Novae a theoretical and observational study Monika D. Soraisam M¨unchen 2016 Novae a theoretical and observational study Monika D. Soraisam Dissertation an der Fakult¨at f¨ur Physik der Ludwig–Maximilians–Universit¨at M¨unchen vorgelegt von Monika D. Soraisam aus Imphal, Manipur, Indien M¨unchen, den 26. Februar 2016 Erstgutachter: Prof. Dr. Rashid Sunyaev Zweitgutachter: Prof. Dr. Gerhard B¨orner Tag der m¨undlichen Pr¨ufung: 31. Mai 2016 Contents Zusammenfassung xi Summary xiv 1 Introduction 1 1.1 Novae ...................................... 1 1.1.1 EvolutionofCVs ............................ 2 1.1.2 Theoryofnovaexplosions ....................... 5 1.1.3 Progressofthenova .......................... 6 1.2 SNeIaandtheenigmaoftheirprogenitors . 7 1.2.1 Singledegeneratescenario . .. .. 9 1.2.2 Doubledegenerateandotherscenarios . 11 1.3 Scope for novae in modern time-domain surveys . .. 12 2 Constraining the role of novae as progenitors of type Ia supernovae 13 2.1 Introduction................................... 13 2.2 Relation between supernova and nova rates . ... 14 2.3 StatisticsofnovaeinM31 ........................... 18 2.3.1 SNIarateinM31............................ 18 2.3.2 NovarateinM31............................ 19 2.3.3 ContributionofnovaetotheSNIarate. 20 2.3.4 Fastnovae................................ 22 2.4 Temporal sampling and completeness of nova surveys . .... 22 2.5 Discussion.................................... 27 2.6 Conclusions ................................... 32 3 Upper limits on mass accumulation by white dwarfs in the unstable nu- clear burning regime 35 3.1 Introduction................................... 35 3.2 Derivation of f(MWD) ............................. 35 3.3 Incompleteness correction of Arp’s survey of M31 (1953-1955) ....... 36 3.4 NovaratedistributioninM31 ......................... 38 vi Contents 3.5 Constraints on mass accumulation in the nova regime using the M31 nova sample...................................... 39 3.6 Summary .................................... 40 4 Populations of post-nova supersoft X-ray sources 41 4.1 Introduction................................... 41 4.2 WD mass distribution in novae in M31 . 43 4.3 Post-outburstSSSphaseofNovae . .. 46 4.4 Post-novaSSSpopulationinM31 . 47 4.4.1 Luminosityfunction .......................... 51 4.4.2 Effective temperature distribution . 54 4.5 Comparison with XMM-Newton observationsofM31 . 56 4.6 Discussion.................................... 57 4.7 Summaryandconclusions ........................... 60 5 A novel method for transient detection in high-cadence optical surveys and its application for a systematic search for novae in M31 63 5.1 Introduction................................... 63 5.2 iPTFM31data ................................. 66 5.3 Spatialrecurrence mapoftherawdetections . .... 67 5.4 Themethod................................... 69 5.4.1 Source detection using WAVDETECT ................... 69 5.4.2 Applicability of WAVDETECT ....................... 72 5.4.3 Characteristics of WAVDETECT detections in the time-domain context 75 5.5 A systematic search for novae in the iPTF M31 observations . .... 79 5.5.1 Lightcurve construction via forced photometry . .. 79 5.5.2 Lightcurvefilteringfornovae. 80 5.6 Results...................................... 82 5.7 Discussion.................................... 86 5.8 Summary .................................... 87 6 Conclusions and outlook 89 A A quick primer of the expansion of the universe 93 B Nova light-curve template 95 C Peak magnitudes of novae 101 Bibliography 105 Acknowledgments 120 List of Figures 1.1 Artist’simpressionofaCV .......................... 2 1.2 Stability conditions for the hydrogen shell burning on the WD surface... 10 2.1 Variation of the ignition mass of the nova and the mass-loss timescale with themassoftheWD .............................. 15 2.2 Cumulative and differential t2 distributions of novae produced by a successful SNIaprogenitor ................................ 17 2.3 Maximal contribution of novae to the SN Ia rate of M31 as a function of assumedmassaccretionrate . 21 2.4 Detection efficiency for novae in M31 as a function of their decline time t2 . 23 2.5 Cumulative detection efficiency of fast novae with t 10daysinM31 . 26 2 ≤ 2.6 Comparison of the ignition mass of nova computed by different authors . 28 2.7 Comparison of observed maximum-magnitude rate-of-decline relation with the results of multicycle nova models of Yaron et al. (2005) . .. 29 3.1 Detection efficiency η ofArp’ssurveyofM31(1953-1955) . 37 3.2 Observed differential nova rate distribution in M31 . .. 38 3.3 Constraints on the fraction of mass that can be accreted in the nova regime atdifferentWDmasses............................. 40 4.1 Theoretical decline time t2 of novae as a function of the WD mass from Yaronetal.(2005) ............................... 44 4.2 (left panel) The inferred WD mass distribution in novae in M31 using the nova samples of Arp (1956) and Darnley et al. (2004) and (right panel) assumed theoretical WD mass distributions in novae . 45 4.3 (left panel) Evolution of the post-nova (unabsorbed) soft X-ray luminosity in the 0.2-1.0 keV band for different WD masses. (right panel) Peak soft X-ray luminosity of the light curves as a function of the WD mass . 48 4.4 (left panel) Evolution of the effective temperature (Teff ) of post-nova SSSs from the nova evolutionary tracks of Wolf et al. (2013). (right panel) Peak effective temperature asafunctionoftheWDmass . 49 4.5 Cumulative (left panel) and differential (right panel) luminosity functions of the post-nova SSSs in M31 for the different WD mass distribution models . 52 viii List of Figures 4.6 Cumulative effective temperature distribution of post-nova SSSs in M31 with 36 unabsorbed luminosity Lx & 10 erg/s (left panel) and the corresponding differential distribution (right panel) ..................... 53 4.7 Effective temperature – luminosity plot for the post-nova SSSs in M31... 55 5.1 A section of a typical M31 field difference image from the iPTF pipeline, containingthebulge .............................. 64 5.2 The outer part, half a degree northward of the center of M31, of the typical difference image from the iPTF pipeline . 65 5.3 Distribution of the observation epochs of the iPTF M31 data . .... 66 5.4 The number of sources detected by the iPTF DI pipeline against the differ- enceimagenumberfortheM31field . 67 5.5 The spatial recurrence image zoomed in on the bulge of M31 . ... 68 5.6 The outer part of the spatial recurrence image, about half a degree north- wardofthecenterofM31 ........................... 70 5.7 The hits image formed by registering the total number of occurrences of any raw detection in the M31 field from the iPTF DI pipeline . 71 5.8 The hits image zoomed in on the bulge with the WAVDETECT sources . 73 5.9 The outer part of the hits image, half a degree northward of the M31 center, with the WAVDETECT sources .......................... 74 5.10 Background pixel value distribution of the hits image . ... 76 5.11 Distribution of counts in the source regions for the detections made by WAVDETECT .................................... 77 5.12 Distribution of the magnitudes for the sources detected in the reference image and those WAVDETECT sources with counterparts in the reference image 78 5.13 Examples of lightcurves of the candidates constructed via forced photometry usingDAOPHOT................................ 81 5.14 Lightcurves of the eight candidates obtained from the nova selection algorithm 83 5.15 Lightcurve obtained using DAOPHOT for the candidate at the position of missednovaM31N2013-10b . 85 B.1 Raw (left panel) and transformed (right panel) light curves of the Galactic nova sample selected from the S class of the catalog compiled by Strope etal.(2010)................................... 96 B.2 Raw (left panel) and transformed (right panel) light curves of the M31 nova samplefromtheWeCAPPcatalog. 97 B.3 Raw (left panel) and transformed (right panel) light curves of the M31 nova samplefromthePTFcatalog ......................... 98 B.4 Co-aligned template light curves from the three different nova samples . 99 C.1 Relation between the maximum magnitude and the rate of decline for ex- tragalacticnovae. ................................ 102 List of Tables 4.1 Models of the WD mass distribution in novae . 43 4.2 Theoretical nova rate for the different WD mass distribution models. 50 4.3 Monte Carlo simulation results for different models of WD mass distribution innovaeinM31................................. 56 5.1 Summary of WAVDETECT detections ...................... 79 5.2 iPTF recovery of M31 novae reported between 09/2013 and 01/2014.... 84 C.1 Mean nova peak magnitudes and their standard deviations . .... 103 x List of Tables Zusammenfassung Die vorliegende Arbeit pr¨asentiert Studien von Novae, die sowohl theoretische als auch Beobachtungsaspekte beinhalten. Da Novae auf Weißen Zwergen (WZn) beheimatet sind, wurde Interesse an ihnen im Zusammenhang mit m¨oglichen Vorg¨angern von Supernovae der Klasse Ia (SNe Ia) generiert. Bei einer Novaexplosion wird der WZ nicht zerst¨ort. Stattdessen stellt er nach dem optischen Ausbruch weiterhin durch stabile Nukleosynthese innerhalb des ¨ubriggebliebenen Wasserstoffmantels Energie zur Verf¨ugung. Demzufolge verschiebt sich das elektromagnetische Spektrum der Novaemission zu h¨oheren Energien, bei denen diese l¨anger anh¨alt als im optischen Bereich. Eine Konsequenz ist, dass die Mehrheit der beobachteten superweichen R¨ontgenquellen als Novae identifiziert werden konnten.