scholarly journals Analysis of IUE spectrograms for Be stars

1994 ◽  
Vol 162 ◽  
pp. 280-281
Author(s):  
T. Eversberg ◽  
J. Dachs ◽  
T. W. Berghöfer ◽  
C. Huilai ◽  
U. Lemmer
Keyword(s):  
Short Wavelength ◽  
High Dispersion ◽  
Be Stars ◽  
Shell Type ◽  
International Ultraviolet Explorer ◽  
Optical Region

Archival high-dispersion spectrograms obtained by the International Ultraviolet Explorer satellite in the short-wavelength (λλ1150–2000Å) region were inspected and analyzed for a total of 33 Be stars, including one Oe star (HR 6397) and three stars showing shell-type spectra in the optical region (48 Lib, ɛ Cap, o Aqr). The following atomic and ionic transitions were investigated: Hi-Lyα, Cii-UV1, Ciii-UV4, Civ-UV1, Nv-UV1, Siii-UV1…-UV4, Siiii-UV2, Siiv-UV1.

scholarly journals FeII, FeIII and MgII spectra of Be stars

1994 ◽  
Vol 162 ◽  
pp. 267-268
Author(s):  
L. H. Barrera ◽  
J. Dachs ◽  
T. W. Berghöfer
Keyword(s):  
Fine Structure ◽  
Wavelength Range ◽  
Ground State ◽  
Resonance Absorption ◽  
High Dispersion ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
International Ultraviolet Explorer ◽  
Optical Region ◽  
Growth Methods

For a total of 33 bright Be stars, archival high-dispersion spectrograms obtained by the International Ultraviolet Explorer (IUE) satellite were analyzed together with optical spectrograms in order to study the FeII, FeIII and MgII spectra in the entire 1600 Å to 6500 Å wavelength range. Ultraviolet FeII resonance lines are always found to be in absorption which usually is of interstellar origin. By applying curve-of-growth methods to equivalent widths measured for FeII multiplets UV-1 through UV-8, column densities of interstellar FeII are derived ranging typically between about 1014 and 1015 cm-2. For a few program stars showing shell-type spectra in the optical region, additional FeII resonance absorption lines are detected starting from excited fine-structure levels above the ground state, pointing to FeII absorption occurring in the dense circumstellar envelope in front of these star. Analysis of their equivalent widths is used to infer typical column densities of circumstellar ground state FeII ions of order 1015 cm-2.

scholarly journals Be stars in the ultraviolet spectral classification system

1994 ◽  
Vol 162 ◽  
pp. 275-276
Author(s):  
Janet Rountree ◽  
George Sonneborn
Keyword(s):  
Stellar Wind ◽  
Classification System ◽  
Classification Criteria ◽  
Ultraviolet B ◽  
High Dispersion ◽  
Be Stars ◽  
Spectral Classification ◽  
International Ultraviolet Explorer ◽  
Optical Region

Rountree and Sonneborn (1991) developed a system for the classification of ultraviolet B-star spectra, using MK standards drawn from the optical region. The observational material consisted of high-dispersion spectra obtained with the Short Wavelength Prime (SWP) camera on the International Ultraviolet Explorer (IUE) spacecraft. The classification criteria were based exclusively on photospheric absorption lines, primarily lines of C III, Si II, and Si III. The stellar wind lines of Si IV, C IV, and N V were not used in the classification.

scholarly journals The Massive Close Binary in the δ Ori A Triple System

2002 ◽  
Vol 187 ◽  
pp. 47-52
Author(s):  
James A. Harvin ◽  
Douglas R. Gies
Keyword(s):  
Cross Correlation ◽  
Short Wave ◽  
Close Binary ◽  
Full Description ◽  
High Dispersion ◽  
Orbital Elements ◽  
Primary Star ◽  
International Ultraviolet Explorer ◽  
Triple Star ◽  
Massive Close Binary

AbstractWe present an analysis of short-wave, high-dispersion ultraviolet spectra of the triple star δ Ori A from the International Ultraviolet Explorer Satellite’s (IUE) Final Archive. These spectra were cross-correlated against AE Aur to find the components’ radial velocities, which were then used to produce the system’s orbital elements. The long-period tertiary star in the δ Ori A system was not seen in the resulting cross-correlation functions (CCFs). The close binary’s eclipses allow the orbit’s inclination to be estimated by modeling of its Hipparcos light curve. The primary star appears to have a mass of 11.2 M⊙ and the secondary seems to have a mass of 5.6 M⊙, both of which are about 1/3 of the expected values for stars of their MK types. Although we expected the massive close binary in the δ Ori A system to be a pre-Roche lobe overflow (RLOF) system, these masses appear to require that it be a post-RLOF system. The full description of this work, including the tomographic separation of the spectra for the close binary’s components, appears in Harvin et al. (2002).

scholarly journals Ubiquitous C IV 1550 Variability in B and Be Stars

1987 ◽  
Vol 92 ◽  
pp. 286-288 ◽  
Author(s):  
G. Sonneborn ◽  
M.P. Garhart ◽  
C.A. Grady
Keyword(s):  
Time Scale ◽  
High Dispersion ◽  
Be Stars ◽  
Line Profiles ◽  
Standard Star ◽  
B Stars ◽  
Short And Long Term ◽  
Resonance Transitions ◽  
Long Term Behavior

Studies of line profile variability of the ultraviolet 1550 Angstrom resonance transitions of C IV in Be stars (Sonneborn et al. 1986; Grady, et al. 1986a,b) have prompted an investigation into the short- and long-term behavior of the C IV lines in other types of B stars. We present examples of two well-studied Be stars, Omega Orionis and 66 Ophiuchi, and two non-Be stars, Beta Cephei and the standard star Zeta Cassiopeiae. Zeta Cas is also known to be a 53 Per variable (see Cox 1983). The IUE SWP high-dispersion spectra of Beta Cep and Zeta Cas have been obtained from the IUE archives. It has been known for some years that the C IV line profiles in Beta Cep vary in a time scale of several days (Fishel and Sparks, 1980). However, it came as a surprise to discover C IV variability in Zeta Cas. Available data allow us to set an upper limit of several months for the time scale of Zeta Cas C IV variability. The principal difference between the C IV variability in Be and non-Be stars appears to be the magnitude and velocity range of the effect.

scholarly journals IUE Studies of Hot Binary Stars

1992 ◽  
Vol 135 ◽  
pp. 393-395
Author(s):  
David J. Stickland
Keyword(s):  
Binary Stars ◽  
Storage Systems ◽  
Optical Disk ◽  
Public Access ◽  
High Dispersion ◽  
Disk Storage ◽  
International Ultraviolet Explorer ◽  
On Line ◽  
To Come ◽  
Reduced Data

The International Ultraviolet Explorer (IUE) was launched on 26th January 1978 and is still fully operational today, with several more years hopefully to come. After six months, the fully–reduced data is consigned to public–access archives maintained by the project agencies (NASA, ESA, and SERC). Thus, in addition to observations from current and future programmes, there are ~12,000 high–dispersion (Δλ ~ 0.15Å) spectra readily available now for research on stars hotter than about mid-B type. Furthermore, a uniform reprocessing, with optimum schemes, of all past IUE images has begun, to create the Final Archive which will be made accessible on–line through optical disk storage systems and will ensure the value of IUE data well into the future.

scholarly journals The peculiar star RX Puppis

1982 ◽  
Vol 70 ◽  
pp. 203-206
Author(s):  
M. Kafatos ◽  
A.G. Michalitsianos
Keyword(s):  
Accretion Disk ◽  
Line Emission ◽  
Wavelength Region ◽  
High Dispersion ◽  
Line Profiles ◽  
Peculiar Star ◽  
Dynamic Activity ◽  
Circumstellar Material ◽  
International Ultraviolet Explorer ◽  
The Continuum

AbstractWe have obtained the first high dispersion observations of RX Puppis in the wavelength region 1200 - 3200 A with the “International Ultraviolet Explorer” (IUE). The anomalies we observed in lines such as He II, C III], C IV, N III], N IV], 0 III], and Si III], that show split line profiles, Doppler displaced component(s) suggest dynamic activity in circumstellar material that probably has the form of rings and/or gas streamers between the cool giant and the hot companion, the Mg II lines show P-Cygni structure arising in the Mira primary. The continuum cannot be due to a star earlier than A0 II and it may arise in an accretion disk around the hot secondary. Moreover, the line emission requires photoionization either from a hot subdwarf or the inner accretion disk.

scholarly journals Results from six multiwavelength campaigns to study short-term FUV flux variability and phase-dependent mass loss in Be stars

1994 ◽  
Vol 162 ◽  
pp. 284-286
Author(s):  
Geraldine J. Peters
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
High Resolution Spectroscopy ◽  
Be Stars ◽  
Short Term ◽  
The Past ◽  
Flux Variability ◽  
Optical Region ◽  
Dependent Mass

During the past six years we have carried through seven multiwavelength, multisite campaigns to investigate the cause for short-term (rapid) photometric and spectroscopic variability in Be stars and assess its importance in driving the mass loss in these objects. These campaigns usually included simultaneous observations in the UV with the IUE and Voyager spacecraft and optical region with ground-based telescopes worldwide (photometry, high resolution spectroscopy, and polarimetry). Typically 10–25 observers from 5–9 countries participated. Stars that have been observed include λ Eri, ω Ori, o And, ∊ Cap, 28 Cyg, η Cen, 48 Lib, ζ Tau, ψ Per, and 2 Vul. We briefly summarize some of the results from the UV study here. Additional results from the ground-based data are given in other papers in this volume by D. Gies, M. Hahula, J. Percy, and D. McDavid.

scholarly journals Influence of the Stellar Wind on the Nebular Ionization in NGC 1535 and 4361

1983 ◽  
Vol 103 ◽  
pp. 338-339
Author(s):  
J. Adam ◽  
J. Köppen
Keyword(s):  
Wind Velocity ◽  
Stellar Wind ◽  
Short Wavelength ◽  
Wavelength Region ◽  
Absorption Lines ◽  
High Dispersion ◽  
High Excitation ◽  
Short Wavelength Region

The high excitation planetaries NGC 1535 and 4361 were observed with IUE satellite in the short wavelength region at high dispersion. In NGC 1535 we found P Cygni profiles of NV 1238, 1242 and OV 1371 lines with a terminal wind velocity of about 2000 km/sec. In NGC 4361 these lines are narrow absorption lines (width 0.5 Å), probably of photospheric origin.

scholarly journals Infrared spectroscopy of Be stars

1994 ◽  
Vol 162 ◽  
pp. 412-413
Author(s):  
R.M. Torres ◽  
A. Damineli-Neto ◽  
J.A. de Freitas Pacheco
Keyword(s):  
Mass Loss ◽  
Near Infrared ◽  
Uv Spectra ◽  
Emission Lines ◽  
Be Stars ◽  
B Stars ◽  
Astrophysical Objects ◽  
Optical Region ◽  
Support Excitation ◽  
Loss Rates

FeII emission lines are present in a variety of astrophysical objects and, in particular, in Be stars, where in some situations they can also be seen in absorption. Selvelli & Araujo (1984) studied a sample of classical Be stars that have FeII emission lines in the optical region. The analysis of IUE spectra of those stars revealed that, for the majority of the objects, neither absorption nor emission FeII features were present in the UV. The conclusion was that their data could not support excitation of FeII by continuum fluorescence. On the other hand, FeIII of circumstellar origin is often seen in absorption in the UV spectra of Be stars (Snow & Stalio 1987 and references therein). This could be an indication that the optical FeII emission lines are originated from recombination and cascade. However, Selvelli & Araujo (1984) argued that, since the multiplet UV 191 of FeII does not appear in emission, that mechanism is probably not relevant. In the present work we report new spectroscopic observations in the near infrared of a sample of 60 Be stars, including the prominent FeII 999.7 nm emission line. This line is also present in the spectra of superluminous B stars for which mass loss rates have recently been estimated (Lopes, Damineli-Neto & Freitas Pacheco 1992). We derived mass loss rates from the infrared line luminosities, in agreement with those derived by other methods. We also found a new evidence of the Be envelope flattening through the FeII/Paδ line ratio.

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