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Full-Text Articles in Physical Sciences and Mathematics
Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos
Ultraviolet Temporal Variability Of The Peculiar Star R Aquarii, S. R. Meier, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
This paper is a comprehensive study of all far-UV spectra obtained with the International Ultraviolet Explorer (IUE) satellite of the symbiotic star R Aquarii (R Aqr) covering a 13 yr period between 1979 and 1992. We have analyzed the ultraviolet emission for the compact H II region and the NE and SW extended "jetlike" filamentary structures. The results of our ultraviolet analysis indicate that the H II region and features A, B, and D of the NE jet are increasing in intensity, while the SW counterjet, feature A', has declined in intensity. We have found much stronger evidence that the …
Evidence Signalling The Start Of Enhanced Counterjet Flow In The Symbiotic System R Aquarii, A. G. Michalitsianos, M. Perez, Menas Kafatos
Evidence Signalling The Start Of Enhanced Counterjet Flow In The Symbiotic System R Aquarii, A. G. Michalitsianos, M. Perez, Menas Kafatos
Mathematics, Physics, and Computer Science Faculty Articles and Research
The velocity structure of strong far-UV emission lines observed in the symbiotic variable R Aqr suggests the start of new jet activity which will probably culminate in the appearance of a series of intense nebular emission knots within a decade. This is indicated by a systematic redward wavelength drift of emission lines, which we have followed with the International Ultraviolet Explorer (IV E) since the discovery of the brilliant northeast jet emission knots more than 10 years ago. The C IV λλ1548, 1550 resonance lines, which previously showed a prominent blue asymmetric wing that extended to velocities in excess -200 …
Ultraviolet And Optical Spectroscopy Of The R Aquarii Symmetrical Jet, J. M. Hollis, R. J. Oliverson, Menas Kafatos, A. G. Michalitsianos, R. M. Wagner
Ultraviolet And Optical Spectroscopy Of The R Aquarii Symmetrical Jet, J. M. Hollis, R. J. Oliverson, Menas Kafatos, A. G. Michalitsianos, R. M. Wagner
Mathematics, Physics, and Computer Science Faculty Articles and Research
The first ultraviolet spectrum of the southwest (SW) component of the symmetrical jet in the R Aquarii binary system has been obtained in the range 1200-2000 A with the International Ultraviolet Explorer (IUE). These results are compared to more encompassing spectra (1200-3200 A) of the central H II region taken at the same time and also similar spectra of the northeast (NE) jet component obtained 6 months earlier. Moreover, optical spectra of both the NE and SW jet components in the range 3400-9800 A were obtained within ~ 6 months and ~ 1 month, respectively, of the ultraviolet spectra. These …
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.
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 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 …
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 …
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 …
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.