Line Profile Structure Research Articles

Line profile variations in classical Cepheids

We have investigated line profiles in a large sample of Cepheid spectra, and found four stars that show unusual (for Cepheids) line profile structure (bumps or/and asymmetries). The profiles can be phase dependent but the behavior persists over many cycles. The asymmetries are unlikely to be due to the spectroscopic binarity of these stars or the specific velocity field in their atmospheres caused by shock waves. As a preliminary hypothesis, we suggest that the observed features on the line profiles in the spectra of X Sgr, V1334 Cyg, EV Sct and BG Cru can be caused by the non-radial oscillations. It is possible that these non-radial oscillations are connected to resonances between the radial modes (, or ).

The Detection of the λ2175 Feature and Further Analysis of the Broad Absorption Line Profile Structure in the Gravitational Lens Candidate UM 425

We obtained Multiple Mirror Telescope spectra of the gravitational lens candidate UM 425 to compare the redshifts and line profile structures of lens components A and B, which are separated by approximately 65. The C IV λ1550 emission in both A and B exhibits broad absorption line (BAL) structure, consistent with the earlier detection of BAL structure in O VI λ1033 and N V λ1240 that was found with the International Ultraviolet Explorer in component A. Cross-correlation of the spectra of A and B using emission lines of C IV λ1550, He II λ1640, N III λ1750, C III] λ1909, and Mg II λ2800 reveals a difference in the redshifts of A and B. However, the detailed BAL profile structure found in the spectra of A and B are strikingly similar to one another, which suggests the system is lensed. The spectra of A and B also indicate significant dust extinction, which we base on the presence of the λ2175 absorption feature in the rest frame of the QSO (zQSO=1.47). This feature is commonly seen in galactic sources but is not generally observed in QSO spectra. Our spectra show the presence of the λ2175 absorption feature in spectra of both images associated with the gravitational lens UM 425. Based upon the strong similarity of BAL profile structure exhibited by UM 425A and UM 425B, particularly the presence of the λ2175 dust absorption feature in spectra of both images, we conclude that UM 425 is a gravitational lens.

The ultraviolet spectrum of the gravitational lens candidate UM 425 = QSO 1120+019: Evidence for broad absorption line (BAL) structure

The UV line profile structure of high-ionization resonance lines found with the International Ultraviolet Explorer (IUE) in the brightest of four multiply imaged sources (image-A) in the `candidate gravitational lens UM 425 = QSO 1120+019 indicates broad absorption line (BAL) structure. The deep-broad trough associated with the O VI line extends to velocities ~-12,000 km s^-1^, and contains discrete features that suggest multicomponent velocity structure. This structure may include contributions from C IV absorption from the early-type galaxy that is believed to lens UM 425. A strong absorption feature in the blue wing of the Lyman-α λ1216 emission line may be a Lyman-α absorption system at a z_Lya_ = 1.437 +/- 0.003, or it may be formed by the superposition of the broad N V λλ1238, 1242 absorption trough on the extended blue emission wing of the QSO Lyman-α line. We obtained a redshift of z_QSO_ = 1.471 +/- 0.003 from Lyman-α λ1215, consistent with the redshift found by Meylan and Djorgovski in the optical. The Lyman-α line appears unusually weak due to the presence of N V λ1240 BAL absorption. A Lyman-limit absorption system at λ912 was not observed in the QSO rest frame. The detection of BAL structure in the other weaker ground-state resonance lines of N II(1) and S IV (1) was not found, suggesting these lines are formed in a region that is distinct from the BAL component. Detection of BAL structure in the other fainter images in this system with HST instrumentation, similar to structure observed here in image A, could provide evidence that UM 425 is a gravitational lens.

Evidence signaling the start of enhanced counterjet flow in the symbiotic system R AquarII

The velocity struture 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 (IUE) since the discovery of the brilliant northeast jet emission knots more than 10 years ago. The C IV wavelengths 1548, 1550 resonance lines, which previously showed a prominent blue asymmetric wing that extended to velocities in excess -200 km/s, exhibit red wing asymmetry that extends to speeds of approximately +200 km/s in late 1992. The C IV line profile structure is consistent with the model proposed by Solf (1993), who explains the appearance of the northeast jet knots in terms of a approximately 300-500 km/s collimated wind that collides with slower moving material expelled earlier in a nova outburst that occurred approximately 190 yr ago. Based upon these high-resolution UV spectra, similar emission structures should appear southwest of the central star when the counterwind (or stream) interacts with material in the southwest inner nebula. The apparent change in direction of flow could result from a precessing accretion disk that alters the projection angle of collimated flow from the disk poles. The direction of the collimated wind may be related to the binary orbit, because the velocity shifts associated with emission lines formed in the flow change direction on a timescale which is comparable to the binary period.

H fine-structure in SN 1987A within the first 111 days*

We present flux-calibrated spectra of the Hα region for SN 1987A at 3 Å resolution, covering the period 1987 February 25 to June 14, the first 111 days of SN 1987A. We find that Hα in SN 1987A shows an undisturbed P Cyg-type profile until March 15, superimposed by variable fine-structure after that date, developing within a few days into a blueshifted peak-like flux excess at –5000 km s−1 and a redshifted flux deficiency at +4400 km s−1. Both features move towards smaller radial velocity with time. They contain roughly 7 per cent of the totally absorbed and emitted Hα flux, respectively. Contributions to the observed Hα profile by line blends can be safely excluded, so that the observed line profile structure is very likely to be caused by scattered Hα photons. Similar fine-structure is also observed at Na I-D and at Paschen-α. We discuss our observations in terms of possible relations to speckle observations (‘mystery spot’) and of models involving a jet or interactions with surrounding pre-existing material. All these models are excluded by the high degree of symmetry of the fine-structure and by the fact that the redshifted component appears as flux deficit. Instead, we propose density inhomogeneities in the inner regions of the envelope as origin, being invisible before March 15 and visible afterwards due to the retreat of the photosphere relative to the faster moving layers of the ejected envelope.

The C IV doublet ratio intensity effect in symbiotic stars

High-resolution UV spectra in the 1200-2000 wavelength range of the symbiotic variable R Aqr and its nebular jet were obtained in July 1987 with the IUE. The line profile structure of the C IV 1548, 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 with radial velocities up to about -100 km/s. The value of the doublet intensity ratio in the R Aqr H II region has been observed in other similar symbiotic stars, such as RX Pup. It is suggested that the anomalous behavior of the C IV doublet intensities may be useful for studying the spatial structure and temporal nature of winds in symbiotic stars.

IUE observations of the peculiar star RX Puppis

The first set of high-dispersion UV observations of RX Pup are presented. Anomalous line profile structure observed in a number of high-excitation emission lines is discussed in context with a model that includes streams and complex mass motions in the system. Anomalies in high-excitation lines 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 continuum in low dispersion is fairly flat around 1200-2000 and rises toward longer wavelengths, and cannot be due to a star earlier than A0 II. Alternatively, it may be from an accretion disk. Photoionizing radiation may be due to the presence of an unseen, hot subdwarf with most probable effective temperature 75,000-90,000 K. Alternatively, it may be due to an accretion disk around a secondary with boundary layer temperature about 100,000 K.

An Interpretation of Anomalous Intensity Ratios Within the Hydrogen-like La Doublet in Optically Thick Laser-produced Plasmas

It is shown that the anomalous intensity ratios of the fine-structure components of MgXIIL. And Al XIII L. observed in optically thick laser-produced plasmas can be explained in terms of the usual radiative and collisional processes provided aIIowance is made for the effect of differential motion on the plasma opacity. The Doppler effect associated with differential expansion causes the red component of the doublet in the peripheral plasma region to overlap the blue component in the central region, leading to preferential absorption of the blue component. Model calculations give intensity ratios in good agreement with experiment, and explain such details of the line profile structure as the so-caIIed short-wave satellite and a component spacing in excess of the theoretical optically thin value. This study further demonstrates the major role played by differential motion in shaping the emergent profile of an opticaIIy thick line from a laser-proouced plasma.