Optical Spectroscopy of Novae in M31

Francesco Di MillePadova University

Asiago Observatory

Collaborators:

Marina Orio INAF-Padova/U. Of Wisconsin

Stefano Ciroi Padova University

Antonio Bianchini Padova University

Piero Rafanelli Padova University

T. Nelson CRESST/UMBC/GSFC

Principal M31 nova optical surveys

Darnley et al. 2004Principal Conclusions:•Nova Rate ~30-40 per year•Novae centrally concentrated•Bulge population

Distribution of the magnitude at maximum for 30 novae in M31 Arp (1956 )

Jun 1953-Jan1955 1000 Plates 290 nights Only 5 novae with maximum missed by more than 1 day

Two nova population in M31?

Optical Spectroscopy of NovaeThe Tololo Scheme (Williams 1992)

Della Valle (2002)

Using the Tololo scheme Della Valle & Livio (1998) showed that novae belonging to the He/N class tend to concentrate close to the Galactic plane with a typical scale height <∼150 pc, whereas FeII novae are distributed more homogeneously up to z ∼ 1000 pc and beyond.

See Shafter (2008) for a review on Nova Population

Despite the large number of novae discovered in M31 there are very few spectra in the literature

The only comprehensive study of novae outside the Galactic and Magellanic Cloud systems is Thomaney & Shafter (1992) who studied photometrically and spectroscopically 9 novae in the M31 bulge

M31 nova discoveries

Adapted from the M31 nova catalog of MPEhttp://www.mpe.mpg.de/~m31novae/opt/m31/index.php (see also Pietsch et al. 2007)

M31 Novae Light curves (Darnley et al. 2004)

Ongoing project Ekar 1.82m telescope+AFOSC Imaging and

Spectroscopy Spectral Range ~ 3600-7500 Å Resolution ~22 Å

TNG 3.6m telescope + Dolores Spectroscopy: Spectral range 330-790

nm, resolution 1.2 nm

TNG OBSERVATIONS

M31N2008-08a

M31N_2008-08a shows the typical spectrum of a nova in the early decline stage. The lines of the Balmer series and the OI (777.3 nm ) emission line are the strongest features in the spectrum. These lines show a double profile with the blue component brighter than the red one.

Gaussian decomposition of the profile of H_alpha gives a FWHM of 1200 km/s and 1350 km/s respectively for the blue and the red component. The presence of the FeII (42) (492.4,501.8, 516.9 nm ) emission lines allows to classify this object as a FeII nova in the Tololo scheme

M31N2008-08b

The recurrent nova candidate M31N_2008-08b spectrum shows a fairly blue continuum and strong Balmer emission lines up to H_delta. The brightest non-Balmer lines are HeII (468.6 nm)+ C III/N III in blend (464 nm). He I (587.6; 667.5; 706.5) lines are also detectable. The FWHM of H_alpha is 850 km/s while H_beta and the HeII (468.6 nm) lines are narrower, FWHM 400 km/s . The presence of the HeI and HeII lines suggests that the object is quite likely a helium nova. The spectrum is similar to the spectra of the recurrent nova V3890 Sgr, taken 10-11 days after maximum by Buckley et al. (1990, IAUC # 5019 ).

M31N2008-08c M31N2008-09b

Not a nova

M31N2008-09c M31N2008-10a

M31N2008-10b M31N2008-12b

Fe II novaFe II nova

M31N-2008-10b

We obtained the first spectra about 2 days after the maximum.The H-alpha and the H-beta lines have a FWHM of about 900 km/s. In addition several FeII multiplets and the OI (777.3 nm ) emission lines are clearly detected, confirming that this object is a nova, and indicating that it belongs to the FeII class of the Tololo scheme

+2

+45

+91

Light curve data : Henze et al. 2008; Barsukova et al.2008

M31-2008-07aM31-2008-11b

SU-UMa-like superoutburst in our own galaxy similar to HS2219+1824 (Kaliswal et al. 2008)

Slow Nova FeII

M31-2008-11c

Not a nova but SN at z=0.07

NOVA M31 2007-11eT182 + AFOSCGr04 +2.1” slit Spectral Range ~ 3600-7500 Å Resolution ~24 Å

2007 Nov 29.82 days after dis

2007 Dec 05.8

Observations were carried out at Asiago Observatory using the 1.82 cm telescope + AFOSC. A 3600 sec spectrum (range 360-750 nm; 2.4 nm resolution) was obtained on 2007 Nov 29.83 about 2 days after the discovery. The spectrum shows a prominent blue continuum and Balmer lines with Halpha FWHM of about 600 km/s. In addition NaI and weak FeII emission lines with a well-marked P-Cygni profile are visible.

The object was observed again, on Dec 05.78 about 8 days post the discovery using the same instrumentation and setup. Emission lines dominate the spectrum, showing strong Balmer lines visible up to H8. FWHM of Halpha and Hbeta increased to approximately 1400 km/s. Significantly strengthened FeII lines, FeII(42), FeII(49), FeII(74), and Ca II H+K emission are now easily detectable. The NaI D is also increased in intensity and shows the most remarkable P-Cygni profile. These features suggest that M31N-2007-11e can be ascribed to the typical FeII class of the Tololo nova classification scheme

Spectroscopic Class of M31 novae

Adapted from the M31 nova catalog of MPE

49 novae with spectral classification 39 FeII10 He/NSee also talk of W. Pietsch

Spatial distribution

Image courtesy of W. Pietsch

Conclusion

We need Spectroscopy to confirm the nature of the optical transient in M31

There are more than 20 novae in M31 every year. Unique opportunity to have a panchromatic (from x-ray to IR) view for a large number of sources in few years.