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 times
Turn 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
M31 novae
seem to be Xray sources
for longer.
Selection
effect?
Probably not.
MW
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 is
not perfectly linear. The nova physics is just a little too
complex (dust, secondary embedded in the nebula, new
episodes of mass loss?)
V5116 Sgr
Only lower emission measure
during minimum (T, N(H) same?)
“Stunted” flare lasting about
1000 s, with rise time ~200 s,
seen once in (almost) every
orbital phase => was it the
same phenomenon driving
the “flare” on V1494 Aql?
Large polar cap with
“spongy” atmosphere”
in a polar system.
“Craters” form in the
atmosphere in the area
where accretion stream
touches/touched surface
(UV emitting surface,
large area subtended)
Cartoon model for V5116 Sgr
interpreted as a polar.
Orbital modulations
P ~1.8 days
We need IXO to
resolve grating spectra
over the orbital phase
for a significant number
of novae, and to probe
abundances, temperature
and effective gravity of
almost any nova in
the Galaxy and in the MC.
CSS 081007: spectrum obtained
only at maximum right after the peak.
T~720,000 K, some emission lines
on WD continuum