There are two primary ways in which the products of nucleosynthesis in stellar interiors may appear at the surface of a star. These are mixing and/or loss of the original unburned stellar envelope. In interacting binaries, overflow can contribute dramatically to envelope loss. The simplest abundance anomalies to be expected from nuclear burning of hydrogen, helium, or carbon would be under or over abundances H, He, C, O, Ne, and Mg. In addition, it is expected that carbon is initially severely depleted, while nitrogen is enhanced during hydrogen burning via the CNO cycle in stars above two solar masses. Other, more subtle anomalies are also expected, and elements heavier than magnesium can be created during very late evolution by nuclear burning in massive stars. Consequently, it is expected that abundance anomalies of various kinds should occur in interacting binaries where one or both stars have lost significant amounts of mass

Mccluskey, Carolina P. S.

English

NASA Technical Reports Server

Final Status Report
covering the period
1 December 1988 - 30 November 1990
f /&
for
NASA GRANT NAG 5-1107
Archival Research Program
International Ultraviolet Explorer
Principal Investigator:
Dr. Carolina P.S. McCluskey
Penn State Allentown Campus
6090 Mohr Lane
Fogelsville, PA 18051-9733
The NASA Technical Officer for this grant is
Dr. Yoji Kondo,
NASA Goddard Space Flight Center, Code 684,
Greenbelt, MD 20771
(NASA-CR-187909) A_UNOANCE ANOMALIES OF
CAR_tjN AND NITi_OGEN IN THE TUE SPECTRA OF
ALGOL-TYPE INTERACTING AINA_TES Fin31 Stetus
Report_, 1 DeC. 1988 - 30 Nov. 1990
(Pcnnsylv_ni3 State Univ.) 12 p CSCL 03A G3/_9
1
N91-25972
https://ntrs.nasa.gov/search.jsp?R=19910016658 2020-03-19T16:51:54+00:00Z
Final Status Report
NASA GRANT NAG 5-1107
1 December 1988 - 30 November 1990
Abundance Anomalies
of Carbon and Nitrogen
in the IUE Spectra
of Algol-type Interacting Binaries
I. Introduction
There are two primary ways in which the products of
nucleosynthesis in stellar interiors may appear at the
surface of a star. These are mixing and/or loss of the
original unburned stellar envelope. In interacting binaries,
overflow can contribute dramatically to envelope loss. The
simplest abundance anomalies to be expected from nuclear
burning of hydrogen, helium, or carbon would be under or over
abundances of H, He, C, O, Ne, and Mg. In addition, it is
expected that carbon is initially severely depleted while
nitrogen is enhanced during hydrogen-burning via the CNO
cycle in stars above 2 solar masses. Other, more subtle
anomalies are also expected and elements heavier than
magnesium can be created during very late evolution by
nuclear burning in massive stars. Consequently, it is
expected that abundance anomalies of various kinds should
2
occur in interacting binaries where or both stars have lost
significant amounts of mass,
The cool subgiant or giant in the classical Algol
systems might be expected to show abundance anomalies since
up to 80% or 90% of the original mass may have been lost in
some cases. Parthasarathy, Lambert, and Tomkin (1983) find
that [Fe/H] = 0.0 ± 0.3, [C/Fe] = -0.5, and [N/Fe] = +0.5 for
the secondaries of U Cep and U Sge. In addition, [C/Fe] =
-0.5 for the very low mass secondary of S Cnc. In
comparision with average field giants, [C/Fe] = 0.25 ± 0.1
and [N/Fe] = +0.5 ± 0.i for these systems. The observed over
abundance of nitrogen is significantly less than expected
from CNO nucleosynthesis while carbon should be i0 - i00
times less abundant than observed. It was proposed that
after some mass loss from the original primary star, mixing
between the core and envelope dilutes the enhancement of
nitrogen and the corresponding carbon deficiency.
It is normally impossible to observe the secondary
star's spectrum with sufficient resolution to allow accurate
abundance analysis because the primary star dominates the
spectrum. Since the primary star has presumably accreted
matter from the secondary star, abundance anomalies might be
expected in its atmosphere. Cugier and Hardorp (1988a,b)
have investigated the [C/H] and [N/H] ratios in many B-type
single stars and the [C/H] ratio in a number of Algol system
primaries. They proposed that rapid rotation can cause large
3
scale mixing and desired to test this hypothesis. Of 108
single stars, only 5 showed nitrogen anomalies but these were
uncorrelated with carbon abundances. No clear cut dependence
on projected rotational velocity was detected, although two
of the most rapidly rotating stars, _ Leo and 2 Aqr, showed
the lowest carbon abundances; 0.07 and 0.02 times the solar
values, respectively. The Algols 8 Lib, RS Vul, and U Sge
had solar carbon abundances as did the B-type binary u Her.
The Algol systems TX UMa, _ Per, Tau, and U CrB exhibit
carbon under abundance of factors of 1.8 - 2.1 with respect
to the sun. Non-LTE (Local Thermodynamic Equilibrium)
effects were investigated and would lead to [C/H] values
larger than the LTE values by 0.i0 - 0.15.
Tomkin and Lambert (1989) determined the chemical
composition of the primary star in the low activity Algol
system R CMa which has a very low mass secondary component.
They found [C/H] = 0.0 ± 0.2, [N/H] = 0.4 ± 0.2, [O/HI = 0.3
± 0.3, [S/H] = 0.I ± 0.2, and [Fe/H] = 0.i ± 0.i. It is
concluded that the previous mass transfer in R CMa must have
been non-conservative and/or that mixing occurred.
Considering all of the assumptions involved, it is difficult
to be certain wherther or not any abundnace anomalies have
been detected in classical Algol systems. In most Algol
systems absorption lines of Si IV, C IV, and sometimes N V
are detected outside of eclipse. These ions are often
detected in emission during the totality phase of primary
eclipse (Plavec 1989). In the dynamic Algols the emission
4
lines are always detectable. Peters and Polidan (1984)
analyzed the C IV absorption in several classical Algol
systems and concluded that carbon is about i0 times under
abundant. However, C IV emission lines detected during
totality in Algols are almost always the strongest emission
lines (Sahade 1986). McCluskey and Sahade (1987) have
suggested that C IV emission is filling in the C IV
absorption, causing it to mimic under abundance. Gimenez and
Claret (1989) study the irradiation of Algol secondaries by
the hot primary star and find that the irradiated spectra can
be very different than the normal spectrum and that some
absorption lines can be filled-in by emission.
An interesting Algol system is V 356 Sgr (A2 II + B3/4
V; P : 8.896 days), which had been observed with the
International Ultraviolet Explorer and Voyager. Polidan
(1988) detected no C IV emission during the total eclipse of
the B-star by the A-star and no carbon was detected in the
A-star's ultraviolet spectrum. Si IV and N V emission are
quite strong during totality. Perhaps the A-star really is
carbon-deficient.
In this report we dlscuss_the measurement of the
equivalent widths of the C II, C IV, and N V resonance
doublets in standard stars and Algol-type binaries.
5
II. Discussion
Table 1 lists equivalent widths of the resonance
doublets of C II, C IV, and N V for 26 standard stars with
spectral types from 09.5 - A5 and of luminosity classes III,
IV, and V. Table 2 lists the same quantities for 23
Algol-type interacting binaries within the same spectral and
luminosity class range. All measurements were made from high
resolution IUE spectra at the GSFC Regional Data Analysis
Facility.
Table I shows that for normal B-type stars N V does not
appear for spectral types later than B2.5 with one exception.
The B3 V star HD 32630 has N V absorption features much
stronger than expected whereas the C II and C IV features are
within the normal range of strengths for B3 V stars. The
reason for this great strength of the nitrogen resonance
doublet is unknown. The resonance doublet of C IV is
detectable in absorption in spectral types as late as B6. No
obvious anomalies are present in the C II and C IV line
strengths for the standard stars with the exception of the B
2.5 IV star HD 35708 in which C IV is much weaker than normal
although C II appears normal. These results are in good
agreement with earlier work, e.g. Slettebak and Carpenter
(1983).
In the Algol binaries, as indicated in Table 2, the C II
line strength are in general very similar to those found in
the standard stars. Only in SX Aur (B3 V) is it a little
weaker than normal. The strongly interacting binary AX Mon
(B2 III) shows considerable excess in strength of C [I, C IV,
and N V lines. This is probably due to extensive mass flow.
The C IV resonance doublet is stronger than it is in the
standard stars in about 66% of the Algol binaries observed.
It is seen in spectral types as late as B9. The N V
absorption is also stronger in about 40% of the Algol systems
than in standard stars and is observed in spectral types as
cool as BS.
7
III. Conclusion
The C II resonance doublet provides a relatively good
indicator of carbon abundance since it is considerably less
influenced by mass flow effects than most other strong
ultraviolet lines in B-type stars. A comparison of C II
equivalent widths in 26 standard stars and 23 Algol binaries
shows that in general the carbon abundance in these two
groups does not differ by more than a factor of 2.
The C IV and N V line strengths are very sensitive to
mass flow and will not provide good abundance determinations
until a detailed understanding of the physical conditions in
which they are formed becomes available. It is of interest
to note that the C IV and N V line strengths in many Algol
systems are similar to those observed in Be stars. A more
detailed discussion of these results is being prepared for
publication.
8
References
Cugier, H. and Hardorp, J. 1988a, A.Ap., 197, 163.
Cugier, H. and Hardorp, J. 1988b, A.Ap., 202, i01.
Gimenez, A. and Claret, A. 1989, Sp. Sci.Rev., 50, 343.
McCluskey, G. E., Jr. and Sahade, J. 1987, in ExDlorin_ the
Universe with the IUE Satellite, ed. Y. Kondo (Dordrecht,
Reidel), p. 427.
Parthasarathy, M., Lambert, D. L., and Tomkin, J.
M.N.R.A.S., 203, 1063.
1983,
Peters, G. J. and Polidan, R. S. 1984, Ap.J., 283, 745.
Plavec, M. J. 1989, Sp. Sci.Rev., 50, 95.
Polidan, R. S. 1988, in A Decade of UV Astronomy with the IUE
fz_, ed. E. J. Rolfe, ESA SP-281, p. 205.
Sahade, J. 1986, in New Insights in Astrophysics, ed. E. J.
Rolfe, ESA SP-263, p. 267.
Slettebak, A. and Carpenter, K. G. 1983, Ap.J.SuppI., 53, 869.
Tomkin, J. and Lambert, D. L. 1989, M.N.R.A.S., 241, 777.
9
Table 1
Standard Stars -- Equivalent Widths
HD Sp T C II C IV N V
15371 B5 IV
32630 B3 V
34816 B0.5 IV
35039 B2 IV
35708 B2.5 IV
36512 B0 V
36959 B1 V
36960 B0.5 V
38666 09.5 V
39060 A5 V
39283 A2 V
50707 B1 IV
53929 B9.5 III
74280 B3 V
80007 A2 IV
89021 A2 IV
90994 B6 V
97633 A2 V
128345 B5 V
183324 A0 V
188665 B5 V
209952 B7 IV
214994 A1 IV
215573 B6 IV
2 88
2 76
0 90
1 42
1 66
1 14
1 20
1 08
1 04
1 96
2 41
1 16
2 27
1 76
1 81
1 81
2 46
1 84
2 67
2 56
2.46
2.9O
2.27
3.00
0 49/0.36
0 54/0.32
1 92/1.29
0 81/0.50
0 15/0.16
2 37/2.00
0 35/0.27
2 00/1.60
3 72/2.71
absent
absent
0.87/0.60
absent
0.50/0.47
absent
absent
0.35/0.28
absent
0.43/0.32
absent
0.44/0.25
absent
absent
absent
absent
1 26/0 67
0 37/0 34
0 32/0 20
0 30/0 19
0 42/0 28
0 40/0 22
0 52/0 30
0 90/0 46
absent
absent
0.20/0.14
absent
absent
absent
absent
absent
absent
absent
absent
absent
absent
absent
absent
i0
HD
Table 1 continued
Standard Stars -- Equivalent Widths
Sp T C II C IV
222661 B9.5 V 2.37 absent
224686 B9 IV 2.94 absent
N V
absent
absent
II
HD Name Sp T C II C IV
Table 2
Algol Binaries -- Equivalent Widths
NV
2.79
2.62
2.33
2 33
2 02
2 37
1 16
2 19
3 30
2 24
2 17
2 15
2 40
1 87
1 89
2 12
3.60
1 42
1 52
1 56
2 77
2 30
2 24
O. 41/0.40
0.25/0.20
0.26/0.26
0.24/0.15
0.23/0.19
2.75/2.60
0.32/0.20
0.80/0.51
0.42/0.34
0.29/0.25
0.42/0.42
0.86/0.42
0.64/0.41
0.91/0.61
0.76/0.50
1486 TV Cas B9 V
3369 _ And B5 V
6882 Phe B6 V
19356 _ Per B8 V
25204 Tau B3 V
29365 HU Tau B8 V
33357 SX Aur B3 V
44701 IM Mon B5 V
45910 AX Mon B2 III
50846 AU Mon B5 V
72754 B8 I
76805 B5 V
93033 TX UMa B8 V
93206 QZ Car B0 I
134687 e Lup B3 III
136175 U CrB B6 V
151676 VIOIO Oph A5 V
151880 u Sco BI.5 V
156633 u Her B2 IV
173787 V356 Sgr B3 V
180939 RS Vul B5 V
181182 U Sge B7 V
185507 a Aql B3 V
0.23/0.13
0.29/0.19
0.38/0.34
2.33/1.57
0.65/0.36
0.42/0.24
O. 39/0.36
0.23/0.17
0.27/-
0.64/0.39
12


Abundance anomalies of carbon and nitrogen in the IUE spectra of Algol-type interacting binaries

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