Nova Vul 1984 no. 2 was observed with IUE from Dec. 1984 through Nov. 1987. The spectra are characterized by strong lines from Mg, Ne, C, Si, O, N, and other elements. Data obtained in the ultraviolet, infrared, and optical show that this nova is ejecting material rich in oxygen, neon, and magnesium

Ferland, Gary

Gallagher, J. S.

Sonneborn, G.

Sparks, Warren M.

Starrfield, S.

Stryker, L. L.

Truran, James W.

Wade, R.

Wagner, R. M.

Williams, R. E.

English

NASA Technical Reports Server

, ._,,-/- ..) ,
N89-10709 163
PRECEDING PAGE BL&NK NOT FILMED
OBSERVATIONS AND SIMULATIONS OF NOVA VUL 1984 #2:
A NOVA WITH EJECTA RICH IN OXYGEN, NEON, AND MAGNESIUM
S. Starrfield
Department of Physics, Arizona State University and
Theoretical Division, Los Alamos National Laboratory
G. Sonneborn
IUE Observatory, Goddard Space Flight Center
L. L. Stryker
Department of Physics, Arizona State University
Warren M. Sparks
Applied Theoretical Physics Division
Los Aiamos National Laboratory
James W. Truran
Department of Astronomy, University of Illinois
Gary Ferland and R. M. Wagner
Department of Astronomy, Ohio State University
J. S, Gailagher
Lowell Observatory
R. Wade
Steward Observatory, University of Arizona
R. E. William_
Cerro Tololo Interamerican Observatory
Robert D. Gehrz and Edward P. Ney
Department of Astronomy, University of Minnesota
Scott Kenyon
Center for Astrophysics, Harvard University
G. Shaviv
Department of Physics, The Technion
C. -C. Wu
Space Telescope Science Institute
ABSTRACT
Nova Vul 1984 #2 has been observed with the IUE
Satellite from December 1984 through November 1987
and we expect to be able to observe it with the IUE
Satellite for at least another two years. These spectra
are characterized by strong lines from Mg, Ne, C, Si,
O, N, and other elements. Data obtained in the ultra-
violet, infrared, and optical show that this nova is
ejecting material rich in oxygen, neon, and magnesium.
1. Introduction
Novae occur in cataclysmic binary systems in which a
Roche lobe filling secondary is losing hydrogen-rich
material through the inner Lagrangian lobe onto a
white dwarf primary. Theoretical studies show that
the accumulating shell of hydrogen on the white dwarf
is unstable to a thermonuclear runaway and simulations
of this phenomena reproduce many of the observed
features of a nova explosion (Starrfield, Truran, and
Sparks 1978; Sparks, Starrfield, and Truran 1978;
Gallagher and Starrfield 1978; Starrfield 1986, 1987;
Starrfield, Sparks, and Truran 1985; 1986; Starrfield,
Sparks, and Shaviv 1987). The models further imply
that the energetics of the outburst, and thus the type
of nova, is not only sensitive to the abundances of the
intermediate mass elements, but also depends on other
factors such as the mass of the accreted shell, white
dwarf mass, and accretion rate (Truran 1982; Starrfield
1986, 1987; Shaviv and Starrfield 1987).
In addition, as a direct result of IUE observations of
previous novae such as V693 CrA (Williams etal. 1985)
and V1370 Aql (Snijders et al. 1987), we were able to
show that there were two classes of novae: those in
which the outburst occurs on a carbon-oxygen white
dwarf and those in which the outburst occurs on an
oxygen-neon-magnesium white dwarf (Starrfield, Sparks,
and Truran 1986).
The third nova to show the characteristics of an
oxygen-neon-magnesium white dwarf was Nova Vul 1984
#2. However, unlike the previous novae, it is a slow
nova that has declined from _a maximum visual magni-
tude of -+5 to -+12 in the last 3.5 years. This has
allowed us to follow its outburst both in the optical
and in the ultraviolet.
In addition, X-ray data were obtained early in the
outburst with Exosat which indicated that as early as
1985 there was a hot source in the system radiating at
a temperature of about 3 x 105K. This high a temper-
ature is fully expected by the numerical modeling
(Starrfield, Sparks, and Truran 1986) and was observa-
tionally confirmed by infrared observations of coronal
lines (Greenhouse et al. 1987). In addition, other
infrared studies found that this nova formed silicate
dust, which implies an overabundance of oxygen with
respect to carbon (Gehrz et al. 1986), and showed
strong infrared evidence for enhanced neon (Gehrz et
al. 1986). All of these data warrant continued
observations of this nova.
A Decade of UV Astronomy with IUE, Proc. Celebratory Symposium, GSFC, Greenbelt, USA, 12-15 April 1988, ESA SP-281, Vol. I (June 1988)
https://ntrs.nasa.gov/search.jsp?R=19890001338 2020-03-20T05:58:16+00:00Z
164 S STARRFIELD ET AL
We are also continuing to model this outburst in order
to learn more about outbursts that occur on oxygen,
neon, magnesium white dwarfs. Further work on this
nova is required since our published studies of
outbursts on oxygen, neon, and magnesium white
dwarfs only produced "fast" outbursts (Starrfield,
Sparks, and Truran 1986). We are currently improving
our hydrodynamic stellar evolution code in order to
calculate new simulations of this nova. These
improvements include the effects of accretion energy
on the evolution, elemental diffusion between the
acereted material and the white dwarf, and a large
nuclear reaction network with new rates.
2. Observations of the Outburst
In Figures 1, 2, and 3, we show SWP ahd LWP images
of Nova Vul 1984 #2 on June 24, 1985 (the LWP image
was obtained on July 2, 1985); September 11, 1986;
and November 15, 1987. These spectra are not the
only ones that we have obtained but were chosen to
represent the changes that have occurred in this object
over time. The spectrum shown in Figure 1 was taken
just after the nebular lines began to appear and the
spectrum shown in Figure 3 is the latest spectrum that
we have obtained. Table 1 gives the lines, their
identification, when known, and whether or not they
were present on a given date.
It is clear from the lines that are present that this is
a "neon" nova. It has virtually the same elements and
ions as found in both Nova V693 CrA (Williams etal.
1985) and Nova V1370 Aql 1982 (Snijders et al. 1987).
The primary indicators are the strength and simul-
taneous presence of [NEW] 1602A and [NEW] 2422A.
We also note that [NeV] 3346A, is one of the strongest
lines in the spectrum. Note that at the same time as
these spectra were taken, Gehrz et al. (1986) reported
that [Nell] 12.gram was strong. The great strength of
these multiple ionization states of neon, all occurring
at the same time, strongly argue for its enhancement
in this nova. The strength of the magnesium and
oxygen lines also argues that these elements are
overabundant. All of the fluxes have been determined
for these spectra and the analysis is presently in
progress. We note that the presence of all of the
forbidden neon lines, both in the ultraviolet and the
optical, plus the forbidden oxygen lines will allow us
to solve for the electron density and temperature
simultaneously.
In addition to the ultraviolet data, we have also
obtained infrared and optical data on this nova. The
infrared data has " been discussed and reviewed by
Gehrz (1988). The data show that this nova formed
silicate grains and is currently exhibiting coronal line
emission. In figures 4 and 5, we show optical spectra
obtained by one of us (RMW) at the 1.8m Perkins
Reflector of the Ohio Wesleyan and Ohio State
Universities at the Lowell Observatory. The spectra
are numbered from the beginning of the outburst.
Note the strong emission from [Ne III] which is still
present even very late in the outburst. There are also
coronal lines present in the optical spectra.
3. Discussion
As already mentioned in Starrfield, Sparks, and Truran
(1986), the presence of an oxygen, magnesium, neon
white dwarf in a close binary system is an important
constraint on our theories of stellar evolution. First,
the calculations of single star evolution show that in
order for a star to survive carbon burning its mass on
the main sequence must exceed about 8M® to 10M®.
Second, for it to end up as a member of a nova system
requires that it had to evolve as a single star for
much of its life before its radius reached to the point
where it interacted with the secondary. At this point,
it had to have lost most of its main sequence mass (if
it had not lost it already) which carried away most of
the angular momentum of the binary. Because it was
in a binary, it lost all of the remaining hydrogen and
helium layers and, possibly, some of the carbon burning
layer. However, the differences in the ejected carbon
abundances of V693 CrA, V1370 Aql, and VI500 Cyg
suggest that the amount of carbon lost is variable. On
the other hand, hot hydrogen burning will produce a
significant amount of carbon from oxygen.
Acknowledgements
This study would not have been possible without the
rapid response of the IUE Observatory to the request
for Target-of-Opportunity observations
and we are grateful for their continued support of
nova observations. The data were reduced with the
facilities of the RDAF at the University of Colorado,
which are supported by NASA Grant NAS5-28731, and
the assistance of T. Armitage. We also acknowledge
partial support for this research from NASA, NSF, and
the DOE through grants to our various institutions.
References
Gallagher, J.S., and Starrfield, S. 1978, Ann. Rev., 16,
171.
Gehrz, R. D. 1988, Ann l_gv Ast An, in press.
Gehrz, R.D., Grasdalen, G.L., Greenhouse, M., Hackwell,
J.A., Hayward,T., and Bentley, A.F. 1986,
Lett., 308, L67.
Gehrz, R.D., Grasdalen, G.L., and HackweU, J.A. 1985,
Ao. J. Lett.. 298, L163.
Greenhouse, M.A., Grasdalen, G.L., Hayward, T.L.,
Gehrz, R. D., and Jones, T. J. 1988, A. J., in
press.
Shaviv, G., and Starrfield, S. 1988, ProceedinRs of IAU
Cell #95: 2nd Conference on Faint Blue Stars, ed.
A. G. D. Philip, D. S.Hayes, and J. Liebert (NY: L.
Davis Press),in press 1987.
Snijders, M.A.J., Batt, T.J., Roche, P.F., Seaton, M.J.,
Morton, D.C., Spoelstra, T.A.T., and Blades, J.C.
1987, M.N.R.A.S., 228, 329.
Sparks, W.M., Starrfield, S., and Truran, J.W. 1978, Ao.
J.,220, I063.
Starrfield, S. 1986, in Radiation Hydrodynamics in Stars
and Comoact Objects. ed. D. Mihalas and K.-H.
Winkler (Springer:New York),p. 225.
Starrfield, S. 1987 in New Insights in Astrophysics:
Eight Years of Ultraviolet Astronomy wilh I_TE,
ed. E. Rolfe, ESA press, (Nordwijk) SP- 263, 239,
1986.
Starrfield, S., Sparks, W.M., and Shaviv, G. 1988, ADJ.,
325, L35.
Starrfield, S., Sparks, W.M., and Truran, J.W. 1985,
Ao.J., 291, 136.
Starrfield, S., Sparks, W.M., and Truran, J.W. 1986,
AD.J. Lett., 303, L5.
Starrfield, S., Truran, J.W., and Sparks, W.M. 1978, A_D.,
J., 226, 186.
Truran, J.W. 1982, in Essays in Nuclear AstroDhwic,%
ed. C.A. Barnes, D.D. Clayton and D.N. Schramm
(Cambridge, Cambridge Univ. Press), p. 174.
Williams, R.E., Sparks, W.M., Gallagher, J.S., Ney, E.P.,
Starrfield, S.G., and Truran, J.W. 1981, ADJ., 251,
221.
Williams, R.E., Ney, E.P., Sparks, W.M., Starrfield, S.,
Truran, J.W. 1985, M.N.R.A.S.. 212, 753.
OBSERVATIONS& SIMULATIONSFNOVAVUL1984# 165
TABLE 1
LINE ID DATE
(A) ION l 2
1216 Lye p p p
1240 NV p p p
1304 OI p
1335 CII p p
1371 OV p
1397 SilV p
1402 OIV] p p
1486 NIV] p p p
1549 C1V p p p
1575 [NeV] p
1602 [NelV] p p p
1640 Hell p p p
1663 [O111] p p p
1750 NIII] p p p
1806 [MgVI] p
1814 Sill p
1846 ?
1857 AIIII p
1892 Si IIl] p p
1909 CIII] p p
2326 Cll]
2422 [NeIV]
2510 [MgVlI]
2604 [AIVI]
2629 [MgVll] p
2670 AIII] p
2800 Mgll p
2835 Pill
2929 [MgV]
2974 [NeV]
3047 OIIl
3133 O111 p
3251 ?
3346 [NeV] p
P
P P
P
P
P P
p
P P
P P P
P P P
P P
P P P
P P
P P P
P P P
P P P
P P P
t.
7
?
2
1200 IdO0 1400 1500 1600 1700 1800 1900
_AVELENGTH (A)
Figure la. The SWP spectrum was obtained on June
24, 1985 at a time when the magnitude of the nova
was +10. It is a 24 minute exposure. Lye was present
at all times but is too strong to show on the same
plot. Note that the flux scaling is different in all of
the plots.
!--F_ ' ' I ' ' ' l__l-r',
.<
'E
°!
o
2200 240O 2600 8800 3000 3200 3400
WAVELENGI H (_)
Figure lb. The LWP spectrum was obtained on July 2,
1985 and is a 4 minute exposure. Note that six months
after discovery this slow nova still shows a cool
continuum. The strong line at 3346A is either [Ne V]
or [Ne I11]. Mg 1I 2800A is very overexposed.
?
7E
u
,Q_,,r7°o7o,, ?_,,_,,% _'y;%,,,%,, j .... ,,,,
1200 1300 1400 1500 1600 1700 1800 1900
WAVELENGTH (_)
2
'o
2200 2400 2600 2800 3000 3200 3400
WAVELENGTH {_)
Figure 2a. The SWP spectrum was obtained on
September 11, 1986. The nova had declined to 11.4
and this was a 38 minute exposure. The strong line at
1602A is [Ne IV].
Figure 2b. The LWP spectrum is a 12 minute exposure
on the same day as the SWP spectrum. By this time
[Ne IV] 2422 is present and strong and the line at
3346A is definitely [Ne V]. The simultaneous presence
of [Ne IV] 1602A and 2422A requires that neon be
enhanced. Again Mg II 2800A is very exposed.
166 S STARRFIELD ET AL
L_ _ _ _ _ ........°%0.? ,T_. P o_...... . .... i .... I '_-
R_
_2
LI,,,I,,,,I, ,, i i I J i i _ q I i t ' _ I I i
1200 1300 1400 1500 1800 1700 1800 1000 2000
WAVELENGTH (_)
7 m
-
2200 24O0 26OO 38OO 3OO0 32OO 34OO
WAVELENGTH (_)
Figure 3a. The SWP spectrum is a 200 minute exposure
and the nova has now declined to 13.4. It was
obtained on November 15, 1987. [Ne IV] 1602A has
declined markedly since the last SWP spectrum was
taken.
Figure 3b. The LWP spectrum was taken on the same
day as the SWP spectrum and is a 40 minute exposure.
While the neon lines are still prominent, Mg II 2800A
has virtually disappeared.
_- + I .... ] .... I _ ' ' ' I .... I ' ' ' '
Nova Vu] 1984 //2
. + - _ __- _ =- =
A Be4
4000 5000 6000 7000 8000
WAVELENGTH (._)
533 -
?-
o j , I ' _ ' '
?
o
,,< ?
.... _'+';'°;', , _ .... i ,'+,';"-,"
400O 5000 50C)0 ?000 0000
IVAVVLFNCTH (_.)
Figure 4. This is a montage of the optical spectra
taken by R.M. Wagner. The number on the RHS of
each spectrum is the day since outburst. Note how
slowly this nova became nebular. The great strength
of the neon lines, with respect to the [O III] lines,
also argues for non-solar neon abundances.
Figure 5. This is the latest optical spectrum of the
nova obtained by Wagner. The [NelV] lines are still
present and strong enough to use to determine the
density and temperature in the region where [O III] is
formed (see text).


Observations and simulations of nova Vul 1984 no. 2: A nova with ejecta rich in oxygen, neon, and magnesium

Observations and simulations of nova Vul 1984 no. 2: A nova with ejecta rich in oxygen, neon, and magnesium

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