet, properties unknown. (cf., (3), making them excellent standardizable distance indicators to nor helium is seensize in of any SN of surveys thein increase, spectra fact there obtained are during events the that outburst. otherwise would However, be as classified the as sample SN Ia’s that additioin, the “zoo” of SNe25). Ia The types most is recent increasing results as (26; 27), surveys find more and more members (e.g., Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors 1. Introduction scenario. Therefore, sincerequired the for existence these of extreme “Super-Chandra” explosions, Ia’s evidently, suggests on that balance DD there are mergers multiple are channels that can PoS(GOLDEN 2017)066 S. Starrfield Li in V5668 Sgr and its implications (Section 5), 2 7 ) allows the mass of the WD to grow as a result of continued 1 − yr

˙ M: in units of M Observations of V445 Pup (Nova Pup 2000) strongly suggest that the SD channel must be In the next Section we discuss problems with the SD scenario. We follow that with Sections The SD scenario can result in light curves and other properties that resemble those of a SN A more serious problem is that it is commonly assumed that only a very narrow range in mass viable. There were no signs ofjust hydrogen after in the discovery, but spectrum there at any wereoptically time strong thick, during lines spectra the of outburst, (29; carbon, especially 30; helium, 31;the and 32; spectra other 33; obtained elements 34). in early Unfortunately, no the inamount complete early, the of abundance outburst analysis hydrogen exist of that to couldV445 enable be Pup a hidden. was determination extremely Nevertheless, of luminous it an beforedeficient is the upper probably carbon outburst, limit extremely star the to small. secondary (34). the isabsence Because thought Since of to one be hydrogen a of or hydrogen existence the helium of defining in V445 characteristics Pup the implies of spectrum thatthe a mass at time transferring SN of any binaries Ia the exist time explosion explosion inevolution. during and which is The hydrogen most the the latest is of spectra outburst absent the show or at that heliumpossible this decline, is to system converted study the is to the still carbon underlying in system during outburst (35). and, the therefore, nova it phase has of not been where we present the 2 codesCO used in WDs our (Section work 4), (Section discuss 3), the our 3 discovery different of studies of accretion onto Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors produce SN Ia explosions including the SD channel (28). accretion. The basis of thisas assumption Figure is 5 the in work (38). ofmasses, (36; This it 37). plot is A has predicted plot 3 that ofresemble regions his those accretion on of results results it. Classical can in Novae. be For hydrogen Since found combination the the with flashes lowest the results which theoretical mass of predictions, are a accretion of normally large rates, Classicalis number Nova expected ejected at (CNe) of than to ejecta, all observational accreted imply WD studies, (39; that in more 40)Chandrasekhar mass accretion Limit. at low However, hydrodynamic rates cannot calculations result of in this the process growth show of that the the WD accreted to the Ia explosion; there are,progenitors however, might significant actually problems be. withbinary, In any involving fact, of a while WD the virtually has suggestions everyhydrogen been for or type suggested helium what of as observed close the a in binary, progenitor, thewith or the SN a not major Ia WD problem so explosion. that is close However, is in thatsuggests transferring virtually either there every material, that is observed these the no binary systems material are isfrom not the hydrogen SN system rich. Ia prior progenitors The to or the presence thatare SN the of losing Ia hydrogen mass hydrogen explosion. and at helium Moreover, prodigious many is ratessystem of lost into explodes the the and suggested local then classes ISM appear of and binaries in thata material the few should spectrum SNe be at Ia present some where when time thereor the after are ISM the narrow material outburst. lines (9). In of fact, hydrogen In(1) there in claim addition, are the that there spectrum it was that was sufficient indicate a hydrogen circumbinary SN in Ia that the exploded spectrum in of aaccretion PTF Symbiotic rate 11kx ( Nova system. that and end with Conclusions in Section 6. 2. Problems with the Single Degenerate Scenario PoS(GOLDEN 2017)066 Ge and 64 S. Starrfield ˙ M. These calcu- ˙ M of this region is 3 but it does have a slight variation with WD mass. Those systems 1 − yr

M 7 − reaction), the OPAL opacities (54, and references therein), the Starlib nuclear 10 × pep 3 ∼ For the highest mass accretion rates in this plot, the results of (36; 37) imply that theThere radius is, of however, a third regime predicted by (36; 37), intermediate between these two, where However, the calculations reported in (36; 37) assume a steady state solution and imply that The codes used are NOVA (45; 46; 47; 48; 49; 50, and references therein) and MESA (51; 52; One feature of NOVA is that it was designed to follow only the first evolution to the TNR. If we the WD rapidly expands to redto giant be dimensions. halted The and implication further here evolution is must that await this the causes collapse accretion of thethe extended material layers. is expected to burn steadily at the rate it is accreted. The central the only parameters that affect the evolution of an accreting WD are its mass and 53, and references therein). NOVA iscode a which one-dimensional (1-D), has implicit, been hydrodynamic, well46). computer tested It against includes a a number nuclear of reaction standard network problems that has and been weapon extended codes to (45; 187 nuclei (up to Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors material must mix with coreincluded material, in the in calculations order of to (36; produce 37). a CN outburst, and that process is not nominally that are accreting at theWD mass steady and, burning by rate some unknown are mechanism,mass the evolving accretion mass range. horizontally transfer The in in implication, the this therefore, binary iswill plot system that result is towards only stuck in a higher in narrow the range this growth of in massin mass accretion the rates of LMC the are WD. However, accreting theUnfortunately, at Super there high Soft are Binary rates insufficient X-ray and Sources SSS arerecent (SSS) observations systems predicted of for to nearby be SN them Ia in to explosionsthe the appear be observations to of steady the CVs rule burning and out only regime other luminous SN systems (41). progenitors.that with Ia Moreover, are accreting progenitors not WDs within show and that the they steady are burning accreting regime at and, rates therefore, the WD cannot be growing in mass. lations do not take intocomposition account of the the chemical composition underlying ofplace, WD, the or if the accreting mixing thermal material, structure of the ofuing) chemical accreted the outbursts underlying material on WD. with the Moreover, the core thermal effectsis and material of well compositional has previous known (or structure taken that contin- of all thewe these WD report parameters (42) on affect are three the different not evolution studiesresults considered. of of of It the the (36; accretion 37) WD of must (43; be Solar 44). revised. material onto In WDs the and Section show 4 that3. the The Stellar Evolution Codes: NOVA and MESA including the reaction rates (55), the Timmes equationsdeveloped of by state (56; (58). 57), and NOVA also thePotekhin includes nuclear reaction electron the network (59) conductivities solver algorithm described for inhave had mixing-length (60, the convection effect and and of the changing references thesmaller therein). initial radii structures and of These larger the surface improvements WDs gravities. so that, for a given mass, theyneed have to follow multiple events onchoice is an MESA accreting which WD, solves then thestellar we 1D evolution. fully must coupled It switch structure is to and based a composition on different equations an code. governing implicit Our finite difference scheme with adaptive mesh refinement PoS(GOLDEN 2017)066

M 11 K) and − 6 reaction reaction − 10 4 reaction is S. Starrfield T × pep pep ∼ pep , two initial WD

sequences). Therefore,

, and 1.35M

, 1.25M ) and this is the phase when most of the 2

1% for the 0.7M . X 0 ∼ ∼ ε , 1.0M

4 K but convection does not start until the temperature in , 0.7M 7

10 ), and seven mass accretion rates ranging from 2 ×

5 L . 2 1 reaction. Therefore, calculations which include the − ∼ pep cm and we halted the evolution. These calculations showed that the and 10 12 . 1

10 − L sequences but ranging down to 3 yr ∼ : 66; 67). While for solar models the energy generation from the

−

ν 10 M + 6 × d − → 10 . At these densities, the rate of energy generation is larger than in those simulations done 3 p × − + − to 2 e Our studies (and those of others) show that most of the time to the TNR is spent in, and most All simulations resulted in a TNR which either ejected some material or, after some time, the In this subsection we report on the first of two studies that investigated the consequence of a g cm 1 Dwarf’s Mass + 4 4% for the 1.25M − p the hydrogen mass fraction (the energymass generation: is accreted. The evolutionnuclear to burning the region TNR reaches begins to accelerate when the peak temperature in the accrete less material then calculations where itAt is this neglected time (all in other the parameters evolution held the constant: energy 49). production depends both on the temperature ( without the inclusion of the of the mass is accreted during,proton the chain. phase when the During principlethe this nuclear surface burning phase, and process there electron is the degenerate is proton- conductivityOne a that reaction is competition that transporting affects between some the the energy energy into production radiative the during diffusion interior. the time proton-proton to chain is the the WDs are growing inenrichment from mass core as material. a result of the accretion of Solar composition material and no ( unimportant save for neutrino losses, in the WD10 envelope the density can reach, or exceed, values of WD radius grew to sequences exhibited the (65) thin shellmass instability. while In the general, high the mass low∼ WDs mass ejected WDs a did small not fraction eject of any their accreted material (a maximum of 4.1 Simulations with NOVA WD accreting stellar material with a Solarwith composition a from study a of secondary accretion donor onto star. a Wefound follow CO in that WD the but multi-D assume studies. that Many mixing typesto occurs of during be close the the binary TNR systems progenitors as with has for a been WD SN WD masses primary Ia are with explosions; suggested a thus wide weaccretion range have onto modeled WDs of with accretion accretion masses onto rates. of a 0.4M NOVA wide was range used of to study the consequences of Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors and sophisticated time step controls;nuclear state-of-the-art reaction rates, modules element provide diffusion, equations boundary(51; of conditions, 52; state, and 53). changes opacity, to The theto mass equation lower of of temperatures the state star and is densitiesHELM the of EOS 2005 the (57) update and SCVH the of EOS PC the (62).is EOS OPAL the (63) This EOS OPAL for opacities EOS (61) the (54) regimes is with with whereopacities supplemented an they the of with are extension low (60). valid. the temperature The opacities choice of of (64) opacity and the electron conduction 4. Simulations of Thermonuclear Runaways that result in the Growth of the White yr luminosities (4 PoS(GOLDEN 2017)066 ˙ M is S. Starrfield ˙ M used in these 1.4 ˙ M and the log of 1.2 shows that it is possible for RNe 2 ˙ M. The log of the 1.0 ˙ M. This is because higher mass WDs • O 0.8 M/M K when the carbon-nitrogen-oxygen cycle (CNO) 5 . Although it is often claimed that only the most 7

10 0.6 × ) is displayed as a function of WD mass for each of the 3 1 − ∼ yr Growth of WD Mass versus WD Mass WD versus Mass WD of Growth 0.4

/year) • O -5.8 -6.5 -6.8 -7.8 -8.8 -9.8 -10.8 0.2 LOG Mdot (M -7 -8 -9 -5 -6

-10 -11

O LOG Growth in Mass (M Mass in Growth LOG /year) • shows the log of the difference between the mass accreted and the mass lost. Each shows the accretion time to the TNR for some of our simulations. Clearly, as the WD 1 2 ˙ M. Finally, for the most massive WDs, the recurrence period can be less than a year which Figure Figure initiate the TNR with a smaller(RNe) amount and of Symbiotic accreted Novae mass. with Givenyears recurrence the (RS times Oph) existence ranging or of longer from Recurrent (T a Novae Pyx, few V407 years Cyg, and (U T Sco) CrB), to Figure about 20 to occur on WDs with masses as low as 0.7M mass increases, the accretion time decreases for the same massive WDs have recurrence times short enoughthe to case agree and with basing the WD observations mass of determinationsNote RNe, for that this RNe it is purely not is on short also recurrence possiblerange times for of is a incorrect. RN outburst tosuggests occur that on a the high RN mass inoccurring WD on M31 for a an with WD extremely an that broad is outburst close period to less the Chandrasekhar than Limit. or about a year (68; 69) must be Figure 1: The logthe growth of in the mass difference (in between units of the M mass accreted and the mass lost. The log of given along a column on the left of the figure. simulations. Each point is thethe amount TNR of for accreted the (less given ejected) simulation. mass The divided lines by connect the the time points to for reach the same Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors the nuclear burning region has reached point is the amount ofgiven accreted simulation. (less ejected) The mass linessimulations divided connect is by given the the along points the time column for to on the reach the same the left of TNR the for figure. the is producing all the nuclear energy. PoS(GOLDEN 2017)066 S. Starrfield ˙ 1.4 M on higher cm while the higher 12 10 1.2 ∼ WD for which it takes more

). cm and the expanding material

12 10 1.0 ∼ (1.35M • O

M 6 M/M − 10 6 0.8 × ) to 6

0.6 (0.4M ˙ yearly time scale. This plot shows that not only is it possible for M increases downward for each WD mass. The time to the TNR

∼ M 4 − 1 yr: M31 RNe 80 yr: T CrB 45 yr: T Pyx 20 yr: RS Oph 10 yr: U Sco 10 × 0.4 1.0 0.1 10.0

100.0

1000.0 TIME to TNR (YR) TNR to TIME ˙ M and the value of The evolution is halted when the outer radius reaches While only a small amount of mass is lost in some of the simulations, that amountWhile would the simulations with NOVA were done with fully 1-dimensional hydrodynamics, they Figure 2: The accretion timea to different the TNR as a function of WD mass. Each of the data points is for decreases downward and to theincreases. right This since plot it also takes shows the lessThe approximate mass location recurrence to times of initiate for each the some of RN TNRM31 the as indicates RN best the its known which RNe. WD approximate explodes mass on recurrenceRNe outbursts time. to occur We on note low mass the WDs position but of they can the also occur for a broad range of Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors increase if the effects ofsimulations. common Finally, envelope as evolution the inTNR mass declines the of from binary the 6 system WD were increases, included the in accreted the mass necessary towere reach only able the to follow theouter first layers outburst to on begin the WD. expandingescape In velocity to and all large became cases optically radii. a thin. TNR Theescaping In amount occurred zones of a and were material few caused lost, not the if cases removed any, from was thestill tabulated the outermost but exerted mass the a mass zoning numerical zones because, pressure reached evenmass on if loss. they the were underlying escaping, layers they and if removed would cause excessive mass WDs. has become optically thin. The lower massmass WD WDs takes take years to only evolve days. to than The one most year extreme for result thedecline is expanding and for material then a to a slow 0.4 become recovery M luminousproduced which by and is ongoing caused hotter. nuclear by There burning the near is conversionnecessary the of an for surface, some initial the being of material long transformed the to into internal climb the energy, out potential of energy the potential well of the WD. PoS(GOLDEN 2017)066 × 4 . Other 1 − yr S. Starrfield , and 6 1

− M yr 7

− M 10 7 − × 6 10 . , exhibits a positive slope 1 × − 6 . yr . , and 1

, 1 1

. This implies an efficiency per 1 1 − M − 7 − yr − yr yr

10 M was followed using three different mass M M 8 × 8 1 8 were used. All WDs consisted of bare CO − − 15% to 20% for Roche lobe overflow, and 6 − − .

∼ yr 10 10 10

× × × M 6 6 . . 9 0 7 . − at a radius of 1.0 R 3 , 1 , 1 1 1 1 10 − ∼ − − and 1.35 M × yr yr yr

6

.

M M M 6 9 9 − − − , 1.0 M 10 10

cm (this is the prescription in NOVA); and (3) Roche Lobe overflow × × 6 12 6 . . , 1 1 − yr

M 10 shows the WD mass as a function of time for 4 different mass accretion rates for a − . For the three lowest mass accretion rates, after the initial growth to the first TNR, the WD accreting at a rate of 1 1 3 10

13% for the Eddington wind prescription, − WD accreting at 1 ∼ × yr 6

. M In this subsection we report on simulations done with MESA, because it is capable of follow- The major differences in the results using these 3 mechanisms was that the accretion efficiency Initial WD masses of 0.7 M Using MESA, we found that in all cases the simulation evolves to a TNR but only a small Figure 7 − 90% for the method used in NOVA. Therefore, in comparison with the NOVA studies, the Ed- 1.35 M evolutionary sequence settles into aeject recurring a pattern fraction of of mass theresumes accreted accretion until mass resulting the via in next an TNRs TNR Eddington which occurs. wind (70). The evolution Once at the 1 mass is lost, accretion ing multiple outbursts on anWD. accreting The WD MESA and, studies thereby, determining followedSolar the composition the and secular evolution experienced evolution of a of large the the to number WD quiescence, of TNRs and as resulting then it in the accreted ejection,portant renewal mass stellar in of loss, following accretion. material return the with long The term treatment a so, behavior of of how mass the rapidly. loss WDs, In after determining order if to theof mass determine TNR growth a the is occurs, 1.35M effects im- and, of if different mass loss prescriptions, the evolution Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors 4.2 Simulations with MESA 10 with the WD growing in mass at a rate of cores (C = 0.357, Oto = be 0.619) 1 at the beginning of accretion. The mass accretion rates were chosen (defined as the mass accreted minuscle) the was mass ejected divided by the mass accreted over a flash cy- loss prescriptions. These were (1)mass Eddington ejected wind when mass the loss outer (70);the layers surface (2) radius exceeded determining equaled the the 10 escape amount of with velocity, an had assumed become ejection optically rate thin, of 10 and ∼ dington wind method ejects a larger amountin of mass the accreted more mass slowly. than NOVA sobecause However, that the it the is WD Eddington more grows wind easily method implemented for was following used repeated in TNRs. the MESA simulations amount of accreted materialthat is the ejected evolutionary and sequences theburning exhibit WDs does the are not (65) growing occur. thin inwho shell An mass. investigated instability, expanded the which accretion study These of implies of studiesthat hydrogen-rich that the our show material sequences steady stability begin onto in of WDs. their thin stableWe Using region, identify shells but their these can with results, systems continued be accretion, with we found evolve those find into in instability. CVs (71), (dwarf, recurrent, symbiotic novae) that show no core cycle of approximately 20%. The recurrencewith time that for this of sequence the is M31 almost RN short that enough is to outbursting agree about once per year (69). accretion rates were used inthe order composition to of separate the different accreted regimes materialcycles was of or Solar. behavior the All when time simulations needed. required were for run Again, long-term for behavior either to many become TNR evident. PoS(GOLDEN 2017)066 . 1 − WD yr : 73),

M 7 S. Starrfield − 10 × . This implies an 4 before contracting . 1 −

yr

, we see that the positive , and 6 M 1 1 8 − − − WD will grow in mass with yr yr 10

. These are U Gem (1.2M × M

M : 76). Therefore, it seems possible 7 7 0

. − − 3 10 10 0.6M ∼ × ∼ × 6 6 . . , 1 1 − 8 . That result is shown in the lower right hand panel yr 1

− implies that a 1.35M M yr 3 8

− M 10 7 : 75), and Z Cam (0.99M − ×

10 6 . × , 1 4 1 . − yr

˙ M = 6 M 9 − 10 × : 74), IP Peg (1.16M 6

. . After approximately seventy-five years of accretion, the WD undergoes a helium flash 3 While the evolution shown in Figure repeated hydrogen flashes, we alsowould cause tested the the WD evolution to to growevolved in determine a radius sequence if to with that accretion of at a a red giant higher as rate proposed by (37;which 36). does Therefore, not we eject any material. The radius of the WD expands to 0.056 R Figure 3: The WD mass as a function of time for 4 different mass accretion rates for a 1.35 M Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors accreting at 1 of Figure For the three lowest mass accretionsequence rates, settles after into the a initial recurring growth patternof to of the the mass accreted first accretion mass TNR, resulting via the in an evolutionary TNRsnext Eddington which wind TNR eject (70). occurs. a Once fraction the Concentrating mass on is lost, the accretion evolution resumes at until 1 the slope shows that the WD is growing in mass at a rate of efficiency per cycle of approximatelyenough 20%. to The agree recurrence with that time of for the this M31 sequence RN is that almost is short outbursting about oncematerial per either year on (69). the surfaceof of (72), the who WD report or that innovae the have their WDs WD ejecta. masses in larger CVs Our than are the results canonical growing could value in explain of mass. the In findings addition, the best studied dwarf SS Cyg (0.8M that some Dwarf Novae couldfrom be mixing SN accreted Ia progenitors with if WDoutbursts there could core act is material. as some a means For barrier to to example, prevent this a convection mixing. thick Further helium work is layer warranted. from previous PoS(GOLDEN 2017)066 , and

S. Starrfield , 1.25 M

• O • O • O • O , 1.15 M • O • O

1.35M 1.25M 1.15M 1.00M 0.8M 0.6M 60006000 onto CO WDs (core composition 1 , 1.00 M −

. The helium flashes are not violent yr 1

− M yr . This radius is less than the typical Roche

1 10 , 0.8 M − M −

7 10 − 9 40004000 × 10 6 . × 6 . Time(s) 2 ∼ CO 25_75 MDTNR 20002000 O) with masses of 0.6 M 16 00 C and 50% • • • • O O O O 12 • • O O 88 88 88 88 00 1010 1010 1010 1010

0.6M 0.8M ×× ×× ×× ×× 1.00M 1.15M 1.25M 1.35M

For this study we accreted at a rate of 1 Our conclusion from this part of the study, where we accrete Solar composition material onto We continue with new simulations of accretion onto CO WDs where we assume that mixing 11 44 33 22 Temperature (K) Temperature Figure 4: The variation with timetime of when the peak temperature temperature in occurs thematerial. for deepest the hydrogen-rich We simulations zone have with around plotted 25% the theidentification core results with material for mass and is all 75% given six accreted inin simulations the time which box. to only The improve differ curve its by for visibility.an WD each increasing As sequence mass. function expected, has of the The been WD peak shifted mass. temperature slightly achieved in each simulation is was 50% Lobe radius of a WD inmass a of CV system. the Therefore, WD such fromflash, helium either flashes the do Roche WD not undergoes Lobe stop succeeding overflow thethe helium or growth flashes in WD envelope roughly the ejection. grows every 75 in After years. mass the During initial at these helium a flashes, rate of Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors and the peak surface velocity reaches only 10 km s WDs of various masses andCO use WD various in accretion a rates typical (with CV both system is NOVA and growing MESA),4.3 in is mass Accretion that toward onto the the CO Chandrasekhar WDs Limit. where Mixing of Core with Accreted material isof assumed accreted material occursin with core an material. earlier study Wethose of use CNe NOVA accretion that for onto formed thisthat CO new dust. formed study white Since and dust dwarfs that note and, (77) timebeen that in we produced an addition, were in additional a CNe primarily number number explosions. concernedoutbursts of of (78; There CNe with pre-solar 79; are have grains now 80; been have a 81;which observed been number improves 82). the of found rates studies In that for of many addition, may of grain we have the formation now light in nuclear use CN reactions. the STARLIB reaction rate library (55) because mass is being lostejection via event an that occurs Eddington with wind. the mass Thus, loss a prescription helium used flash in is NOVA. not the dynamic mass PoS(GOLDEN 2017)066 ∼ simulation S. Starrfield

C abundance strongly 12 20002000 . 4 • O • O • O • O • O • O .

1.35M 1.25M 1.15M 1.00M 0.8M 0.6M C present in the material the more 12 15001500 . Moreover, the WDs in 4 of the nearest CVs

10 K and the temperature rise to the peak of the TNR 35M 8 . 1 10 10001000 ∼ × Time(s) K and convection was well underway. The accretion of So- 7 10 × 0 . 500500 3 ∼ CO 50_50 MDTNR 00 • • • • OOOO • • OO 88 88 88 88 . Although it is commonly assumed that a CO WD should not have a mass exceeding 00 , our simulations, which suggest that WDs can accrete mass and grow to the Chandrasekhar C in these simulations when we switch to this composition, the peak temperature is higher

1010 1010 1010 1010 12

0.8M 0.6M ×× ×× ×× ×× 1.25M 1.15M 1.00M 1.35M

In order to increase the amount of accreted material, we assume the results of the multi- There is a major change in the way we treat the composition of the accreting material in this 22 88 66 44 Temperature (K) Temperature 15M . 1 Limit, indicate that there should be massivewe CO note WDs in that CN LMC systems. 1991 In exhibitedprobably support a of requires super this a Eddington assumption, luminosity WD for mass more exceeding than 2 weeks (83) which lar material onto WDs of(40; various 85; masses 86). and mass Atboth accretion this nuclei rates point abundances and has in the been the associated published evolution microphysics) that we elsewhere we switched have to used in the our mixed previous studies composition (this includes dimensional studies that show that sufficientenvelope material from by the convectively core associated is instabilities dredged-upences into after the therein). the accreted TNR Therefore, is weburning well first regime underway exceeded accreted (84, a and Solar refer- Mixture until the temperature in the nuclear 1.35 M are more massive than the canonical value for single WDs of 0.6M rapidly the simulation evolves to a TNR with less accreted mass. study as compared to ourthe previous studies. mixing of In core our previous andaccrete work, accreted half except material core for and occurs (79), half from we Solartests the assume (accreted) that beginning that material will of (49, be the and published references simulation elsewhere, therein). so we From that came a we to variety of realize that the initial for each of these massesreaches than a in the peak 25% temperature core exceedingis matter 6 so simulations. rapid In that fact, the aevolution time 1.35M shock for forms this series and of moves sequences through is shorter the than envelope that in in Figure a few seconds. Note that the influences the amount of accreted material since the more Figure 5: The variationand with 50% time accreted of matter the formore temperature the for six the WD masses simulations that with we 50% studied. core matter Because there is significantly Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors PoS(GOLDEN 2017)066 4

C ) in 12 1 − ) around

S. Starrfield ) in solar units (L 1 • O • O • O • O • O • O − 60006000 1.35M 1.25M 1.15M 1.00M 0.8M 0.6M K. Because the abundance of 8 10 × 3 . 11 40004000 calculation reaches a peak temperature exceeding

K while the simulation on the lowest mass WD that we 8 10 shows the same evolution but for the simulations with 50% Time(s) × 5 4 . CO 25_75 MDTNR CO 25_75 C. The 1.35M 20002000 . Figure 5 12 , reaches the lowest peak temperature of 1 ) around the time of peak temperature during the TNR on both sets of simulations.

00

• • • • O O O O • • OO 66 88 77 99 1111 1010 1212 K and the temperature rise to the peak of the TNR is so rapid that a shock forms and moves 8

1010 1010 1010 1010

0.8M 0.6M 1010 1010 1010 1.35M 1.25M 1.15M 1.00M The next two figures show the variation with time of the total nuclear luminosity (erg s The following plots show the evolution of the various simulations done for this paper. The Total Nuclear Luminosity (Solar Units) (Solar Luminosity Nuclear Total 10 × is less in these simulationstakes than longer in to the go 50% through the core peakaxis - of is 50% the longer accreted TNR than and in matter begin Figure simulations, the the decline to evolution quiescence so that the time studied, 0.6M 6 through the envelope in a few seconds. reaches the highest temperature of 3 core and 50% accreted material.there The peak is temperature significantly is higher more for each of these masses because solar units (L shows the variation with time of theof temperature peak in temperature the in deepest the hydrogen-rich zone simulation.core around matter This the and plot time 75% shows accreted the matter. evolution As for expected, the the simulations simulation with on a 25% WD with a mass of 1.35M Figure 6: The variation with time of the total nuclear luminosity (erg s (49; 50, and references therein)and and the proceed decline. through the In addition, resttion we of of assume the either the evolution 25% results to core of peak and (87)are temperature 75% and identified accreted use on material an or the accreted 50% plus plotscompositions: core core as thermal and composi- structure, either 50% spatial accreted 25_75 structure, material. or and Those total 50_50. amount of The accreted same mass. initialacronym: model MDTNR is stands used for fordescribe the Mixing either two the During Solar the accretion TNR. results or Other the studies Mixing to From Beginning be (MFB) reported results. elsewhere Figure Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors the time of peak temperaturezones during taking the part TNR in on the explosion bothmass to is sets given obtain of on the the simulations. plotted plot numbers. and Wesmall the integrated “glitches” The evolution that over identification time appear is all with on the each the same decline WD in as are for caused small by each amounts convection of of moving the in fresh temperature and nuclei plots.The out to and the bringing nuclear burning regime. PoS(GOLDEN 2017)066 Be 7 Li and 20002000 7 Be. For 7 • O • O • O • O S. Starrfield • O • O Li in recent 7 Be can decay 7 0.8M 0.6M 1.35M 1.25M 1.15M 1.00M Be abundances in Be and the amount 7 7 Be and 7 15001500 while the ejected abundances of 13 − 10 53 day half-life, it is also a measure of ∼ shows our predicted ∼ 8 10001000 Li) has required us to redo the earlier calculations Li with a 12 Time(s) 7 7 CO 50_50 MDTNR shows the plot for 50% core matter (and 50% accreted 7 but for the simulation with 50% core matter and 50% 6 , respectively. 500500 Be decays to 5 . The TNR reaches sufficiently high temperatures to deplete the 7

Li Be abundance. (mass fraction). All our sequences eject enriched 7 7 5 − Li to and Figure Li abundances by mass fraction are 7 7 4 00 Be+ 7 • • • • O O O O • • O O Li present in the accreted material so that the ratio is really that of the ejected 88 66 shows the evolution of nuclear energy production for the simulations with 25% core mat- 7 1010 1212 1414 6 1010 1010

0.8M 0.6M 1010 1010 1010

1.25M 1.15M 1.00M 1.35M

There are two major results that we present in the next two figures. First, is the amount of

O Total Nuclear Luminosity/L Nuclear Total Li so we only report the • 7 Be are on the order of 10 to matter). Note that bothwith the those horizontal in axes Figure and vertical axes are different for each plot but agree the ejecta as a functionplot of the WD ratio of mass fororiginal all the CO enrichedexample, sequences the ejected done for7 this paper. We of enrichment increases as a function of WD mass. We halt the evolution before the ter (and 75% accreted matter) while Figure Figure 7: The same plot as in Figure produced during the TNR. Since the amount of lithium produced inmay the outburst. be Clearly, the CN galactic should produce sourcefor a of CN great this deal explosions, of with nucleus a as morehigh originally recent dispersion predicted study spectroscopy by by (88) of (90). forsection bright The which red discovery CN also of giants near includes both and a the (89) new peak discovery of of their outburst (reviewed in the next Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors accreted matter. Note that the horizontal and vertical axes differ in these two plots. We integrated over all zones takingtification part with in each the WD explosion to massof obtain is the the given temperature plotted on plots. numbers. the The Themoving plot small iden- “glitches” in and that the and appear evolution out on time and theFigure is decline bringing the are in caused same small by as amounts convection for of each fresh nuclei to the nuclear burning regime. with updated compositions and microphysics. Figure PoS(GOLDEN 2017)066 ≤ , the TNR S. Starrfield 1.41.4

Li 7 sequence ejects

Li to 7 sequence with 25% core Be+

) 7 1.21.2 • O ) or gaining mass (WD mass

Ca are overproduced in CO nova 40 0M . Li present in the accreted material so 7 1 ∼ Cl, and 1.01.0 35 S, 33 13 P, ). This plot is based on similar plots in (91). The 31 10 O, CO White Dwarf Mass (M 17 0.80.8 N, Be.(Mixing From Beginning = MFB) 7 15 C, 13 Be abundances in the ejecta as a function of WD mass for all the CO 7 Be, 7 0.60.6 MFB 5050 MDTNR 2575 MDTNR 5050 MFB 2575 shows the second major result: the percent of ejected mass (ejected over accreted) 9 1010 100100 10001000 ). Therefore, we predict that for most observed CO classical novae the WD is gaining mass

1000010000

Figure Finally, in this section we show the production plot for the 1.35M O

Li Be/ Li+

• Be is important. As long known, the CN outburst on a CO WD ejects mainly the odd light

7 7 7 7 ejecta. production plots for the other sequencesplot will be only published shows elsewhere. the While stable normallyof nuclei a in production the ejected material,isotopes. for our It simulations shows the that ejecta abundance Figure 8: The predicted enriched sequences done for this paper. While we plot the ratio of as a function of WDlooks mass strange for (a all negative 20%) the becauseejected sequences we that almost need we to no evolved. emphasize material the Thetoward as fact the bottom that of a Chandrasekhar most the Limit. result of vertical ourare of The axis sequences those only the where we sequences TNR mix that after and, the ejectcore TNR therefore, matter a is and significant underway the (MDTNR). 75% amount Examining WD accreted of thea is sequences (Solar) material sufficient with composition growing 25% amount we in of find mass materialresulting that explosion. and only Clearly, the the those 1.25M sequences WD with ishave 50% either core probably matter the losing and WD mass 50% losing accreted as mass matter a could (WD masses result exceeding of the TNR and as a result of the explosion. Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors reaches sufficiently high temperatures tothat deplete the the ratio initial is that of the ejected 1.0M matter and 75% accreted matter (Figure PoS(GOLDEN 2017)066 ). The 12 S. Starrfield and Figure 1.41.4 11 = JD 2,457,097.134). A low emission line and an emerging 0 β Li, here we report on our (Wagner, 7 ) 1.21.2 • O 14 1.01.0 Li was reported for V1369 Cen (92). V5668 Sgr was 8.4 m Large Binocular Telescope (LBT). PEPSI is the 7 Be which decays into × 7 CO White Dwarf Mass (M Li I 6707.76 Å in the post-outburst spectra of V5668 Sgr (Nova 0.80.8 7 0.60.6 MFB 2575 MFB 5050 Solar MDTNR 2575 MDTNR 5050 00 6060 4040 2020 8080 -20-20

100100

Given our predictions for enriched We observed V5668 Sgr on 30 nights between 2015 Apr 3 and 2016 June 5 UT. Our detections Ejected Mass/Accreted Mass (%) Mass Mass/Accreted Ejected Li in V5668 Sgr 7 7 mag as the result of dust formation (ATEL 7643, 7748, 7862, 7986) reaching a minimum on highest resolution spectrometer available on any 8-10part m of class the telescope. 3830Å Our to spectra 9065Å270,000. covered region Six all in cross or three dispersers cover exposures six at wavelength spectral settings where resolutions two of are 43,000, observed simultaneously. 120,000 or equivalent width of theincreased. Li line We declined did not duringhigh detect the resolution this observations optical line as spectroscopy byInstrument the using Day (PEPSI: ionization the 42 93) of Potsdam built of the Echelle for the ejecta Polarimetric the outburst. 2 and Our Spectroscopic discovery was based on Figure 9: The percentThe of value ejected of “-20” mass on divided theto by bottom show the of clearly the accreted that vertical mass most axistherefore, of as was the done a the sequences to function WD ejected expand of was the almostthat WD vertical no growing axis mass. material eject in in as a order mass a significant toward result(MDTNR). amount of the the of Chandrasekhar TNR Limit. material and, are The those only where sequences we mix after5. the TNR is underway of Li were significant and persisted over the course of 7 nights (Figure Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors Woodward, Starrfield et al.from 2018 in explosive production preparation) second of directSgr detection 2013 of No. spectral lines 2).discovered arising by The J. first Seach detectionresolution (IAUC of spectrum 9275) obtained by on Powles (IAUC 2015 9275) showedFe Mar an H II 15.634 emission UT line spectrum (t suggesting5th that magnitude it in was an mid-March. Fe∼ II-type After classical a nova. slow The decline novaday reached for 110. the The first light curve 80 then days, recovered to the 9th brightness mag declined by the end of our observations. PoS(GOLDEN 2017)066 C. 12 S. Starrfield Ca 4040 Ar Cl Li mass fraction ratio of 7 S P ” and all isotopes of a given -axis is the atomic mass and Be/ ∗ x 7 3030 CO 25_75 MDTNR CO 25_75 Si • O Be in this plot because of its large Al 7 1.35M Mg Na A Ne Be in V5668 Sgr on day 69 and a comparison of 15 7 F 2020 Be was created in the TNR as predicted by (89) and 7 O C allowing more material to be accreted before the TNR is N 12 C Be 7 1010 sequence. However, we include Li is depleted during the evolution. The 7

Li + 7 He H 00 44 22 00 66 -6-6 -2-2 -4-4 In addition, reducing thelower metallicity also to reduces values the in initial agreement with the LMC, SMC, or even outburst that is less violent and hardly any material (accreted plus core) is ejected during the initiated (95; 79). New studies with lower metallicities are in progress. 1010 1010 1010 1010

-axis is the logarithmic ratio of the abundance divided by the Solar abundance. As in (91), 1010 1010 1010

y

O X/X 1. The amount of accreted material is an inverse2. function ofTherefore, the accreting Solar initial material abundance (rather of than mixed) allows for more matter to be accreted. 3. Therefore, either no mixing with the core or mixing too early with the CO core results in an • (90). 6. Conclusions 4200 on Day 13. This strongly suggests that the the most abundant isotope ofelement a are given connected element by is solid designatednumber lines. of by isotopes an Any are “ significantly isotope enriched above in 1.0 the is ejecta. overproduced in the ejectaPEPSI and can a also be fedTelescope by (VATT) and a the 350m LBT. fiber (94) runningtheir observed between and the 1.8 our m results Vatican gives Advanced for Technology the first time a measurement of the Figure 10: The abundancesthe (mass ejecta fraction) for of the theoverproduction. 1.35M stable In isotopes fact, from hydrogen to calcium in Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors PoS(GOLDEN 2017)066 S. Starrfield Li after we 7 Be which decays to 7 16 . Such studies are in progress. 1 − yr

M Li region and showing that the wavelength agrees in velocity with Ca, Fe, H, and 7 10 − 10 × Li absorption line has faded by day 20.3 and is gone by day 69.2 as the ionization steadily 7 0 . Be in CN explosions. have ended our simulations.7 This result is in agreement with the observations of enriched tures and ejected more materialand moving 75% at accreted matter. higher The velocities exceedingly than highvations. ejecta those This velocities with result do only can not likely agree 25% with be2 core the fixed obser- by increasing the mass accretion rate to values above during the TNR and does not affect the total amount of accreted material. with observations of the ejecta abundances (84, and references therein). outburst. The WD is growingwith in NOVA and mass. repeated outbursts We with have MESA. shown this both by following one outburst 7. Our simulations confirm that CO novae are overproducing 6. Simulations with 50% core matter plus 50% accreted matter reached higher peak tempera- 5. This mixing occurs via convective entrainment (dredge-up of core gas into the accreted gas) 4. The multi-dimensional studies show that there is sufficient mixing during the TNR to agree Figure 11: Spectra were obtainedusing on 30 either nights 1 between x 2015so 8.4 April that 3 m and our or 2016 spectral 2 June resolutiona 5. x was fixed 12 8.4 either 120,000 epochs m 270,000 for (1 LBT theof km/s) Dispersion VATT. mirrors. the or 7 3830Å mÅ/pixel. 120,000 18 to (2 epochs 9065Å Our km/s)smoothed. region. spectral using for coverage the These These the included spectra 3 1.8 LBT all were plots m and or reducedemphasizing show VATT part the using fiber V5669 the Sgr feed PEPSI on pipeline 3Na. and days The are (day not number is given on top of each panel) increased. Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors PoS(GOLDEN 2017)066 S. Starrfield in mass as a result of the shrinking in mass as a result of the Classical Nova growing 17 of the accreted material, implying that the white dwarf is material implying that the white dwarf is nova. phenomena. Since thesimulations, properties we of predict that observed the WD COa in nova result the of typical outbursts CO the agree nova outburst. explosions better is growing with in these mass as SS thanks F. Giovanelli for inviting SS to give this talk and G. Shaviv for interesting discus- 8. Simulations with 50% core and 50% accreted matter ejected, in some cases, a large fraction 9. Simulations with 25% core and 75% accreted matter ejected only a fraction of the accreted Figure 12: This figure shows theto evolution day of 21.3. the lithium line from day 13.3 (our first observation) sions at the meeting.Program This grant work was 14-ATP14-0007 supported and in theSS part acknowledges U.S. partial by DOE support NASA under from underthe NASA the Contract U.S. and Astrophysics No. Department HST Theory of grants Energy, DE-FG02- to Office 97ER41041. ASU of and Nuclear WRH Physics. is Our supported results by benefitted from collabora- 7. Acknowledgements Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors PoS(GOLDEN 2017)066 S. Starrfield 18 Hydrodynamic Simulations of CNe: Accretion onto CO White Dwarfs as SN Ia Progenitors tions and/or information exchange withinresearch NASA’s Nexus coordination for network Exoplanet sponsored System by Science NASA’s Science (NExSS) Mission Directorate. 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