Ultraviolet spectral data from the OAO 3 satellite are being used to study interstellar absorption lines and stellar and circumstellar lines in hot stars. The interstellar data are beneficial in analyzing the depletions of heavy elements from the gas phase and in elucidating how these depletions depend on physical conditions. Abundances in separate velocity components were determined from line profiles. Observations were carried out for interstellar abundances, both atomic and molecular, towards a number of stars. The better quality data are being analyzed for profile information and the lesser data are being used in curve-of-growth analyses. Molecular observations were carried out as well, N2 was sought; interstellar C2 was detected and its rotational excitation utilized to establish limits in interstellar cloud temperatures. An extensive search for H2O resulted in a tentative identification which will produce new information on chemical reaction rates. Interstellar depletions and grain properties in the rho Ophiuchi cloud, stellar wind variability, and circumstellar lines are also under study

Snow, T. P., Jr.

English

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Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19790012771 2020-03-21T23:11:17+00:00Z
This grant supported research with data obtained with the Copernicus
satellite. Some of the data used were obtained before the grant initiation
date, while the PI was still on the research staff at Princeton; and the
rest were obtained through the Copernicus Guest Investigator program, after
the PI's move to the University of Colorado.
The original proposal and the attached T43 form both outline the
scientific goals of the study. The T43 form also serves to briefly summarize
the results of the past year's research, and to outline the intended research
plans urOd er a new NASA grant which is forthcoming.
To expand on the bare-bones information in the T43 form regarding
scientific results achieved during the past year, the following few paragraphs
describe in somewhat more detail a few of the more outstanding accomplishments.
First, with regard to the interstellar depletion study, two important
studies were completed. Ore, carried out with graduate student Karie Meyers,
involved a detailed profile analysis of absorption lines in the ; Ophiuchi
cloud. It was found that refractory elements such as iron are much less
depleted in the higher-velocity cloud in the line of sight. This shows that
the process which accelerated the cloud to its velocity of some 15 Km S r (LSR)
also destroyed the grains, releasing material to the gas phase. This had
previously been observed for clouds with much higher velocities, but not for
zoo
e
April 17, 1979
wv 2A2^^4
(NASA-CP-15A446)	 ANALYSIS OF 1ILTRAVIOLET	
N70-2.0942
SPECTROPHOTnMETRIC DATA r FROM COPEPNHCr'A02/MF
Final Report (Colorado iniv.) 	
CSCL 03A	 OnclasA01	 G3/89 19437	 y
Final Re port - Grant 14SG-5246	 z 99 9^
Analysis of Ultraviolet Spectrophotometric Data from Copernicus
Theodore P. Snow, Jr., Principal Investigator
This grant supported resear ch with data obtained with the Copernicus
satellite. Some of the data used were obtained before the grant initiation
date, while the Pi was still on the research staff at Princeton.; and the
rest were obtained through the Copernicus Guest Investigator pro g ram, after
the PI's move to the University of Colorado.
The original proposal and the attached T43 form both outline the
scientific goals of the study. The T43 form also serves to briefly sum.Tarize
t.^ .e results of the east year's research, and to outline the intended research
z1 ns unfer a new NASA g rant which is forthcoming.
To expand on the bare-bones infoi-oration in the T43 fcrr, recardir.=
scie tific results achieved durin g
 the past y ear, the following few paragraphs
Gescr'be in somew *— at more detail a _°el: of the --ore outstanding accomplis h" eats.
irst, with regard to the interstellar depletion study, two L portant
studies were com p leted. One, carried out with graduate student {arie :levers,
involved a detailed profile anal ysis of absorption lines in the ; Ophiuchi
cloud. It was found that refractor y elements such as iron are much less
depleted in the higher-velocity cloud in the line of sight. This shows that
the process which accelerated the cloud to its velocity of some 15 ti:.r ^-/ (?.SR)
also destroyed the grains, releasing r..aterial to the gas phase. This had
prey icusiv been observed for clouds with much higher velocities, but not for
n
athose with only moderate speeds. These results, soon to appear in the
Assttrp2hys ical Journal, will provide valuable constraints for models of
grain destruction in interstellar shocks.
A second depletion study, recently completed in collaboration with
E. B. Jenkins of Princeton, involved an analysis of conditions within the
P Opiuchi cloud complex, where previous analyses of optical data had
shown that grain growth has ocurred in the densest regions. The Copernicus
study, soon to be submitted to the Astrophysical Journal, has revealed
that most of the gas in the line of sight is either completely devoid of
heavy elements, or is so dense that even species with low ionization
potentials are in the atonic form. Either interpretation argues for a
dense cloud core. C oarricus data confirm that the grains in this region
are unusually large and that the density is high. This tends to support
the hypothesis that the depletions result from accretion of heavy elements
into grains inside interstellar clouds, in constrast with theories that the
depletions result from the grain formation process.
The important outcome of a number of studies of early-type stars
(e.g. Snow and Hayes 1978; Glettebak and Snow 1978; Snow and Wegner 1979;
Marlbough and Snow 1979) can be summarized simply by saying that variability
is common in the UV spectra of hot stars with winds and/or extended
atmospheres. Every star studied closely shows fluctuations in line profiles.
Continuing analysis of the timescales of these variations and of their
relationship from one ion to another will provide invaluable information
on the winds, their stability, and, ultimately, the nature of their regions.

11o. PRIOR
B. INSTITUTION CATEGORY CODE
	 it. COARENT
L N6	
^
12. BUDGET
13. t)ESCRIPTION ra. ltr+rf statement oa strotrty of invsttiEation, 6. PrnYren and aeromp lishmenis of Prior veer. C. What will Os aeeomptiehedthis ? 00F as writ as how and why: and d. Summary Si6tiairayhyi
a. Strategy: To utilize ultraviolet spectral data from Copernicus in studies of
interstellar absorption lines and of stellar and circumstellar lines in
hot stars. The interstellar work has been aimed primarily at analyzing
the depletions of heavy elements from the gas phase and at elucidating_
how these depletions depend on physical conditions. This work has utilized
line profiles to determine abundances in separate velocity components.
Also of interest are interstellar molecular abundances, which are derived
from equivalent width measurements; such measurements provide important
information on the density of diffuse clouds, which may also be applied
to the dark clouds that are characterized by the presence of complex
molecules. The stellar and circumstellar research is directed towards
hot stars with winds and/or extended atmospheres. Of prime interest
is the variability in these winds which appears now to be quite common.
Studies of the timescale of the fluctuations and of their effects on the
ionization balance can provide valuable insights into the stability of
the winds and, ultimately, may help unearth the driving force behind them.
Another aspect of the hot star observations has to do with the circumstellar
shell absorption lines which appear in the spectra of some stars, particularly
the Be stars. These shells may be low-velocity manifestations of the
stellar wind phenomena, and it is especially important to understand their
relationship to the winds.
b. Progress of past years Observations were carried out for interstellar
abundances, both atomic and molecular, towards a number of stars, as part
of a comprehensive survey in which 1 am participating. The better quality
data are being analyzed for profile information and the lesser data are
being used in curve-of-growth analyses. One study of profiles (Snow and
Meyers, 1979) has been completed, and another (Meyers and Snow, 1979)
is well on its way. Molecular observations have been carried out as well,
12 was sought (Lutz, Owen and Snow, 1978); interstellar C 2 was detected
and its rotational excitation utilized to establish limits in interstellar
cloud temperatures (Snow, 1978). An extensive search for H2O has resulted
Continued on Attached Sheet
TECHNICALTYPED NAME AND SIGNATURE	
I
DATE
MONITOii
APPROVING
	
TYPED NAME AND SIGNATURE	 DATE
OFFICIAL
NASA FORM T43 DEC 74 REPLACES NASA FORM TS WHICH IS OBSOLETE.
:c o1N I PAS BLANK NOT MAW
Research and Technology Resume
	
2
Tide: Analysis of ultraviolet
Spectrophot matric Data
from Copernicus
in a tentative identification which will produce new information on
chemical reaction rates (Snow and Smith, 1979). A detailed analysis of
interstellar depletions and grain properties in the p Ophiuchi cloud .
is nearing completion (Snow and Jenkins, 1979). Several papers on stellar
wind variability (Snow and Mayes, 1978; Wegner and Snow, 1978; Slettebak
and Snow, 1978) and on circumstellar lines (Marlborough and Snow, 1979;
Snow, Peters, aandMathieu, 1979) have been completed as well.
c. Plans for coming year: Additional observations are to be carried out,
both for the interstellar abundance survey and for studies of extended
atmospheres, the latter emphasizing variability in the spectra of
Be stars. In addition, analyses of the interstellar depletion data will
be continued, with special attention to identifying which grain
population is responsible for the depletions.
d. Bibliography:
Snow, Jr., T. P., 1979, "Ultraviolet Observations of Interstellar
Molecules and Grains from Spacelab," Proc. Conf. Astr. Ap. from Spacelab,
Ed. P. L. Bernacca and R. Ruff ini (Dordrecht: Reidel); fn press.
Marlborough, M. J., T. P. Snow, Jr., and A. Slettebak, 1978, "Ultraviolet
and Optical Spectral Variability in the Be Star Y Cassiopaefa: A Coronal
Model for the Circumstellar Envelope," Astrophys. J., 224, 157.
Snow, Jr., T. P., 1978, "The Kinetic Temperature of the Interior of the
{ Ophiuchi Cloud from Copernicus Observations of Interstellar C2
Molecules," Astrophys. J. (Letters) 202, L93.
Snow, Jr., T. P., J. L. Linsky, 1979, "Ultraviolet Spectroscopy of the
Outer Layers of Stars," Proc. Conf. Astr. Ap from Spacelab, ed. P. L.
Bernacca and R. Ruffini (Dordrecht: Reidel), in press.
Wegner, G. A. and T. P. Snow, Jr., 1978, "Short-Term Visible and Ultraviolet
Variations in the Spectrum of ; Puppis," Astrophys. J. (Letters), 226, L25.
Lutz, B. L., T. Owen, and T. P. Snow, Jr., 1979, "A Search with Copernicus
for Interstellar r2 in Diffuse Clouds," Astrophys. J., 227, 159.
Ambartsumian, B. A., L. Mirzoyan, and T. P. Snow, Jr., 1979, "Ultraviolet
Observations of P Cygni with Copernicus," Astrophys. J., 227, 519 (also
Astrofisica, in press).
Snow, Jr., T. P., and D. P. Hayes, 1978, "Ultraviolet Spectrophotometry
and Visible-Wavelength Polarimetry of Stellar Wind Variability in d
Orionis A," Astrophys. J., 226, 897.
Snow, Jr., T. P., and E. B. Jenkins, 1979, "Interstellar Depletions and
Par-Ultraviolet Extinction in the cOphiuchi Cloud," Astrophys. J.,
submitted.
Research and Technology Resume
	
3
Title: Analysis of ultraviolet
Spectrophotometric Data
from Copernicus
Schwartz, R. D., T. P. Snow, Jr., and W. L. Upson, 1478, "A Search with
Copernicus for Ultraviolet Emission Lines from the Planetary Nebula
NGC 3242," Astron. J., 83, 1420.
Snow, Jr., T. P., 1979, "An Ultraviolet View of Stellar Winds," IAU
Sympositim 83, Mass Loss and Evolution of 0-Type Stars, ed. P. S. Conti
and C. de Loore (Dordrecht: Reidel), in press.
McCray, R. A., and T. P. Snow, Jr., 1979, "The Violent Interstellar
Medium," Ann. Rev. Astr. Astrophys., 17, in press.
Snow, Jr., T. P., and K. A. Meyers, 1979, "interstellar Abundances in the
4 Ophiuchi Clouds," Astrophys. J., in press.
Smith, W. H., and T. P. Snow, Jr., 1979, "Copernicus Observational
Searches for OH and H2O in Diffuse Clouds," Astrophys. J., in press.
Snow, Jr., T. P., G. J. Peters, and R. D. Mathieu, 1979, "A Survey of
Ultraviolet Circumstellar Absorption Lines in the Spectra of Early
Be and Shell Stars," Astrophys. J. Suppl., 39, 359. -
Slettebak, A., and T. P. Snow, Jr., 1978, "Spectrophotometric Variability
in the Be Star y Cas: Simultaneous Ultraviolet and Ha Observations,"
Astrophys. J. (Letters), 224, L127.
:Marlborough, J. Vii., and T. F. Snow, Jr., 1978, "Changes in the Ultraviolet
Spectrum of the 'Sass-losing Be Star 59 Cygni", Astrophys. J., in press.
Snow, Jr., T. P., E. J. Weiler and W. R. Oeeerle, 1979, "Neva Observations
of Interstellar Abundances and Depletions of Boron, Vanadium, Chromium,
and Cobalt", Astrophys. J., submitted.
Snow, Jr., T. P., G. A. Wegner and P. Kunasz, 1979, "Ultraviolet and
Visible-Wavelength Observations of Wind Variability in ; Puppis", in
preparation.
Snow, Jr., T. P. and W. H. Smith, 1979, "Possible Detection of Interstellar
H2O towards ; Ophinchi", in preparation.
Snow, Jr., T. P., 1979, "On the Nature of the Grains Responsible for
Tnterstellar Gas Depletions", in preparation.


Analysis of ultraviolet spectrophotometric data from Copernicus

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