Optical spectroscopy of Galactic field classical Be stars

ABSTRACT In this study, we analyse the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800–9000 Å. We re-estimated the extinction parameter (AV) for our sample stars using the newly available data from Gaia DR2 and suggest that it is important to consider AV while measuring the Balmer decrement (i.e. D34 and D54) values in classical Be stars. Subsequently, we estimated the Balmer decrement values for 105 program stars and found that ≈20 per cent of them show D34 ≥ 2.7, implying that their circumstellar disc are generally optically thick in nature. One program star, HD 60855 shows H α in absorption – indicative of disc-less phase. From our analysis, we found that in classical Be stars, H α emission equivalent width values are mostly lower than 40 Å, which agrees with that present in literature. Moreover, we noticed that a threshold value of ∼10 Å of H α emission equivalent width is necessary for Fe ii emission to become visible. We also observed that emission line equivalent widths of H α, P14, Fe ii 5169, and O i 8446 Å for our program stars tend to be more intense in earlier spectral types, peaking mostly near B1-B2. Furthermore, we explored various formation regions of Ca ii emission lines around the circumstellar disc of classical Be stars. We suggest the possibility that Ca ii triplet emission can originate either in the circumbinary disc or from the cooler outer regions of the disc, which might not be isothermal in nature.

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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.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100036502 ◽

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.

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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 ◽

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.

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High-Resolution Emission-Line Spectroscopy of Be Stars: Comparison of Hα and Weak Emission Lines

International Astronomical Union Colloquium ◽

10.1017/s0252921100116240 ◽

1987 ◽

Vol 92 ◽

pp. 208-210

Author(s):

Reinhard W. Hanuschik

Keyword(s):

High Resolution ◽

Emission Line ◽

Rotational Velocity ◽

Outer Radius ◽

Emission Lines ◽

Be Stars ◽

Line Profiles ◽

Component Structure ◽

Double Peak Structure ◽

Disk Component

AbstractFor a number of bright southern Be stars, high-resolution, high S/N spectroscopy has been performed for Hα, Si II λ6371 and four Fe II emission lines. With the exception of four stars, both Hα and weak emission line profiles exhibit resolved double-peak structure. Peak separation increases with stellar projected rotational velocity. In many cases, Hα profiles (but not Fe II lines) show resolved fine-structure (inflections in the flanks) indicating a two-component structure of the disk. Envelope models with arbitrary density and rotational velocity laws have been fitted to the Fe II line profiles with satisfactory results. It is found that the innermost Hα disk component also emits the Fe II lines and has an average outer radius of 5 r*; density falls off as r-l.5 or more rapidly. The outer disk component emits the faint and narrow secondary component of Hα lines with average outer radius 20 r*. The envelopes of the four stars with a strong, dominating single peak both in Hα and Fe II either are dominated by strong radial motions or, more likely, have elliptical disk-like structure.

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Dependence of equivalent width of quasar emission lines on UV-optical spectral index

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314004086 ◽

2013 ◽

Vol 9 (S304) ◽

pp. 282-283 ◽

Cited By ~ 1

Author(s):

Olena Torbaniuk ◽

Ganna Ivashchenko

Keyword(s):

Emission Line ◽

Spectral Index ◽

Equivalent Width ◽

Emission Lines ◽

Baldwin Effect ◽

Quasar Spectra ◽

Composite Spectra ◽

Spectral Ranges ◽

The Baldwin Effect ◽

Line Equivalent Width

AbstractUsing 192 composite spectra stacked from subsamples of individual SDSS quasar spectra binned in spectral index, αλ, and logarithm of monochromatic luminosity at 1450 Å, log l1450, and modelling separate spectral ranges with superposition of emission lines it was found that: there is a dependence of emission line equivalent width (EW) on αλ (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected, while for the lines for which the Baldwin effect is not observed any αλ-dependence was found.

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Properties of LBGs with [OIII] detection at z > 3: The importance of including nebular emission data in SED fitting

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900276x ◽

2019 ◽

Vol 15 (S341) ◽

pp. 201-205

Author(s):

Fang-Ting Yuan ◽

Denis Burgarella ◽

David Corre ◽

Veronique Buat ◽

Médéric Boquien ◽

...

Keyword(s):

Physical Properties ◽

Emission Line ◽

Equivalent Width ◽

Spectroscopic Data ◽

Rest Frame ◽

High Redshift ◽

Emission Lines ◽

Emission Data ◽

Strong Emission ◽

The Difference

AbstractAt high redshift, the contribution of strong emission lines to the broadband photometry can cause large uncertainties when estimating galaxy physical properties. To examine this effect, we investigate a sample of 54 LBGs at 3 < zspec < 3.8 with detected [OIII] line emissions. We use CIGALE to fit simultaneously the rest-frame UV-to-NIR SEDs of these galaxies and their emission line data. By comparing the results with and without emission line data, we show that spectroscopic data are necessary to constrain the nebular model. We examine the K-band excess, which is usually used to estimate the emissions of [OIII]+Hβ lines when there is no spectral data, and find that the difference between the estimation and observation can reach up to > 1 dex for some galaxies, showing the importance of obtaining spectroscopic measurements of these lines. We also estimate the equivalent width of the Hβ absorption and find it negligible compared to the Hβ emission.

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Rapid variability of Hα emission line in Be stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900214964 ◽

1994 ◽

Vol 162 ◽

pp. 254-256

Author(s):

B. G. Anandarao ◽

A. Chakraborty ◽

R. Swaminathan ◽

B. Lokanadham

Keyword(s):

Emission Line ◽

Emission Lines ◽

Be Stars ◽

Rapid Variability ◽

Fabry Perot ◽

Dark Counts ◽

Hα Emission

We have initiated an observational campaign on some bright Be stars in order to investigate the rapid variability in emission lines using a Fabry-Perot spectrometer(λ/δλ = 104; FSR = 21.3Å) at the Nasmyth focus of the 1.22 m JRO telescope at Hyderabad, India. The PMT dark counts were 1 – 2sec-1. Here we report our first observations on four stars.

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Pole-On Cataclysmic Variables as Be Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100116628 ◽

1987 ◽

Vol 92 ◽

pp. 460-462

Author(s):

R. F. Garrison

Keyword(s):

Cataclysmic Variables ◽

Variable Stars ◽

Emission Lines ◽

Cataclysmic Variable ◽

Be Stars ◽

Class A ◽

Be Star ◽

H Ii Region ◽

Hydrogen Lines ◽

Balmer Decrement

Cataclysmic-variable stars (CVs) are technically Be stars, since Balmer emission lines appear in their spectra. In general, CV spectra are so unusual that they are easily recognized. The main features are extremely broad, shallow hydrogen lines with broad, faint emission cores. The Balmer emission decrement is very slow, more like that of an H II region than that of a normal Be star. The Balmer decrement in cataclysmic variable stars has been discussed by Elitzur, et al.If a CV were viewed pole-on, the spectrum might be quite different. It could exhibit a smooth continuum or may even resemble a normal Be star, except for the Balmer decrement. In this case, there may be a bright cataclysmic variable lurking in the Be star class. A possible example is the star NS 274-67, an 03e star described by Conti et al. (1986), which has Balmer emission from H-beta to H-ep-silon, but no nebular emission at [0 II] or [0 III].

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The polarization of Hβ in γ Cas

Symposium - International Astronomical Union ◽

10.1017/s0074180900214927 ◽

1994 ◽

Vol 162 ◽

pp. 232-233

Author(s):

Y.M. Jiang ◽

G.A.H. Walker ◽

N. Dinshaw ◽

J.M. Matthews

Keyword(s):

Emission Line ◽

Intensity Profile ◽

Emission Lines ◽

Absorption Feature ◽

Be Stars ◽

Good Match ◽

Be Star ◽

Image Position ◽

Relationship Of ◽

The Relationship

High resolution (0.15 Å/pixel) spectropolarimetry across the Hβ emission line of the Be star γ Cas is presented (solid line in Figure B), as well as the intensity profile (Figure A). Earlier observations of the linear polarization across the emission lines (PL) in Be stars (Coyne 1975, Poeckert 1975) found that PL is inversely proportional to the total intensity of the emission line. However, our data clearly show that the width of the polarization profile is much wider than that of the emission line. The dotted line in Figure B gives PL, based on the relationship of: which follows directly from Coyne (1975), where IA is the intensity of the underlying Hβ absorption feature, Itotal the observed intensity profile, and PC the polarization in the adjacent continuum. The underlying stellar profile of Hβ (dotted line in Figure C), adopted from models by Hubeny (1988), gives a good match to the wings of the depolarization profile.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936957 ◽

2020 ◽

Vol 634 ◽

pp. A111 ◽

Cited By ~ 2

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.

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