Broad Balmer Emission Research Articles

Substantial Doppler broadening of atomic-hydrogen lines in dc and capacitively coupled RF plasmas

The mechanism of extraordinary broadening of the Balmer lines of hydrogen admixed with noble gases in a dc glow discharge and a capacitively coupled rf discharge is studied over a wide range of pressure and gas compositions to test the field acceleration model (Cvetanovic et al 2005 J. Appl. Phys. 97 033302). High-resolution optical emission spectroscopy is performed parallel to the electrode axis (end-on) and perpendicular to the electrode axis (side-on) along with Langmuir probe measurements of plasma density and electron temperature for the parallel plate rf capacitive discharge case. Sharp pin-shaped tungsten dc electrodes are also used to minimize the backscattering of ions that are theorized by a field acceleration model to be heated in the sheath region. An excessively broad and symmetric (Gaussian) Balmer emission line corresponding to 20–60 eV of hydrogen atom energy is observed in Ar/H2 and He/H2 plasmas when compared with the majority species atom temperatures. Energy is transferred selectively to hydrogen atoms whereas the atoms of admixed He and Ar gases remain cold (<0.5 eV). Since there is neither a preferred ion nor atom in the field acceleration model, one should also observe enhanced temperature hydrogen and helium atoms in He/H2 discharges where the atomic mass is more comparable (4 : 1).

SDSS J2125−0813: the evidence for the origination of optical Fe ii emission lines from an accretion disc near a central black hole

Abstract We report on the radio-quiet quasar SDSS J2125−0813 which obviously emits optical Fe ii emission lines and double-peaked broad Balmer emission lines. Using the accretion disc model for double-peaked, broad, low-ionization emission lines, we reproduce the composite line spectra at the optical band between 4100 and 5600 Å. Broad Fe ii emission lines can be fitted simultaneously with the broad Hβ and Mg i lines, such that all broad lines have an elliptical disc profile with the same disc parameters. This result indicates that the optical Fe ii emission lines originate from the accretion disc near the central black hole which produces the double-peaked broad Balmer emission lines. Furthermore, we find that the object has a dimensionless accretion rate , which is much larger than the accretion rate for the advection-dominated accretion flow (ADAF) mode, and that the energy budget of the accretion disc is enough to power the double-peaked broad Balmer emission lines.

Rest‐Frame Optical Spectroscopic Classifications for Submillimeter Galaxies

We report the results of a systematic near-IR spectroscopic survey using the Subaru, VLT, and Keck Telescopes of a sample of high-redshift ULIRGs mainly composed of submillimeter-selected galaxies. Our observations span the rest-frame optical range containing nebular emission lines such as Hβ, [O III] λλ4959, 5007, and [O II] λ3727, which are essential for making robust diagnostics of the physical properties. Using the Hα/Hβ emission line ratios, we derive internal extinction estimates for these galaxies similar to those of local ULIRGs: A_V ~ 2.9 ± 0.5. Correcting the Hα estimates of the star formation rate for dust extinction results in rates that are consistent with those estimated from the far-IR luminosity. The majority (>60%) of our sample show spectral features characteristic of AGNs (although this partially reflects an observational bias), with ~65% exhibiting broad Balmer emission lines. A proportion of these sources show relatively low [O III] λ5007/Hβ line ratios, which are similar to those of narrow-line Seyfert 1 galaxies, suggesting low-mass black holes that are rapidly growing. In the subsample of our survey with both [O III] λ5007 and hard X-ray coverage, at least ~60% show an excess of [O III] λ5007 emission, by a factor of 5-10, relative to the hard X-ray luminosity compared to the correlation between these two properties seen in Seyfert galaxies and QSOs locally. From our spectral diagnostics, we propose that the strong [O III] λ5007 emission in these galaxies arises from shocks in dense gaseous regions. Due to sensitivity and resolution limits, our sample is biased to strong-line emitters and hence our results do not yet provide a complete view of the physical properties of the whole high-redshift ULIRG population.

Discovery and Evolution of an Unusual Luminous Variable Star in NGC 3432 (Supernova 2000ch)

ABSTRACTWe present photometric and spectroscopic observations of SN 2000ch, an unusual and extremely luminous variable star located in the galaxy NGC 3432. The object was discovered on 2000 May 3.2 during the course of the Lick Observatory Supernova Search, at an unfiltered magnitude of about 17.4. Prediscovery images obtained in 1997, 1998, and 2000 April show the object with R = 19.2–19.5 mag. Optical spectra obtained beginning on 2000 May 6 show a smooth, flat continuum and strong, broad hydrogen Balmer emission lines at wavelengths consistent with the cataloged redshift of NGC 3432, strengthening the association of the variable with the galaxy. Photometric monitoring reveals a complex and erratic light curve over a time span of ∼10 days. Subsequent optical spectra over the next ∼3 months continued to show strong Balmer emission lines with a mean full width at half‐maximum intensity ∼1550 km s−1 and a distinct red asymmetry. A spectrum obtained 9 months after the outburst is similar to the previous spectra, but the integrated flux in Hα is nearly half that observed during the outburst. The object’s photometric behavior, spectrum, and luminosity suggest that it is a very massive and luminous variable star and might be related to some luminous blue variable stars such as η Carinae and SN 1997bs in NGC 3627. The brightest apparent magnitude implies an absolute magnitude of MV ≈ - 12.7 at the distance of NGC 3432, a value that is comparable to η Car during its outburst in the mid‐19th century.

Modeling of emission spectra of the flaring red dwarf EV Lac: Active regions, flares, and microflares

Echelle spectrograms of the flaring red dwarf EV Lac obtained on the Nordic Optical Telescope are used to study the chromosphere of the star during the impulsive flare of 23:19 UT on August 30, 1994, and in two nearby time intervals when UBV RI photometry showed the star to be in a quiescent state. The high spectral resolution of the observations enabled the detection of broad Balmer emission wings in the nonflaring state, which are interpreted as evidence for microflares. Semiempirical models for active regions in the chromosphere, flares, and microflares are constructed and used to compare the main physical characteristics of these structures. The place of the detected microflares in the overall energetics of flare events in EV Lac is discussed.

Variability of the Broad Balmer Emission Lines in 3C 390.3 from 1992 to 2000

We describe the results of an optical spectral monitoring campaign on the Seyfert galaxy 3C 390.3 carried out with a CCD spectrograph at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory in 1992-2000. Light curves for the Hα and Hβ emission lines and for the continuum in both the Hα and Hβ spectral regions are given. The lag between the continuum and Hβ emission-line variations (specifically the cross-correlation centroid τcent) is found to be τcent = 89 days, more than twice the lag found in an earlier investigation by Dietrich et al. We attribute this discrepancy to the difference between continuum autocorrelation functions for these two time series, which have very different durations. We show that a single emission-line transfer function is able to reproduce both cross-correlation results. The recovered transfer function for the Hβ line has a peak at a lag of 20 days, a tail that extends up to 300 days, and little or no correlation near zero lag. We find that the Hα line, which varies with a markedly lower amplitude than Hβ, has a lag of τcent = 162 days. We find no significant difference in lag between the blue and red wings of either Hα or Hβ, effectively ruling out kinematics dominated by simple radial motion. However, emission-line profile variations were clearly detected over the duration of the monitoring campaign. The mean and rms profiles computed for three selected time intervals are significantly different and show no correlation between profile width and continuum flux. Over the duration of the campaign, the red central part of the line profiles strongly decreased with respect to the total line flux. Moreover, the red bump nearly completely disappeared, while the blue bump has become more prominent. We find that some discrete profile features appear to propagate across the line profile, and we see such features moving in both directions, blue to red and vice versa. Variations in two profile segments at line-of-sight velocity ±(7500-9500) km s-1 are found to be poorly correlated with variations in the continuum or in other profile segments. Our conjecture is that the observed evolution of the Balmer line profiles in 3C 390.3 may be the result of the rotational redistribution of matter in a Keplerian disk and changes in the relative strength of an additional line component that dominates in the red central part of the profile. We conclude that the evolution of the broad-line profiles in 3C 390.3 in the context of the current models of the broad-line region remains unclear.

NGC 3065: A Certified LINER with Broad, Variable Balmer Lines

Motivated by the X-ray properties of the galaxy NGC 3065, we have obtained new optical spectra that reveal that it has a low-ionization nuclear emission-line region (LINER) as well as broad Balmer emission lines, establishing it as an active galactic nucleus. We also examined an older spectrum from the CfA Redshift Survey that lacks broad Balmer lines, indicating that these lines appeared sometime after 1980. Thus NGC 3065 joins the set of LINERs with broad, variable Balmer lines, which includes such well-known galaxies as NGC 1097 and M81. Inspired by the sometimes double-peaked profiles of the variable Balmer lines in other LINERs, we speculate that the broad Balmer lines of NGC 3065 also come from an accretion disk. We illustrate the plausibility of this hypothesis by fitting a disk model to the observed Hα profile. We also estimate the mass of the central black hole to be (9 ± 4) × 107 M☉ from the properties of the host galaxy, which leads to the conclusion that the accretion rate is only ~2 × 10-4 times the Eddington value, a property that appears to be common among LINERs. At such a low relative accretion rate, the inner accretion disk can turn into a vertically extended ion torus, which can illuminate the outer thin disk and power the broad-line emission. The reason for the sudden appearance of broad Balmer lines is an open question, although we suggest two possible explanations: (1) tidal disruption of a star or (2) a sudden transition in the structure of the accretion disk.

A Black Hole Greater Than 6 [ITAL]M[/ITAL][TINF]⊙[/TINF] in the X-Ray Nova XTE J1118+480

Observations of the quiescent X-ray nova XTE J1118+480 with the new 6.5 m Multiple Mirror Telescope have revealed that the velocity amplitude of the dwarf secondary is 698 ± 14 km s-1 and the orbital period of the system is 0.17013 ± 0.00010 days. The implied value of the mass function, f(M) = 6.00 ± 0.36 M☉, provides a hard lower limit on the mass of the compact primary that greatly exceeds the maximum allowed mass of a neutron star (~3 M☉). Thus, we conclude that the compact primary is a black hole. Among the 11 dynamically established black hole X-ray novae, the large mass function of XTE J1118+480 is rivaled only by that of V404 Cyg. We estimate that the secondary supplies 34% ± 8% of the total light at 5900 A and that its spectral type is in the range from K5 V to M1 V. A double-humped I-band light curve is probably due to ellipsoidal modulation, although this interpretation is not entirely secure because of an unusual 12 minute offset between the spectroscopic and photometric ephemerides. Assuming that the light curve is ellipsoidal, we present a provisional analysis that indicates that the inclination of the system is high and the mass of the black hole is correspondingly modest (M1 10 M☉). The broad Balmer emission lines (FWHM = 2300-2900 km s-1) also suggest a high inclination. For the range of spectral types given above, we estimate a distance of 1.8 ± 0.6 kpc.

Two Highly Polarized Quasi-stellar Objects Discovered by the Two Micron All Sky Survey

We present optical observations of two remarkable new active galactic nuclei (AGNs) discovered by the Two Micron All Sky Survey. Both are classified as quasi-stellar objects (QSOs) based on their optical spectra, near-IR colors, and near-IR and [O III] λ5007 luminosities, but their optical polarizations are among the highest seen for nonblazar AGNs—approaching 15% for 2MASSI J151653.2+190048. The polarized light spectrum for each object exhibits broad Balmer emission lines but lacks the narrow lines that are evident in the total light spectrum. This is most pronounced for the type 1.5 object 2MASSI J165939.7+183436, where broad lines dominate only in polarized light. The polarization properties of these AGNs suggest that dust near the nucleus at least partially obscures the AGNs and that material probably intermixed with the narrow-line-emitting gas scatters nuclear light into our line of sight. These QSOs illustrate the variety of highly polarized AGNs that have been missed by traditional optical search techniques and demonstrate that such objects are exposed by surveys in the near-IR.

SN 1997ab and its progenitor's wind

SN1997ab belongs to a class of luminous type II SNe which are thought to be powered by the interaction of the shock wave with a dense circumstellar medium. We report the discovery of narrow P-Cygni profiles atop broad Balmer emission lines, an unambiguous signature of a dense and slow circumstellar wind due to mass loss in the final stages of the progenitor's life.

Extended Broad Balmer Emission in the Seyfert 1 Galaxy Markarian 509

We present two-dimensional spectroscopic observations of the circumnuclear region of Mrk 509. The spectra show extended (off-nuclear) broad Balmer emission (FWZI>15,000 km s-1) in a region of about 8'' in diameter (8 kpc if H -->0=50 km s-1 Mpc-1). These features are interpreted as reflected radiation coming from the unresolved active nucleus. The nearly isotropic appearance of the scattering region can be explained within the framework of the unified picture for active galactic nuclei, if the scatterers lie outside the galaxy's disk; otherwise, the present observations would not support simple anisotropic models for the Seyfert nucleus in Mrk 509.

Transient double-peaked line emission as signatures of accretion events around supermassive black holes

We discuss the recent appearance of very broad (FWZI∼2000 km s −1) double-peaked Balmer emission lines in the nuclei of the galaxies NGC 1097, Pictor A and M 81. Such profiles are rare, and only found in about 10% of broad-line radio galaxies. In the most accepted scenario, they are the signature of relativistic gas motions around a supermassive nuclear black hole. We make a parallel between the properties of the above three nuclei: while Pictor A is a radio-galaxy similar to the others where the double-peaked profile is found, NGC 1097 and M 81 are low-luminosity nuclei located in spiral hosts. The latter galaxies nevertheless share the key characteristics of more powerful radio galaxies with double-peaked lines: narrow emission-line ratios typical of LINERs, double-peaked Balmer lines which are on average twice as broad as those of typical radio loud AGN and the presence of jets. These properties suggest that low-luminosity LINERs harbor similar nuclear engines as the most luminous active galactic nuclei (AGN), only less powerful. In these less powerful AGN, it is more easy to witness individual accretion events. Here we propose that the transient double-peaked lines are due to such events producing transient accretion disks around a supermassive nuclear black hole. We discuss, in particular, the case of NGC 1097, for which we show that the double-peaked profile and its variation over a time interval of ∼ 4 years can be well reproduced by a model of an elliptical accretion ring which could have formed from the debris released by the disruption of a star by a nuclear supermassive black hole.

Scattered Nuclear Continuum and Broad Hα in Cygnus A

We have discovered scattered broad Balmer emission lines in the spectrum of Cygnus A, using the Keck II Telescope. Broad Hα appears in polarized flux from components on either side of the nucleus and, to a lesser extent, in the nucleus. The full-width at half-maximum of broad Hα is 26,000 km s-1, comparable to the widest emission lines seen in broad-line radio galaxies. Scattered active galactic nucleus light provides a significant contribution to the total flux at 3800 A (rest) of the western component, where the polarization rises to 16%. The spatially integrated flux of Cygnus A at 5500 A can be decomposed into an elliptical galaxy fraction (Fg = 0.70), a highly polarized blue component (FC1 = 0.15), a less polarized red component (FC = 0.09), and a contribution from the nebular continuum (0.06). Imaging polarimetry shows a double fan of polarization vectors with circular symmetry that corresponds to the ionization cone seen in Hubble Space Telescope images. Our results are consistent with scattering of light from a hidden quasar of modest luminosity by an extended, dusty narrow-line region.

Faint Object Camera imaging and spectroscopy of NGC 4151

We describe ultraviolet and optical imaging and spectroscopy within the central few arcseconds of the Seyfert galaxy NGC 4151, obtained with the Faint Object Camera on the Hubble Space Telescope. A narrowband image including (O III) lambda(5007) shows a bright nucleus centered on a complex biconical structure having apparent opening angle approximately 65 deg and axis at a position angle along 65 deg-245 deg; images in bands including Lyman-alpha and C IV lambda(1550) and in the optical continuum near 5500 A, show only the bright nucleus. In an off-nuclear optical long-slit spectrum we find a high and a low radial velocity component within the narrow emission lines. We identify the low-velocity component with the bright, extended, knotty structure within the cones, and the high-velocity component with more confined diffuse emission. Also present are strong continuum emission and broad Balmer emission line components, which we attribute to the extended point spread function arising from the intense nuclear emission. Adopting the geometry pointed out by Pedlar et al. (1993) to explain the observed misalignment of the radio jets and the main optical structure we model an ionizing radiation bicone, originating within a galactic disk, with apex at the active nucleus and axis centered on the extended radio jets. We confirm that through density bounding the gross spatial structure of the emission line region can be reproduced with a wide opening angle that includes the line of sight, consistent with the presence of a simple opaque torus allowing direct view of the nucleus. In particular, our modelling reproduces the observed decrease in position angle with distance from the nucleus, progressing initially from the direction of the extended radio jet, through our optical structure, and on to the extended narrow-line region. We explore the kinematics of the narrow-line low- and high-velocity components on the basis of our spectroscopy and adopted model structure.

RJ 051542+0104.7: A new magnetic, eclipsing, cataclysmic variable

We present photometric and spectroscopic observations of a recently identified X-ray bright, magnetic cataclysmic variable, RJ 051542+0104.7. The X-ray source was discovered serendipitously by Walter et al. (1994; Walter & Zoonematkermani 1994), and their data imply the presence of a heated white dwarf compatible with a magnetic accretion column. Buckley (1994) has reported the presence of circular polarization. Our optical photometry shows that the system undergoes eclipses with a period of 7.9835 +/- 0.0002 hours. The eclipse is 1 magnitude deep and appears to be total. Our spectra were all obtained near eclipse and show a strong blue continuum with broad Balmer emission as well as He II (4686 and 5411 A), C III/N III (4650 A) and He I lines. The blue continuum and emission lines disappear during eclipse, leaving only the spectrum of a M0 star. Using the observed magnitude during eclipse and ignoring interstellar extinction, the distance is approximately 500 pc. For the secondary to fill its Roche lobe, it must be at least 20% larger than that of a normal dM0 star. This may indicate the red dwarf is far from local thermodynamic equilibrium (LTE) due to strong magnetic braking. We find evidence for cyclotron humps in the continuum spectrum which imply a magnetic field strength in the cyclotron emitting region of up to 55 MG. The unexpected existence of a long period AM Her system should provide constraints on models of polar evolution.

The Broad Emission Line Profiles and Profile Variability of the Seyfert 1 Galaxy Arakelian 120: Erratum

Hα and Hβ broad emission-line profiles of the Seyfert galaxy Arakelian 120 from the past ∼10 yr, representing over 100 spectroscopic observations, are presented. The broad emission-line profiles of the Balmer lines are complex in structure and variable; the profile variations themselves are complex. We attempt to isolate separate emitting components within the profiles through profile differencing and profile fitting. If Gaussian-like, at least four separate components are present in the broad Balmer emission lines. The broad emission-line profiles of other emission lines (optical and UV) are also presented, and evidence is given for a stratified BLR

The broad emission-line profiles and profile variability of the Seyfert 1 galaxy Arakelian 120

view Abstract Citations (35) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Broad Emission-Line Profiles and Profile Variability of the Seyfert 1 Galaxy Arakelian 120 Korista, Kirk T. Abstract We present Hα and Hβ broad emission-line profiles of the Seyfert galaxy Arakelian 120 from the past ~10 yr, representing over 100 spectroscopic observations. The broad emission-line profiles of the Balmer lines are complex in structure and variable; the profile variations themselves are complex. We attempt to isolate separate emitting components within the profiles through profile differencing and profile fitting. If Gaussian-like, at least four separate components are present in the broad Balmer emission lines. The broad emission-line profiles of other emission lines (optical and UV) are also presented, and evidence is given for a stratified BLR. Using the results of Joly, we demonstrate that the Fe II multiplets 25 and 36 (in addition to m42) may be present in the Hβ profile and in its "red shelf." Publication: The Astrophysical Journal Supplement Series Pub Date: April 1992 DOI: 10.1086/191654 Bibcode: 1992ApJS...79..285K Keywords: Emission Spectra; Line Spectra; Seyfert Galaxies; Astronomical Spectroscopy; Balmer Series; Charge Coupled Devices; H Alpha Line; H Beta Line; Astrophysics; GALAXIES: INDIVIDUAL NAME: ARAKELIAN 120; GALAXIES: SEYFERT; LINE: PROFILES full text sources ADS | data products SIMBAD (6) NED (1) MAST (1) Related Materials (1) Erratum: 1992ApJS...82..445K

Spectral variations in the broad-line region of NGC 6814

Summary We present optical spectroscopy of the Seyfert galaxy NGC 6814 obtained at the SAAO over a two-year period from 1983 May to 1985 October. During this period, the spectrum changed from Seyfert 1 to more closely resemble that of Seyfert 1.8-1.9. The Hβ flux decreased by more than a factor of 2 within two months. The decrease in the broad Balmer emission line strength was coupled with a decrease in the X-ray output.

A Rotating, Magnetic, Radiation-Driven Wind Model Applied to Be Stars

With their rotating, magnetic, radiation-driven wind model, Friend &amp; MacGregor (1984) found that rapid rotation and an open magnetic field could enhance the mass loss rate (ṁ) and terminal velocity (V∞) in an 0 star wind. The purpose of this paper is to see if this model could help explain the winds from Be stars. The following features of Be star winds need to be explained: 1) Be stars exhibit linear polarization (Coyne &amp; McLean 1982), indicating an enhanced equatorial density. 2) There appears to be enhanced mass loss (at low velocity) in the equatorial plane, from IRAS observations of Waters (1986). 3) The width of the broad Balmer emission lines remains unexplained.

NGC 6212 - an X-ray-selected active elliptical galaxy

Optical and X-ray data on the elliptical galaxy NGC 6212 are reported. The X-ray flux varies by a factor of four on a time scale of months. The optical spectrum shows broad Balmer emission lines and narrow forbidden lines which are typical of low-luminosity X-ray selected Seyfert galaxies. The continuum is predominantly stellar, with no evidence for a nonthermal contribution. Narrow emission lines extend at least 11 kpc from the nucleus and are used to derive a rotation curve. The X-ray variability and relatively weak radio emission of NGC 6212 are not unusual for Seyfert galaxies.