16104319
The Lick AGN Monitoring Project: Broad-line Region Radii and Black Hole Masses from Reverberation Mapping of Hβ
We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0: 05) Seyfert 1 galaxies with expected masses in the range � 10 6 -10 7 Mand also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to all ow for a time lag to be measured between the continuum fluctuations and the response to these fluctuation s in the broad Hemission. We present here the light curves for all the objects in this sample and the subseq uent Htime lags for the nine objects where these measurements were possible. The Hlag time is directly related to the size of the broad-line reg ion in AGNs, and by combining the Hlag time with the measured width of the Hemission line in the variable part of the spectrum, we determine the virial mass of the central sup ermassive black hole in these nine AGNs. The absolute calibration of the black hole masses is based on the normalization derived by Onken et al., which brings the masses determined by reverberation mapping into agreement with the local MBH -�? relationship for quiescent galaxies. We also examine the time lag response as a function of velocity across the Hline profile for six of the AGNs. The analysis of four leads to rather ambiguous results with relatively flat time lags as a function of velocity. However, SBS 1116+583A exhibits a symmetric time lag response around the line center reminiscent of simple models for circularly orbiting broad -line region (BLR) clouds, and Arp 151 shows an asymmetric profile that is most easily explained by a simple g ravitational infall model. Further investigation will be necessary to fully understand the constraints place d on physical models of the BLR by the velocity- resolved response in these objects. Subject headings:galaxies: active - galaxies: nuclei - galaxies: Seyfert
119183491
SN 2008iy: an unusual Type IIn Supernova with an enduring 400-d rise time
We present spectroscopic and photometric observations of the Type IIn supernova (SN) 2008iy. SN 2008iy showed an unprecedentedly long rise time of ~400 d, making it the first known SN to take significantly longer than 100 d to reach peak optical luminosity. The peak absolute magnitude of SN 2008iy was M r ≈ -19.1 mag, and the total radiated energy over the first ~700 d was ~2 x 10 50 erg. Spectroscopically, SN 2008iy is very similar to the Type IIn SN 1988Z at late times and, like SN 1988Z, it is a luminous X-ray source (both SNe had an X-ray luminosity L X > 10 41 erg s -1 ). SN 2008iy has a growing near-infrared excess at late times similar to several other SNe IIn. The Hα emission-line profile of SN 2008iy shows a narrow P Cygni absorption component, implying a pre-SN wind speed of ~100 km s -1 . We argue that the luminosity of SN 2008iy is powered via the interaction of the SN ejecta with a dense, clumpy circumstellar medium. The ~400-d rise time can be understood if the number density of clumps increases with distance over a radius ~1.7 x 10 16 cm from the progenitor. This scenario is possible if the progenitor experienced an episodic phase of enhanced mass loss < 1 century prior to explosion or if the progenitor wind speed increased during the decades before core collapse. We favour the former scenario, which is reminiscent of the eruptive mass-loss episodes observed for luminous blue variable (LBV) stars. The progenitor wind speed and increased mass-loss rates serve as further evidence that at least some, and perhaps all, Type IIn SNe experience LBV-like eruptions shortly before core collapse. We also discuss the host galaxy of SN 2008iy, a subluminous dwarf galaxy, and offer a few reasons why the recent suggestion that unusual, luminous SNe preferentially occur in dwarf galaxies may be the result of observational biases.
15307631
Two topics in QCD sum rules: Bounds on light quark and scalar gluonium masses
QCD Laplace sum-rules are briefly reviewed and two sum-rule applications are presented. For scalar gluonium, upper bounds on the lightest state are obtained from ratios of Laplace sum-rules, and the role of instantons and the low-energy theorem on these bounds is investigated. For the light-quark masses, fundamental inequalities for Laplace sum-rules are developed, which lead to a lower bound on the average of the up and down quark masses.
120140404
Mass, width, and decay constant of the first pion-excitation: a QCD sum rule approach
A Laplace QCD sum rule treatment of the first pion excitation (Π) as a subcontinuum resonance in the pseudoscalar channel is presented. Parameters characterizing this resonance are obtained via a global sum rule fit to the hadronic (π+Π+continuum) content of the appropriate sum rule, incorporating 1) Breit-Wigner departures from the narrow resonance approximation, 2) explicit direct single-instanton contributions, and 3) purely perturbative field-theoretical contributions to two- and three-loop order. The results of this analysis [MΠ=1.15±0.28 GeV, ΓΠ<0.48 GeV, r≡FΠ2MΠ4/fπ2mπ4=4.7±2.8; uncertainties are 90% confidence levels] are consistent with the present empirical range of the Π(1300) mass, and predict a rather large decay constant for this resonance. A by-product of this analysis is the prediction (mu+md)/2=7.7±2.2 MeV for the light quark masses evaluated at an energy scale of 1 GeV.
10453103
Extended BRS symmetry and gauge independence in on-shell renormalization schemes
Extended BRS symmetry is used to prove gauge independence of the fermion renormalization constant Z2 in on-shell QED renormalization schemes. A necessary condition for gauge independence of Z2 in on-shell QCD renormalization schemes is formulated. Satisfying this necessary condition appears to be problematic at the three-loop level in QCD.
122067606
Thermodynamics and quantum aspects of black holes in (1+1) dimensions
The thermodyamics and quantum properties of black holes in two-dimensional spacetime is investigated. It is demonstrated that the relationships between mass, temperature and entropy of the black hole following from a standard Euclidean analysis agree with those obtained from a quantum field theoretic treatment of vacuum stress-energy. The authors show that such black holes tend to quantize in units of a fundamental mass parameter in order to maximize their entropy. Finally, estimates are made of the back-reaction on the black hole from quantum stress-energy, and a modified form of the model particle detector is used to demonstrate a quantum version of the equivalence principle.
18165035
MASSLESS SCALAR FIELD PROPAGATOR IN A QUANTIZED SPACETIME
We consider in detail the analytic behaviour of the non-interacting massless scalar field two-point function in H. S. Snyder's discretized non-commuting spacetime. The propagator we find is purely real on the Euclidean side of the complex p2 plane and goes like 1/p2 as p2→0 from either the Euclidean or Minkowski side. The real part of the propagator goes smoothly to zero as p2 increases to the discretization scale 1/a2and remains zero for p2>1/a2. This behaviour is consistent with the termination of single-particle propagation on the ultraviolet side of the discretization scale. The imaginary part of the propagator, consistent with a multiparticle-state spectral function branch discontinuity, is finite and continuous on the Minkowski side, slowly falling to zero when 1/a2<p2<∞. The multi-particle aspect of this spectral function within the Kallen-Lehmann representation of the propagator leads to the interpretation that the propagation of free-fields in a quantized spacetime is analogous to propagation of interacting fields in a continuous spacetime.