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Articles 31 - 60 of 76
Full-Text Articles in Astrophysics and Astronomy
Moderate-Resolution Spectroscopy Of The Lensed Quasar 2237+0305: A Search For Ca Ii Absorption Due To The Interstellar Medium In The Foreground Lensing Galaxy, P. Hintzen, S. P. Maran, A. G. Michalitsianos, C. B. Foltz, F. H. Chafee, Menas Kafatos
Moderate-Resolution Spectroscopy Of The Lensed Quasar 2237+0305: A Search For Ca Ii Absorption Due To The Interstellar Medium In The Foreground Lensing Galaxy, P. Hintzen, S. P. Maran, A. G. Michalitsianos, C. B. Foltz, F. H. Chafee, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
The gravitational lens system 2237 + 0305 consists of a low-redshift barred spiral galaxy (z = 0.0394) centered on a more distant quasar (z = 1.695). Because the lensing galaxy is nearly face on, spectroscopy of the background quasar affords a unique opportunity to study the interstellar medium in the galaxy's center and buW:. We report moderate-resolution spectroscopy of QS02237 + 0305 yielding a 3u upper limit of 72 rnA forthe rest equivalent width of Ca II K absorption d);le to gas in the intervening galaxy. Since gas in the Milky Way "thick disk" typically produces 220 mA Ca II …
Comparisons Of Sio Maser And Long-Period Variable Positions In The Aquarii And Omicron Ceti Binary Systems, J. M. Hollis, M. C. H. Wright, W. J. Welch, P. R. Jewell, H. E. Crull, Menas Kafatos, A. G. Michalitsianos
Comparisons Of Sio Maser And Long-Period Variable Positions In The Aquarii And Omicron Ceti Binary Systems, J. M. Hollis, M. C. H. Wright, W. J. Welch, P. R. Jewell, H. E. Crull, Menas Kafatos, A. G. Michalitsianos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We have determined that the absolute position of the centroid of SiO maser-emitting spots toward both R A~r ~nd o Cet are coincident with the position of the long-period variables (LPVs) in these binary systems to within the errors of measurement. The SiO positions were determined with the Hat Creek interferometer while the LPV positions were determined with the 8 inch (20 em) transit circle of the US Naval Observatory: These results contradict an earlier report of a circumbinary SiO maser far removed from the LPV in the R Aqr binary system, and we suggest statistical reasons for the discrepancy. …
Sanduleak's Star (Lmc Anonymous): Its Similarity In The Far-Ultraviolet With The Luminous Object N Carinae And Sn 1987a, A. G. Michalitsianos, Menas Kafatos, S. N. Shore
Sanduleak's Star (Lmc Anonymous): Its Similarity In The Far-Ultraviolet With The Luminous Object N Carinae And Sn 1987a, A. G. Michalitsianos, Menas Kafatos, S. N. Shore
Mathematics, Physics, and Computer Science Faculty Articles and Research
Spectra obtained in the far UV wavelength range 1200-2000 A with the International Ultraviolet Explorer (IUE) of the peculiar emission object LMC Anonymous, or Sanduleak's Star in the Large Magellanic Cloud, indicate the presence of circumstellar-high-excitation gas, which is rich in CNO processed material. Although LMC Anonymous is a field star whose nebular line-forming region can not be resolved, and whose mass may be considerably smaller than the massive-luminous galactic object η Carinae, the far-UV spectrum of LMC Anonymous closely resembles that of the S Condensation of η Carinae. The similarity between LMC Anonymous and the S Condensation is apparent …
R Aquarii: Evidence For A Two-Sided Radio Jet And A Circumbinary Sio Maser, Menas Kafatos, J. M. Hollis, F. Yusef-Zadeh, A. G. Michalitsianos, M. Elitzur
R Aquarii: Evidence For A Two-Sided Radio Jet And A Circumbinary Sio Maser, Menas Kafatos, J. M. Hollis, F. Yusef-Zadeh, A. G. Michalitsianos, M. Elitzur
Mathematics, Physics, and Computer Science Faculty Articles and Research
We have detected collimated 4.86 GHz (~6 cm) radio continuum emission southwest (SW) of the symbiotic vanable R Aquarii by combining data corresponding to different configurations of the Very Large Array (VLA). In the xontext of a previously reported northeast (NE) 6 cm jet structure, the orientation of the newly found SW radto structure suggests bipolar symmetry, extending to distances of ~2500 AU on either side of the central H II region. The amorphous morphology of the new collimated SW structure is distinct from the discrete radio knots NE of the central object. Further, we have determined the radio spectral …
Rx Puppis: Detection Of Asymmetrical Radio Structure, J. M. Hollis, F. Yusef-Zadeh, T. J. Cornwell, R. J. Oliverson, A. G. Michalitsianos, Menas Kafatos
Rx Puppis: Detection Of Asymmetrical Radio Structure, J. M. Hollis, F. Yusef-Zadeh, T. J. Cornwell, R. J. Oliverson, A. G. Michalitsianos, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Subarcsecond ( ~0':3 x ~0':1) observations of the RX Puppis symbiotic system with the Very Large Array (VLA) have resolved 2 cm continuum emission which deviates from a previously reported circularly symmetric radio distribution. The radio structure is comprised of at least three nearly colinear components. Under the assumption that the strongest feature is coincident with the hot star, the other two features lie 230 and 590 AU distant. These radio features are reminiscent of small-scale radio structure detected toward R Aquarii, another symbiotic star system, and probably represents material ejected from the RX Puppis system at an earlier epoch.
R Aquarii: The Large-Scale Optical Nebula And The Mira Variable Position, A. G. Michalitsianos, R. J. Oliverson, J. M. Hollis, Menas Kafatos, H. E. Crull, R. J. Miller
R Aquarii: The Large-Scale Optical Nebula And The Mira Variable Position, A. G. Michalitsianos, R. J. Oliverson, J. M. Hollis, Menas Kafatos, H. E. Crull, R. J. Miller
Mathematics, Physics, and Computer Science Faculty Articles and Research
The R Aquarii symbiotic star system is surrounded by a large-scale optical nebula. We present observations of the nebular [O III] structure and discuss its morphological significance in context with previously observed small-scale radio-continuum features, which may be related. We suggest that a precessing accretion disk may explain the global features of both the large-scale optical emission and the small-scale radio emission. Moreover, we have determined an accurate position of the system's Mira, which suggests that a recent theoretical model, yielding an egg-shaped central H II region for symbiotic systems with certain physical parameters, may apply to R Aquarii. The …
The C Iv Doublet Ratio Intensity Effect In Symbiotic Stars, A. G. Michalitsianos, Menas Kafatos, R. P. Fahey, R. Viotti, A. Cassatella, A. Altamore
The C Iv Doublet Ratio Intensity Effect In Symbiotic Stars, A. G. Michalitsianos, Menas Kafatos, R. P. Fahey, R. Viotti, A. Cassatella, A. Altamore
Mathematics, Physics, and Computer Science Faculty Articles and Research
The first successful high-resolution ultraviolet spectra in the λλ 1200-2000 wavelength range of the symbiotic variable R Aquarii and its nebular Jet were obtained in 1987 July with the International Ultraviolet Explorer (IUE). The line profile structure of the C IV λλ1548, 1550 doublet in the jet indicates multicomponent velocity structure from an optically thin emitting gas. The C IV doublet profiles in the compact H II region engulfing the Mira and hot companion binary also suggest multicomponent structure, in which the radial velocities range up to ~ -100 km s^- 1. The value of the doublet intensity ratio in …
Supershells And Propagating Star Formation, R. Mccray, Menas Kafatos
Supershells And Propagating Star Formation, R. Mccray, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Stellar winds and repeated supernovae from an OB association will create a cavity of coronal gas in the interstellar medium, with radius greater than 100 pc, surrounded by a dense, expanding shell of cool interstellar gas. If the association has a typical initial mass function, its supernovae explosions will inject energy into the supershell at a nearly constant rate for about 5 x 10^7 yr. The supershell loses its interior pressure and enters the snowplow phase when radiative cooling becomes important or when the shell bursts through the gas disk of a galaxy, typically after a few times 10^7 yr …
The Large Scale Radio Structure Of R Aquarii, J. M. Hollis, Menas Kafatos, A. G. Michalitsianos, R. J. Oliverson, F. Yusef-Zadeh
The Large Scale Radio Structure Of R Aquarii, J. M. Hollis, Menas Kafatos, A. G. Michalitsianos, R. J. Oliverson, F. Yusef-Zadeh
Mathematics, Physics, and Computer Science Faculty Articles and Research
Radio continuum observations of the R Aquarii symbiotic star system, using the compact D configuration of the VLA at 6 em wavelength, reveal a large-scale ~2' structure engulfing the binary which has long been known to have a similar optical nebula. This optical/radio nebula possesses - 4 X 10^42 ergs of kinetic energy which is typical of a recurrent nova outburst. Moreover, a cluster of a dozen additional 6 em radio sources were observed in proximity to R Aquarii; most of these discrete sources lie ~3' south and/ or west of R Aquarii and, coupled with previous 20 cm data, …
Evidence For Extended Radio Emission Surrounding Rx Puppis, J. M. Hollis, R. J. Oliverson, Menas Kafatos, A. G. Michalitsianos
Evidence For Extended Radio Emission Surrounding Rx Puppis, J. M. Hollis, R. J. Oliverson, Menas Kafatos, A. G. Michalitsianos
Mathematics, Physics, and Computer Science Faculty Articles and Research
We report evidence for ~1" extended structure in 6 cm continuum emission emanating from the symbiotic star system RX Puppis. We did not detect hourly continuum flux changes as suggested in previous radio experiments by others. Our observations indicate that the predominant nature of the radio emission is thermal and consistent with an optically thick stellar wind emanating from the symbiotic star system. Our results are discussed with regard to other similar stellar binary systems.
Sub-Arc Second 2 Centimeter Continuum And Sio Spectral Line Observations Of R Aquarii, J. M. Hollis, A. G. Michalitsianos, Menas Kafatos, M. C. H. Wright, W. J. Welch
Sub-Arc Second 2 Centimeter Continuum And Sio Spectral Line Observations Of R Aquarii, J. M. Hollis, A. G. Michalitsianos, Menas Kafatos, M. C. H. Wright, W. J. Welch
Mathematics, Physics, and Computer Science Faculty Articles and Research
ub-arc second (- 0'.'15) VLA observations at 2 em have resolved the previously reported 6 em H II region, which engulfs the R Aquarii binary system, into two components. The stronger 2 em component is itself partially resolved (distorted in shape), which may be a consequence of the long-period variable (LPV) wind being subjected to the intense ionizing radiation field of the hot companion's accretion disk, which we suspect is precessing. The distorted radio contours of the central H II region may also suggest that one hemisphere of the extended LPV envelope is directly illuminated by the intense radiation field …
The Unusual Ultraviolet Variability Of The Qso 3c 232, C. Bruhweilier, Menas Kafatos, U. J. Sofia
The Unusual Ultraviolet Variability Of The Qso 3c 232, C. Bruhweilier, Menas Kafatos, U. J. Sofia
Mathematics, Physics, and Computer Science Faculty Articles and Research
After examining ultraviolet IUE spectra of 18 QSOs with z > 0.35, we find that one object, 3C 232 (z = 0.533), stands out as exhibiting highly unusual spectral and continuum variability. The H 1-Lya shows at least 50% variability on a time scale of roughly a month, while the ultraviolet continuum exhibited approximately a factor of 2 decrease in a day. The magnitude of the UV continuum variability is reminiscent of that seen in the optically violent variables at visual wavelengths. Several spectral features at wavelengths shortward of H I-Lya in the rest frame are identified. A brief discussion COJ?lparing …
High Dispersion Untraviolet Spectra Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, R. P. Fahey
High Dispersion Untraviolet Spectra Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, R. P. Fahey
Mathematics, Physics, and Computer Science Faculty Articles and Research
High spectral resolution observations of the peculiar star RX Puppis obtained with the International Ultraviolet Explorer suggest the presence of a complex gaseous ring system which surrounds an accreting hot secondary. The anomalous line intensity ratio of the C IV A.A-1548, 1550 doublet during the observations exceeded the optically thick limit, implying the presence of a high-velocity wind. Additionally, the C IV doublet exhibits about four or five narrow emission components, which are redshifted up to velocities of at least - + 300 km s -I (with respect to the rest wavelength).
The R Aquarii System At Optical And Radio Wavelengths, J. M. Hollis, Menas Kafatos, A. G. Michalitsianos, H. A. Mcalister
The R Aquarii System At Optical And Radio Wavelengths, J. M. Hollis, Menas Kafatos, A. G. Michalitsianos, H. A. Mcalister
Mathematics, Physics, and Computer Science Faculty Articles and Research
Observations of the symbiotic binary R Aquarii environment were obtained with the Very Large Array (VLA) at 2, 6, and 20 em at the same epoch. The observed spectral index and strong linear polarization reveal that emission from the compact double radio source discovered in previous observations is nonthermal; thus, this source is not associated with R Aquarii but is an extragalactic background object. The spectral index of the compact nebula surrounding R Aquarii indicates that the emission is thermal and the nebula is ionized by an unseen, hot companion to the Mira-like variable R Aquarii. As expected, this region …
Variable Ultraviolet Emission In Sy Muscae, A. G. Michalitsianos, Menas Kafatos
Variable Ultraviolet Emission In Sy Muscae, A. G. Michalitsianos, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Following the enhancement in ultraviolet flux which we reported previously, we have continued monitoring the symbiotic variable SY Muscae with the International Ultraviolet Explorer (JUE). Over the course of one year, the prominent emission lines of N v, 0 v, C rv, He II appear to be gradually decreasing in absolute intensity. This appears to coincide with a steady decline in electron density in the emission line forming region, as suggested from the Sim] :\1892 and Cm] :\1909 intensity ratio. Our data is consistent with a sudden ejection event in which material expelled from the surface of a hot Teff …
The High-Energy Spectrum Of Hot Accretion Disks, J. A. Eilek, Menas Kafatos
The High-Energy Spectrum Of Hot Accretion Disks, J. A. Eilek, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
A hot, two-temperature accretion disk can be a strong γ-ray and relativistic particle source. This occurs when the accretion rate is high enough -- M/ M ≥ 3 X 10^-9 α γr^-1 for a canonical Kerr black hole-due to the high ion temperature in the inner disk. We present detailed photon and particle spectra for specific disk models. The predicted γ-ray flux is as high as 10% of the bolometric luminosity in sub-Eddington models. Most of the γ-radiation is continuous, due to the π^0 decay, emitted around 100 MeV but degraded to a few MeV in optically thick models. Spectral …
Observations Of Two Peculiar Emission Objects In The Large Magellanic Cloud, Menas Kafatos, A. G. Michalitsianos, D. A. Allen, R. E. Stencel
Observations Of Two Peculiar Emission Objects In The Large Magellanic Cloud, Menas Kafatos, A. G. Michalitsianos, D. A. Allen, R. E. Stencel
Mathematics, Physics, and Computer Science Faculty Articles and Research
Ultraviolet and visual wavelength spectra were obtained of two peculiar emission objects, Henize S63 and Sanduleak.'s star in the Large Magellanic Cloud. Previously not observed in the near- or far-ultraviolet, both objects exhibit strong permitted and semiforbidden line emission. Estimates based on the absolute continuum flux of the hot companion star in Hen S63 indicate that it rivals the luminosity of the carbon star primary. The emission-line profile structure in both objects does not suggest Wolf-Rayet type emission. Carbon in Sanduleak.'s star (LMC anonymous) is conspicuously absent, while N v, N IV], and N III] dominate the UV emission-line spectrum. …
High Spatial Resolution Vla Observations Of The R Aquarii Jet, Menas Kafatos, J. M. Hollis, A. G. Michalitsianos
High Spatial Resolution Vla Observations Of The R Aquarii Jet, Menas Kafatos, J. M. Hollis, A. G. Michalitsianos
Mathematics, Physics, and Computer Science Faculty Articles and Research
High spatial resolution observations (~1") of the jet feature associated with the symbiotic variable R Aquarii were obtained with the Very Large Array (VLA). The peak radio intensity of the jet lies at a 29~3 P.A. with respect to the radio emission from R Aquarii itself. If the line defined by the jet and star is extended ~196", it intercepts a previously reported and heretofore unresolved radio source. In our high spatial resolution 6 cm map, this feature is resolved into a compact double radio source, whose peak intensity lies on an axis defined by the jet and star. The …
A Brightening Of The Symbiotic Variable Sy Muscae, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, G. Wallerstein
A Brightening Of The Symbiotic Variable Sy Muscae, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, G. Wallerstein
Mathematics, Physics, and Computer Science Faculty Articles and Research
The symbiotic variable SY Muscae has been observed with IUE in September 1980 and June 1981 and in the photographic region in May 1981. The entire ultraviolet spectrum brightened between September and June by about a factor of 5. The spectrum shows high excitation including emission from N v and high electron density, about 10^10 cm^-3 as determined from various line ratios in the ultraviolet. The optical spectrum is dominated by permitted lines; even [0 m] is very weak again indicating high density in the ionized region. The increase in ultraviolet continuum and line emission may be due to enhanced …
Ultraviolet Observations Of Four Symbiotic Stars, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, R. W. Hobbs
Ultraviolet Observations Of Four Symbiotic Stars, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
Observations were obtained with the International Ultraviolet Explorer (IUE) of four symbiotic stars. The UV spectra of YY Her, SY Mus, CL Sco, and BX Mon are characterized by varying degrees of thermal excitation. We have analyzed these low resolution spectra in terms of line-blanketed model atmospheres of early A, B, and F type stars in order to identify the nature of the hot companion in these systems. The expected emission from early main sequence stars does not fully explain the observed distribution of UV continuum energy over the entire IUE spectral range (1200-3200 A). More likely the observed continuum …
International Ultraviolet Explorer Observations Of The Aquarii Jet, A. G. Michalitsianos, Menas Kafatos
International Ultraviolet Explorer Observations Of The Aquarii Jet, A. G. Michalitsianos, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
Ultraviolet spectra were obtained with the International Ultraviolet Explorer of the newly discovered optical-radio jet feature in the symbiotic variable R Aquarii. The far-UV continuum of the jet is characterized by strong continuum which rises with decreasing wavelength in the 1200-2000 A wavelength range and is considerably different in appearance from the relatively flat continuum exhibited by ionized nebulosity in the central star. Prominent Si III] and Si II emission lines seen in the central region are virtually absent in the jet. This could reflect the depletion of silicon in the feature, the result of grain formation in material that …
Iue Observations Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, W. A. Feibelman
Iue Observations Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, W. A. Feibelman
Mathematics, Physics, and Computer Science Faculty Articles and Research
We have obtained the first high-dispersion observations of RX Pup in the wavelength region 1200-2000 A with the International Ultraviolet Explorer. RX Pup has been classified a symbiotic star and has been compared to slow novae as well as to 11 Carinae. The anomalies that we observed in high-excitation lines in RX Pup such as He II, 0 III], C III], C IV, and Si IIIl that show split line profiles, Doppler displaced multiple components, and possible inverse P Cygni profiles inN III] and N IV J suggest dynamic activity in circumstellar material that probably has the form of rings …
Ultraviolet Spectrum Of The Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, R. A. Fesen, R. A. Parise, C. A. Harvel, Menas Kafatos, V. L. Trimble
Ultraviolet Spectrum Of The Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, R. A. Fesen, R. A. Parise, C. A. Harvel, Menas Kafatos, V. L. Trimble
Mathematics, Physics, and Computer Science Faculty Articles and Research
Data from 65 hours of observation of the Crab Nebula with the International Ultraviolet Explorer are reported, together with new ground-based spectrophotometry. We have measured the important C IV λ1549, He II λ1640, and C III] λ1908 emission line intensities and placed upper limits on other ultraviolet features for the brightest filamentary region in the nebula. We have also measured some ultraviolet continuum surface brightnesses at two places in the Crab. The emission lines imply an average ionic abundance ratio n(C^+2)/n(O^+2 ) in the range from 0.4 to 1.5 in the observed gaseous condensations. The elemental abundance ratio of carbon …
Ultraviolet Observations Of The 1980 Eclipse Of The Symbiotic Star Ci Cygni, R. E. Stencel, A. G. Michalitsianos, Menas Kafatos, A. A. Boyarchuk
Ultraviolet Observations Of The 1980 Eclipse Of The Symbiotic Star Ci Cygni, R. E. Stencel, A. G. Michalitsianos, Menas Kafatos, A. A. Boyarchuk
Mathematics, Physics, and Computer Science Faculty Articles and Research
Secular and eclipse variations of UV lines and continua during the course of nearly a full orbit of the symbiotic binary CI Cygni are presented. High-excitation resonance lines have brightened on an orbital time scale and show minimal effects of eclipse, while intercombination lines have faded and show pronounced but nontotal eclipse effects. The data are discussed in terms of mass transfer from the extended cool envelope of the red giant to a compact secondary. The formation of an accretion disk is a transitory phenomenon in which viscosity eventually dissipates the disk over orbital time scales. A large-scale low-density nebula …
Radio And Optical Observations Of The R Aquarii Jet, R. J. Sopka, G. Herbig, Menas Kafatos, A. G. Michalitsianos
Radio And Optical Observations Of The R Aquarii Jet, R. J. Sopka, G. Herbig, Menas Kafatos, A. G. Michalitsianos
Mathematics, Physics, and Computer Science Faculty Articles and Research
VLA observations at 6 cm and Lick Observatory optical plates of R Aquarii indicate the existence of a jetlike feature extending 7" -10" from the central star. A wide field map at 6 cm shows an unresolved compact radio source which lies close to the axis defined by the jet at a distance of ~ 3' from R Aqr. Episodic mass transfer in this symbiotic variable could explain the erratic outbursts that R Aqr is known to undergo. Formation of an accretion disk and the accompanying radio-optical jet may characterize the observed outbursts in this system.
Oh Emission In The Direction Of Tv Gem And Bi Cyg, L. W. Brown, R. W. Hobbs, A. G. Michalitsianos, Menas Kafatos
Oh Emission In The Direction Of Tv Gem And Bi Cyg, L. W. Brown, R. W. Hobbs, A. G. Michalitsianos, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
OH maser main-line emission at 1665 MHz has been detected in the direction of two late-type supergiants, TV Gem (Mllab) and BI Cyg (M3Iab), with the 43-m telescope and 18-cm receiver at NRAO-Green Bank. Detection of two new OH maser sources here is particularly interesting in view of the relatively small number of late-type supergiants that are known as molecular radio sources or associated in close proximity with OH emission clouds. The infrared, ultraviolet, and radio properties of these stars are discussed briefly.
Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Iue Observations Of Circumstellar Emission From The Late Type Variable R Aquarii (M7 + Pec), A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
IUE observations of R Aquarii (M7 + pec) have been obtained in low dispersion in order to study its circumstellar emission. Strong permitted, semiforbidden, and forbidden emission lines are identified that are superposed on a bright ultraviolet continuum. From our analysis we deduce that the strong emission-line spectrum that involves C III], C IV, Si III], [0 II], and [0 III] probably arises from a dense compact nebula the size of which is comparable to the binary system of which R Aqr is the primary star. Low-excitation emission lines of Fe II, Mg II, 0 1, and Si II suggest …
150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown
150 Ghz Observations Of Three Radio Galaxies, Menas Kafatos, R. W. Hobbs, S. P. Maran, L. W. Brown
Mathematics, Physics, and Computer Science Faculty Articles and Research
Radio galaxies were observed for the first time at 150 GHz. The central sources in Cyg A and 3C Ill were detected, as were the two radio lobes of Cyg A. No emission was found from the central source in 3C 236. Each of these three central sources has been previously discussed as the site of the energy supply for the associated distant components. The millimeter-wavelength emission from the central sources in Cyg A and 3C 111 is probably due in each case to a compact component that is optically thin to synchrotron radiation above about 35 GHz. These components …
Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Iue Observations Of Two Late Type Stars: R Aql And W Hya, Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
Ultraviolet spectra of two late type M stars R Aql and W Hya were obtained with the International Ultraviolet Explorer (IUE). Spectra were obtained of R Aql near maximum (cf>=0.21) and minimum (cf>=0.65) of the visible light curve. We find that the absolute flux intensity of the Mgn resonance doublet (2796 A, 2803 A) is essentially the same at these phases in the visible light curve. A nebular emission feature at 3133 A is detected at minimum light in R Aql that is possibly due to 0 III. Mg II emission is totally absent in W Hya, which …
Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs
Mathematics, Physics, and Computer Science Faculty Articles and Research
IUE observations of the late type star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between 1100 and 2000 A suggests that this object is a binary system in which the secondary is identified as the central star of a planetary nebula with Teff 105 K. The ultraviolet spectrum is characterized by semiforbidden and allowed transition lines, of which the C IV (1548 A, 1550 A) doublet is particularly strong. A general absence of strong forbidden line emission suggests that the compact nebula in which both primary and secondary stars are embedded has …