One of the major results from the IUE may prove to be the knowledge gained by studies of the ultraviolet spectra of symbiotic stars. Symbiotics combine spectral features of a cool M giant like photosphere with strong high excitation emission lines of nebular origin, superposed. The UV spectra are dominated by intense permitted and semiforbidden emission lines and weak continua indicative of hot compact objects and accretion disks. Two symbiotics, AR Pav and CI Cyg are thought to be eclipsing binaries and IUE observations during the 1980 eclipse of CI Cygni are discussed

Boyarchuk, A. A.

Kafatos, M.

Michalitsianos, A. G.

Stencel, R. E.

English

One of the major results from the IUE may prove to be the new knowledge gained by studies of the ultraviolet spectra of symbiotic stars. Symbiotics combine spectral features of a cool M giant-like photosphere with strong high excitation emission lines of nebular origin, superposed. An excellent pre-UV review has been given by Swings (i). The UV spectra are dominated by intense permitted and semi-forbidden emission lines and weak continua indicative of hot compact objects and accretion disks. Two symbiotics, AR Pay and CI Cyg are thought to be eclipsing binaries, and we have begun IUE observations during the predicted 1980 eclipse of CI Cygni.https://digitalcommons.chapman.edu/scs_books/1004/thumbnail.jp

Michalitsianos, Andrew G.

Kafatos, Menas

Boyarchuk, Alexander A.

Chapman University Digital Commons

Chapman UniversityChapman University Digital CommonsMathematics, Physics, and Computer ScienceFaculty Books and Book Chapters Mathematics, Physics, and Computer Science1981Ingress Observations of the 1980 Eclipse of theSymbiotic Star CI CygniR. E. StencelAndrew G. MichalitsianosMenas KafatosChapman University, kafatos@chapman.eduAlexander A. BoyarchukFollow this and additional works at: http://digitalcommons.chapman.edu/scs_booksPart of the Instrumentation Commons, and the Stars, Interstellar Medium and the GalaxyCommonsThis Book is brought to you for free and open access by the Mathematics, Physics, and Computer Science at Chapman University Digital Commons. Ithas been accepted for inclusion in Mathematics, Physics, and Computer Science Faculty Books and Book Chapters by an authorized administrator ofChapman University Digital Commons. For more information, please contact laughtin@chapman.edu.Recommended CitationStencel, R.E., Michalitsianos, A.G., Kafatos, M., Boyarchuk, A.A. (1981) Ingress observations of the 1980 eclipse of the symbiotic starCI Cygni. In R.D. Chapman (Ed.), The Universe at Ultraviolet Wavelengths: the First Two Years of International Ultraviolet Explorer.Proceedings of a symposium held at NASA Goddard Space Flight Center, Greenbelt, MD, May 7-9, 1980 (pp. 459-460).NASA Conference Publication 21 71 NAsA-cp-2fl I 19810017357 The Universe ofe$nteixational I I I [ *  - i ? - 1  by f> t $  $ 4 "  A r : !  [ J : : , k  2 b & . L 2 r t  . I .  t f ' 3 ,  ,,,- jb!ili & '  , a T ?  \ h\fl;, 1,  1 5  8c l i  ( I l'l-r*: I +  I ' J ~ P .  ' i  i ' ' ~ , I ' < i ' I  w Proceedings of a symposium held at NASA Goddard Space Flight ~en'ter Greenbelt, Maryland May 7-9, 1980 INGRESS OBSERVATIONS OF T_E 1980 ECLIPS_ OF T_E SYMBIOTIC STAR CI CYGNIRobert E. StencelJoint Institute for Laboratory Astrophysics - Univ. of Colo.& NBSAndrew G. MichalitsianosLaboratory for Astronomy and Solar Physics - Goddard Space Flight CenterMinas KafatosDepartment of Physics, George Mason UniversityAlexander A. BoyarchukCrimean Astrophysical Observatory, U.S.S.R. Academy of SciencesINTRODUCT IONOne of the major results from the IUE may prove to be the new knowledgegained by studies of the ultraviolet spectra of symbiotic stars. Symbioticscombine spectral features of a cool M giant-like photosphere with stronghigh excitation emission lines of nebular origin, superposed. An excellentpre-UV review has been given by Swings (i). The UV spectra are dominated byintense permitted and semi-forbidden emission lines and weak continua indica-tive of hot compact objects and accretion disks. Two symbiotics, AR Pay andCI Cyg are thought to be eclipsing binaries, and we have begun IUE observa-tions during the predicted 1980 eclipse of CI Cygni.SYSTEM PARAMETERSPeriodic albeit irregular light curve variations suggest that CI Cyg isan eclipsing binary, with the elements: minimum light = JD 2411902+855.25E.Boyarchuk has predicted ingress to begin about April i0, 1980 and egress toend about August 18, 1980, with a nearly I00 day totality. The visual mag-nitude range fluctuates between +i0 m and +12m with outbursts to +9m known.Light curves are described by Mattei (2) and Belyakina (3).QUESTIONS TO BE ADDRESSEOObviously the time variation of the UV line and continuum flux can beused to constrain the physical dimensions of the line-emitting regions andthereby used to discriminate among various excitation mechanisms. It may bepossible to determine something about the origin and extent of mass transfer.Since the system inclination is known, information about the existence andnature of an accretion disk might be obtained, as well. These questions areposed in the light of recent IUE studies which will also be presented at thisconference. In particular, Plavec (4) argues that a connection between BetaLyr stars, W Ser stars and symbiotics (AR Pav) can be made in commonality ascase B mass-transferring binaries (rates of -6 or more in the log) and accre-tion onto non-degenerate stars. IUE observations of RW Hya by Kafatos etal. (5) have been used to argue that tidal interaction on the cool objectcan greatly augment the intrinsic stellar wind and lead to the observedaccretion effects° The visibility of UV continua from accretion disks amongsymbiotics may be a complicated function of densities and viewing angles.459We hope to be able to address several of these concerns with eclipse obser-vations of CI Cyg.PRE-INGRESS AND INGRESS OBSERVATIONSAt the time of this writing we have obtained spectra on March 16, and April16 and 25. The March 16 spectra in SWP and LWR are remarkably similar toRW Hya (5) in showing numerous strong high excitation emission lines fromspecies like permitted N V and C IV and semi-forbidden O IV, O III and N III,among others. In contrast to RW Hya where evidence for a I00,000 K continuunis seen, CI Cyg shows a weak Balmer continuum emission falling off towardshigher frequencies. Also CI Cyg shows strong O III lines at 3047 and 3133 Awhich are frequently seen in Miras and planetary nebulae but not strongly inRW _ya. These are Bowen fluoresced by }_ II Lye. The measured line fluxesin CI Cyg are generally 2 to i0 percent of those in RW Hya. C IV 1550 forexample had an integrated_flux of about 2E-II ergs/cm2/s on March 16, 1980.We note that for reasonable assumptions about distance (cf. 5) for CI Cygni,we can compare fluxes in C IV against Mg II for symbiotics much as Ayres hasdone for normal cool stars (see paper by Ayres in these proceedings) andfind symbiotics like CI Cyg and RW Hya lie three orders of magnitude abovethe C IV-_ II flux correlation for normal cool stars. We interpret this tobe a manifestation of different physical mechanisms involved: magneto-acoustic heating of the outer atmosphere for normal cool stars, versusphotoionization-recombination for the symbiotics.A preliminary comparison of the spectra obtained during ingressindicate a substantial decrease in the continuum at all wavelengths and anoticeable drop in the emission line flux from the higher excitation lines,particularly in the 1400 % blend of Si IV and O IV. A lie at 2830 A due toHe I also appears to be decreasing in strength, while the O III lines at3047 _ and 3133 _ may have slightly increased in strength. These changes aresuggestive of a stratified nebula, where the highest excitation regions arecentralized and of dimensions less than that of the M giant, of order 1012em. This region could represent the actual accretion disk. The O Ill linesmay arise from a more extended region (Bowen fluoresced), perhaps comparableto the orbital separation, of order 1014 cm. It is not obvious that we havedetected a hot companion star, given the weak cool continuum. Comparisonwith observations well out of eclipse and during a burst stage would beuseful. If other observers would like to supplement the observing plan,collaboration would be welcomed.REFERENCESi. Swings, P.,"Symbiotic Stars and Related Peculiar Objects" 1970 in Sp__ectroTiscop!c Astrophysics, G. Herbig, ed4 Berkeley, U. of Calif. Press, p. 189.2. Mattei, J.,"The Symbiotic Star CI Cygni", 1977 J.R.A.S.C. 70, 325.3. Belyakina, T. "Observations of CI Cygni in 1977-78", Info. Bull. Var.Stars, No. 1602.4. Plavec, M.,"IUE Observations of Long Period Eclipsing Binaries:Accretion onto Non-Degenerate Stars", 1980 U.C.L.A. Preprint No. 86.5. Kafatos, M., A.Michalitsianos, and R. Hobbs, "IUE Observations of RWHya", Astroph_s. J., 1980 in press.460

Ingress Observations of the 1980 Eclipse of the Symbiotic Star CI Cygni

NASA Technical Reports Server

INGRESS OBSERVATIONS OF T_E 1980 ECLIPS_ OF T_E SYMBIOTIC STAR CI CYGNI
Robert E. Stencel
Joint Institute for Laboratory Astrophysics - Univ. of Colo.& NBS
Andrew G. Michalitsianos
Laboratory for Astronomy and Solar Physics - Goddard Space Flight Center
Minas Kafatos
Department of Physics, George Mason University
Alexander A. Boyarchuk
Crimean Astrophysical Observatory, U.S.S.R. Academy of Sciences
INTRODUCT ION
One of the major results from the IUE may prove to be the new knowledge
gained by studies of the ultraviolet spectra of symbiotic stars. Symbiotics
combine spectral features of a cool M giant-like photosphere with strong
high excitation emission lines of nebular origin, superposed. An excellent
pre-UV review has been given by Swings (i). The UV spectra are dominated by
intense permitted and semi-forbidden emission lines and weak continua indica-
tive of hot compact objects and accretion disks. Two symbiotics, AR Pay and
CI Cyg are thought to be eclipsing binaries, and we have begun IUE observa-
tions during the predicted 1980 eclipse of CI Cygni.
SYSTEM PARAMETERS
Periodic albeit irregular light curve variations suggest that CI Cyg is
an eclipsing binary, with the elements: minimum light = JD 2411902+855.25E.
Boyarchuk has predicted ingress to begin about April i0, 1980 and egress to
end about August 18, 1980, with a nearly I00 day totality. The visual mag-
nitude range fluctuates between +i0 m and +12m with outbursts to +9m known.
Light curves are described by Mattei (2) and Belyakina (3).
QUESTIONS TO BE ADDRESSEO
Obviously the time variation of the UV line and continuum flux can be
used to constrain the physical dimensions of the line-emitting regions and
thereby used to discriminate among various excitation mechanisms. It may be
possible to determine something about the origin and extent of mass transfer.
Since the system inclination is known, information about the existence and
nature of an accretion disk might be obtained, as well. These questions are
posed in the light of recent IUE studies which will also be presented at this
conference. In particular, Plavec (4) argues that a connection between Beta
Lyr stars, W Ser stars and symbiotics (AR Pav) can be made in commonality as
case B mass-transferring binaries (rates of -6 or more in the log) and accre-
tion onto non-degenerate stars. IUE observations of RW Hya by Kafatos et
al. (5) have been used to argue that tidal interaction on the cool object
can greatly augment the intrinsic stellar wind and lead to the observed
accretion effects° The visibility of UV continua from accretion disks among
symbiotics may be a complicated function of densities and viewing angles.
459
https://ntrs.nasa.gov/search.jsp?R=19810017406 2020-03-21T12:27:03+00:00Z
We hope to be able to address several of these concerns with eclipse obser-
vations of CI Cyg.
PRE-INGRESS AND INGRESS OBSERVATIONS
At the time of this writing we have obtained spectra on March 16, and April
16 and 25. The March 16 spectra in SWP and LWR are remarkably similar to
RW Hya (5) in showing numerous strong high excitation emission lines from
species like permitted N V and C IV and semi-forbidden O IV, O III and N III,
among others. In contrast to RW Hya where evidence for a I00,000 K continuun
is seen, CI Cyg shows a weak Balmer continuum emission falling off towards
higher frequencies. Also CI Cyg shows strong O III lines at 3047 and 3133 A
which are frequently seen in Miras and planetary nebulae but not strongly in
RW _ya. These are Bowen fluoresced by }_ II Lye. The measured line fluxes
in CI Cyg are generally 2 to i0 percent of those in RW Hya. C IV 1550 for
example had an integrated_flux of about 2E-II ergs/cm2/s on March 16, 1980.
We note that for reasonable assumptions about distance (cf. 5) for CI Cygni,
we can compare fluxes in C IV against Mg II for symbiotics much as Ayres has
done for normal cool stars (see paper by Ayres in these proceedings) and
find symbiotics like CI Cyg and RW Hya lie three orders of magnitude above
the C IV-_ II flux correlation for normal cool stars. We interpret this to
be a manifestation of different physical mechanisms involved: magneto-
acoustic heating of the outer atmosphere for normal cool stars, versus
photoionization-recombination for the symbiotics.
A preliminary comparison of the spectra obtained during ingress
indicate a substantial decrease in the continuum at all wavelengths and a
noticeable drop in the emission line flux from the higher excitation lines,
particularly in the 1400 % blend of Si IV and O IV. A lie at 2830 A due to
He I also appears to be decreasing in strength, while the O III lines at
3047 _ and 3133 _ may have slightly increased in strength. These changes are
suggestive of a stratified nebula, where the highest excitation regions are
centralized and of dimensions less than that of the M giant, of order 1012
em. This region could represent the actual accretion disk. The O Ill lines
may arise from a more extended region (Bowen fluoresced), perhaps comparable
to the orbital separation, of order 1014 cm. It is not obvious that we have
detected a hot companion star, given the weak cool continuum. Comparison
with observations well out of eclipse and during a burst stage would be
useful. If other observers would like to supplement the observing plan,
collaboration would be welcomed.
REFERENCES
i. Swings, P.,"Symbiotic Stars and Related Peculiar Objects" 1970 in Sp__ectroTi
scop!c Astrophysics, G. Herbig, ed4 Berkeley, U. of Calif. Press, p. 189.
2. Mattei, J.,"The Symbiotic Star CI Cygni", 1977 J.R.A.S.C. 70, 325.
3. Belyakina, T. "Observations of CI Cygni in 1977-78", Info. Bull. Var.
Stars, No. 1602.
4. Plavec, M.,"IUE Observations of Long Period Eclipsing Binaries:
Accretion onto Non-Degenerate Stars", 1980 U.C.L.A. Preprint No. 86.
5. Kafatos, M., A.Michalitsianos, and R. Hobbs, "IUE Observations of RW
Hya", Astroph_s. J., 1980 in press.
460


Ingress observations of the 1980 eclipse of the symbiotic star CI Cyngni

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