Ultraviolet studies of astronomical sources are discussed. Some studies utilized IVE data. Non-radiative shock at the edge of the Cygnses Loop, stellar flares, local interestellar medium, hot galaxies, stellar mass ejection, contact binaries, double quasars, and stellar chromosphere and coronae are discussed

Dupree, A. K.

Giampapa, M. S.

Hartmann, L. W.

Huchra, J. P.

Noyes, R. W.

Raymond, J. C.

English

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(NASA-CR-168189) CUBBINED ULIRAVIOLEZ 	 DOH"l-'13074
s	 STUUIIES OF ASTRONUMICAL 506BCES Semiannual
Eeport, 1 Aug. 1981 - 31 Jan. 1982
(Smithsoviau Asttophyzica! observatory)	 Unclas
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for the Period 1 August 1981 through 81 January 1082
Prkxoei UwesUpators
Ors. A. L Dupree, M. & Giaapapa; J. P. Huchre;
R. W. Moyer; L. W. Nartmaann; J. C. Raym=W
March 1982.
Prepared for
National AKa autics and space Adiarristration
Crawbaft, MD 20771
andt aw a institution
Astrophysical Observatory
CambrMOe, MA 02188
The Smithsonian Astrophysicai Observatory
and the Harvard CONGO Observatory
are members of the
Center for
Combined Ultraviolet Studies of Astronomical Sources
NASA Grant NAG687
Semiannual Report No. 3
For the Period 1 August 1981 through 31 January 1982
Principal Investigators
Drs. A. K. Dupree; M. S. Giampapa; J. P. Huchra;
R. W. Noyes; L. W. Hartmann; J. C. Raymond
March 1982
Prepared for
National Aeronautics and Space Administration
Greenbelt, MD 20771
Smithsonian Institution
Astrophysical Observatory
Cambridge. MA 02138
The Smithsonian Astrophysical Observatory
and the Harvard College Observatory
are members of the
Center for Astrophysics
The NASA Technical Officer for this Grant is Dr. Albert Boggess
Code 883, Laboratory for Astronomy and Solar Physics
Goddard Space Flight Center, Greenbelt, MD 20771
Combined Ultraviolet Studies of Astronomical Sources
Supernova Remnants
WE observations of a non-radiative sh ick at the edge of the Cygnus Loop,
together with complementary optical observations, were presented at the 159th
meeting of the AAS. These observations seem to answer the old question of
electron-ion equilibration in shock fronts. The probable detection of O 111] A1666
and strong upper limits on C III] and IV lines from the SNR in NGC4449 yield limits
on the abundance ratio and on the precursor mass. These results were presented
at the 159th AAS meeting. A paper on the distance to Tycho's supernova remnant
based on WE and optical interstellar lines is being prepared by J. Black and J. Ray-
mond.
Stellar Flares
Preliminary analysis of the flare on EQ Peg detected by WE and the Z-machine
at Mt. Hopkins suggests that this was more like a surge than a solar flare in that
the emission measure distribution was strongly peaked at about 10 5 K.
Local Interstellar Medium
Two of the four allocated shifts for study of the local interstellar medium have
been used. The most surprising result Is detection of C IV Interstellar absorption
towards a star only 40 pc. away.
Hot Galaxies
WE spectra at the irregular galaxies N4214 and N4670 are dominated by 0
stars. In N4214, the C IV line Is in P Cygni. These UV spectra show no strong
emission lines although the optical spectra are dominated by recombination lines.
The HP luminosity and the UV flux are generated by severs! hundred 0 stars. The
-2-
WE spectrum of MK 36 also shows no emission lines but very weak absorption. It
is very blue, still rising shortward of Ly a. The UV to IR energy distribution is
almost Rayleigh-Jeans, leaving little room for evolved red stars in any spectral
region.
Mass Loss from Stars
In November 1981 we obtained a new high-dispersion SWO spectrum for the
hybrid atmosphere star a TrA in which we were able to erpose for 19 hours by
taking advantage of a low-background shift 2. It was already known that the high-
temperature emission lines in this star were very wide; C IV X1548,1550 widths
were estimated to be — 200 km s-1 , and the optically thin Si III X1892 and C II
X1909 lines exhibit FWHM -- 100 km s-1 ,  With the longer exposure we estimate a
C IV line width which is even larger than before, — 230 km s"1 . In addition, we
have detected several new lines which went unobserved in our previous 8 hour
exposures. The N V ^ 1238 line is detected weakly, exhibiting a FWHM — 150-190
km s 1 . Broad He 11 A1640 Is found, with a width of at least 60 km s"1 , Si IV
X1393 is detected with width — 140 km s -1 . Redshifted C II X1335 is also
observed, with a relatively narrow line width. The observation of lines from ions of
different excitation enables us to obtain a more comprehensive picture of atmos-
pheric dynamics and its relationship to mass loss than previously possible. Model-
ing of these data is presently underway.
Contact Binaries
All of the observations of W UMa type stars have been reduced and the phase
dependence of chromospheric emissions evaluated. Both the short and long period
system show a modulation of chromospheric flux that is similar to the optical modu-
lation with two minirna per orbital period. Howe , /or, In several systems the depth of
primary and secondary minima is reversed from the c,,,tically determined depths indl-
J
-3-
cating a distinctly different atmospheric structure between the components. Gen-
erally the surface fluxes of ultraviolet emissions are comparable to those of solar
active regions, but in the longest period systems (such as Epsilon CrA and S Ant)
the transition region fluxes of 106 K material are surprisingly large - several hun-
dred times the solar surface flux - a fact which may be related to the evolutionary
structure of a dwarf atmosphere. X-rays from these systems appear low - both
suggesting Ciat the irteractic 1 . atween the components may accelerate the
effects of a stellar wind.
In one system, Epsilon CrA, we have discovered the heretofore undetected
secondary component by its extreme (600 km s 1 ) velocity variation found in the
Mg 11 line at orbital elongations. Such systems present the unique opportunity to
evaluate the rotation-activity correlation that was apparent from our very first IUE
studies.
Many of these results were presented In preliminary form at the Santa Cruz
Summer Workshop on Cataclysmic Variables and Related Objects.
Double Quasars
Observations were completed consisting of two long exposures made in May
and December 1981 corresponding to the alignment of the Long Wavelength Large
Aperture with both components. These observations were made in collaboration
with R. Wilson and P. Gondhalekhar in the U.K. The deconvolution of the spectra of
the two components is non-trivial since they are separated by about 6 seconds of
arc on the sky. A scheme has been devised at the CfA Reduction Facility that
uses the point spread function determined by a standard star, and the position of
the two quasar spectra derived from average fluxes, to fix four of the six parame-
ters necessary to establish the two gaussian profiles of the spectra perpendicular
to the dispersion. Then an iterative scheme requiring a minimum of X 2 was used to
obtain the flux In each spectrum. Our preliminary result from the May 1981 data
...	 .....s
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Indicates a ratio which is different from the near simultaneous VLA measurement
and may indicate the presence of spectral variations in one component.
The Transition Regions and Coronae of Solar-Type Stars
Observations for this program were obtained with the WE satellite during April
1 to 3, 1981 and January 3 to 4, 1982. To date, 4 of the 5 observing shifts allo-
cated to this program have been utilized. The remaining shift Is scheduled for
March 2, 1982. The observations consist of SWP and LWR Images acquired In the
low dispersion mode through the large aperture. The data thus far acquired have
been reduced and we are presently combining the results with existing X-ray data
from HEAO-B in order to develop theoretical models for the outer atmospheres of
these stars. An Important preliminary result from this program is the following: the
observed UV and X-ray emission are most compatible with the existence of young,
compact, high-pressure corona) loop structures In the atmospheres of active-
chromosphere, late-type stars. We presented this result at the Annual UCL Astron-
omy Colloquium, 14-17 September 1981. We are currently in the process of
extending this preliminary result and we will present a paper on this program at the
WE Symposium during April 1982.
High Dispersion, Long Wavelength Studies of T Tauri Stars
The IUE observations for this program have been successfully obtained. We
have also acquired high resolution (uncalibrated) Ca II K line profiles for the targets
In our program with the Mt. Hopkins 80 inch telescope and echells spectrograph.
We are now reducing the high dispersion WE data and we have presented (prelim-
Inary) calibrated Mg 11 h and k line profiles at the AAS meeting in Boulder during
January 1982 (Glampapa at al. 1981, B.A.A.S., 13, 811). We have initiated some
exploratory atmospheric model calculations with the PANDORA radiative transfer
code. Furthermore, these IUE observations have revealed the existence of chro-
3
d
-5-
mospheric line profile variability In T Tauri stars. Thus, additional high dispersion
IUE spectra will be required to discern the range of physical conditions that may
exist in single T Tauri stars.
Ultraviolet Studies of Evolved Chromospheres and Coronae In Giants
In the Praesepe Cluster
Ana , sis of ultraviolet spectra of evolved stars in open clusters will provide
Important Information on the evolution of chromospheres and coronae in cool stars.
VAth IUE, we have been comparing chromospheric and coronal emissions in the KO
III stars in the Praesepe cluster, thought to be several hundred million years old.
We are complementing the ultraviolet data with ground-based spectra of the chro-
mospheric Ca 11 K emission cores. While the remainder of our IUE observations are
scheduled for mid-March, our earlier UV data combined with the optical spectra sug-
gest there is a spread of chromospheric activity among these ostensibly similar,
coeval, giants. This suggests that a "hidden parameter", %part from effoctive tem-
perature and stellar gravity, controls the atmospheric emissions. Our earlier IUE
observations of KO III stars in the Hyades cluster, whose stars are about twice as
old as those in Praesepe, revealed a similar disparity between these homogeneous
giants. A comparison of the ultraviolet emission in the giants in the Hyades and
Praesepe clusters may reveal the parameter governing the strength of chromos-
pheric and coronas' emissions for these evolved stars.
VV Cephei
The analysis of a large quantity of IUE data on VV Cephei (45 LWR images and
38 SWP images) continues. Progress made during late 1981 as a result of the
visit of Dr. A. V. Holm includes: (1) the extension of the UV light curve to include
the most recent low-dispersion data, (2) measurement of equivalent widths of prom-
inent emisaion features such as Fe II ).1788 1, (3) comparison of absorption line
. ...
	 --..46
-6-
profiles of the hot secondary star with those of standard &type stars, and (4) the
idertification of numerous Fe II multiplets of rather high excitation potential In the
high-dispersion spectra.
The absorption line profile of C 11 1!1335 x in W Cep is very similar to that of
Dra (B6 III), suggesting that the spectral type of the secondary may be late Be.
The UV spectrum of the secondary Is still strongly masked by overlying absorption
due to the M-star atmosphere even 4 years after eclipse, and further analysis will
be required to establish the nature of the secondary.
t --
Several sequences of absorption lines arising in the lowest two doublet states
of Fe II, viz. a2G and a2H, have been identified In the 1750-2000 X region of the
W Cep spectra. These states have excitation potentials of 2.00 and 2.55 eV,
respectively, and their populations may be useful in probing the structure of the
extended cool atmosphere.
Some of the recent results on W Cep have been presented by W. Hagen at
the North American. Workshop on Symbiotic Stars In Boulder during June 1981.
Active Regions on Solar-Type Dwarfs as a Function of
Rotation and Age
In October 1981, sequences of observations were obtained, spaced at
several-day intervals, recording chromospheric and transition zone emission from
lower main sequence stars. The stars were selected from a group of stars under
joint study by SAO and Mt. Wilson scientists to determine their rotational modula-
tion, and were observed simultaneously with H-K photometry from Mt. Wilson. One
star, HD206860 (GO, 4.7-day rotation period), was experiencing large rotational
modulation at the time and showed significant enhancements of upper chromos-
pheric and transition zone lines in the ultraviolet, correlated with H-K flux. Data for
this and four other stars observed are currently under analysis.
r
-7-
1981
Observations and TiAoory of Mass Loss In Late-Type Stars. L. Hartmann In Proc.
NATO Advanced Study Institute on Solar Phenomena In Stara and Stellar Systems.
ed. R. M. Bonnet and A. K. Dupree, (D. Reldel), p. 331.
Chromosoheres ant' Coronae In Binary Systems. A. K. Dupree in Proc. NATO
Advance Study Instit^to on ajar Phenomena In Stars and Stellar Syste ms, ed. R.
M. Bonne . find A. K. Dupree, (D. ; eidei), p. 407.
On the Ralat4,,,iship Bb^ween Coronae and Mass Loss In Late-Type Stars. L. Hart-
mann, :r..	 Uup-., e, avd J. Raymond, Astrophys. J., 246, 193.
Mass to •..: +rer 'col Stars. A. K. Dupree in Effects of Mass Loss on Stellar Evolu-
tYvr- kiA! : t,r, ;;. A!^. 159), ed. C. Chlosi and R. Stalio, (D. Reldel), P. 87.
,cord ;, gated X-ray, I 1 1traviolet and Optical Observations of AM Her, U Gem and SS
Cyg. G. Fa^,blano, L. Hartmann, J. Raymond, Steiner, G. Branduardi-Raymont, and
^. Matilaky, Astrophys. J., 243, 911.
Ultraviolet Emission of the Vela Supernova Remnant and the Cygnus Loop. J. C.
Raymond, J. H. Black, A. K. Dupree, L. Hartmann, and R. S. Wolff, Astrophys. J., 244,
100.
Short-Timescale Variability of Chromospheric Ca 11 in Late-Type Stars. S. L. Baliu-
nas, L. Hartmann, A. H. Vaughan, W. Llller, and A. K. Dupree, Astrophys. J., 246,
473.
WE Ultraviolet and Optical Chromospheric Studies of Late-Type Giants in the Hyades
Cluster. S. L. Baliunas, L. Hartmann, and A. K. Dupree, in The Universe at Ultraviolet
Wavelengths - The First Two Years of IUE, (ad. R. D. Chapman) NASA Conference
Publication 2171, p. 326.
WE Ultraviolet Observations of W UMa Stars. A. K. Dupree and S. Preston, In The
Universe at Ultraviolet Wavelengths - The First Two Years of IUE, (ad. R. D. Chap-
man) NASA Conference Publication 2171, p. 333.
The Astrophysical Interest of EUV Observations of Extra-Solar Objects. A. K.
Dupree, Space Science Reviews, 29, 479.
WE Observations of Pre-Main Sequence Stars. I. Mg II and Ca 11 Resonance Line
Fluxes for T Tauri Stars. M. S. Giampape, N. Calvet, C. L. Imhoff, and L. V. Kuhl,
Astrophys. J., 261, 113 (Dec. 1981 Issue).
Ultraviolet Observation of a Non-Radiative Shock Wave. J. C. Raymond, R. Fesen,
and T. R. Gull, BAAS, 13, 887.
X-ray, Optical and UV Observations of the Supernova Remnant in NGC4449. W. P.
Blair, J. C. Raymond, R. Kirshner, and P. F. Winkler, BAAS, 13, 796.
-s-
Ultraviolet and Optical S pectrum Studies of a Andromedae: Evidence for Atmos-
pheric Inhomogeneitles. S. L. Baliunas and A. K. Dupree, Astrophys. J., in press.
Ultraviolet Observations of Stellar Chromospheec Activity. L. Hartmann, A. K.
Dupree, and J. C. Raymond, Astrophys. J., 282, 214.
Ultraviolet Spectra of the LMC X-ray Transient A0638-88. J. C. Raymond, Astro-
phys. J., in press.
Stellar Activity, A. K. Dupree in Proceedings of the Second Cambridge Workshop on
Cool Stars. Stellar Systems. and the Sun. (eds. M. S. Giampapa and L. Golub), SAO
Special Report 392, in press.
Observations of Cataclysmic Variables with IUE. L. Hartmann and J. C. Raymond, In
The Universe at Ultraviolet Wavelengths - The First Two Years of /UE, (ed. R. D.
Chapman) NASA Conference Publication 2171, p. 496.
Coordinated IUE, Einstein and Optical Observations of Accreting Degenerate Dwarfs.
G. Fabbiano, J. E. Steiner, L. Hartmann, and J. C. Raymond, In The Universe at Ultra-
violet Wavelengths - The First Two Years of IUE, (ed. R. D. Chapman) NASA Confer-
ence Publication 2171, p. 601.
WE Observations of Supernova Remnants. J. C. Raymond, In The Universe at Ultra-
violet Wavelengths - The First Two Years of IUE, (ad. R. D. Chapman) NASA Confer-
ence Publication 2171, p. 696.
High Resolution, Absolute Flux Profiles of the Mg II h and k Lines for T Tauri Stars.
M. S. Giampapa, C. Morossi, M. Ramelia, and C. L. Imhoff, BAAS, 13, 811.
Far Ultraviolet and X-ray Evidence Concerning the Chromospheres and Coronae of
the T Tauri Stars, in Proceedings of the Second Cambridge Workshop on Cod Stars.
S tellar Sylijems. and the Sun. (eds. M. S. Giampapa and L. Golub), SAO Special
Report 392, in press


Combined ultraviolet studies of astronomical sources

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