Novae in outbursts!What are we learning from X-rays?

Marina Orio

INAF-Padova

And U Wisconsin

How do we learn and what do we want to learn from “supersoft” novae?

• Only way to probe the WD!• Need frequent monitoring but also want to “go deep”

and obtain high resolution spectra.• Swift has been exceptionally useful extending nova

coverage to many more objects for longer times (frequent snapshot observations)

• Long exposures are also necessary to monitor time variability - typical of novae on time scales ranging from minute to hour- periodic and aperiodic

• High resolution spectra offer unique insight into atmospheric layer close to H-burning shell.

Turn-on and turn-off timesTurn on: delayed by self absorption in the wind/shell, depends on the mass/chemistry of the ejecta. Generally nova is “on” when mass loss ceases.

Turn off: IF the abundances are those of CNO ashes, long t(off) implies mass increase on secular time scales. Also indicates quantity of accreted mass before outburst.

M31

MW

M31 novae seem to be X-ray sources for longer.

Selection effect? Probably not.

Other M31(temptative,partial Chandra HRC-I results)

A new picture of the outburst is emerging

• We are beginning to obtain statistical correlations with different physical parameters.

• Nova outbursts do not seem to have a unique, continuous mass loss mechanism (not discussed in present talk)

• There are 3 possibilities for the burning material composition: re-accreted, WD erosion, CNO-ashes: at least in RS Oph and V4743 Sgr we “see” old CNO ashes

• Periodic variations of the SSS with the orbital/rotational period, pointing out at an important role of the magnetic field.

Figure includes GQ Mus, N LMC 2005, V4743 Sgr, V5116 Sgr, V1974 Cyg, RS Oph V2491 Cyg. V723 Cas and “Catalina nova” confirm picture with lower limits (not plotted).

Relationship between t(3) and T(X-ray turnoff) exists but isnot perfectly linear. The nova physics is just a little toocomplex (dust, secondary embedded in the nebula, newepisodes of mass loss?)

“Stunted” flare lasting about1000 s, with rise time ~200 s,seen once in (almost) every orbital phase => was it the same phenomenon driving the “flare” on V1494 Aql?

V5116 Sgr

Only lower emission measureduring minimum (T, N(H) same?)

Large polar cap with “spongy” atmosphere” in a polar system.“Craters” form in the atmosphere in the area where accretion streamtouches/touched surface (UV emitting surface, large area subtended)

Cartoon model for V5116 Sgr interpreted as a polar.

Orbital modulationsP ~1.8 days

CSS 081007: spectrum obtained only at maximum right after the peak.T~720,000 K, some emission lines on WD continuum

We need IXO toresolve grating spectraover the orbital phasefor a significant numberof novae, and to probeabundances, temperatureand effective gravity ofalmost any nova inthe Galaxy and in the MC.