1. Spectroscopic Observations of Novae V1065 CENTAURI and V1280 SCORPII Using 45 cm Cassegrain Telescope at Arthur C Clarke Institute, Sri Lanka S. Gunasekera, Janaka Adassuriya, I. Medagangoda Arthur C Clarke Institute Sri Lanka UN Workshop on BSS & IHY 2007 held on September 21-25, 2009 in Daejeon, South Korea 1

2. Monk-Gillieson type Spectrograph 45cm reflector donated by Japanese Government in 1996 45cm Telescope and Spectrograph at ACCIMT 2

3. Telescope Specifications Effective Aperture 45 cm Effective Focal Length 5400 mm F Number f/12 Theoretical Resolving Power 0.31 arcseconds Maximum Visual Magnitude 15 Spectrograph & CCD Specifications Spectral Resolution at H-α (λ/Δλ) = 22000 Plane reflective grating 1200 grooves/mm SBIG ST 7 CCD camera (765 x 510 pixels) 3

4. What is a Nova ?  Nova is a star that suddenly increases its light output and then fades away to its former in few months or years.  Hydrogen-rich material accretes on the white dwarf’s from its red-dwarf companion.  White dwarf’s masses ranges from 0.5 – 1.4 solar mass.  The material gradually accumulates and compressed rising the temperature.  When temperature is 20 million K, Hydrogen ignited by CNO cycle.  The nuclear reactions runs away expanding the shell. 4

5. Classification of Nova Spectroscopic Classification of Nova  Fe II type nova (R. E. Williams) Adopted from R.E. Williams, AJ 1992 5  He/N type Nova (R. E. Williams)

6. Classifications of Nova Light Curves t2t2 t3t3 t 2 - Time for light curve to decay 2 magnitudes from peak t 3 - Time for light curve to decay 3 magnitudes from peak Speed Classt 2 (days)m v (mag d -1 ) Very Fast< 10> 0.20 Fast11 - 250.18 - 0.08 Moderately Fast26 - 800.07 - 0.025 Slow81 - 1500.024 - 0.013 Very Slow151 - 2500.013 - 0.008 Image reference http://www.AAVSO.org.htm 6

7. Light curve classification by H. W. Duerbeck (1981) Adopted from H. W. Duerbeck, ASP 1981 7

8. Objectives of the observation  Analyze the novae spectra in Hα (6563 ⁰A) region and explain the structural variations of the profile with the time.  Compare and contrast the profiles of two novae.  Estimate the distance to the nova using light curve. SpecificationsV1065 CENV1280 SCO Date of discoveryJan 23.35 UT 2007Feb 4.86 UT 2007 RA 2000 11 h 43.2 m 16 h 57 m 41 s Dec 2000 -58 0 03’-32 0 20’ 34” Peak of the Nova2007 Jan 25.982007 Feb 16.75 Max. apparent magnitude8.74.0 Observations 2007 Jan 31 (5.9 days) 2007 Feb 09 (15.0 days) 2007 Feb 20 (26.0 days) 2007 Feb 20 21:21:32 2007 Feb 20 21:39:25 Exposure Time20 min10 min 8

9. IRAF PC version( RedHat Linux) 2.12.2 is used to reduce the spectroscopic raw data. Data reduction steps include:  Dark subtraction  Flat field correction  Wavelength calibration (reference Fe-Ne)  Normalization to stellar continuum 9

10. Spectroscopic Observations Hydrogen Alpha line at 6563 A⁰ Resolution 0.3 A⁰/Pixel H-α profile of V1065 CEN 6 days after maximum H-α Profiles of V1280 SCO 4 days after maximum 10

11. -4000 -2000 0 2000 4000 Velocity (km/s) 1 2 4 3 5 -4000 -2000 0 2000 4000 Velocity (km/s) 1.0 1.5 2.0 2.5 3.0 3.5 -4000 -2000 0 2000 4000 Velocity (km/s) 1 2 4 3 5 31JAN (6 days) 9FEB (15 days) 20FEB (26 days) H-α profiles of V1065 CEN 11

12. -4000 -2000 0 2000 4000 Velocity (km/s) 20FEB (26 d) 9FEB (15 d) 31JAN (6 d) 12 Hα profiles for V1065 CEN

13. 13 Blending Hα profiles of V1065 CEN Hα (6563) 20FEB (26 days) N II (6583) O II (6539)

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15. 15 Analysis of Periodic Variations of V1065 CEN DateEquivalent Width ( o A)IBIB IRIR V B (km/s)V R (km/s) 31 Jan 2007 (5.9)2105.3985.213-364179 09 Feb 2007 (15.0)1203.2903.649-336221 20 Feb 2007 (25.8)1904.8855.148-316275  I B /I R ratio changes drastically  Slight drop of intensity after 15 days and increased again  Blue component moves towards the line center while the red is moving away from the line center  N II line immerged after 26 days shows the nova begins nebular stage

16. -4000 -2000 0 2000 4000 Velocity (km/s) 0.75 1.75 1.50 1.25 1.00 2.00 H-α profile of V1280 SCO 16 20FEB (4 days)

17. -4000 -2000 0 2000 4000 Velocity (km/s) 1 2 4 3 5 -4000 -2000 0 2000 4000 Velocity (km/s) 0.75 1.75 1.50 1.25 1.00 2.00 V1065 CENV1280 SCO 17 Nova V1065 CEN is He/N-type spectra which characterize a broad (Gaussian FWHM 49 o A), saddle shaped asymmetric H  profile without absorption components. The emission causes by discrete shell.He/N-type Nova V1280 SCO is Fe II type nova with prominent P-Cyg absorption and narrow emission line (Gaussian FWHM 26 o A) which evidences a wind-like structure.Fe II type

18. H-α profile of V1280 SCO -4000 -2000 0 2000 4000 Velocity (km/s) 0.75 1.75 1.50 1.25 1.00 2.00 20FEB (4 days) 18

19. P-Cyg Profile λ₀ λ 1 2 3 19 1 2 3 Line of site 2

20. Observation of P-Cyg Structure -4000 -2000 0 2000 4000 Velocity (km/s) 1 2 4 3 5 31JAN (6 days) -4000 -2000 0 2000 4000 Velocity (km/s) 0.75 1.75 1.50 1.25 1.00 2.00 20FEB (4 days) 2300 km/s 716 km/s 20 The expansion velocities to the direction of line of site were taken from the minima of P-Cyg profile.  Expansion velocity for V1065 CEN = 2300 km/s  Expansion velocity for V1280 SCO = 716 km/s V1065 CEN V1280 SCO

21. 21 Absorption versus Emission lines of Novae star gas cloud SλSλ IλoIλo IλIλ  For optically thin case τ λ << 1  Emission line on the top of the background intensity  Novae show emission line in Hα region -4000 -2000 0 2000 4000 Velocity (km/s) 0.75 1.75 1.50 1.25 1.00 2.00 -4000 -2000 0 2000 4000 Velocity (km/s) 1 2 4 3 5  Optical depth of V1280 SCO > Optical depth of V1065 CEN  Absorption line on the background intensity S λ – Source function I λo - Background intensity (star) I λ - Observed intensity

22. 22 Absorption versus Emission lines of Novae Line of sight λ₀ λ The main difference between the spectra of V1065 CEN and V1280 SCO is the absence of prominent P-Cyg profile in V1065 CEN. This can be explained by the inclination to the line of site of the two systems and the equatorial bulge. Red Giant White Dwarf

23. Photometric Analysis 23  The photometric analysis was done by using the light curve data.  The location of the Arthur C Clarke Observatory inappropriate for photometric analysis.  The light curve data were taken from American Association of Variable Star Observers (AAVSO) website http://www.aavso.org/data/download/http://www.aavso.org/data/download/

24. 24 Light Curves for V1065 CEN mvmv JD 2454000+ mBmB  MATLAB curve fitting tool is used to fit the curves to the data points.  The light curve of V1065 CEN is B a type.type.  t 2 and t 3 were taken from the light curves.  Absolute magnitudes for V band (M v ) and for B band (M B ) were calculated using the Maximum Magnitude /rate of decline (MMRD) relationship. M = b n log t n + a n Where M – absolute magnitude n – 2 or 3 a n and b n are constants Light curve data archived from www.aavso.org

25. 25. Basic Parameters of Nova V1065 CEN Parameter VB Maximum apparen magnitudes m V =+8.69  0.08m B =+ 9.12  0.07 Color index at maximum light (B-V)=+0.43 Apparent magnitudes 15 days after maximum m V15 =+10.23m B15 =+10.62 Time taken to decline 2 magnitudes (t2) t 2V =20.654 daysdayst 2B =22.604 days Time taken to decline 3 magnitudes (t3) t 3V =28.026 days t 3B =30.885 days Mean absolute magnitude at maximum M v =-7.58  0.18 M B =-7.75±0.25 Intrinsic color index at maximum light (B-V)max=M B -M v =-0.17 Distance modules m V -M v =(8.69-(-7.58))=16.27  0.20m B -M B =(9.12-(-7.75))=16.87  0.26 Mean distance modules 16.57  0.33 Color excess at maximum light E B-V =0.43-(-0.17)= 0.6 Visual extinction Av=3.2xEB-V=1.92 Unreddened distance module 16.57-1.92=14.65 Distance to the nova 8.51  0.33 kpc The distance estimation by Andrew Helton, University of Minnesota, is 7.9 kpc which is close to our estimation.

26. 26 Light Curve for V1280 SCO Visual magnitude JD 2454000+ Light curve data archived from www.aavso.org  The light curve of V1280 SCO is A o type.type.

27. 27 Basic Parameters of Nova V1280 SCO ParameterValue Maximum visual magnitude (m v )4.0 ± 0.2 Time at max. visual magnitude (t o )2454148.25 t212.21 days (0.48 mag/d)days t314.14 days JD after 15 days from maximum2454163.25 JD Apparent magnitude after 15 days m v15 7.5 ± 0.2 Mean absolute magnitude at maximum(M v ) -8.7±0.1 Distance modulem v - M v = 4.0-(-8.7)=12.7±0.2 Distance to the nova3.47±0.2 kpc

28. White Dwarf Mass 28 White dwarf mass is estimated by the relationship given by Mario Livio ( AJ 1991) M B max ≈ -8.3 – 10 log (M wd /M o ) where M o is solar mass For nova V1065 CEN M wd ≈ 0.88 M o For nova V1280 SCO M wd ≈ 1.09 M o

29. 29 Conclusions  Hα Profile of V1065 CEN is originated by He/N type nova  Broad emission line (Gaussian FWHM = 49 o A)  High expansion velocity (2500 km/s)  Shape of the profile  Photometric analysis shows that the nova V1065 CEN is comparatively slow (t 2 =21 d)  The unaltered Hα profiles  M wd = 0.88 M o Comparatively low mass white dwarf reveals the low absolute magnitude (M v = -7.58)  Hα profile of V1280 SCO is originated by Fe II type nova  Narrow emission line (Gaussian FWHM = 26 o A)  Low expansion velocity (716 km/s)  Shape of the profile  Photometric analysis shows that the nova V1280 SCO in very fast (t 2 = 12 d)  Hα profile could not be observed after few days  M wd = 1.09 M o comparatively high mass white dwarf evolves very quickly raising the absolute magnitude up to M v = -8.7

30. 30 Conclusions  Different geometry of the binary system affects to make the prominent P-Cyg profile in Hα region.  The coincidence line of sight and the equatorial bulge is also very important for the presence of P-Cyg structure in V1280 SCO.  The absence of prominent P-Cyg structure in V1065 CEN reveals the line of sight and the disk of accretion is apart from some extent.

31. Thank You 31

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