PSR J0045-7319: A Dual-line Binary Radio Pulsar
Binary radio pulsars are superb tools for mapping binary orbits, because of the precision of the pulse timing method.
binary radio pulsar↗
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Radio science and the International Halley Watch
The radio observations planned for the perihelion passage of Halley's comet in 1986 within the framework of the International Halley Watch (IHW) are reviewed. The roles of radar astronomy, continuum radio astronomy, and spectral-line radio astronomy in investigating the size and surface characteristics of the cometary nucleus, the nature and kinematics of the parent molecules sublimating into the coma, the properties of the coma particulate matter, and the cometary plasma are examined. Problems related to the inaccuracy of comet position data and lacks of background-source information, simultaneous submillimeter observations, and Southern-Hemisphere radio observing time are discussed; and the observatories participating in the IHW network are listed in tables with their instrument parameters.
Irvine, W. M.↗
The correlation between water production rates and visual magnitudes in comets
From the visual magnitudes of the International Comet Quarterly data base and the OH radio lines measured at the Nancay radio telescope, the law log Q(H2O) = 30.74 (+/-0.02) - 0.240 (+/-.003) m(sub h) is derived from a sample of 13 comets.
Jorda, L.↗
Carbon lines at limitedly low frequencies
Detection of several absorption recombination radio lines of carbon at 26 MHz in Cas A direction resulted in an attempt to select similar situations (a gas cloud projection on the intense source of the nonthermal radio emission) that are promising for detecting lines of such a kind. Recommendations are given for observations to be made.
Valtts, I. Y.↗
The Trails of Superluminal Jet Components in 3C 111
The parsec-scale radio jet of the broad-line radio galaxy 3C 111 has been monitored since 1995 as part of the 2cm Survey and MOJAVE monitoring observations conducted with the VLBA. Here, we present results from 18 epochs of VLBA observations of 3C 111 and from 18 years of radio flux density monitoring observations conducted at the University of Michigan. A major radio flux-density outburst of 3C 111 occurred in 1996 and was followed by a particularly bright plasma ejection associated with a superluminal jet component. This major event allows us to study a variety of processes associated with outbursts of radio-loud AGN in much greater detail than possible in other cases: the primary perturbation gives rise to the formation of a forward and a backward-shock, which both evolve in characteristically different ways and allow us to draw conclusions about the workflow of jet-production events; the expansion, acceleration and recollimation of the ejected jet plasma in an environment with steep pressure and density gradients are revealed; trailing components are formed in the wake of the primary perturbation as a result of Kelvin- Helmholtz instabilities from the interaction of the jet with the external medium. The jet-medium interaction is further scrutinized by the linear-polarization signature of jet components traveling along the jet and passing a region of steep pressure/density gradients.
Kadler, M.↗
The detection of the oh and other molecular lines in the radio spectrum of the interstellar medium.
OH and other molecular lines detection in radio spectrum of interstellar medium
FREE RADICAL↗
Testing the Pair Reflection Model for AGN
This project involved the interpretation of X-ray observations of AGN, and more specifically, evaluation and interpretation of the spectra in terms of the pair-reflection model. The grant was originally awarded on 3/14/94. We have now completed this work, which led to a number of publications. We found that reflection features are common in Seyfert galaxies, and may also be present in their radio-loud analogs, the broad-emission-line radio galaxies. In the latter case, however, a strong, nonthermal component is also present, and can swamp the thermal reflection spectrum.
Urry, C. Megan↗
IUE spectra and a resulting model of Seyfert 2 galaxies
Nearly simultaneous optical and ultraviolet observations of several Seyfert 2 galaxies are presented. A mean optical to ultraviolet emission line spectrum for Seyfert 2 galaxies is determined, and these intensities are compared with predictions of photoionization models. The UV to X-ray nonthermal continuum which ionizes this gas is examined. The results suggest that an obscuring layer does not hide an underlying broad-line region, and that narrow-line objects such as Seyfert 2 and narrow-line radio galaxies are physically different from broad-line objects, at least in not having an inner broad-line region. The absence of extinction also distinguishes these classical Seyfert 2 galaxies from the narrow-line X-ray galaxies, which X-ray evidence suggests may be extinguished Seyfert 1 galaxies.
Ferland, G. J.↗
Radio-Loud AGN: The Suzaku View
We review our Suzaku observations of Broad-Line Radio Galaxies (BLRGs). The continuum above 2 approx.keV in BLRGs is dominated by emission from an accretion flow, with little or no trace of a jet, which is instead expected to emerge at GeV energies and be detected by Fermi. Concerning the physical conditions of the accretion disk, BLRGs are a mixed bag. In some sources the data suggest relatively high disk ionization, in others obscuration of the innermost regions, perhaps by the jet base. While at hard X-rays the distinction between BLRGs and Seyferts appears blurry, one of the cleanest observational differences between the two classes is at soft X-rays, where Seyferts exhibit warm absorbers related to disk winds while BLRGs do not. We discuss the possibility that jet formation inhibits disk winds, and thus is related to the remarkable dearth of absorption features at soft X-rays in BLRGs and other radio-loud AGN.
Sambruna, Rita↗
The X-Ray Reflection Spectrum of the Radio-Loud Quasar 4C 74.26
The relativistic jets created by some active galactic nuclei are important agents of AGN feedback. In spite of this, our understanding of what produces these jets is still incomplete. X-ray observations, which can probe the processes operating in the central regions in the immediate vicinity of the supermassive black hole, the presumed jet launching point, are potentially particularly valuable in illuminating the jet formation process. Here, we present the hard X-ray NuSTAR observations of the radio-loud quasar 4C 74.26 in a joint analysis with quasi-simultaneous, soft X-ray Swift observations. Our spectral analysis reveals a high-energy cutoff of -183+3551 keV and confirms the presence of ionized reflection in the source. From the average spectrum we detect that the accretion disk is mildly recessed, with an inner radius of Rin4180 Rg. However, no significant evolution of the inner radius is seen during the three months covered by our NuSTAR campaign. This lack of variation could mean that the jet formation in this radio-loud quasar differs from what is observed in broad-line radio galaxies.
black hole physics – galaxies: active – quasar↗
The detection of the oh and other molecular lines in the radio spectrum of the interstellar medium.
Oh and other molecular lines detection in radio spectrum of interstellar medium
LINE SPECTRUM↗
X-Ray Spectrum of a Narrow-Line QSO
During the reporting period, seven papers using ASCA data, supported in whole or in part by this grant, were published or submitted to refereed journals. Their abstracts are given in this report, and the complete bibliographic references are listed in the Appendix. Titles include (1) A Broad-Band X-ray Study of the Geminga Pulsar; (2) ASCA Observations of PSR 1920+10 and PSR 0950+08; (3) X-ray and Optical Spectroscopy of IRAS 20181-2244: Not a Type 2 QSO, but a I Zw I Object; (4) Models for X-ray Emission from Isolated Pulsars; (5) Optical and X-ray Spectroscopy of 1E 0449.4-1823: Demise of the Original Type 2 QSO; (6) The ASCA Spectrum of the Broad-Line Radio Galaxy Pictor A: A Simple Power Law with No Fe Ka Line; and (7) ASCA Spectra of NGC 4388 and ESO 103-G35: Absorption, Reflection, and Variability in Intermediate Type Seyfert Galaxies.
Halpern, Jules P.↗
Feeding and Feedback in the Powerful Radio Galaxy 3C 120
We present a spectral analysis of a 200-kilosecond observation of the broad-line radio galaxy 3C 120, performed with the high-energy transmission grating spectrometer on board the Chandra X-Ray Observatory. We find (i) a neutral absorption component intrinsic to the source with a column density of log N (sub H) equals 20.67 plus or minus 0.05 square centimeters; (ii) no evidence for a warm absorber (WA) with an upper limit on the column density of just log N (sub H) less than 19.7 square centimeters, assuming the typical ionization parameter log xi approximately equal to 2.5 ergs per second per centimeter; the WA may instead be replaced by (iii) a hot emitting gas with a temperature kT approximately equal to 0.7 kiloelectronvolts observed as soft X-ray emission from ionized Fe L-shell lines, which may originate from a kiloparsec-scale shocked bubble inflated by the active galactic nucleus (AGN) wind or jet with a shock velocity of about 1000 kilometers per second determined by the emission line width; (iv) a neutral Fe K alpha line and accompanying emission lines indicative of a Compton-thick cold reflector with a low reflection fraction R approximately equal to 0.2, suggesting a large opening angle of the torus; (v) a highly ionized Fe XXV emission feature indicative of photoionized gas with an ionization parameter log xi equal to 3.75 (sup plus 0.38) (sub minus 0.27) ergs per second per centimeter and a column density of log N (sub H) greater than 22 square centimeters localized within approximately 2 pc from the X-ray source; and (vi) possible signatures of a highly ionized disk wind. Together with previous evidence for intense molecular line emission, these results indicate that 3C 120 is likely a late-state merger undergoing strong AGN feedback.
black hole physics – galaxies: active – line: ↗
The infrared properties of quasars and radio galaxies - Testing the unification schemes
The IRAS data base is used to compare the mid-FIR properties of two classes of radio-loud AGN whose LF radio emission arises in large-scale radio lobes. The two primary samples consist of 42 quasars and 75 narrow-line radio galaxies selected on the basis of their 178 MHz radio flux density from the 3 CR catalog and having redshifts of not less than 0.3 and Galactic latitudes of not less than 20 deg. The mid-FIR emission was found to be about four times stronger on average in the quasars than in the radio galaxies. Even though the radio galaxies are systematically weaker mid-FIR sources than the quasars, they are still exceptionally luminous (about 10 exp 12 solar luminosities) in the mid-FIR. These powerful radio galaxies contain potent sources of radiation that are either hidden or energetically unimportant at shorter wavelengths.
Heckman, Timothy M.↗
High redshift radio galaxies
High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.
Mccarthy, Patrick J.↗
The highly obscured nucleus of 3C 219
The detection of a strong, and possibly broad, Paschen-alpha line from the narrow-line radio galaxy 3C 219 is reported. The detected flux is larger than predicted from the H-alpha line and the case B recombination. This implies the presence of a highly reddened line-emitting region in the nucleus.
Fabbiano, G.↗
Polarization of Line Emission from an Accretion Disk and Application to ARP 102B
We model the polarization properties of line emission from an accretion disk under a range of assumptions about the source function and electron-scattering optical depth tau(sub es). For small values of tau(sub es) and modest viewing angles, polarization can be in excess of the Chandrasekhar result for tau(sub es) = infinity. The polarization vector can be either parallel or perpendicular to the projected direction of the disk axis. The polarization properties of the double-peaked H-alpha emission line of the broad-line radio galaxy Arp 102B observed by Antonucci, Hurt, and Agol can be understood in terms of electron scattering and line broadening within the line-emitting region if tau(sub es) is of order unity, and if the position angle of polarization is parallel to the projected disk axis. The required small tau(sub es) is consistent with the hypothesis that the Balmer lines in Arp 102B are produced by photoionization of the disk atmosphere.
Chen, Kaiyou↗
The solar corona above active regions - A comparison of extreme ultraviolet line emission with radio emission
Solar corona above active regions - comparison of extreme ultraviolet line emission with radio emission
ULTRAVIOLET RADIATION↗