scholarly journals Effects of Eccentric Orbit of BF Cygni on IUE and Optical Spectra

1988 ◽  
Vol 103 ◽  
pp. 299-300
Author(s):  
J. Mikolajewska ◽  
M. Mikolajewski
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Spectra ◽  
Emission Lines ◽  
Recent Analysis ◽  
Emission Region ◽  
Galactic Rotation ◽  
Resonance Emission ◽  
High Ionization ◽  
Cosmic Abundance

A recent analysis of all available photometric data has resulted in a new ephemeris for BF Cyg: MIN=JD 2415058 + 756.8E. Simultaneously, optical spectra collected in 1979–1986 showed periodic changes of all emission lines (Mikolajewska 1987; Mikolajewska & lijima 1987). It is interesting that the forbidden lines of [OIII] varied in antiphase to the permitted emission lines and optical brightness.IUE spectra taken in 1979–1981 showed a strong hot continuum and high ionization resonance emission lines of NV, SilV CIV, intercombination lines of NIV], NIII], SiIII], CIII] and OIII] as well as Hell emission. The observed λ2200Å interstellar absorption band suggests E(B-V)≃0.3. Taking into account the interstellar reddening distribution in the vicinity of BF Cyg (Lucke 1978; Mikolajewska & Mikolajewski 1980), the observed extinction implies a distance d≲1.5kpc. This distance is in good agreement with the observed low value of the systemic radial velocity (∼15 km/s, Fig.1) of BF Cyg and the standard galactic rotation law. The standard extinction curve with E(B-V)=0.3 (Seaton 1979) was used for reddening correction of the spectra. The UV continuum of BF Cyg can be interpreted as a combination of a hot subdwarf (Teff≃60000K, L≃2500L⊙ for d=1.5kpc) and hydrogen bf+ff emission (Te≃10000K). The emission measure of the nebular (bf+ff) continuum varied from ∼4×1059cm−3 at maximum to ∼1059cm−3 at minimum. Assuming cosmic abundance of Si/C the observed SiIII]/CIII] line ratio implies ne≃2×l010cm−3 at the photometric maximum and ne≃3×109cm−3 at the minimum. We assume that these values are representative of the region where the bulk of the HI Balmer and intercombination line emission is produced. The ratio of NV(1240)/NIV(1720) gives Te(NV)≃11500K close to the value derived for the Balmer emission region from the UV continuum fit.

scholarly journals Dissecting the EUV Spectrum of Capella

1996 ◽  
Vol 152 ◽  
pp. 105-112 ◽  
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
Extreme Ultraviolet ◽  
Emission Measure ◽  
Continuous Distribution ◽  
Line Emission ◽  
Local Maximum ◽  
Abundance Ratio ◽  
Emission Lines ◽  
Cool Star ◽  
The Individual ◽  
The Continuum

Extreme ultraviolet spectra of Capella, obtained at various orbital phases over the past two years by the EUVE satellite, show strong emission lines from a continuous distribution of temperatures (~ 105 − 107.3 K). In addition to the strong He II λ303.8, the spectra are dominated by emission lines of highly ionized iron. Strong lines of Fe IX, XV, XVI, and XVIII–XXIV are used to construct emission measure distributions for the individual pointings, which show several striking features, including a minimum near 106 K and a local maximum at 106.8 K. Furthermore, intensities of the highest temperature lines (Te > 107 K) show variations (factors of 2–3) at different orbital phases, while the lower temperature Fe lines show variations of about 30% or less. The low variability of most of the strong low temperature features motivates a detailed analysis of the summed spectrum. With ~ 280 ks of total exposure time, we have measured over 200 emission features with S/N ≥ 3.0 in the summed spectrum. We report here initial results from the analysis of this spectrum. We can now identify lines of Fe VIII and X–XIV, as well as a number of electron density and abundance diagnostic lines.We also report here the first direct measurement of the continuum flux around ~ 100 Å in a cool star atmosphere with EUVE. The continuum flux can be predicted from the emission measure model based on Fe line emission, and demonstrates that the Fe/H abundance ratio is close to the solar photospheric value.

scholarly journals The “Gravitational Lens” 3C 321: A Remarkable Impostor

1987 ◽  
Vol 124 ◽  
pp. 761-765
Author(s):  
Alexei V. Filippenko
Keyword(s):  
Radio Galaxy ◽  
Line Emission ◽  
Careful Analysis ◽  
Gravitational Lens ◽  
Emission Lines ◽  
Optical Data ◽  
High Ionization ◽  
Spectrum Radio ◽  
Hα Emission

Recent observations of the radio galaxy 3C 321 are presented. The optical nucleus consists of two components (A, B), separated by ∼ 4″ (∼ 6 kpc), whose low-resolution spectra strongly resemble those of high-ionization type 2 Seyfert nuclei. The relative intensities of the emission lines differ in A and B by less than 1%, and their profiles are almost identical. 3C 321 appears to be a convincing example of a gravitationally lensed object.Careful analysis of high-quality radio and optical data, however, reveals that the system is almost certainly not a lens. The equivalent widths of the emission lines are roughly twice as high in B than in A, and there are significant spatial offsets between regions of bright continuum and line emission. A slight, but fundamental, difference is visible in the two Hα emission profiles. The radial velocities of A and B are discrepant by 31 ± 10 km s−1. Finally, component A is nearly coincident with a flat-spectrum radio core, whereas B is next to an extended, steep-spectrum knot of radio emission.This object should serve as a warning to lens hunters: beware of impostors, whose true properties may be difficult to ascertain without extensive optical and radio observations.

scholarly journals Evidence for rapid disc formation and reprocessing in the X-ray bright tidal disruption event candidate AT 2018fyk

2019 ◽  
Vol 488 (4) ◽  
pp. 4816-4830 ◽  
Author(s):  
T Wevers ◽  
D R Pasham ◽  
S van Velzen ◽  
G Leloudas ◽  
S Schulze ◽  
...  
Keyword(s):  
Light Curve ◽  
Optical Spectra ◽  
Emission Lines ◽  
Tidal Disruption ◽  
X Ray ◽  
Physical Conditions ◽  
High Ionization ◽  
Optical Light Curve ◽  
Narrow Emission ◽  
Disruption Event

ABSTRACT We present optical spectroscopic and Swift UVOT/XRT observations of the X-ray and UV/optical bright tidal disruption event (TDE) candidate AT 2018fyk/ASASSN–18ul discovered by ASAS–SN. The Swift light curve is atypical for a TDE, entering a plateau after ∼40 d of decline from peak. After 80 d the UV/optical light curve breaks again to decline further, while the X-ray emission becomes brighter and harder. In addition to broad H, He, and potentially O/Fe lines, narrow emission lines emerge in the optical spectra during the plateau phase. We identify both high-ionization (O iii) and low-ionization (Fe ii) lines, which are visible for ∼45 d. We similarly identify Fe ii lines in optical spectra of ASASSN–15oi 330 d after discovery, indicating that a class of Fe-rich TDEs exists. The spectral similarity between AT 2018fyk, narrow-line Seyfert 1 galaxies, and some extreme coronal line emitters suggests that TDEs are capable of creating similar physical conditions in the nuclei of galaxies. The Fe ii lines can be associated with the formation of a compact accretion disc, as the emergence of low-ionization emission lines requires optically thick, high-density gas. Taken together with the plateau in X-ray and UV/optical luminosity this indicates that emission from the central source is efficiently reprocessed into UV/optical wavelengths. Such a two-component light curve is very similar to that seen in the TDE candidate ASASSN–15lh, and is a natural consequence of a relativistic orbital pericentre.

scholarly journals Optical and X-ray studies of three polars: RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737

2019 ◽  
Vol 491 (1) ◽  
pp. 201-214 ◽  
Author(s):  
Arti Joshi ◽  
J C Pandey ◽  
Ashish Raj ◽  
K P Singh ◽  
G C Anupama ◽  
...  
Keyword(s):  
White Dwarf ◽  
Optical Spectra ◽  
Emission Lines ◽  
X Ray ◽  
Long Period ◽  
Photometric And Spectroscopic Observations ◽  
High Ionization ◽  
Orbital Periods ◽  
Actual Size ◽  
Balmer Decrement

ABSTRACT We present optical photometric and spectroscopic observations, and an analysis of archival X-ray data of three polars: RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737. Optical light curves of these three polars reveal eclipse-like features that are deep, total, and variable in shape. The optical and X-ray modulations of RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737 are both found to occur at the orbital periods of 2.393 ± 0.003 h, 3.672 ± 0.001 h, and 4.347 ± 0.001 h, respectively. RX J0859.1+0537 is found to be a polar that lies in the region of the period gap, whereas RX J0749.1–0549 and RX J0649.8–0737 are found to be long-period polars above the period gap. The eclipse length is found to be 61 min for RX J0749.1–0549 in the Rband, which is the highest among the long-period eclipsing polars. The radius of the eclipsed light source is found to be more than the actual size of the white dwarf for these three systems, indicating that the eclipsed component is not only the white dwarf but also appears to include the presence of an extended accretion region. Optical spectra of these systems show the presence of high-ionization emission lines along with the strong Balmer emission lines with an inverted Balmer decrement. Cyclotron harmonics are also detected in the optical spectra from which we infer magnetic field strength of the surface of the white dwarf to be 49 ± 2 MG, 43.5 ± 1.4 MG, and 44 ± 1 MG for RX J0859.1+0537, RX J0749.1–0549, and RX J0649.8–0737, respectively.

scholarly journals MODELING THE SS 433 JET BENDS

2008 ◽  
Vol 17 (10) ◽  
pp. 1925-1930 ◽  
Author(s):  
H. L. MARSHALL ◽  
CLAUDE R. CANIZARES ◽  
NORBERT S. SCHULZ ◽  
SEBASTIAN HEINZ ◽  
TODD C. HILLWIG ◽  
...  
Keyword(s):  
Emission Measure ◽  
Line Emission ◽  
Optical Emission ◽  
Local Environment ◽  
Emission Lines ◽  
X Ray ◽  
Ss 433 ◽  
Jet Cooling ◽  
Doppler Shifts ◽  
Optical Line

We fit Chandra HETGS data obtained for the unusual X-ray binary SS 433. While line strengths and continuum levels hardly change, the jet Doppler shifts show aperiodic variations that probably result from shocks in interactions with the local environment. The X-ray and optical emission line regions are found to be related but not coincident as the optical line emission persists for days while the X-ray emission lines fade in less than 5000 s. The X-ray spectrum of the blueshifted jet shows over two dozen emission lines from plasma at a variety of temperatures. The emission measure distribution derived from the spectrum can be used to test jet cooling models.

scholarly journals An imaging spectroscopic survey of the planetary nebula NGC 7009 with MUSE

2018 ◽  
Vol 620 ◽  
pp. A169 ◽  
Author(s):  
J. R. Walsh ◽  
A. Monreal-Ibero ◽  
M. J. Barlow ◽  
T. Ueta ◽  
R. Wesson ◽  
...  
Keyword(s):  
Line Emission ◽  
Emission Lines ◽  
Ionized Gas ◽  
Physical Conditions ◽  
Very Large Telescope ◽  
High Ionization ◽  
Integral Field Spectrograph ◽  
First Time ◽  
Considerable Detail ◽  
Standard Techniques

Aims. The spatial structure of the emission lines and continuum over the 50″ extent of the nearby, O-rich, PN NGC 7009 (Saturn Nebula) have been observed with the MUSE integral field spectrograph on the ESO Very Large Telescope. This study concentrates on maps of line emission and their interpretation in terms of physical conditions. Methods. MUSE Science Verification data, in <0.6″ seeing, have been reduced and analysed as maps of emission lines and continuum over the wavelength range 4750–9350 Å. The dust extinction, the electron densities and temperatures of various phases of the ionized gas, abundances of species from low to high ionization and some total abundances are determined using standard techniques. Results. Emission line maps over the bright shells are presented, from neutral to the highest ionization available (He II and [Mn V]). For collisionally excited lines (CELs), maps of electron temperature (Te from [N II] and [S III]) and density (Ne from [S II] and [Cl III]) are available and for optical recombination lines (ORLs) temperature (from the Paschen jump and ratio of He I lines) and density (from high Paschen lines). These estimates are compared: for the first time, maps of the differences in CEL and ORL Te’s have been derived, and correspondingly a map of t2 between a CEL and ORL temperature, showing considerable detail. Total abundances of only He and O were formed, the latter using three ionization correction factors. However, the map of He/H is not flat, departing by ~2% from a constant value, with remnants corresponding to ionization structures. An integrated spectrum over an area of 2340 arcsec2 was also formed and compared to 1D photoionization models. Conclusions. The spatial variation of a range of nebular parameters illustrates the complexity of the ionized media in NGC 7009. These MUSE data are very rich with detections of hundreds of lines over areas of hundreds of arcsec2 and follow-on studies are outlined.

scholarly journals The possible detection of iron line emission from Sco X-1

1970 ◽  
Vol 37 ◽  
pp. 138-143
Author(s):  
S. S. Holt ◽  
E. A. Boldt ◽  
P. J. Serlemitsos
Keyword(s):  
Dead Time ◽  
Line Emission ◽  
Differential Spectrum ◽  
Thermal Source ◽  
Measured Temperature ◽  
Iron Line ◽  
High Ionization ◽  
Cosmic Abundance

A rocket-borne measurement carried out on March 3, 1969 has yielded a net (dead-time-corrected) exposure of 104 cm2 sec to the differential spectrum of X-radiation from Sco X-1. The data are fully consistent with radiation from an optically thin thermal source, even to the extent that K-emission from high ionization states of iron appears to be present. Such iron emission is consistent with cosmic abundance at the measured temperature.

scholarly journals Inhomogeneous winds: the nature of emission-line profile variations in Wolf-Rayet spectra

1999 ◽  
Vol 193 ◽  
pp. 250-251
Author(s):  
Sébastien Lépine ◽  
Anthony F.J. Moffat
Keyword(s):  
Line Profile ◽  
Radial Direction ◽  
Fractal Structure ◽  
Line Emission ◽  
Emission Lines ◽  
Emission Region ◽  
Dynamical Structure ◽  
Wind Model ◽  
Large Fluctuations ◽  
Emission Line Profile

We present the results of simulations which show that stochastic line-profile variations (LPVS) of Wolf-Rayet emission lines can be reproduced with an inhomogeneous wind model, in which line-emission arises from a large number of discrete wind emission elements (DWEES). A comparison between simulations and LPVS from 9 WR stars provides useful information about the nature of the inhomogeneous and dynamical structure of the wind. Although the detailed spatial/fractal structure of the inhomogeneous wind is poorly constrained by analysis of LPVS, simulations suggest the wind to be highly fragmented, being composed of at least 104 DWEES in the line-emission region. Analysis of lpv patterns reaveal DWEES to be associated with large fluctuations in the velocity field. These fluctuations are locally anisotropic; the velocity dispersions of DWEES. are systematically larger in the radial direction (≈vr ≍ 200 km s−1) than in the transverse direction (σvθ ≈ 50 kms−1). lpv patterns also yield estimates of the wind acceleration, which can be used to test hypotheses about the wind velocity-law.

Discovery of five new Galactic symbiotic stars in the VPHAS+ survey

2021 ◽  
Vol 502 (2) ◽  
pp. 2513-2517
Author(s):  
Stavros Akras ◽  
Denise R Gonçalves ◽  
Alvaro Alvarez-Candal ◽  
Claudio B Pereira
Keyword(s):  
Spectroscopic Data ◽  
Selection Criterion ◽  
Optical Spectra ◽  
Emission Lines ◽  
High Rate ◽  
Symbiotic Stars ◽  
Selection Of

ABSTRACT We report the validation of a recently proposed infrared (IR) selection criterion for symbiotic stars (SySts). Spectroscopic data were obtained for seven candidates, selected from the SySt candidates of Akras et al. by employing the new supplementary IR selection criterion for SySts in the VST/OmegaCAM Photometric H-Alpha Survey. Five of them turned out to be genuine SySts after the detection of H α, He ii, and [O iii] emission lines as well as TiO molecular bands. The characteristic O vi Raman-scattered line is also detected in one of these SySts. According to their IR colours and optical spectra, all five newly discovered SySts are classified as S-type. The high rate of true SySts detections of this work demonstrates that the combination of the H α emission and the new IR criterion improves the selection of target lists for follow-up observations by minimizing the number of contaminants and optimizing the observing time.

scholarly journals Restframe UV-to-optical spectroscopy of APM 08279+5255

2018 ◽  
Vol 617 ◽  
pp. A118 ◽  
Author(s):  
F. G. Saturni ◽  
M. Bischetti ◽  
E. Piconcelli ◽  
A. Bongiorno ◽  
C. Cicone ◽  
...  
Keyword(s):  
Emission Lines ◽  
Magnification Factor ◽  
Uv Spectrum ◽  
Reverberation Mapping ◽  
Broad Absorption Line ◽  
Near Ir ◽  
A Value ◽  
High Ionization ◽  
Single Epoch ◽  
Absorption Features

We present the analysis of the restframe optical-to-UV spectrum of APM 08279+5255, a well-known lensed broad absorption line (BAL) quasar at z = 3.911. The spectroscopic data were taken with the optical DOLoRes and near-IR NICS instruments at TNG, and include the previously unexplored range between C III] λ1910 and [O III] λλ4959,5007. We have investigated the possible presence of multiple BALs by computing “balnicity” and absorption indexes (i.e., BI, BI0, and AI) for the transitions Si IV λ1400, C IV λ1549, Al III λ1860, and Mg II λ2800. No clear evidence for the presence of absorption features is found in addition to the already known, prominent BAL associated to C IV, which supports a high-ionization BAL classification for APM 08279+5255. We also studied the properties of the [O III], Hβ, and Mg II emission lines. We find that [O III] is intrinsically weak (F[OIII]∕FHβ ≲ 0.04), as it is typically found in luminous quasars with a strongly blueshifted C IV emission line (~2500 km s−1 for APM 08279+5255). We computed the single-epoch black hole mass based on Mg II and Hβ broad emission lines, finding MBH = (2 ÷ 3) × 1010μ−1 M⊙, with the magnification factor μ that can vary between 4 and 100 according to CO and restframe UV-to-mid-IR imaging respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation, the EWMgII ~ 27 Å measured for APM 08279+5255 translates into an Eddington ratio of ~0.4, which is more consistent with μ = 4. This magnification factor also provides a value of MBH that is consistent with recent reverberation-mapping measurements derived from C IV and Si IV.

Sign in / Sign up

Export Citation Format

Share Document