scholarly journals Emission-line kinematics as a probe of the central engine in QSOs

1986 ◽  
Vol 119 ◽  
pp. 331-336
Author(s):  
Amri Wandel
Keyword(s):  
Energy Source ◽  
Emission Line ◽  
Dynamic Models ◽  
Accretion Rate ◽  
Central Mass ◽  
Large Sample ◽  
Physical Conditions ◽  
Central Engine ◽  
Central Energy ◽  
The Continuum

We investigate the constraints on dynamic models for the line-emitting regions in quasars and AGN. The parameters characterising the central energy source (Mass, efficiency, accretion rate) are calculated in terms of the physical conditions in the line emitting gas. In a large sample the central mass (calculated assuming the emission-line clouds are bound) is proportional to the continuum luminosity. We find typical values of L/LE∼10−2±0.5, e∼0.1-l%, and Ṁ/ṀE∼1–10.

scholarly journals The Relationship Between the Emission-Line Spectra and X-Ray/UV Continuum

1997 ◽  
Vol 159 ◽  
pp. 252-253
Author(s):  
Youjun Lu ◽  
Tinggui Wang
Keyword(s):  
Emission Line ◽  
Inverse Correlation ◽  
Baldwin Effect ◽  
Spectral Parameters ◽  
X Ray ◽  
Physical Conditions ◽  
Broad Emission ◽  
The Baldwin Effect ◽  
The Relationship ◽  
The Continuum

According to photoionization calculations, the broad emission-line (BEL) spectrum depends not only on the physical conditions of line-emitting gas, but also on the spectral shape of incident ionizing continuum, especially from the UV to X-ray. Analysis of emission-line spectra and their correlations with the continuum, therefore, provide a way of probing the anisotropy of ionizing continuum on the BLR scale, which is predicted by current models. Previous works have concentrated on explaining the Baldwin effect, an inverse correlation between equivalent width and continuum luminosity. In this contribution, we present the results of an analysis of 75 AGNs which have well-determined soft X-ray spectral parameters from ROSAT and UV line and continuum measurements.

scholarly journals Cyclotron Emission Features in the Spectra of Polars with Low Accretion Rates

2004 ◽  
Vol 190 ◽  
pp. 201-207
Author(s):  
E. D. Gospodchikov ◽  
A. V. Serber
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Accretion Rate ◽  
Hot Spot ◽  
Physical Conditions ◽  
Accretion Rates ◽  
Cyclotron Emission ◽  
Cyclotron Harmonics

AbstractWe calculate non-LTE transfer of cyclotron-harmonics radiation in the hot spot of an accreting magnetic white dwarf (WD) in the case where the contribution of the accretion column to the observed radiation is negligible. The observed cyclotron spectra of a polar with a low accretion rate are found. Based on the theory developed, we interpret the cyclotron emission line spectra of the systems and determine physical conditions in the emission regions of HS 1023+3900 and HS 0922+1333.

Ionized gas kinematics and luminosity profiles of Low-z Lyman Alpha Blobs

2019 ◽  
Vol 15 (S359) ◽  
pp. 413-414
Author(s):  
María P. Agüero ◽  
Rubén Díaz ◽  
Mischa Schirmer
Keyword(s):  
Emission Line ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Lyman Alpha ◽  
Gas Kinematics ◽  
The Universe ◽  
Very High ◽  
The Continuum

AbstractThis work is focused on the characterization of the Seyfert-2 galaxies hosting very large, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2−0.34. With a space density of 4.4 Gcp−3 at z ∼ 0.3, these “Low Redshift Lyman-α Blob” (LAB) host galaxies are amongst the rarest objects in the universe, and represent an exceptional and short-lived phenomenon in the life cycle of active galactic nuclei (AGNs). We present the study of GMOS spectra for 13 LAB galaxies covering the rest frame spectral range 3700–6700 Å. Predominantly, the [OIII]λ5007 emission line radial distribution is as widespread as that of the continuum one. The emission line profiles exhibit FWHM between 300–700 Km s−1. In 7 of 13 cases a broad kinematical component is detected with FWHM within the range 600–1100 Km s−1. The exceptionally high [OIII]λ5007 luminosity is responsible for very high equivalent width reaching 1500 Å at the nucleus.

scholarly journals The X-Ray Nova GRO J0422+32 in Decline and Quiescence

1996 ◽  
Vol 158 ◽  
pp. 399-400
Author(s):  
M. R. Garcia ◽  
P. J. Callanan ◽  
J. E. McClintock ◽  
P. Zhao
Keyword(s):  
Emission Line ◽  
Emission Region ◽  
Dwarf Novae ◽  
X Ray ◽  
First Order ◽  
Band Emission ◽  
Line Region ◽  
Hα Emission ◽  
The Stability ◽  
The Continuum

We have followed the X-ray nova GRO J0422+32, spectroscopically and photometrically, throughout the decline to quiescence.In the final stages of decay (days 430…880 after the outburst, see Callanan et al. (1995) for the epoch 1995), the equivalent width (EW) of the Hα emission increases monotonically and the R magnitude decreases monotonically. This suggests that the flux in the Hα line is constant, while the continuum fades. The Hα flux is the product of the R band flux (F(R), arbitrarily scaled to 100 at R = 19 mag) and the EW, and is shown in the last column of the table below. The Hα flux varies by only ~ 30% while the continuum fades by a factor of eight (from R = 19 mag to R = 21.3 mag). So, to first order, the Hα luminosity is constant in the final stages of decay. While it is generally the case that the emission line EWs in individual dwarf novae also increase during the decay, the exact behavior seen in GRO J0422+32 is not what is seen for dwarf novae (on average). Using the relation between EW[Hβ] and Mv given in figure 6 of Patterson (1984), we would expect a factor of ~ 5 variation in the Hα flux during days 430…880. The stability of the Hα flux implies that somehow the emission line region is ‘disconnected’ from the continuum (R–band) emission region.

scholarly journals A search for accreting young companions embedded in circumstellar disks

2019 ◽  
Vol 622 ◽  
pp. A156 ◽  
Author(s):  
G. Cugno ◽  
S. P. Quanz ◽  
S. Hunziker ◽  
T. Stolker ◽  
H. M. Schmid ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Giant Planet ◽  
Circumstellar Disks ◽  
Primary Star ◽  
Very Large Telescope ◽  
Upper Limits ◽  
Spread Function ◽  
Open Question ◽  
Host Stars ◽  
The Continuum

Context. In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question. Aims. We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. Methods. We analyzed observations of six young stars (age 3.5–10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the Hα filter (656 nm) and a nearby continuum filter (644.9 nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology. Results. We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both Hα and the continuum. We derive new astrometry (r=62.8−2.7+2.1 mas and PA=(98.7±1.8)°) and photometry (ΔN_Ha = 6.3−0.3+0.2 mag, ΔB_Ha = 6.7 ± 0.2 mag and ΔCnt_Ha = 7.3−0.2+0.3 mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (Ṁ ≈ 1−2 × 10−10 M⊙yr−1). A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142, and MWC 758 and calculate that processes involving Hα fluxes larger than ~ 8 × 10−14–10−15 erg s−1 cm−2 (Ṁ > 10−10−10−12 M⊙yr−1) can be excluded. Furthermore, flux upper limits of ~10−14−10−15 erg s−1 cm−2 (Ṁ < 10−11–10−12 M⊙yr−1) are estimated within the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude Hα signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b.

scholarly journals X-ray Spectroscopy of the Ultra-soft Transient 4U1543-47

1990 ◽  
Vol 115 ◽  
pp. 205-208
Author(s):  
H. van der Woerd ◽  
N.E. White ◽  
S.M. Kahn
Keyword(s):  
Emission Line ◽  
Compact Object ◽  
Relativistic Effects ◽  
Emission Feature ◽  
Continuum Emission ◽  
X Ray ◽  
Black Hole Candidate ◽  
Transmission Grating ◽  
Cool Plasma ◽  
The Continuum

AbstractThe X-ray transient 4U1543-47 was observed in 1983 by the EXOSAT observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). Two emission line features are resolved. A broad (FWHM ~2.7 keV) line at 5.9 keV is detected in the GSPC, which we interprete as a redshifted and broadened iron Kα line. The Une broadening and redshift may arise from either Compton scattering in a cool plasma with small optical depth (τ ≈ 5), or from Doppler and relativistic effects in the vicinity of a compact object. The spectrum below 2 keV, obtained with the TGS, shows evidence for a broad emission line feature at 0.74 keV, which may be an iron L-transition complex. However, we find that such an emission feature could be an artifact caused by an anomalously low interstellar absorption by neutral Oxygen. The continuum emission is extremely soft and is well described by an unsaturated Comptonized spectrum from a very cool plasma (kT = 0.84 keV) with large scattering depth (τ ≈ 27). The continuum spectrum is strikingly similar to that of black hole candidate LMC X-3.

scholarly journals H2O maser emission from the Seyfert 2 galaxy IC 2560: evidence for a super-massive black hole and a probe for mass-accretion rate

2002 ◽  
Vol 206 ◽  
pp. 400-403
Author(s):  
Yuko Ishihara ◽  
Naomasa Nakai ◽  
Naoko Iyomoto ◽  
Kazuo Makishima ◽  
Phil Diamond ◽  
...  
Keyword(s):  
Black Hole ◽  
High Velocity ◽  
Accretion Rate ◽  
Rotating Disk ◽  
Massive Black Hole ◽  
Central Mass ◽  
Maser Emission ◽  
Mass Accretion Rate ◽  
Systemic Velocity ◽  
Velocity Drift

Our observations of H2O masers have detected some high-velocity features and a secular velocity drift of the systemic features in the Seyfert 2 Galaxy IC 2560. The high-velocity features were blue- and red-shifted from the systemic velocity of 220-420 km s−1 and 210-350 km s−1, respectively. The velocity of the systemic features drifted at a secular rate of 2.62 km s−1 yr−1. Assuming the existence of a compact rotating disk as in NGC 4258, IC 2560 possesses a nuclear disk with inner and outer radii of 0.07 pc and 0.26 pc, respectively, and a confined mass of 2.8 × 106M⊙ at the center, making the central density > 2.1 × 109M⊙ pc−3. Such a dense object cannot be a cluster of stars, and this strongly suggests that the central mass is a super-massive black hole. Since the 2-10 keV luminosity of IC 2560 is 1 × 1041 erg s−1, the mass accretion rate of the suggested black hole must be 2 × 10−5M⊙ yr−1.

scholarly journals Composite Models: A Tool for Interpreting the Emission-Line Spectra of Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 316-317
Author(s):  
S.M. Viegas-Aldrovandi ◽  
M. Contini
Keyword(s):  
Energy Source ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
Additional Energy ◽  
Physical Conditions ◽  
Dilute Gas ◽  
Composite Models ◽  
Line Widths ◽  
Narrow Emission

In the last decade, emission-lines from a large number of active galactic nuclei (AGN) have been observed. Most of the models built to explain the observed narrow emission-lines are based on photoionization. Although these photoionization models account for the observed general features, many points remain unexplained and several authors suggest an additional energy source (Ferland and Mushotzky 1984, Ferland and Osterbrock 1986, Stasinska 1984, Viegas-Aldrovandi and Gruenwald 1988). Another possible explanation is suggested by the emitting cloud motions, which account for the observed line widths. If the clouds are moving throughout a dilute gas (n0 ≃ 300 cm−3), a shock can develop. Then, the physical conditions in the cloud are determined by the coupled effect of photoionization and shock hydrodynamics.

scholarly journals Brown dwarf jets: Investigating the universality of jet launching mechanisms at the lowest masses

2010 ◽  
Vol 6 (S275) ◽  
pp. 396-399
Author(s):  
Emma Teresa Whelan ◽  
Francesca Bacciotti ◽  
Tom Ray ◽  
Catherine Dougados
Keyword(s):  
Accretion Rate ◽  
T Tauri Stars ◽  
Brown Dwarf ◽  
Central Mass ◽  
Mass Accretion Rate ◽  
T Tauri ◽  
Mass Outflow ◽  
The Common ◽  
Protostellar Objects

AbstractRecently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass <0.1M⊙ and those driven by CTTSs. In particular we wish to understand how the the ratio of the mass outflow to accretion rate compares to what has been measured for CTTSs.

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