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

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.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002483 ◽

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.

O and Of Stars

10.1017/s0074180900098685 ◽

1973 ◽

Vol 49 ◽

pp. 93-107

Author(s):

Peter S. Conti

Keyword(s):

Visible Spectrum ◽

Emission Lines ◽

Absorption Lines ◽

Evolutionary Status ◽

Be Stars ◽

Type B ◽

No Emission ◽

Hot Stars ◽

Hydrogen Lines ◽

My intention here is to discuss the ‘high temperature’ portion of this symposium and call attention to those stars that are called Of. There are some similarities in spectral appearance to WR stars, e.g. emission lines. I should first like to define what I think are the essential differences among four groups of hot stars;O stars: Stars that have only absorption lines in the visible spectrum. Type O is distinguished from type B by the presence of He ii 4541 at MK dispersion. It may be that some (supergiants) O stars will have emission lines in the rocket UV region but this description will be primarily concerned with ground based observations.Of stars: These are O type stars that also have λλ 4634,40 N iii in emission above the continuum. In addition to normal O star absorption lines and N iii emission, they may also have other lines in emission. I will discuss this further below.Oe stars: These are O type stars that have emission in the hydrogen lines (or at least at Hα), but with no emission in N iii or in other lines. I personally think that this small class of objects is related to the Be stars in their evolutionary status and in their emission mechanism.WR stars: These stars are primarily characterized by emission lines. The only absorption lines seen are violet shifted (P Cyg type). Although in some cases emission lines appear which are similar to those found in some Of stars, the latter types always have some unshifted absorption lines present. Several Of stars have P Cyg profiles in some lines.

Variability of the Ultraviolet Continuum and Emission Lines of NGC 3783

10.1017/s0074180900175928 ◽

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 ◽

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.

SDSS-IV MaNGA: the spectroscopic discovery of strongly lensed galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sty653 ◽

2018 ◽

Vol 477 (1) ◽

pp. 195-209 ◽

Cited By ~ 12

Author(s):

Michael S Talbot ◽

Joel R Brownstein ◽

Adam S Bolton ◽

Kevin Bundy ◽

Brett H Andrews ◽

...

Keyword(s):

Emission Line ◽

Narrow Band ◽

Signal To Noise Ratio ◽

Gravitational Lens ◽

Emission Lines ◽

High Signal ◽

Common Source ◽

Narrow Band Image ◽

Background Emission ◽

Field Unit

Abstract We present a catalogue of 38 spectroscopically detected strong galaxy–galaxy gravitational lens candidates identified in the Sloan Digital Sky Survey IV (SDSS-IV). We were able to simulate narrow-band images for eight of them demonstrating evidence of multiple images. Two of our systems are compound lens candidates, each with two background source-planes. One of these compound systems shows clear lensing features in the narrow-band image. Our sample is based on 2812 galaxies observed by the Mapping Nearby Galaxies at APO (MaNGA) integral field unit (IFU). This Spectroscopic Identification of Lensing Objects (SILO) survey extends the methodology of the Sloan Lens ACS Survey (SLACS) and BOSS Emission-Line Survey (BELLS) to lower redshift and multiple IFU spectra. We searched ∼1.5 million spectra, of which 3065 contained multiple high signal-to-noise ratio background emission-lines or a resolved [O ii] doublet, that are included in this catalogue. Upon manual inspection, we discovered regions with multiple spectra containing background emission-lines at the same redshift, providing evidence of a common source-plane geometry which was not possible in previous SLACS and BELLS discovery programs. We estimate more than half of our candidates have an Einstein radius ≳ 1.7 arcsec, which is significantly greater than seen in SLACS and BELLS. These larger Einstein radii produce more extended images of the background galaxy increasing the probability that a background emission-line will enter one of the IFU spectroscopic fibres, making detection more likely.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100039853 ◽

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 ◽

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.

Variability of the Emission-Line Spectrum of the Nucleus of the Seyfert Galaxy NGC 7469

10.1017/s0074180900010858 ◽

1975 ◽

Vol 67 ◽

pp. 605-609

Author(s):

I. I. Pronik

Keyword(s):

Emission Line ◽

Seyfert Galaxy ◽

Emission Lines ◽

Time Variability ◽

Variable Time ◽

Balmer Lines ◽

Hα Emission ◽

Emission Line Spectrum ◽

Hydrogen Lines ◽

Ngc 7469

It is shown that the emission lines of the NGC 7469 nucleus spectrum are variable. Time variability of hydrogen lines is less than 20 days. The Hα emission line is at the profile base about a factor of two narrower than the Hγ line. Estimation of the density of hydrogen envelope, where Balmer lines wings were emitted, gives the value of about 108–109 cm−3.

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

10.1017/s0074180900212266 ◽

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 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.

IUE Observations of Novae

Highlights of Astronomy ◽

10.1017/s1539299600004019 ◽

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 ◽

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.

Electron temperatures of flare plasmas from emission line fluxes

International Astronomical Union Colloquium ◽

10.1017/s0252921100153801 ◽

1989 ◽

Vol 104 (2) ◽

pp. 59-62

Author(s):

E.R. Houdebine ◽

C.J. Butler ◽

M. Rodono ◽

P.M. Panagi ◽

B.H. Foing

Keyword(s):

Emission Line ◽

Spectral Range ◽

Emission Lines ◽

Flare Loop ◽

Stellar Flares ◽

Spectral Diagnostics ◽

Preliminary Model ◽

Cooling Phase ◽

Flare Plasma

SummaryWe present spectral diagnostics for the fluxes of emission lines, in the spectral range 3600-4400 Å, during the cooling phase of stellar flares on dMe stars. Using these diagnostics, electron temperatures have been computed for flares on AD Leonis, Proxima Centauri and UV Ceti. This preliminary model assumes a single flare loop containing a homogeneous, stationary optically-thin flare plasma.

How Large are Quasar Broad-Line-Regions? Results from a Program to Monitor the PG Quasars

10.1017/s0074180900175886 ◽

1994 ◽

Vol 159 ◽

pp. 399-399

Author(s):

Dan Maoz ◽

Buell T. Jannuzi ◽

Paul S. Smith ◽

Shai Kaspi ◽

Hagai Netzer

Keyword(s):

Large Amplitude ◽

Sampling Interval ◽

Light Curves ◽

The Other ◽

Emission Lines ◽

Broad Line ◽

High Luminosity ◽

Optical Continuum ◽

Low Amplitude ◽

We have monitored spectrophotometrically a subsample (28) of the Palomar-Green Bright Quasar Sample for two years in order to measure the sizes of the broad-line regions of high-luminosity AGNs. Half of the quasars showed optical continuum variations with amplitudes in the range 20–75%. In most objects with continuum variations, we detect correlated variations in the broad Hα and Hβ emission lines. The amplitude of the line variations is usually 2–4 times smaller than the optical continuum fluctuations. The lines respond to the continuum variations with a lag that is smaller than or comparable to our typical sampling interval (a few months). This suggests that the quasars have broad-line regions smaller than about 1 lt-year. The figures below show spectra and light curves for one of the quasars. Two of the quasars monitored show no detectable line variations despite relatively large-amplitude continuum changes. This could be a stronger manifestation of the low-amplitude line-response phenomenon we observe in the other quasars. Further details appear in Maoz et al. (1994, ApJ, Jan 20, in press).