PoS(GOLDEN 2017)054 https://pos.sissa.it/ 9% longer than the orbital period), as reported earlier by other ∼ ∗ [email protected] [email protected] [email protected] [email protected] Speaker. authors from observations in 2005.radic events, Possibly, because superhumps in arise all the quickly other in observingdetected. runs RR analysed We Pic, no also significant but superhump determined are signal an was hump spo- actual period version and orbital of period, the analysing Stolz-Schoembsstars, separately and relation dwarf conclude between novae, that classical super- this novae and relationclysmic nova-like is variables of (CVs), general in validity spite fortioned of above. all small We superhumpers emphasize but among the significant importance the differences of cata- suchof among a the the study interrelation sub-types in between context men- the with different the sub-classes stilllong-term open of CV question CVs, evolution. crucial for our understanding of the We present an re-analysis ofclassical all nova RR available Pictoris. time-resolved The photometry hump lightvariations from curve over phased the the with literature last the 42 orbital for period years the variations shows in in significant shape the and disc amplitude structure. which Additionally,in possibly we 2007, are found caused with evidence by the for long-term same the period presence ( of superhumps ∗ 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 Variables11-16 and September, Related 2017 Objects IV Palermo, Italy Linda Schmidtobreick European Southern Observatory, Chile E-mail: Nikolaus Vogt Universidad de Valparaíso, Chile E-mail: Claus Tappert Universidad de Valparaíso, Chile E-mail: Irma Fuentes Morales Universidad de Valparaíso, Chile E-mail: Photometric long-term variations and superhump occurrence in the Classical Nova RR Pictoris PoS(GOLDEN 2017)054 ]). 18 ], 15 min 27 88pc; [ ± 48 h, which has . 3 388 = = d orb ] derived a more precise P 7 mag. The photometric 2 mag in 1925. Currently . . 26 ]). ]. In general, the following 1 1 12 28 = ∼ V ] in the V band. In all of them at V 3 ]. In a recent work [ ] from 1972 to 1984 over 23 nights. In eight of 19 1 27 ] during four nights in December 1972 and three nights of ] at its maximum brightness 24 5 ]. Additionally, they have undergone several changes and tran- 24 ]. The presence of superhump in classical novae can be used as a tool to under- 19 ], QPOs and positive superhumps [ 6 ) by [ sh P least one complete orbital cycle was observed. them at least one orbital period was covered. Light curves in five nights observed in January 1980 by [ white light data in January 1974.cycle. All these observations have covered more than oneHigh-speed orbital photometry in white light of [ UBV photometry observed by [ The motivation for the present investigation was the discovery already mentioned of an addi- The light curves of RR Pic analysed are composed of published observations made by different Cataclysmic variables (CVs) are close interacting binary systems where a late-type dwarf star One of the brightest and nearest novae known is RR Pictoris (distance • • • tional period that is 8.6 perperiod cent ( longer than the orbitalstand one, the which state was of interpreted the as system a in superhump general, and of theIn disc properties this decades work after we the present nova anova eruption. explosion re-analysis observations. of all We also available add photometrichump new data light data curves of during taken RR the during Pic past 2013–2014 after decadesical and its in search study a classical for the systematic superhumps way. orbital in Furthermore RRnovae, we Pic nova-like perform and stars a compare and method- our dwarf results novae. with those known for other classical 2. Compilation of historical light curves and new observations authors, complemented by newunpublished data data obtained is given in as on-line 2013 supplementary and data associated 2014. to [ An observing log for hitherto orbital ephemeris from all availablefurthermore photometric found variations humps in observed the in O–C diagram the that past could five imply decades. the presence They of a third body. campaigns were analysed: sient features over the decades since its eruption, showing eclipse-like characteristics [ fills its Roche lobecase and of a transfers weak mass –or towards absent–star magnetic is the field accumulated white of forming the dwarf an WD,primary accretion (WD) the reaches disc primary transferred a around material critical the component. from value, WD. the thefusion Once secondary reactions surface In the producing temperature accumulated a of mass thermonuclear the on runaway, WD whichunderwent the increases is a known and nova as eruption triggers a are nuclear nova called eruption. classical CVs novae (for that details see [ Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris 1. Introduction Its nova eruption was discovered by [ the stellar remnant appears to be in a state of quiescence, with periodicities [ light curves of RR Pic show as a permanent feature a periodic hump of been identified as the orbital one [ PoS(GOLDEN 2017)054 = (3.1) orb P E ) 15 ( . sh P ]. The integration time was 30 4 895 c/d, corresponding to . 6 = 145025959 . 0 d f 0 ) + ] during the first semester of 2005, covering 18 15 ( 19 2 3664 . ], which is based on Discrete Fourier Transform (DFT) to 7 in the early 1980s. As a second permanent light curve property ) the step-like feature seems to be less pronounced. 2438815 m m 0.2 ) = 0.05 > ∼ max ( 04 software [ . 1 HJD PERIOD in 2005 and ]. The mean phased-folded light curves were computed by averaging the data points m 26 ] obtained UBV photoelectric photometry in five nights in October 1982. We analysed the 6 . The orbital phase of each campaign was calculated using the long-term ephemeris of the seconds with a cadence of 2-3 minutes. published B differential band light curves. The Center Backyard Astrophysics (CBA)differential kindly photometry provided in us white with light1999 additional and of unpublished 2007 RR by different Pic, amateur obtained astronomers. in aDifferential total photometric data of obtained 50 by [ nightscomplete between orbital cycles. In addition we obtained newand V 16 band March 2014, photometry using in theDesert 81 robotic (ROAD), nights situated 40 between in cm 21 telescope San November at Pedro the 2013 de Remote Atacama, Observatory Chile Atacama [ [ h To ensure that the residual light curves of all campaigns were not contaminated by the presence The orbital light curve properties of RR Pic during the past 42 years can be summarised in We used the • • • • 48 . of harmonics and aliases of the orbital period, we extracted up to the sixth orbital harmonics from 3.2 Search for superhumps: a new detectionIn in 2007 RR Pic, thewith superhump smaller phenomenon amplitude than is that anpossible of in additional the the orbital periodic residual hump. data modulation afterfound Therefore, in subtraction close of a the to the search the light dominant for orbital frequency. curve superhumps one Any is could additional frequency be only potentially associated with a derived by [ the following way: thebetween dominant 0.28 orbital hump waswe always found present, a secondary but minimum withpresent. or variable step-like When amplitude the feature hump at amplitude phases is 0.65–0.7like low, this feature which feature corresponding seems is to to more the pronounced, be total looking minimum always for like in a an the large eclipse- whole amplitude orbital hump light ( curve. On the other hand, and are shown in Fig. 3.1 Variations of orbital light curve 3. Results Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris search peridiocities in the lightknown curves. orbital frequency In as all the3 campaigns dominant the peak respective close periodogram to showedorbital the hump maximum: PoS(GOLDEN 2017)054 (3.3) (3.2) 02 h. The 6 per cent . . 0 8 ± ≈ ε 77 . noise level, which 3 ] for details) in the 7 σ = sh P . 2 E E ) ) 6 4 ( ( we show the Fourier spectra of (c). Within the errors, this new 2 3 1569 1577 . . a). Instead, we do find a clear detection d d 0 0 ]). The superhump light curves shapes 3 + + 13 ,[ orb ] in 2005, with a period excess 04 c/d is equivalent to . 07167 54719 P . . 3 0 / 19 ) ). In order to check whether this null detection can ± t orb ∆ P 37 / . 6 , is considered for further superhump analysis. Only in − 2454114 2453409 2 sh = 01 h, where we have used the actual frequency resolution of . P 0 . sh ) = ) = f 1 ± ] gave a new version of this relation, in the form = ( 2 min min ε ( ( 79 . ]. [ 3 23 = HJD HJD , centred on the orbital frequency and scaled to the residual amplitudes 2 sh P ], hereafter campaign 2005–2) and the 2007 CBA campaign we found signals 19 02 c/d; b and c). . 0 3 found first by [ ± sh 33 P . ). Choosing the minimum as zero point for the superhump phase yields the ephemeris 6 b) is clearly absent in the 2005–1 data (January; Fig. 2 In this context, we investigated the role of RR Pic into the well-known close relation between Among all CVs which are neither dwarf novae nor AM CVn stars, positive superhumps (with Although the 2005 CBA observations (campaign 2005–1) were performed only about one 3 and = 0) have been reported for seven classical post-novae and 17 nova-like variables. Properties for sh > orb f The corresponding phase-folded light curve is shown in Fig. P Comparing both averaged phased lightFig. curves, the superhump found inof the 2005–2 superhump (February–April; in the 2007signal. data. The The residual spectrum highest showed peak severalother found peaks neighbouring close at to peaks the refer orbital to one-cycle(Fig. per day aliases, as is evident from the spectral window 4. Discussion 4.1 RR Pic in context with other superhumpers ε classical novae are shown in Table in both sets are rather0.6–0.7 similar, (Fig. being slightly asymmetric with maxima around superhump phases the residuals light curvescheck for the selected possible campaigns presence of whichan any covered periodic artificial at signal sample associated containing least directly the twovalue. to same orbital the time Periodograms sampling, cycles. values of we of those created each To shown artificial set as data data inserts represent versus in the a Fig. individual constant spectral magnitude windows, which are range from 0 to 30corresponds c/d. to the A dashed signal line near in the Fig. orbital period that exceeds the 3 superhump period is identical to thatlonger found than by the [ orbital period ( for each campaign. The noise spectrumin was certain calculated frequency as the steps average of of a the remainder size amplitudes defined by the box size parameterthe (see 2005 [ data ([ according to these criteria, which are highlighted with an arrow in Fig. month before the 2005–2 campaign, we did( not find any significant signal close to the 2005–2 signal Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris the data. In this manner, we analyse all campaigns. In Fig. this campaign as error in frequency, i.e., 1 be attributed to thethe time superhump, resolution we and folded the those2005–2. with coverage ephemeris of corresponding the to data the instead first of minimum observed the in real absence of PoS(GOLDEN 2017)054 (4.1) . For 2 ] 1 ] ] ], ] ] 9 8 10 17 ] 22 ], [ ], [ 31 ], [ ], [ ], [ Ref. 14 10 89 minutes) are larger 30 15 . 12 0 ], This work, [ = 19 σ 3 h). sh > P orb ]. If we consider all dwarf novae, we P 2 2 h. The results are listed in Table sh > P orb 9% longer than the orbital period. Equally (d) (d) · P sh b P ∼ + 4 a and standard deviation ( ). We have repeated the calculation of these authors ] derived a standard deviation of only 0.53 minutes = 2 a 4.1 orb P , where all novae and nova-like stars are individualised, as 4 Name Type RR Cha Na 0.14010 0.1444 [ 2 h. Generally, the differences between the groups considered here are V630 Sgr Na 0.11793 0.1242 [ from equation ( V4633 Sgr Na 0.12557 0.1277 [ V1974 Cyg Na 0.08126 0.08522 [ < Properties of post-novae with confirmed positive superhumps. < 120 minutes, i.e. below the period gap between 2 and 3 hours. Most SU orb RR Pic (1925) Nb 0.14502 0.1577 [ CP Pup (1942) Na 0.06126 0.0625 [ orb P ] and additionally we find evidence for the presence of most likely the same sh P V603 Aql (1918) Na 0.13820 0.14646 [ P 19 Table 1: 32 minutes. Nova-like stars seem to have smaller slopes than the remaining groups . 1 = σ Classical Novae We present the first systematic analysis of collected optical light curves of the classical nova ], but did not reveal any evidence for superhumps, implying the superhump is a repetitive, but 19 RR Pic spanning 42 years,hump from and 1972 to its 2014. amplitudethe varies We found accretion significantly that disc over the is the light undergoing differentdetection curve long-term made observing shape changes. by of epochs, [ Furthermore, the suggesting orbital we that corroborate the superhump 5. Conclusions for the period range even get positive superhump in 2007important CBA was data, the fact a that period CBA[ data have been obtained insporadic 2005 event, only arising one quickly. month before those by UMa stars are located belowperiod this determination gap, because and it the is Stolz–Schoembsvariation, relation normally at is much least now easier for a to non-eclipsing popular observe cases. tool superhumps for than [ any orbital while the post-novae behave similar toof the dwarf only novae, seven however suffering post-novae. fromcompared the to All small those number of groups displaymarginal, confirming larger that standard the Stolz–Schoembs deviations relation above seemsany to sub-type the be of valid period CVs, for as gap, most shown superhumpers in of Fig. for this method to get including new data, and extended it for cases with well as the SU UMa type dwarf novae above the period gap ( the dwarf novae below the period gap,in slope the actually available sample of 182 cases, compared to [ Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris PoS(GOLDEN 2017)054 ], with more recent N 20 represents the number of ]). The fact that post- N 21 ], [ correspond to the parameters 25 b ], [ σ 11 and ) a ], [ min b 16 ( σ sh ]. P 2 · b + b a 5 ) = a σ refers to the standard deviation. min ( σ orb P a ] 2 120 min 5.39120 min 0.52 3.66120 min 0.9162 0.49 14.09 0.0052 0.9329 1.62 0.53 0.0053 0.8474 68 0.89 0.0114 182 1.90 35 ≤ ≤ > to the mean errors, (Na,Nb) 16.04 4.62 0.8531 0.0221 5.96 24 b + σ NL All CVs 7.83 0.42 0.8899 0.0036 2.32 241 Derived by [ DN P DN P DN P All DNNLNa, Nb 7.09 0.40 0.8964 17.77 6.11 0.0038 6.14 1.32 6.36 0.8418 217 0.9193 0.0280 0.0352 6.26 4.33 17 7 linear fit considering different sub-samples of CVs. and a orb σ P for dwarf novae, classical novae and nova-like stars, and conclude that this relation is − sh orb P P 1003 We give a list of seven post-novae and 17 nova-like stars with positive superhumps recorded, This apparently also includes post-novae, with RR Pic being just one more case in a still and sh [1] Fuentes-Morales I., et al., 2018, MNRAS,[2] 474, 2493 Gänsicke B. T., et al., 2009, MNRAS,[3] 397, 2170 Haefner R., Metz K., 1982, A&A,[4] 109, 171 Hambsch F.-J., 2012, Journal of the American Association of Variable Star Observers (JAAVSO),[5] 40, Jones H. S., 1928, Nature, 121,[6] 862 Kubiak M., 1984, Acta Astron., 34,[7] 331 Lenz P., Breger M., 2005, Communications in[8] Asteroseismology, 146,Lipkin 53 Y. M., Leibowitz E. M., 2008, MNRAS, 387, 289 and conclude that in orderor to common determine in whether classical the novae, superhumpintervals. it phenomenon In is addition, is imperative we to an also monitor unusual determineP post-novae event a systematically revised version for of long the time Stolz–Schoembs relation between small sub-sample. This shouldnova not eruption come represents as a a recurrent surprise, event since in it a has CV long long-term been cycle suspected [ that the of general validity for all superhumpers among CVs. observational evidence corroborating this hypothesisnovae present (e.g. the same [ phenomenonlong-term evolution as of other CVs. CVs, further strengthens our understanding of the References Table 2: Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris of the linear fit, stars in each sub-sample. The first row shows the fit found by [ PoS(GOLDEN 2017)054 6 25 years ago, when I stayed at Gosha Observatory, I intended to Thanks for your comment. 1997, PASP, 109, 468 of Physics Conference Series Vol. 637, Classical Nova Explosions. pp 323-327 Fuentes-Morales I., 2017, PASP, 129, 014201 [9] Mason E., et al., 2013, MNRAS, 436, 212 perform the same observations of RR Pic,that but you I had failed success because in of the bad same weather. observations. I feel happy toIRMA know FUENTES: DISCUSSION KENJI TANABE’s Comment: Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris [10] Mróz P., et al., 2015, ApJS,[11] 219, 26 Mróz P., et al., 2016, Nature,[12] 537, 649 Olech A., 2002, Acta Astron., 52,[13] 273 Patterson J., 1998, PASP, 110, 1132 [14] Patterson J., Warner B., 1998, PASP, 110,[15] 1026 Patterson J., Kemp J., Saad J., Skillman D. R., Harvey D., Fried[16] R., ThorstensenPatterson J. 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A., Warner B., 2002, MNRAS, 335, 44 PoS(GOLDEN 2017)054 1.4 1.2 2007 1981 1982 1980-1 2005-1 2005-2 1980-2 1 1972-1973 2013-2014 1973-1974 2000-2001 0.8 0.6 7 0.4 0.2 phase (P=0.145025959 days) 0.0 -0.2 -0.4 0 0 0 0 0 0 0 0 0 0 0

0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 normalized magnitude normalized Orbital phase of the old nova RR Pic over the last 42 years, folded with the ephemeris given in ). 3.1 Figure 1: Eq. ( Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris PoS(GOLDEN 2017)054 ). 3.3 , the arrows point σ 2 2 2 1.75 1.75 1.75 1.5 1.5 1.5 1.25 1.25 1.25 (c) 2007 CBA 1 1 1 (a) 2005-1 (b) 2005-2 8 phase (0.1577 days) phase (0.1569 days) phase (0.1577 days) 0.75 0.75 0.75 2007 data folded with superhump ephemeris ( 0.5 0.5 0.5 residuals of the 2005–1 data folded with superhump ephemeris (c) (a) 0.25 0.25 0.25 0 0 0 0 0 0

0.05 0.05 0.05 -0.05 -0.05 -0.05 differential magnitude differential Periodigrams for the residual data after subtracting the orbital frequency and its harmonics for Superhump phase averaged into 0.02 phase bins for normalised differential magnitude light curves the same but for the 2005–2 data (b) ) 3.2 ( Figure 3: after subtracting the orbital frequency. to suspected superhump frequencies andorbital the frequency. inset plot shows the spectral window centred at the dominant Figure 2: 2005 and 2007 CBA campaigns. The dashed line corresponds to the noise level of 3 Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris PoS(GOLDEN 2017)054 . Dwarf sh P 120 min. < sh P 9 ) for all sub-types of CVs in the entire range of orb P − sh P ] for SU UMa type dwarf novae with 2 120 min are represented as crosses, all nova-like stars as filled squares, all classical novae > sh P The Stolz–Schoembs relation ( Figure 4: novae with as empty squares and thethe classical linear nova fit RR found Pic by as [ an inverted empty triangle. The grey line corresponds to Photometric long-term variations andIrma superhump Fuentes occurrence Morales in the Classical Nova RR Pictoris