scholarly journals IUE Observations of Novae

1980 ◽  
Vol 5 ◽  
pp. 285-291
Author(s):  
Warren M. Sparks ◽  
Chi-Chao Wu ◽  
Albert V. Holm ◽  
Francis H. Schiffer
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Wavelength Range ◽  
Emission Lines ◽  
First Year ◽  
Time Behavior ◽  
International Ultraviolet Explorer ◽  
Ultraviolet Wavelength ◽  
Visual Magnitude ◽  
The Continuum

In addition to offering observing time on a regular schedule, the International Ultraviolet Explorer (IUE) satellite is also being used to observe “targets of opportunity.” Novae represent one of the most exciting targets of opportunity and also one of the most difficult because of their rapid time behavior. During the first year of operation of IUE we were extremely fortunate to have three bright novae outbursts occur: Nova Cygni 1978, WZ Sagittae, and U Scorpii.Nova Cyg 1978, a fast nova, reached a maximum apparent visual magnitude of 6.2 on September 12, 1978 (Slovak and Vogt 1979). Figure 1 shows the relative flux of Nova Cyg 1978 in the long ultraviolet wavelength range (1900-3200Å) at several different times. One day after maximum (Sept. 13), the nova is still in its absorption line phase. At this point it looks like a supergiant F star with mostly Fell absorption lines (also see Cassatella et al. 1979). Later spectra show the emergence of emission lines, which is the characteristic behavior of novae in the visual. Magnesium II at 2800Å is the strongest emission line in this part of the spectrum for at least a month after outburst. The last spectrum (Nov. 1) shows mainly semi-forbidden lines of carbon, nitrogen, and oxygen. It should also be noted that the slope of the continuum flattens as the nova evolves.

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

Dissecting quasars with the J-PAS narrow-band photometric survey

2019 ◽  
Vol 15 (S356) ◽  
pp. 12-16
Author(s):  
Silvia Bonoli ◽  
Giorgio Calderone ◽  
Raul Abramo ◽  
Jailson Alcaniz ◽  
Narciso Benitez ◽  
...  
Keyword(s):  
Emission Line ◽  
Wavelength Range ◽  
Software Package ◽  
Narrow Band ◽  
Active Galaxies ◽  
Emission Lines ◽  
Low Resolution ◽  
Strong Emission ◽  
Optical Wavelength ◽  
Quasar Spectra

AbstractThe J-PAS survey will soon start observing thousands of square degrees of the Northern Sky with its unique set of 56 narrow band filters covering the entire optical wavelength range, providing, effectively, a low resolution spectra for every object detected. Active galaxies and quasars, thanks to their strong emission lines, can be easily identified and characterized with J-PAS data. A variety of studies can be performed, from IFU-like analysis of local AGN, to clustering of high-z quasars. We also expect to be able to extract intrinsic physical quasar properties from the J-PAS pseudo-spectra, including continuum slope and emission line luminosities. Here we show the first attempts of using the QSFit software package to derive the properties for 22 quasars at 0.8 < z < 2 observed by the miniJPAS survey, the first deg2 of J-PAS data obtained with an interim camera. Results are compared with the ones obtained by applying the same software to SDSS quasar spectra.

scholarly journals Variability of the Ultraviolet Continuum and Emission Lines of NGC 3783

1994 ◽  
Vol 159 ◽  
pp. 403-403
Author(s):  
G.A. Reichert
Keyword(s):  
Seyfert Galaxy ◽  
Light Curves ◽  
Emission Lines ◽  
Power Density Spectrum ◽  
Ultraviolet Continuum ◽  
Density Spectrum ◽  
International Ultraviolet Explorer ◽  
Monitoring Effort ◽  
Ngc 5548 ◽  
The Continuum

On behalf of the International AGN Watch, I report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of seven months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or “dips,” the first lasting ≲ 20 days and the second ≲ 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became “harder” when brighter. The variations in the continuum occurred simultaneously at all wavelengths (Δt < 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Lyα) the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or “lag.” As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) ∼ 0 days for He II+O III], and ∼ 4 days for Lyα, and C IV. The data further suggest lags of ∼ 4 days for Si IV+O IV], and 8–30 days for Si III]+C III]. Uncertainties in these quantities are likely to be of order 2–3 days for the stronger features (Lyα, C IV), and 3–4 days for the weaker ones (He II+O III], Si IV+O IV], Si III]+C III]). Mg II lagged the 1460 Å continuum by ∼ 9 days, although this result depends on the method of measuring the line flux, and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over time scales of ≲ 2 days, and that the character of the continuum variability may change with time.

scholarly journals The Timescales of Variations in Continuum and Hydrogen Lines During Stellar Flares

1983 ◽  
Vol 71 ◽  
pp. 239-243
Author(s):  
B.R. Pettersen
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Light Curves ◽  
Emission Lines ◽  
Continuum Radiation ◽  
Stellar Flares ◽  
Hydrogen Lines ◽  
The Continuum

AbstractLight curves of major stellar flares have been used to study the behavior of U-B, B-V, and V-R. The majority of the flux transmitted through these filters is continuum radiation, but U and B are affected by emission lines. The variability of Ha and H$ emission lines were monitored through narrow band filters. The timescales of emission line variability are considerably longer than those for the continuum, and the emission line flare peak occurs a few minutes after the continuum flare maximum. No variability in lines at a timescale of seconds is detected in our data.

scholarly journals Absorption Systems in High Redshift QSOs

1977 ◽  
Vol 74 ◽  
pp. 193-222 ◽  
Author(s):  
A. Boksenberg
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
High Redshift ◽  
Ground Level ◽  
Emission Lines ◽  
Absorption Lines ◽  
Absorption System ◽  
Characteristic Emission

In addition to the characteristic emission lines, absorption lines frequently are seen in the spectra of QSOs, usually those with high redshift (zem ≳ 1.8). About 10 percent of all QSOs listed in the compilation of Burbidge et al. (1976a) are recorded as having at least one ‘identified’ absorption system, meaning that a pattern of several selected observed lines can be matched with the apparent wavelengths of transitions (generally from the ground level) in a physical plausible group of atoms or ions at the same, although arbitrary, redshift (Bahcall 1968, Aaronson et al. 1975). Identified absorption line redshifts range from being comparable with the associated emission line redshifts, to having very much smaller values with relative velocities exceeding 0.5c in the QSO frame. Added to this, there are many QSOs having absorption lines not yet recognised as belonging to identified systems, both those objects already having one or more identifications, and others with none.

scholarly journals Velocity-Resolved Line Response of the Emission Lines in the High-Luminosity (Mv ≈ −24) Seyfert 1 Galaxy Fairall 9

1997 ◽  
Vol 159 ◽  
pp. 151-154
Author(s):  
W. Wamsteker ◽  
M.C. Recondo-González ◽  
P.M. Rodríguez-Pascual ◽  
R. Vio ◽  
F. Makino
Keyword(s):  
Emission Line ◽  
Emission Lines ◽  
X Rays ◽  
High Luminosity ◽  
Spectral Variability ◽  
Model Calculations ◽  
Photoionization Model ◽  
Large Wavelength ◽  
The Continuum

AbstractA detailed emission-line decomposition has been made from 15 years of observations with the IUE satellite of the highly variable Seyfert 1 galaxy Fairall 9, allowing us to study the line variability as a function of velocity and continuum brightness. The variability over the different velocity domains of the broad lines has been related to the continuum variability over a large wavelength domain from the X-rays to the infrared. Clear delays were established between the redshifted and blueshifted parts of the lines in Lyα and C IV, with the red sides of the lines responding faster with no delay and the blue sides responding with a delay of some 230 days. The observed spectral variability behavior of the continuum has been used as input for photoionization model calculations and the combined constraints from the models and differences for gas at different velocities define the structure and motions in the BLR.

scholarly journals Solar EUV Rocket Telescope and Spectrograph (SERTS) Observations of Fe XII Emission Lines

1996 ◽  
Vol 152 ◽  
pp. 531-536
Author(s):  
F.P. Keenan ◽  
R.J. Thomas ◽  
W.M. Neupert ◽  
V.J. Foster ◽  
C.J. Greer ◽  
...  
Keyword(s):  
Active Region ◽  
Emission Line ◽  
Electron Temperature ◽  
Observational Data ◽  
Electron Density ◽  
Wavelength Range ◽  
Solar Spectrum ◽  
Emission Lines ◽  
First Time ◽  
Good Agreement

Abstract.Theoretical electron density sensitive emission line ratios involving transitions in the 186–383 Å wavelength range are compared with observational data for a solar active region and a subflare, obtained by the Solar EUV Rocket Telescope and Spectrograph (SERTS). Electron densities derived from the majority of the ratios are consistent with one another, and are also in good agreement with the values of density estimated from diagnostic lines in other species formed at similar temperatures to Fe XII. These results provide observational support for the general accuracy of the diagnostic calculations. In addition, our analysis indicates that a line at 283.70 Å in the active region spectrum is the 3s23p32D3/2−3s3p42P1/2 transition in Fe XII, the first time (to the best of our knowledge) that this line has been identified in the solar spectrum. Several of the line ratios considered are predicted to be relatively insensitive to the adopted electron temperature and density, and the generally good agreement found between theory and observation for these provides evidence for the reliability of the SERTS instrument calibration. The application of the Fe XII diagnostics to EUVE observations of the F5 subgiant Procyon is briefly discussed.

scholarly journals Near-IR spectroscopic monitoring of WR 140 (WC7pd+O4-5) during the 2001 periastron passage

2003 ◽  
Vol 212 ◽  
pp. 253-254
Author(s):  
Watson P. Varricatt ◽  
Peredur M. Williams ◽  
Nagarhalli M. Ashok
Keyword(s):  
Emission Line ◽  
Ir Spectrum ◽  
Emission Lines ◽  
X Ray ◽  
Spectroscopic Monitoring ◽  
Near Ir ◽  
Wind Activity ◽  
Ir Spectroscopic ◽  
Emission Line Profile ◽  
The Continuum

The near-IR spectrum of the periodic dust making WCpd+O4-5 binary WR 140 was monitored to cover the 2001 periastron passage and maximum colliding-wind activity. The He i λ1.083μm emission-line profile showed the appearence of a subpeak on epochs close to periastron passage. The evolution of the subpeak was consistent with the motion of the stars and the colliding wind region. The appearance and evolution of the emission subpeak suggests that the theoretical 1/r dependence of X-ray flux does not hold, so that there is no need to change the values of eccentricity and epoch of periastron passage derived from the RV orbit. JHK spectra show variations of the continuum and and dilution of the emission lines, in agreement with the production and cooling of dust.

scholarly journals Spectroscopic CCD Search for the Unseen Companions in Three Single-Line WNL Binaries

1991 ◽  
Vol 143 ◽  
pp. 258-258
Author(s):  
Andre Grandchamps ◽  
Anthony F. J. Moffat
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Wavelength Range ◽  
Single Line ◽  
The Masses

We have obtained some 15 CCD spectra at different orbital phases for each of the SBl systems HD193928 (WN6), HD197406 (WN7), and CQ Cep (WN7), in an attempt to detect the companion, determine its orbit and estimate the masses. The wavelength range of the spectra is λλ3600 - 4200Å, with 1.4Å/pixel and < S/N > ≈ 100/pixel. We compare the best emission-line (N IV λ4058Å) with the best absorption-line (H9 λ3835Å).

scholarly journals Line Ratio Diagnostics Applicable to Astronomical Spectra in the 50–3000 Å Wavelength Region

1996 ◽  
Vol 152 ◽  
pp. 595-596
Author(s):  
F.P. Keenan
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Wavelength Range ◽  
Wavelength Region ◽  
Line Ratio ◽  
Iron Ions ◽  
Nickel Ions

A bibliography has been produced of the most reliable emission and absorption line ratio diagnostic calculations currently available for application to the spectra of astrophysical sources in the UV and EUV wavelength region (50-3000 Å). References are listed containing diagnostics for species in the Li through P isoelectronic sequences, as well as the iron ions Fe II-Fe XXIII and nickel ions Ni XVII-Ni XXV. Also given is the wavelength range for which diagnostic calculations are presented in each reference, along with the type of diagnostic considered. These include, for example, emission line ratios for determining electron temperatures and densities, and absorption line diagnostics for evaluating hydrogen densities.

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