Basic characteristics of the classical novae V 2 4 6 7 Cyg and V2468 Cyg

1. Basic characteristics of the classicalnovae V2467 Cyg and V2468 Cyg S. Shugarov(1, 2), D. Chochol (1), I. Volkov T(2). Pribulla (3) Astronomical Institute SAV, Tatranská Lomnica Sternberg Astronomical Institute, Moscow AI & UO Friedrich-Schiller Univ., Jena

2. V2467 Cygni (Nova Cygni 2007) • Discovery:Akihiko Tago (Nakano 2007, IAU Circ. 8821) • March 15.787, 2007 • brightness 7.4 mag – estimated by Tago • position (Nishiyama & Sakamoto, IAU Circ. 8821): • α(2000) = 20 h28m12.52s • δ(2000) = 41° 48’ 36".5 • Progenitor: Steeghs et al. (2007) – the field observed in 2004 with • Isaac Newton Telescope at La Palma and its Wide Field Camera. Progenitor – r’ = 18.46 mag, i’ = 17.49 mag. For reddening • E(B-V) ~ 1.0-1.5 optical SED corresponds to A/F dwarf exhibiting a modest Hα excess. It is consistent with CV progenitor accreting at a high rate. Estimated distance 1.5-4 kpc, outburst amplitude • ~ 12 mag is typical for Fe II-class galactic nova.

3. Spectroscopy: Munari et al.(2007) spectra of the nova on March 18.16 UT at Asiago. Fe II class nova (Williams, 1992), expansion velocity derived from Fe II emission lines is 900 km/s, P Cygni type absorptions in Hα and Hβ with velocities 900 km/s and 1900 km/s. Christian Buil, Castanet Tolosan, spectrum on March 17.18 UT /www.astrosurf.com/~buil/us/ncyg3/obs 28 cm telescope + LHIRES III spectrograph (1200 l/mm grating) + Audine KAF0402ME CCD camera, R = 6800 in Hα P Cygni type absorption in Hα with velocity 900 km/s

4. According to Tomov et al. (2007), at the end of March the spectrum was dominated by Balmer and Fe II emission lines. The velocities of P Cyg absorptions increased from 1300 km/s and 2290 km/s on March 24 to 1405 km/s and 2590 km/s on April 1, 2007. Nova has very strong O I 844.6 nm emision. OI flux could indicate an extremely high oxygen overabundance. • The absorptions belong to the expanding outer envelope and to the stellar wind.

5. Hα and [OIII] line profiles: DDO Canada, 31.7.2007 The nebular emission line profiles suggest a non-spherical ejection of the shell: equatorial ring and polar blobs, RVblobs = -190 km/s, 330 km/s, RVring= -750 km/s, 780 km/s

6. CCD image (0.5m telescope Stará Lesná)

7. V light curve of V2467Cyg: the first year after the outburst Light curve shows quasi-periodic (P ~ 20-24 days) brightness variations, caused by probable pulsations of the nova envelope (Schenker, 1999).

8. Brightness maximum of the nova: 2007, March 16.95: V = 7.67, B = 9.39. V, B light curves were used to find the rates of decline: t 2,V = 8 days t 3,V = 18 days t 2,B = 12 days t 3,B = 25 days According to Downes and Duerbeck (2000) the nova can be classified as the fast (t2<13, t3<30 days) super-Eddington Fe IInova, which shows smooth lightcurve with well-defined maximum,and quasi-periodic light oscillations in later evolution. We have estimated the absolute magnitudes of nova at maximum using the relations by Schmidt, 1957; Della Valle and Livio, 1995; Downes & Duerbeck, 2000: MV,max = –8.75 ± 0.07MB,max = –8.18 ± 0.02 Using MB,max and formula given by Livio (1992) MB,max = - 8.3 - 10.0 log(Mwd/Msun) We estimated the white dwarf mass Mwd = 0.97 ± 0.05 Msun

9. Colour excess can be found from: • comparison of the observed (B-V)max = 1.72 affected by extinction with intrinsic (B-V)in,max = 0.57 • E(B-V) = 1.15 • relation of van den Bergh & Younger (1987) who found that novae two magnitudes below maximum have an unreddened colour index B-V = - 0.02. The observed colour is (B-V) = 1.15 • E(B-V) = 1.17 • from the flux ratios of O I (8446 Å and 1.1287 μm ) lines. • The intrinsic flux ratios of the Lyβ-fluoresced O I lines are precisely known, so any departure from them is a good indicator of interstellar reddening. Mazuk et al. (IAUC 8848) and Russell et al. (IAUC 8888) derived E(B-V) = 1.5 and 1.7 • Mean value: E(B-V) = 1.38 ± 0.12 • Corresponding absorptions: • AV = 4.3 ± 0.4 AB = 5.7 ± 0.5 • Distance to the nova: d = 2.5 ± 0.3 kpc

10. Discovery of rapid oscillations in V2467 Cyg QPO ~35 min, in RC filter, CCD observations with 0.5m telescope, AISAS Observatory at Stará Lesná, May 30, 2008 and June 1, 2008.

11. V2467 Cyg: rapid variability on July 26 and 31, 2008.

12. The 35-min waves were observed from April till Sept. 2008. The amplitude of this oscillations strongly decreased thereafter. In October, 26 only variations connected probably with the orbital periodicity were seen

13. Light curve in V-band and color-indices:

14. The reddening of colour indices B-V and U-B during the first 150-200 days was detected. Later the bluering of these indices and V-R color indices was determined. After the trend removal, we found the orbital variability. From April, 2008 till now the orbital period is: 0.15961 day, or 3h 50m. The next Fig. shows the periodogram of our Rc data, orbital and short-periodic variability of V2467 Cyg. We found two possible values of the second (shorter) period: 36.4 and 35.5 min (one-day alias). Similar periods was detected by Swierczynski et al(2008). Also the peaks, corresponding to the beat period (1/P beat = 1/P sec -1/P orb) are present.

15. During the decline, the Rc light curve shows different periods.

16. Swierczynsky et al (this conference) found orbital period 0.d159613 at 2008 and 0.d15308 at 2007. We didn’t find any orbital period in 2007 with sure, but ready to check our data with other algorithm. Secondary period of Swierczynsky et. al is one-day alyas to our period: 1/Pswiercz.=41.56 d-1; 1/Pour_work=40.56 d-1. Our data show more consistency with the last value.

17. The secondary waves may be caused by rotation of WD (SeeSwierczynski et.al (2008 and this conference) or its pulsations. We believe that the nature of these variations may be connected with the pulsations of the white dwarf, since the form and the amplitude are strongly unstable. The time intervals between the minima or maxima exhibit small changes from cycle to cycle. But the average value of the short period is approximately constant. The orbital light curve is highly distorted by the secondary waves.

18. The track of V2467 Cyg on the two-colour diagrams: WILL BE ANOTHER FIGURES!!!

19. We found the following values of the periods: JD 2454200 – 54330: P = 21.4 d JD 2454550 – 54750: Pshort=0.002469 d JD 2454550 – 54970: Porb = 0.159618 d Because the short period existed only on the light curve decline and was not absolutely stable, we assume that this star cannot be an intermediate polar. In the case of the intermediate polar (Swierczynski, 2008) the variability induced by the axial rotation should repeat accurately. However for a complete explanation of this periodicity, it is necessary to obtain the polarimetric and X-ray observations.

20. V2468 Cygni (Nova Cygni 2008) • Discovery: Hiroshi Kaneda (IAU Circ. 8927) • March 7.801, 2008 • brightness 8.2 mag – unfiltered CCD frames • position K.Kadota (IAU Circ. 8927): • α(2000) = 19 h 58m 33.39s • δ(2000) = 29° 52’ 06".5 • Progenitor: USNO-B1 1198-0459968 (R =18 mag) visible only on POSS-II red plates, not on blue ones. If it is the progenitor, the amplitude of the outburst > 12 mag in the B band (Henden & Munari, 2008, IBVS 5822).

21. CCD image of the nova taken on 2008, March 12 with the 0.5m telescopeat the AISAS Observatory Stará Lesná

22. Spectroscopy: Nogami,Kuriyama,Iwata (IAUC 8927): low-resolution spectrum of the nova (4000 – 8000 Å) at March 8.794 with 1.88m telescope at Okayama Astrophysical Observatory: blue continuum with strong Balmer and Fe II lines with prominent P-Cyg profiles, FWHM of the emission component of Hα about 1000 km/s, shift of Hα absorption from emission peak: 880 km/s. Beaky (IAU Circ. 8928) spectra of the nova on March 11.46 UT at Truman Observatory: Fe II class nova (Williams, 1992). Our Hα spectra (R = 12 000) taken with 1.88m telescope at the David Dunlap Observatory. P Cyg type absorptions: March 17: 1140 km/s, March 23: 1210 km/s Expanding outer envelope March 17: 2300 km/s Wind with the terminal velocity 2600 km/s

23. Photometry: V light curve during 100 day after outburst. CCD photometry: AAVSO, VSNET, Meduza, our data (colour symbols), AAVSO visual estimates (points) Ephemeris for minima: 2454539.2 (4) + 6.9(2) x E days Ephemeris for maxima: 2423538.04(15) + 2.351(11) x E days

24. In the next slides we show the light curves of V2468 Cyg from the outburst till present time in the UBVRcIc – passbands. We see a number of outbursts with cycles around 64.7 day. The colour-indices during these outbursts strongly changed, the variation of colours are shown in the next figures.

25. Color variations of V2468 Cyg

26. Track of V2468 Cyg on the U-B / B-V / V-R diagrams

27. The outburst activity was observed only during declining about of 200 days. The light curve folded with the period 64.7 day is shown in this slide. We can say that about of 30 day there are no any outbursts and another 30 days show the strong activity.

28. We did not determine the sure orbital period. But the possible period 0.28326 day (with a small probability - orbital) we found on the interval of JD 2454930-975 after series of outbursts mentioned above. The phase diagram of the possible orbital period of V2468 Cyg: P=6h 48m.

29. Maximum brightness of nova: 2008, March 9.474 : V = 7.57, B = 8.504. V and B light curves were used to find the rates of decline: t 2,V = 9 days t 3,V = 20 days t 2,B = 10 days t 3,B = 22 days We have estimated the absolute magnitudes of nova at maximum using the relations by Della Valle and Livio, 1995; Downes & Duerbeck, 2000; Schmidt, 1957; Pfau 1976; Livio 1992: MV,max = -8.70 ± 0.07 MB,max = -8.27 ± 0.02 Using the derived MB,max and formula given by Livio (1992) MB,max = - 8.3 - 10.0 log(Mwd/Msun) we can estimate the mass of the white dwarf in V2468 Cyg as Mwd = 0.99 ± 0.01 Msun

30. Colour excess can be found from: • comparison of the observed (B-V)max = 0.934 affected by extinction with intrinsic (B-V)in,max = 0.43 • E(B-V) = 0.504 • relation of van den Bergh & Younger (1987) who found that novae two magnitudes below maximum have an unreddened colour index B-V = - 0.02 • E(B-V) = 0.78 • from the flux ratios of O I (8446 Å and 1.1287 μm ) lines. • Rudy et al. (IAUC 8936) derived E(B-V) = 0.77 • Mean value: E(B-V) = 0.68 ± 0.07 • Corresponding absorptions: • AV = 2.11 ± 0.21 AB = 2.78 ± 0.28 • Distance to the nova: d = 6.5 ± 0.9 kpc

31. Main conclusions: We found the orbital period for V2467Cyg on the one year time interval which agrees with periods given bySwierczynski, 2008 on the shorter time interval (~20 d). We propose that the short periodicity of V2467Cyg, take place in summer- authum 2008 could be explained by pulsations of WD.

32. We found the cycles of activity for both stars. The tracks on the color-indices diagrams have been plotted. We determined a possible orbital period for V2468 Cyg (0.28326 d).

33. References Beaky, M. M.,2008 "V2468 Cygni = Nova Cygni 2008", IAU Circ., 8928, 2 Della Valle, Massimo; Livio, Mario, 1995, "The Calibration of Novae asDistance Indicators", Astrophysical Journal v.452, p.704 Downes, Ronald A.; Duerbeck, Hilmar W.,2000, "Optical Imaging of Nova shells and the Maximum Magnitude-Rate of Decline Relationship", The Astronomical Journal, Volume 120, Issue 4, pp. 2007-2037. Henden, Arne; Munari, Ulisse, 2008,"Photometric Sequences and Astrometric Positions of Nova Vul 2007 N.2 and Nova Cyg 2008", Information Bulletinon Variable Stars, 5822, 1. Nakano, S.; Tago, A.; Nishiyama, K.; Sakamoto, T., 2007,"V2467 Cygni = Nova Cygni 2007", IAU Circ., 8821, 1 Nakano, S.; Kaneda, H.; Kadota, K.,2008, "Nova Cygni 2008", IAU Circ., 8927, 2

34. Livio, Mario, 1992, "Classicalnovaeandtheextragalacticdistancescale", AstrophysicalJournal, Part 1, vol. 393, no. 2. S. Mazuk, D. K. Lynch, R. J. Rudy, R. W. Russell, R. L., 2007, "V2467 CYGNI", IAU Circ., 8428 Munari, U.; DallaVia, G.; Valisa, P.; Dallaporta, S.; Castellani, F., 2007, "V2467 Cygni = NovaCygni 2007", CentralBureauElectronicTelegrams, 897, 1 Nogami, D.; Kuriyama, J.; Iwata, I., 2008, "NovaCygni 2008", IAU Circ., 8927 Pfau, W., 1976, "RecalibrationoftheabsolutemagnitudesofnovaeandapplicationtonovaCygni 1975.", Astron. Astrophys., Vol. 50, p. 113 - 115 Rudy, R. J.; Russell, R. W.; Lynch, D. K.; Woodward, C. E., 2008, "V2468 Cygni", IAU Circ., 8936, 2 Russell, R. J.; Rudy, R. J.; Lynch, D. K.; Woodward, C. E., 2007, "V2467 Cygni", IAU Circ., 8888, 1

35. Schmidt, T., 1957, "DieLichtkurven-LeuchtkraftbeziehungNeuerSterne", VeroeffentlichungenderUniversitaets-SternwartezuGoettingen, v. 7, pp.1-21 Schwarz, G.; Osborne J.P.; Page K.; Drake J.J.; Krautter J.,2008, Sep 27,"Two SSS SwiftX-rayspectraofNovaCyg 2007", ATel #1747 Steeghs, D.; Drew, J.; Greimel, R.; Barlow, M.; Gaensicke, B.; Drake, J.; Witham, A., 2007, "TheprogenitorofNovaCygni 2007 (=V2467 Cyg)", TheAstronomer'sTelegram, #1031 Swierczynski, E.; Ragan E.; Galan C.; Mikolajewski M., 2008, Sep.18, "Nova V2467 Cygaspossibleintermediatepolar", ATEL # 1723 Tomov, T.; Mikolajewski, M.; Ragan, E., etal, 2007, "V2467 Cyg - A NovawithExtremelyStrong O I 8446 Emission", Information BulletinonVariableStars, 5779, 1. vandenBergh, S.; Younger, P. F., 1987, "UBV photometryofnovae", AstronomyandAstrophysicsSupplementSeries, vol. 70, no. 1, Williams, Robert E., 1992, "Theformationofnovaespectra", AstronomicalJournal, vol. 104, p. 725-733.