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

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Monk-Gillieson type Spectrograph

45cm reflector donated by Japanese Government in 1996

45cm Telescope and Spectrograph at ACCIMT

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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)

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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.

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Classification of NovaSpectroscopic Classification of Nova

Fe II type nova (R. E. Williams)

Adopted from R.E. Williams, AJ 19925

He/N type Nova (R. E. Williams)

Classifications of Nova Light Curves

t2

t3

t2 - Time for light curve to decay 2 magnitudes from peak

t3 - Time for light curve to decay 3 magnitudes from peak

Speed Class t2 (days) mv (mag d-1)

Very Fast < 10 > 0.20

Fast 11 - 25 0.18 - 0.08

Moderately Fast 26 - 80 0.07 - 0.025

Slow 81 - 150 0.024 - 0.013

Very Slow 151 - 250 0.013 - 0.008

Image reference http://www.AAVSO.org.htm6

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.

Specifications V1065 CEN V1280 SCO

Date of discovery Jan 23.35 UT 2007 Feb 4.86 UT 2007

RA2000 11h 43.2m 16h 57m 41s

Dec2000 -580 03’ -320 20’ 34”

Peak of the Nova 2007 Jan 25.98 2007 Feb 16.75

Max. apparent magnitude 8.7 4.0

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 Time 20 min 10 min

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IRAF PC version( RedHat Linux) 2.12.2 is used to reduce thespectroscopic raw data.

Data reduction steps include: Dark subtraction Flat field correction Wavelength calibration (reference Fe-Ne) Normalization to stellar continuum

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Spectroscopic ObservationsHydrogen 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

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-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

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-4000 -2000 0 2000 4000 Velocity (km/s)

20FEB (26 d)

9FEB (15 d)

31JAN (6 d)

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Hα profiles for V1065 CEN

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Blending Hα profiles of V1065 CEN

Hα (6563)

20FEB (26 days)

N II (6583)

O II (6539)

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Analysis of Periodic Variations of V1065 CEN

Date Equivalent Width (oA) IB IR VB (km/s) VR (km/s)

31 Jan 2007 (5.9) 210 5.398 5.213 -364 17909 Feb 2007 (15.0) 120 3.290 3.649 -336 22120 Feb 2007 (25.8) 190 4.885 5.148 -316 275

IB/IR 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

-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

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20FEB (4 days)

-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 CEN V1280 SCO

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Nova V1065 CEN is He/N-type spectra which characterize a broad (Gaussian FWHM 49 oA), saddle shaped asymmetric H profile without absorption components. The emission causes by discrete shell.

Nova V1280 SCO is Fe II type nova with prominent P-Cyg absorption and narrow emission line (Gaussian FWHM 26 oA) which evidences a wind-like structure.

H-α profile of V1280 SCO

-4000 -2000 0 2000 4000 Velocity (km/s)

0.75

1.75

1.50

1.25

1.00

2.0020FEB (4 days)

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P-Cyg Profile

λ₀

λ

1

2

3

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1

2

3

Line of site

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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

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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

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Absorption versus Emission lines of Novae

Line of sight

Line of sight

λ₀λ

λ₀

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

Photometric Analysis

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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/

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Light Curves for V1065 CEN

mv

JD 2454000+

mB

JD 2454000+

MATLAB curve fitting tool is used to fit the curves to the data points. The light curve of V1065 CEN is Ba type. t2 and t3 were taken from the light curves. Absolute magnitudes for V band (Mv) and for B band (MB) were calculated using the Maximum Magnitude /rate of decline (MMRD) relationship.

M = bn log tn + anWhere M – absolute magnitude n – 2 or 3 an and bn are constants

Light curve data archived from www.aavso.org

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. Basic Parameters of Nova V1065 CEN

Parameter V B Maximum apparen magnitudes mV=+8.69±0.08 mB=+ 9.12±0.07

Color index at maximum light (B-V)=+0.43

Apparent magnitudes 15 days after maximum mV15=+10.23 mB15=+10.62

Time taken to decline 2 magnitudes (t2) t2V=20.654 days t2B=22.604 days

Time taken to decline 3 magnitudes (t3) t3V=28.026 days t3B=30.885 days

Mean absolute magnitude at maximum Mv=-7.58±0.18 MB=-7.75±0.25

Intrinsic color index at maximum light (B-V)max=MB-Mv=-0.17

Distance modulesmV-Mv=(8.69-(-7.58))=16.27±0.20 mB-MB=(9.12-(-7.75))=16.87±0.26

Mean distance modules 16.57±0.33

Color excess at maximum light EB-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.

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Light Curve for V1280 SCO

Visu

al m

agni

tude

JD 2454000+

Light curve data archived from www.aavso.org

The light curve of V1280 SCO is Ao type.

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Basic Parameters of Nova V1280 SCO

Parameter Value Maximum visual magnitude (mv) 4.0 ± 0.2 Time at max. visual magnitude (to) 2454148.25 t2 12.21 days (0.48 mag/d) t3 14.14 days JD after 15 days from maximum 2454163.25 JD Apparent magnitude after 15 days mv15 7.5 ± 0.2

Mean absolute magnitude at maximum(Mv) -8.7±0.1 Distance module mv - Mv = 4.0-(-8.7)=12.7±0.2 Distance to the nova 3.47±0.2 kpc

White Dwarf Mass

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White dwarf mass is estimated by the relationship given by Mario Livio ( AJ 1991)

MBmax ≈ -8.3 – 10 log (Mwd/Mo) where Mo is solar mass

For nova V1065 CEN Mwd ≈ 0.88 Mo

For nova V1280 SCO Mwd ≈ 1.09 Mo

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Conclusions Hα Profile of V1065 CEN is originated by He/N type nova

Broad emission line (Gaussian FWHM = 49 oA) High expansion velocity (2500 km/s) Shape of the profile

Photometric analysis shows that the nova V1065 CEN is comparatively slow (t2=21 d) The unaltered Hα profiles

Mwd = 0.88 Mo Comparatively low mass white dwarf reveals the low absolute magnitude (Mv = -7.58)

Hα profile of V1280 SCO is originated by Fe II type nova Narrow emission line (Gaussian FWHM = 26 oA) Low expansion velocity (716 km/s) Shape of the profile

Photometric analysis shows that the nova V1280 SCO in very fast (t2= 12 d) Hα profile could not be observed after few days

Mwd = 1.09 Mo comparatively high mass white dwarf evolves very quickly raising the absolute magnitude up to Mv = -8.7

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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.

Thank You

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