Astrophysics
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New submissions for Thu, 20 Nov 08
- [1] arXiv:0811.2997 [ps, pdf, other]
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Title: Expected high energy emission from GRB 080319B and origins of the GeV emission of GRBs 080514B, 080916C and 081024BComments: 8 pages, including 3 figures and 1 tableSubjects: Astrophysics (astro-ph)
We calculate the high energy (sub-GeV to TeV) prompt and afterglow emission of GRB 080319B that was distinguished by a naked-eye optical flash and by an unusual strong early X-ray afterglow. There are three possible sources for high energy emission: the prompt optical and $\gamma$-ray photons IC scattered by the internal shock electrons, the prompt photons IC scattered by the early external reverse-forward shock electrons, and the higher band of the synchrotron and the synchrotron self-Compton emission of the external shock. There should have been in total $\sim 500$ high energy photons detectable for the Large Area Telescope (LAT) onboard the Fermi satellite, and $> 30$ photons of those with energy $> 10$ GeV. The $> 10$ GeV emission had a duration about twice that of the soft $\gamma$-rays. AGILE could have observed these energetic signals if it was not occulted by the Earth at that moment. The physical origins of the high energy emission detected in GRB 080514B, GRB 080916C and GRB 081024B are also discussed. These observations can be reasonably interpreted by available high energy emission models based on our current understanding of GRBs and afterglows.
- [2] arXiv:0811.2998 [ps, pdf, other]
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Title: Inflation might be caused by the rightAuthors: Gabriela Barenboim (U. Valencia and IFIC)Comments: 15 pages, 4 figuresSubjects: Astrophysics (astro-ph)
We show that the scalar field that drives inflation can have a dynamical origin, being a strongly coupled right handed neutrino condensate. The resulting model is phenomenologically tightly constrained, and can be experimentally (dis)probed in the near future. The mass of the right handed neutrino obtained this way (a crucial ingredient to obtain the right light neutrino spectrum within the see-saw mechanism in a complete three generation framework) is related to that of the inflaton and both completely determine the inflation features that can be tested by current and planned experiments.
- [3] arXiv:0811.3012 [ps, pdf, other]
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Title: Black hole quasinormal mode spectroscopy with LISAComments: 10 pages, 5 figuresSubjects: Astrophysics (astro-ph)
The signal-to-noise ratio (SNR) for black hole quasinormal mode sources of low-frequency gravitational waves is estimated using a Monte Carlo approach that replaces the all-sky average approximation. We consider an eleven dimensional parameter space that includes both source and detector parameters. We find that in the black-hole mass range $M\sim 4$-$10\times 10^6M_{\odot}$ the SNR is significantly higher than the SNR for the all-sky average case, as a result of the variation of the spin parameter of the sources. This increased SNR may translate to a higher event rate for the Laser Interferometer Space Antenna (LISA). We also study the directional dependence of the SNR, and show at which directions in the sky LISA will have greater response.
- [4] arXiv:0811.3018 [ps, pdf, other]
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Title: Constraints on the Low-Energy Cutoff in the Electron Distribution of the PKS 0637-752 JetComments: 23 pages, 4 figures, accepted for publication in ApJSubjects: Astrophysics (astro-ph)
We re-analyze the Chandra ACIS spectrum of the kpc-scale jet in PKS 0637-752 to investigate the possible low energy cutoff in the relativistic electron spectrum producing the non-thermal radiation in the scenario of inverse Compton emission off the cosmic microwave background. This was among the first objects targeted by the Chandra Observatory and gives a unique opportunity to study the low energy X-ray emission free of detector contamination. As previously reported in the literature, the spectrum can be fit by a power law, with the slope predicted by the radio spectrum, modified by low energy absorption through the Galaxy as determined from the spectrum of the quasar core and by HI 21 cm observations. We obtain a marginally better fit with an model of inverse Compton emission produced by an electron population that exhibits a cutoff at (gamma_min delta_10) between about 50 and 80 (assuming Gamma = delta). This range for gamma_min is higher than has previously been assumed in broad-band spectral fits to the jet emission. The observed optical flux can be used to place a lower limit on gamma_min; the constraint is not very strong, but does suggest that gamma_min must be higher than 1 to avoid overproducing the optical emission. We investigate the effect of uncertainties in the column density for galactic absorption as well as the calibration of Chandra for these early observations. Finally, we discuss the implication of these limits on the jet luminosity in this source.
- [5] arXiv:0811.3020 [pdf, other]
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Title: An Energetic AGN Outburst Powered by a Rapidly Spinning Supermassive Black HoleAuthors: B.R. McNamara (U. Waterloo), F. Kazemzadeh (U. Waterloo), D.A. Rafferty (Penn State), L Birzan (Penn State), P.E.J. Nulsen (CfA), C.C. Kirkpatrick (U. Waterloo), M. W. Wise (U. Amsterdam)Comments: 37 pages, 10 figures, submitted to ApJSubjects: Astrophysics (astro-ph)
Powering the 10E62 erg AGN outburst in the MS0735.6+7421 cluster's central galaxy by accretion implies that its putative supermassive black hole (SMBH) grew by ~6E8 solar masses or nearly 1/3 of its mass over the past 100 Myr. Guided by data at several wavelengths, we place restrictive upper limits on the amount of cold gas and star formation near the nucleus of <10E9 solar masses and <2 solar masses per year, respectively. These limits imply that much of the preexisting gas in the inner several kpc must have been consumed by its SMBH during the past 100 Myr at the rate of ~3-5 solar masses per year, or roughly 1/10 of the Eddington rate, while leaving no trace of star formation. These properties are inconsistent with an accretion-powered AGN. We suggest instead that MS0735's AGN is powered by a rapidly-spinning black hole. The rotational energy and power are consistent with the cavity and shock energetics and their ages inferred from X-ray observations. The host galaxy's unusually large, 3.8 kpc stellar core may have been scoured-out in part during the inspiral of one or more SMBH's, thus endowing the merged remnant with its enormous size and spin. A maximally-spinning, 1E9 solar mass SMBH contains enough rotational energy, ~10E62 erg, to quench a cooling flow over its lifetime and to contribute significantly to the excess entropy found in the hot atmospheres of groups and clusters. We suggest two modes of AGN feedback are quenching star formation in elliptical galaxies centered in cooling halos at late times. An accretion mode that operates in gas-rich systems, and a spin mode that operates at modest accretion rates. The central galaxy's large core and demanding AGN power suggest it harbors a >10E10 solar mass ultramassive black hole.
- [6] arXiv:0811.3031 [ps, pdf, other]
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Title: Substructure in the cold front cluster Abell 3667Comments: 13 pages, 12 figures and 2 tables. Accepted for publication in ApJSubjects: Astrophysics (astro-ph)
We present evidence for the existence of significant substructure in the cold front cluster Abell 3667 based on multi-object spectroscopy taken with the 3.9m Anglo Australian Telescope. This paper is the second in a series analyzing the relationship between cold fronts observed in Chandra X-ray images and merger activity observed at optical wavelengths. We have obtained 910 galaxy redshifts in the field of Abell 3667 out to 3.5 Mpc, of which 550 are confirmed cluster members, more than doubling the number of spectroscopically confirmed members previously available and probing some 3 mag down the luminosity function. From this sample, we derive a cluster redshift of z=0.0553 +/-0.0002 and velocity dispersion of 1056 +/- 38 km/s and use a number of statistical tests to search for substructure. We find significant evidence for substructure in the spatial distribution of member galaxies and also in the localized velocity distributions and, in spite of this evidence, find the global velocity distribution does not deviate significantly from a Gaussian. Using combined spatial and velocity information, we find the cluster can be separated into two major structures, with roughly equal velocity dispersions, but offset in peculiar velocity from each other by ~500 km/s, and a number of minor substructures. We propose two scenarios which explain the radio and X-ray observations. Our data show the cold front is directly related to cluster merger activity, and also highlights the extent of optical data required to unambiguously detect the presence of substructure.
- [7] arXiv:0811.3032 [ps, pdf, other]
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Title: Three-Dimensional Simulations of Solar and Stellar Dynamos: The Influence of a TachoclineAuthors: M.S. Miesch (HAO/NCAR), M.K. Browning (CITA), A. S. Brun (CEA/Saclay), J. Toomre (JILA/Univ. Colorado), B.P. Brown (JILA/Univ. Colorado)Comments: 14 pages, 5 color figures, to appear in Proc. GONG 2008/SOHO XXI Meeting on Solar-Stellar Dynamos as Revealed by Helio and Asteroseismology, held August 15-18, 2008, Boulder, CO, Astronomical Soc. Pac. Conf. Series, volume TBDSubjects: Astrophysics (astro-ph)
We review recent advances in modeling global-scale convection and dynamo processes with the Anelastic Spherical Harmonic (ASH) code. In particular, we have recently achieved the first global-scale solar convection simulations that exhibit turbulent pumping of magnetic flux into a simulated tachocline and the subsequent organization and amplification of toroidal field structures by rotational shear. The presence of a tachocline not only promotes the generation of mean toroidal flux, but it also enhances and stabilizes the mean poloidal field throughout the convection zone, promoting dipolar structure with less frequent polarity reversals. The magnetic field generated by a convective dynamo with a tachocline and overshoot region is also more helical overall, with a sign reversal in the northern and southern hemispheres. Toroidal tachocline fields exhibit little indication of magnetic buoyancy instabilities but may be undergoing magneto-shear instabilities.
- [8] arXiv:0811.3035 [ps, pdf, other]
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Title: The [O II] lambda 3727 Luminosity Function at z ~ 1Comments: 9 pages, 5 figures, 2 tables, submitted to ApJ, in emulateapj styleSubjects: Astrophysics (astro-ph)
We measure the evolution of the [O II] lambda 3727 luminosity function at 0.75 < z < 1.45 using high-resolution spectroscopy of ~ 14,000 galaxies observed by the DEEP2 galaxy redshift survey. We find that brighter than L([O II])=10^{42} erg s^{-1} the luminosity function is well-represented by a power law dN/dL \propto L^{\alpha} with slope \alpha ~ -3. The number density of [O II]-emitting galaxies above this luminosity declines by a factor of \gtrsim 2.5 between z ~ 1.35 and z ~ 0.84. In the limit of no density evolution, the characteristic [O II] luminosity, defined as the luminosity where the space density equals 10^{-3.5} dex^{-1} Mpc^{-3}, declines by a factor of ~ 1.7 over the same redshift interval. These results imply a ~ 25% per Gyr decrease in the amount of star formation in galaxies during this epoch. Integrating the observed [O II] luminosity function assuming a faint-end power-law slope of -1.3 +/- 0.2, we derive the integrated star formation rate density in four redshift bins centered around z ~ 1, and find that the evolution is consistent with previous measurements based on independent star formation rate indicators.
- [9] arXiv:0811.3037 [ps, pdf, other]
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Title: Red supergiants as potential Type IIn supernova progenitors: Spatially resolved 4.6 micron CO emission around VY CMa and BetelgeuseComments: 16 pages, AJ acceptedSubjects: Astrophysics (astro-ph)
We present high-resolution 4.6micron CO spectra of the circumstellar environments of two RSGs that are potential SN progenitors: Betelgeuse and VY CMa. Around Betelgeuse, 12CO emission within 3arcsec follows a mildly clumpy but otherwise spherical shell, smaller than its 55arcsec shell in KI lambda7699. In stark contrast, 4.6micron CO emission around VY CMa is coincident with bright KI in its clumpy asymmetric reflection nebula, within 5arcsec of the star. Our CO data reveal redshifted features not seen in KI spectra of VY CMa, indicating a more isotropic distribution of gas punctuated by randomly distributed asymmetric clumps. The relative CO and KI distribution in Betelgeuse arises from ionization effects within a steady wind, whereas in VY CMa, KI is emitted from skins of CO cloudlets resulting from episodic mass ejections 500--1000 yr ago. In both cases, CO and KI trace potential pre-SN circumstellar matter: we conclude that an extreme RSG like VY CMa might produce a Type IIn event like SN1988Z if it were to explode in its current state, but Betelgeuse will not. VY CMa demonstrates that LBVs are not necessarily the only progenitors of SNe IIn, but it underscores the requirement that SNe IIn suffer enhanced episodic mass loss shortly before exploding.
- [10] arXiv:0811.3039 [ps, pdf, other]
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Title: Identikit 1: A Modeling Tool for Interacting Disk GalaxiesComments: 22 pages, 16 figures. Accepted by The Astronomical Journal; to appear February 2009. To get a copy with high-resolution figures, use the web interface, or download software, see this http URLSubjects: Astrophysics (astro-ph)
By combining test-particle and self-consistent techniques, we have developed a method to rapidly explore the parameter space of galactic encounters. Our method, implemented in an interactive graphics program, can be used to find the parameters required to reproduce the observed morphology and kinematics of interacting disk galaxies. We test this system on an artificial data-set of 36 equal-mass merging encounters, and show that it is usually possible to reproduce the morphology and kinematics of these encounters and that a good match strongly constrains the encounter parameters.
- [11] arXiv:0811.3046 [pdf, other]
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Title: New SETI Sky Surveys for Radio PulsesAuthors: Andrew Siemion (1,4), Joshua Von Korff (3), Peter McMahon (4,5), Eric Korpela (2), Dan Werthimer (2,4), David Anderson (2), Geoff Bower (1), Jeff Cobb (2), Griffin Foster (1), Matt Lebofsky (2), Joeri van Leeuwen (1), William Mallard (4), Mark Wagner (4) ((1) Astronomy Department, University of California, Berkeley, CA, USA (2) Space Sciences Laboratory, University of California, Berkeley, CA, USA (3) Physics Department, University of California, Berkeley, CA, USA (4) Berkeley Wireless Research Center, Berkeley, CA, USA (5) Computer Science Department, Stanford University, Stanford, CA, USA)Comments: 9 pages, 6 figures, Invited to appear in Acta AstronauticaSubjects: Astrophysics (astro-ph)
Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye.
A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from neutron stars, emissions from cosmic strings or perhaps extraterrestrial civilizations, but to-date few searches have been conducted capable of detecting them.
We are carrying out two searches in hopes of finding and characterizing these uS to mS time scale dispersed radio pulses. These two observing programs are orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye" experiment observes a 100 square degree field by pointing each 6m ATA antenna in a different direction; by contrast, the Astropulse sky survey at Arecibo is extremely sensitive but has 1/3,000 of the instantaneous sky coverage. Astropulse's multibeam data is transferred via the internet to the computers of millions of volunteers. These computers perform a coherent de-dispersion analysis faster than the fastest available supercomputers and allow us to resolve pulses as short as 400 nS. Overall, the Astropulse survey will be 30 times more sensitive than the best previous searches. Analysis of results from Astropulse is at a very early stage.
The Fly's Eye was successfully installed at the ATA in December of 2007, and to-date approximately 450 hours of observation has been performed. We have detected three pulsars and six giant pulses from the Crab pulsar in our diagnostic pointing data. We have not yet detected any other convincing bursts of astronomical origin in our survey data. (Abridged) - [12] arXiv:0811.3053 [ps, pdf, other]
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Title: Clustering of Meter-wave Luminous Objects toward MonocerosComments: PASJ 60, No. 6 (Dec. 25, 2008 issue) in pressSubjects: Astrophysics (astro-ph)
A distribution of the meter-wave luminous objects, which are bright at frequency 74 MHz (a wavelength of 4 m) but not detectable at 1.4 GHz (21 cm) in the VLA surveys, shows a notable concentration in a scale of a few degrees toward Monoceros [(l, b)=(225, 4)]. We argue that it is a part of giant radio relics associated with a nearby cluster of galaxies with cz~2400$ km s^{-1} centered on the spiral galaxy NGC 2377. The angular separation of these objects from the clustering center is consistent with the separation of distant relics to the cluster center if scaled by distance. This fact implies that the concentrations of meter-wave luminous objects can be used as a tracer of the structure of the Local Supercluster and it's vicinity.
- [13] arXiv:0811.3092 [ps, pdf, other]
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Title: Pairing mechanisms for binary starsAuthors: M.B.N. Kouwenhoven (1,2), A.G.A. Brown (3), S.P. Goodwin (1), S.F. Portegies Zwart (2), L. Kaper (2) ((1) Sheffield, (2) Amsterdam, (3) Leiden)Comments: 4 pages, 2 figures, in: Galactic and stellar dynamics in the era of high-resolution surveys, Boily C., Combes F., Hensler G., eds., Strasbourg (France), March 2008, in press (Astron. Nachr.)Subjects: Astrophysics (astro-ph)
Knowledge of the binary population in stellar groupings provides important information about the outcome of the star forming process in different environments. Binarity is also a key ingredient in stellar population studies and is a prerequisite to calibrate the binary evolution channels. In these proceedings we present an overview of several commonly used methods to pair individual stars into binary systems, which we refer to as the pairing function. Many pairing functions are frequently used by observers and computational astronomers, either for the mathematical convenience, or because they roughly describe the expected outcome of the star forming process. We discuss the consequences of each pairing function for the interpretation of observations and numerical simulations. The binary fraction and mass ratio distribution generally depend strongly on the selection of the range in primary spectral type in a sample. These quantities, when derived from a binary survey with a mass-limited sample of target stars, are thus not representative for the population as a whole.
- [14] arXiv:0811.3095 [ps, pdf, other]
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Title: An extensive photometric study of the Blazhko RR Lyrae star MW Lyr: II. Changes in the physical parametersAuthors: J. Jurcsik, Á. Sódor, B. Szeidl, Z. Kolláth, H. A. Smith, Zs. Hurta, M. Váradi, A. Henden, I. Dékány, I. Nagy, K. Posztobányi, A. Szing, K. Vida, N. VityiComments: 10 figures, 2 tables. Accepted for publication in MNRASSubjects: Astrophysics (astro-ph)
The analysis of the multicolour photometric observations of MW Lyr, a large modulation amplitude Blazhko variable, shows for the first time how the mean global physical parameters vary during the Blazhko cycle. About 1-2 percent changes in the mean radius, luminosity and surface effective temperature are detected. The mean radius and temperature changes are in good accordance with pulsation model results, which show that these parameters do indeed vary within this order of magnitude if the amplitude of the pulsation changes significantly. We interpret the phase modulation of the pulsation to be a consequence of period changes. Its magnitude corresponds exactly what one expects from the detected changes of the mean radius assuming that the pulsation constant remains the same during the modulation. Our results indicate that during the modulation the pulsation remains purely radial, and the underlying mechanism is most probably a periodic perturbation of the stellar luminosity with the modulation period.
- [15] arXiv:0811.3098 [ps, pdf, other]
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Title: A new method for determining physical parameters of fundamental mode RR Lyrae stars from multicolour light curvesComments: 12 pages, 10 figures, 4 tables. Accepted for publication in MNRASSubjects: Astrophysics (astro-ph)
We present a new method for determining physical parameters of RRab variables exclusively from multicolour light curves. Our method is an Inverse Photometric Baade-Wesselink analysis which, using a nonlinear least squares algorithm, searches for the effective temperature (T_eff) and pulsational velocity (V_p) curves and other physical parameters that best fit the observed light curves, utilising synthetic colours and bolometric corrections from static atmosphere models. The T_eff and V_p curves are initially derived from empirical relations then they are varied by the fitting algorithm. The method yields the variations and the absolute values of the radius, the effective temperature, the visual brightness, and the luminosity of individual objects. Distance and mass are also determined. The method is tested on 9 RRab stars subjected to Baade-Wesselink analyses earlier by several authors. The physical parameters derived by our method using only the light curve data of these stars are well within their possible ranges defined by direct Baade-Wesselink and other techniques. A new empirical relation between the I_C magnitude and the pulsational velocity is also presented, which allows to construct the V_p curve of an RRab star purely from photometric observations to an accuracy of about 3.5 km/s.
- [16] arXiv:0811.3104 [ps, pdf, other]
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Title: On the nature of the extragalactic number counts in the K-bandAuthors: G. Barro, J. Gallego, P.G. Pérez-González, C. Eliche-Moral, M. Balcells, V. Villar, N. Cardiel, D. Cristobal-Hornillos, A. Gil de Paz, R. Gúzman, R. Pelló, M. Prieto, J. ZamoranoComments: 18 pages, 22 figures, Accepted by Astronomy & AstrophysicsSubjects: Astrophysics (astro-ph)
We investigate the causes of the different shape of the $K$-band number counts when compared to other bands, analyzing in detail the presence of a change in the slope around $K\sim17.5$. We present a near-infrared imaging survey, conducted at the 3.5m telescope of the Calar Alto Spanish-German Astronomical Center (CAHA), covering two separated fields centered on the HFDN and the Groth field, with a total combined area of $\sim0.27$deg$^{2}$ to a depth of $K\sim19$ ($3\sigma$,Vega). We derive luminosity functions from the observed $K$-band in the redshift range [0.25-1.25], that are combined with data from the references in multiple bands and redshifts, to build up the $K$-band number count distribution. We find that the overall shape of the number counts can be grouped into three regimes: the classic Euclidean slope regime ($d\log N/dm\sim0.6$) at bright magnitudes; a transition regime at intermediate magnitudes, dominated by $M^{\ast}$ galaxies at the redshift that maximizes the product $\phi^{\ast}\frac{dV_{c}}{d\Omega}$; and an $\alpha$ dominated regime at faint magnitudes, where the slope asymptotically approaches -0.4($\alpha$+1) controlled by post-$M^{\ast}$ galaxies. The slope of the $K$-band number counts presents an averaged decrement of $\sim50%$ in the range $15.5<K<18.5$ ($d\log N/dm\sim0.6-0.30$). The rate of change in the slope is highly sensitive to cosmic variance effects. The decreasing trend is the consequence of a prominent decrease of the characteristic density $\phi^{\ast}_{K,obs}$ ($\sim60%$ from $z=0.5$ to $z=1.5$) and an almost flat evolution of $M^{\ast}_{K,obs}$ (1$\sigma$ compatible with $M^{\ast}_{K,obs}=-22.89\pm0.25$ in the same redshift range).
- [17] arXiv:0811.3105 [ps, pdf, other]
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Title: Radio Bimodality: Spin, Accretion Mode, or Both?Authors: M. Sikora (Nicolaus Copernicus Astronomical Center)Comments: 4 pages, accepted for publication in Astronomische Nachrichten (issue dedicated to the Proceedings of "The 4th Workshop on Compact Steep Spectrum and GHz-Peaked Spectrum Radio Sources" held at Riccione, Italy, 26-29 May 2008)Subjects: Astrophysics (astro-ph)
A new scenario is suggested to explain a large diversity of the AGN radio properties and their dependence on the galaxy morphology. The scenario is based on the assumption that the growth of supermassive BHs is dominated by the accretion only during the quasar (high accretion rate) phase, otherwise - by mergers with less massive black holes. Following that, BHs are expected to spin much faster in giant ellipticals than in disk galaxies. Within the frame of the spin paradigm this explains the observed relation of the radio-dichotomy with the galaxy morphology. Various theoretical and observational aspects of such a dichotomy are discussed. In particular, the issue of the intermittency and suppression of a jet production at high accretion rates is addressed and a scenario for production of powerful, extended radio sources is drafted.
- [18] arXiv:0811.3106 [ps, pdf, other]
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Title: Detecting the effect of Globular Cluster impacts on the disk of the Milky WayComments: 14 pages, 8 figuresSubjects: Astrophysics (astro-ph)
The crossing of the Galactic disk by a Globular Cluster could produce star formation due to gravitational focussing or compression of disk material. We report on simulations of the effect on disk material which reveal that the crossing can sometimes cause local gravitational focussing of disk material. We also present the salient points of a little-known paper by Levy (2000), that shows that strong compression can result from the shock wave generated by GC disk crossing. The main thrust of our paper is a search for remnants of disk crossings by Globular Clusters. Using the gravitational potential of the Galaxy to locate the position of the most recent crossings of a subset of fifty-four Globular Clusters reveals that systematic errors and uncertainties in initial conditions limit the scope for unequivocal identification. From the subset of fifty-four, six possible search sites with the best constraints are retained for further scrutiny. Three of the six potentially promising search areas in the disk are from Globular Clusters NGC 3201, 6397 and NGC 6838, for which we cannot rule out some observed star associations observed nearby as being remnants. The three other of the six areas are too large to provide meaningful identification of remnants. Also, a possible remnant (open cluster NGC6231) is shown not to be due to Globular Cluster impact, contrary to a previous report. In a more wide-ranging screening of one hundred and fifty-five Globular Clusters we identify which Globular Clusters are compatible with being responsible for the formation of any of the Galaxy's five most prominent Star Super Clusters.
- [19] arXiv:0811.3108 [ps, pdf, other]
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Title: Resolving a broad PCygni line profile to quantify the fast outflow in the luminous Seyfert galaxy PG1211+143Subjects: Astrophysics (astro-ph)
We report two new XMM-Newton observations of PG1211+143 in December 2007, finding further evidence of the fast outflow of highly ionised gas, first detected in 2001. Stacking the new spectra with those from two earlier XMM-Newton observations reveals a broad PCygni profile in the Fe K band, showing the fast outflow to have a large covering factor, and confirming its significance as a powerful feed of mechanical energy into the host galaxy.
- [20] arXiv:0811.3111 [ps, pdf, other]
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Title: Red giant stellar collisions in the Galactic CentreComments: 21 pages, 21 figures, accepted by MNRASSubjects: Astrophysics (astro-ph)
We show that collisions with stellar--mass black holes can partially explain the absence of bright giant stars in the Galactic Centre, first noted by Genzel et al, 1996. We show that the missing objects are low--mass giants and AGB stars in the range 1-3 M$_{\odot}$. Using detailed stellar evolution calculations, we find that to prevent these objects from evolving to become visible in the depleted K bands, we require that they suffer collisions on the red giant branch, and we calculate the fractional envelope mass losses required. Using a combination of Smoothed Particle Hydrodynamic calculations, restricted three--body analysis and Monte Carlo simulations, we compute the expected collision rates between giants and black holes, and between giants and main--sequence stars in the Galactic Centre. We show that collisions can plausibly explain the missing giants in the $10.5<K<12$ band. However, depleting the brighter ($K<10.5$) objects out to the required radius would require a large population of black hole impactors which would in turn deplete the $10.5<K<12$ giants in a region much larger than is observed. We conclude that collisions with stellar--mass black holes cannot account for the depletion of the very brightest giants, and we use our results to place limits on the population of stellar--mass black holes in the Galactic Centre.
- [21] arXiv:0811.3123 [ps, pdf, other]
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Title: Mean-field dynamos in random Arnold-Beltrami-Childress and Roberts flowsComments: 7 pages, Physical Review E, submittedSubjects: Astrophysics (astro-ph)
We study magnetic field evolution in flows with fluctuating in time governing parameters in electrically conducting fluid. We use a standard mean-field approach to derive equations for large-scale magnetic field for the fluctuating Arnold-Beltrami-Childress (ABC) flow as well as for the fluctuating Roberts flow. The derived mean-field dynamo equations have growing solutions with growth rate of the large-scale magnetic field which is not controlled by molecular magnetic diffusivity. Our study confirms the Zeldovich idea that the nonstationarity of the fluid flow may remove the obstacle in large-scale dynamo action of classic stationary flows and provide fast dynamos.
- [22] arXiv:0811.3139 [pdf]
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Title: The case for optical interferometric polarimetryAuthors: Nicholas M. Elias II, Carol E. Jones, Henrique R. Schmitt, Anders M. Jorgensen, Michael J. Ireland, Karine PerrautComments: This is a white paperSubjects: Astrophysics (astro-ph)
Within the last 10 years, long-baseline optical interferometry (LBOI) has benefited significantly from increased sensitivity, spatial resolution, and spectral resolution, e.g., measuring the diameters and asymmetries of single stars, imaging/fitting the orbits of multiple stars, modeling Be star disks, and modeling AGN nuclei. Similarly, polarimetry has also yielded excellent astrophysical results, e.g., characterizing the atmospheres and shells of red giants/supergiants, modeling the envelopes of AGB stars, studying the morphology of Be stars, and monitoring the short- and long- term behavior of AGNs. The next logical evolutionary step in instrumentation is to combine LBOI with polarimetry, which is called optical interferometric polarimetry (OIP). In other words, measurements of spatial coherence are performed simultaneously with measurements of coherence between orthogonal polarization states.
- [23] arXiv:0811.3143 [ps, pdf, other]
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Title: Reconciling MOND and dark matter?Comments: 9 pagesSubjects: Astrophysics (astro-ph)
Observations of galaxies suggest a one-to-one analytic relation between the inferred gravity of dark matter at any radius and the enclosed baryonic mass, a relation summarized by Milgrom's law of modified Newtonian dynamics (MOND). However, present-day covariant versions of MOND usually require some additional fields contributing to the geometry, as well as an additional hot dark matter component to explain cluster dynamics and cosmology. Here, we envisage a slightly more mundane explanation, suggesting that dark matter does exist but is the source of MOND-like phenomenology in galaxies. We assume a canonical action for dark matter, but also add an interaction term between baryonic matter, gravity, and dark matter, such that standard matter effectively obeys the MOND field equation in galaxies. We show that even the simplest realization of the framework leads to a model which reproduces some phenomenological predictions of cold dark matter (CDM) and MOND at those scales where these are most successful. We also devise a more general form of the interaction term, introducing the medium density as a new order parameter. This allows for new physical effects which should be amenable to observational tests in the near future. Hence, this very general framework, which can be furthermore related to a generalized scalar-tensor theory, opens the way to a possible unification of the successes of CDM and MOND at different scales.
- [24] arXiv:0811.3166 [ps, pdf, other]
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Title: Combining semi-analytic models with simulations of galaxy clusters: the need for AGN heatingComments: 16 pages and 10 colour figures. Submitted to MNRASSubjects: Astrophysics (astro-ph)
[Abridged] We investigate the effect of energy feedback from galaxies on the intracluster medium (ICM) using a novel approach that couples a non-radiative cosmological hydrodynamical N-body simulation to a semi-analytic model (SAM) of galaxy formation. The SAM we employ is the Munich L-Galaxies model presented by De Lucia & Blaizot (2007). For each model galaxy, we calculate the energy returned to the ICM by Type II supernovae (SNe) and active galactic nuclei (AGN) and inject it into the gas component of the simulation at the appropriate location and time. To assess the impact of this feedback on the ICM, we focus on two key observables of galaxy groups and clusters: the X-ray luminosity-temperature (L-T) relation and the halo gas fraction. Using a suite of test simulations, we demonstrate that the level of stellar and AGN feedback predicted by L-Galaxies is insufficient to explain the observational data. This is because the energy liberated by quiescent 'radio' mode accretion onto the central black hole only reduces the rate at which gas can cool out of the halo in L-Galaxies, rather than heating intracluster gas. We address this problem by incorporating a model of AGN feedback into our hybrid approach that allows for explicit heat input into the ICM. The model we adopt is that used in the version of the Durham SAM GALFORM recently developed by Bower et al. (2008). With this AGN feedback scheme, we obtain an L-T relation that is in excellent agreement with observational data over a wide range of mass scales. The stellar and gas fractions of our simulated objects are also consistent with observations. Simultaneously reproducing these observed properties of groups and clusters is notoriously difficult in direct hydrodynamical simulations. These encouraging results demonstrate the potential power of our method.
- [25] arXiv:0811.3173 [ps, pdf, other]
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Title: VLBI Observations of SN 2008DSubjects: Astrophysics (astro-ph)
We report on two epochs of VLBI observations of the Type Ib/c supernova SN 2008D, which was associated with the X-ray outburst XRF 080109, At our first epoch, at t=30 days after the explosion, we observed at 22 and 8.4 GHz, and at our second, at t=133 days, at 8.4 and 5.0 GHz. The VLBI observations allow us to accurately measure the source's size and position at each epoch, and thus constrain its expansion velocity and proper motion. We find the source at best marginally resolved at both epochs, allowing us to place a 3sigma upper limit of ~0.75c on the expansion velocity of a circular source. For an elongated source, our measurements are compatible with mildly relativistic expansion. However, our 3sigma upper limit on the proper motion is 4 micro-arcsec/day, corresponding to an apparent velocity of <0.6c, and is consistent with a stationary flux centroid. This limit rules out a relativistic jet such as an gamma-ray burst jet away from the line of sight, which would be expected to show apparent proper motion of >c. Taken together, our measurements argue against the presence of any long-lived relativistic outflow in SN 2008D. On the other hand, our measurements are consistent with the non-relativistic expansion velocities of <30,000 km/s and small proper motions (<500 km/s) seen in typical supernovae.
- [26] arXiv:0811.3179 [ps, pdf, other]
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Title: The chemical abundances in the Galactic Centre from the atmospheres of Red SupergiantsAuthors: Ben Davies (1,2), Livia Origlia (3), Rolf-Peter Kudritzki (4), Don F. Figer (2), R. Michael Rich (5), Francisco Najarro (6) ((1) Leeds; (2) RIT; (3) Bologna; (4) IfA Hawaii; (5) UCLA; (6) CSIC Madrid)Comments: 23 pages, 5 figs. Accepted for publication in ApJSubjects: Astrophysics (astro-ph)
The Galactic Centre (GC) has experienced a high degree of recent star-forming activity, as evidenced by the large number of massive stars currently residing there. The relative abundances of chemical elements in the GC may provide insights into the origins of this activity. Here, we present high-resolution $H$-band spectra of two Red Supergiants in the GC (IRS~7 and VR~5-7), and in combination with spectral synthesis we derive abundances for Fe and C, as well as other $\alpha$-elements Ca, Si, Mg Ti and O. We find that the C-depletion in VR~5-7 is consistent with the predictions of evolutionary models of RSGs, while the heavy depletion of C and O in IRS~7's atmosphere is indicative of deep mixing, possibly due to fast initial rotation and/or enhanced mass-loss. Our results indicate that the {\it current} surface Fe/H content of each star is slightly above Solar. However, comparisons to evolutionary models indicate that the {\it initial} Fe/H ratio was likely closer to Solar, and has been driven higher by H-depletion at the stars' surface. Overall, we find $\alpha$/Fe ratios for both stars which are consistent with the thin Galactic disk. These results are consistent with other chemical studies of the GC, given the precision to which abundances can currently be determined. We argue that the GC abundances are consistent with a scenario in which the recent star-forming activity in the GC was fuelled by either material travelling down the Bar from the inner disk, or from the winds of stars in the inner Bulge -- with no need to invoke top-heavy stellar Initial Mass Functions to explain anomalous abundance ratios.
- [27] arXiv:0811.3197 [ps, pdf, other]
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Title: Hubble Space Telescope survey of the Perseus Cluster - I: The structure and dark matter content of cluster dwarf spheroidalsComments: accepted for publication by MNRASSubjects: Astrophysics (astro-ph)
We present the results of a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) study of dwarf galaxies in the core of the rich nearby Perseus Cluster, down to M_V=-12. We identify 29 dwarfs as cluster members, 17 of which are previously unstudied. All the dwarfs we examine are remarkably smooth in appearance, and lack internal features. Based on these observations, and the sizes of these dwarfs, we argue that some of the dwarfs in our sample must have a large dark matter content to prevent disruption by the cluster potential. We derive a new method, independent of kinematics, for measuring the dark matter content of dEs, based on the radius of the dwarf, the projected distance of the dwarf from the cluster centre, and the total mass of the cluster interior to it. We find that the mass-to-light ratios of these dwarfs are comparable to those of the Local Group dSphs, ranging between 1 and 120.
- [28] arXiv:0811.3198 [ps, pdf, other]
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Title: Hubble Space Telescope Survey of the Perseus Cluster: II. Photometric scaling relations in different environmentsComments: accepted for publication by MNRASSubjects: Astrophysics (astro-ph)
We investigate the global photometric scaling relations traced by early-type galaxies in different environments, ranging from dwarf spheroidals, over dwarf elliptical galaxies, up to giant ellipticals (-8 mag > M_V > -24 mag). These results are based in part on our new HST/ACS F555W and F814W imagery of dwarf spheroidal galaxies in the Perseus Cluster. These scaling relations are almost independent of environment, with Local Group and cluster galaxies coinciding in the various diagrams. We show that at M_V ~ -14 mag, the slopes of the photometric scaling relations involving the Sersic parameters change significantly. We argue that these changes in slope reflect the different physical processes that dominate the evolution of early-type galaxies in different mass regimes. As such, these scaling relations contain a wealth of information that can be used to test models for the formation of early-type galaxies.
- [29] arXiv:0811.3201 [pdf]
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Title: Fabrication and Test of Pixelated CZT Detectors with Different Pixel Pitches and ThicknessesAuthors: Q. Li (1), A. Garson (1), P. Dowkontt (1), J. Martin (1), M. Beilicke (1), I. Jung (2), M. Groza (3), A. Burger (3), G. De Geronimo (4), H. Krawczynski (1), (1). (Department of Physics, Washington University in St. Louis, St. Louis, MO, USA) (2). (Physik. Inst., Universitat Erlangen-Nurnberg, Erlangen, Germany) (3). (Department of Physics, Fisk University, Nashville, TN, USA) (4). (Instrumentation Devision, Brookhaven National Laboratory, Upton, NY, USA)Comments: 6 pages, 17 figures, 2008 IEEE NSS/MIC conference, DresdenSubjects: Astrophysics (astro-ph)
The main methods grown Cadmium Zinc Telluride (CZT) crystals with high yield and excellent homogeneity are Modified Horizontal Bridgman (MHB) and High Pressure Bridgman (HPB) processes, respectively. In this contribution, the readout system based on two 32-channel NCI-ASICs for pixellated CZT detector arrays has been developed and tested. The CZT detectors supplied by Orbotech (MHB) and eV products (HPB) are tested by NCI-ASIC readout system. The CZT detectors have an array of 8x8 or 11x11 pixel anodes fabricated on the anode surface with the area up to 2 cm x2 cm and the thickness of CZT detectors ranges from 0.5 cm to 1 cm. Energy spectra resolution and electron mobility-lifetime products of 8x8 pixels CZT detector with different thicknesses have been investigated.
Cross-lists for Thu, 20 Nov 08
- [30] arXiv:0809.3496 (cross-list from nucl-th) [ps, pdf, other]
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Title: Lowest Order Constrained Variational Calculation of the Polarized Nuclear Matter with the Modern $AV_{18}$ PotentialComments: 19 pages, 6 figuresJournal-ref: Phys. Rev. C76 (2007) 035803Subjects: Nuclear Theory (nucl-th); Astrophysics (astro-ph)
The lowest order constrained variational method is applied to calculate the polarized symmetrical nuclear matter properties with the modern $AV_{18}$ potential performing microscopic calculations. Results based on the consideration of magnetic properties show no sign of phase transition to a ferromagnetic phase.
- [31] arXiv:0809.3497 (cross-list from nucl-th) [ps, pdf, other]
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Title: Polarized Neutron Matter: A Lowest Order Constrained Variational ApproachComments: 23 pages, 8 figuresJournal-ref: Phys. Rev. C75 (2007) 045804Subjects: Nuclear Theory (nucl-th); Astrophysics (astro-ph)
In this paper, we calculate some of the polarized neutron matter properties, using the lowest order constrained variational method with the $AV_{18}$ potential and employing a microscopic point of view. A comparison is also made between our results and those of other many-body techniques.
- [32] arXiv:0809.3498 (cross-list from nucl-th) [ps, pdf, other]
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Title: Spin Polarized Asymmetrical Nuclear Matter and Neutron Star Matter Within the Lowest Order Constrained Variational MethodComments: 21 pages, 11 figuresJournal-ref: Phys. Rev. C77 (2008) 015805Subjects: Nuclear Theory (nucl-th); Astrophysics (astro-ph)
In this paper, we calculate properties of the spin polarized asymmetrical nuclear matter and neutron star matter, using the lowest order constrained variational (LOCV) method with the $AV_{18}$, $Reid93$, $UV_{14}$ and $AV_{14}$ potentials. According to our results, the spontaneous phase transition to a ferromagnetic state in the asymmetrical nuclear matter as well as neutron star matter do not occur.
- [33] arXiv:0810.3310 (cross-list from nucl-th) [ps, pdf, other]
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Title: Lowest order constrained variational calculation of polarized neutron matter at finite temperatureComments: 18 pages, 7 figures. Phys. Rev. C (2008) in pressSubjects: Nuclear Theory (nucl-th); Astrophysics (astro-ph)
Some properties of the polarized neutron matter at finite temperature has been studied using the lowest order constrained variational (LOCV) method with the $AV_{18}$ potential. Our results indicate that spontaneous transition to the ferromagnetic phase does not occur. Effective mass, free energy, magnetic susceptibility, entropy and the equation of state of the polarized neutron matter at finite temperature are also calculated. A comparison is also made between our results and those of other many-body techniques.
- [34] arXiv:0810.3552 (cross-list from cond-mat.stat-mech) [ps, pdf, other]
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Title: Lowest Order Constrained Variational calculation for Polarized Liquid 3He at Finite TemperatureComments: 17 pages, 7 figures. Int. J. Mod. Phys. B 27 (2008) in pressSubjects: Statistical Mechanics (cond-mat.stat-mech); Astrophysics (astro-ph); Other (cond-mat.other)
We have investigated some of the thermodynamic properties of spin polarized liquid $^3\mathrm{He}$ at finite temperature using the lowest order constrained variational method. For this system, the free energy, entropy and pressure are calculated for different values of the density, temperature and polarization. We have also presented the dependence of specific heat, saturation density and incompressibility on the temperature and polarization.
- [35] arXiv:0810.5343 (cross-list from hep-ph) [ps, pdf, other]
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Title: Dark energy, the electroweak vacua and collider phenomenologyComments: 8 pages, 3 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc)
Higher dimensional non-renormalizable operators may modify the Standard Model Higgs potential in many interesting ways. Here, we consider the appearance of a second vacuum which may play an important role in cosmology. For the certain range of parameters, the usual second order electroweak phase transition is followed by a first order phase transition that may drive the late time accelerated expansion of the universe. Such a potential contains kink-like solutions which in turn can play a crucial role in reconstructing the global shape of the potential in colliders, as we explicitly demonstrate.
- [36] arXiv:0811.0877 (cross-list from gr-qc) [ps, pdf, other]
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Title: Matter and Dark Energy in 4 Dimensions From an Empty Kaluza-Klein SpacetimeComments: 11 pages, two figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Theory (hep-th)
We consider the third order Lovelock equations without the cosmological constant term of an empty $n(\geq 8)$-dimensional Kaluza-Klein spacetime $\mathcal{M}^{4}\times \mathcal{K}^{n-4}$, where $\mathcal{K}^{n-4}$ is a constant curvature space, and show that the emptiness of the higher-dimensional spacetime imposes a constraint on the metric function(s). We, first consider the effects of this constraint equation in the context of black hole physics, and present an asymptotically (A)dS charged black hole solution in 4 dimensions in the absence of electromagnetic field and the cosmological constant. This 4-dimensional solution has Riessner-Nordstrom-(A)dS behavior at large $r$ and it satisfies the Kaluza-Klein idea of being empty in higher dimensions. In the context of cosmology, we show that one may have an accelerated expanding universe without a cosmological constant term or the concept of dark energy in 4 dimensions. These two solutions show that one may have dark energy and matter, with non-traceless energy-momentum tensor, in 4 dimensions out of pure curvature of the empty higher-dimensional Kaluza-Klein spacetime.
- [37] arXiv:0811.2237 (cross-list from gr-qc) [ps, pdf, other]
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Title: Newtonian Aspects of General Relativistic Galaxy ModelsComments: 7 pages, no figures, talk given at the XV National Conference of Astronomers of Serbia, Belgrade, 2-5 October 2008Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph)
Many cosmological observations call for the existence of dark matter. The most direct evidence for dark matter is inferred from the measured flatness of galactic rotation curves. The latter is based on Newtonian gravity. Alternative approaches to the rotation curve problem by means of general relativity have recently been put forward. The class of models of interest is a subset of the axially symmetric and stationary solutions of Einstein's equations with rotating dust. As a step toward the understanding of general relativistic galaxy models, we analyse rigidly as well as non-rigidly rotating (Post-)Newtonian spacetimes. We find that the Newtonian limit of the considered general relativistic galaxy model leads to Post-Newtonian terms in the metric.
- [38] arXiv:0811.2935 (cross-list from math.CA) [ps, pdf, other]
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Title: Spin Wavelets on the SphereAuthors: Daryl Geller (1), Domenico Marinucci (2) ((1) Stony Brook University, (2) University of Rome Tor Vergata)Comments: 37 pagesSubjects: Classical Analysis and ODEs (math.CA); Astrophysics (astro-ph); Differential Geometry (math.DG); Statistics (math.ST)
In recent years, a rapidly growing literature has focussed on the construction of wavelet systems to analyze functions defined on the sphere. Our purpose in this paper is to generalize these constructions to situations where sections of line bundles, rather than ordinary scalar-valued functions, are considered. In particular, we propose {\em needlet-type spin wavelets} as an extension of the needlet approach recently introduced by Narcowich, Petrushev and Ward, and then considered for more general manifolds by Geller and Mayeli. We discuss localization properties in the real and harmonic domains, and investigate stochastic properties for the analysis of spin random fields. Our results are strongly motivated by cosmological applications, in particular in connection to the analysis of Cosmic Microwave Background polarization data.
- [39] arXiv:0811.2969 (cross-list from hep-ph) [ps, pdf, other]
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Title: Gravitino Dark Matter and the Flavour Structure of R-violating OperatorsComments: 19 pages, 6 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics (astro-ph)
We study gravitino dark matter and slow gravitino decays within the framework of R-violating supersymmetry, with particular emphasis on the flavour dependence of the branching ratios. The dominant decay modes and final state products turn out to be very sensitive to the R-violating hierarchies. Mixing effects can be crucial in correctly deriving the relative magnitude of the various contributions, particularly for heavy flavours with phase space suppression. The study of the strength of different decay rates for the gravitino is also correlated to collider signatures expected from decays of the Next-to-Lightest Supersymmetric Particle (NLSP) and to single superparticle production.
Replacements for Thu, 20 Nov 08
- [40] arXiv:0712.4310 (replaced) [ps, pdf, other]
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Title: 1122 Hz rotation of XTE J1739-285 as a probe of quark matter in the interior of the neutron starComments: 4 pages, 3 figuresSubjects: Astrophysics (astro-ph)
- [41] arXiv:0804.0909 (replaced) [ps, pdf, other]
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Title: Delay Time Distribution Measurement of Type Ia Supernovae by the Subaru/XMM-Newton Deep Survey and Implications for the ProgenitorAuthors: Tomonori Totani (1), Tomoki Morokuma (2), Takeshi Oda (1), Mamoru Doi (3), Naoki Yasuda (3) ((1) Kyoto, (2) NAOJ, (3) Tokyo)Comments: Matches the final version to be published in PASJ. A very minor bug in the visibility time calculation has been fixed, resulting in slight changes in the derived DTD (<~ 10%). Conclusions are not affected at all. The font error of the labels in Fig 3 also fixedSubjects: Astrophysics (astro-ph)
- [42] arXiv:0805.2950 (replaced) [ps, pdf, other]
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Title: On the time variability of geometrically-thin black hole accretion disks I : the search for modes in simulated disksComments: 20 pages, 15 figures. Accepted for publication in The Astrophysical Journal. High resolution version available at this http URLSubjects: Astrophysics (astro-ph)
- [43] arXiv:0806.0377 (replaced) [ps, pdf, other]
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Title: A Hemispherical Power Asymmetry from InflationComments: 5 pages, 2 figures; v3 reformatted with minor corrections made and refs. added; to appear in PRDSubjects: Astrophysics (astro-ph)
- [44] arXiv:0806.4389 (replaced) [ps, pdf, other]
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Title: About a (standard model) universe dominated by the right matterComments: 14 pages, 3 figures. References on late time enthropy release included, several points clarifiedSubjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics (astro-ph)
- [45] arXiv:0807.0448 (replaced) [ps, pdf, other]
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Title: Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiationAuthors: Dan N. VollickComments: 8 pages, change of title plus minor changesJournal-ref: Phys. Rev. D 78, 063524 (2008)Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Theory (hep-th)
- [46] arXiv:0808.1593 (replaced) [ps, pdf, other]
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Title: High-energy Particle Acceleration and Production of Ultra-high-energy Cosmic Rays in the Giant Lobes of Centaurus AComments: 12 pages, 8 figures, accepted by MNRAS. v3 fixes a typo in the reference list, otherwise unchanged from v2Subjects: Astrophysics (astro-ph)
- [47] arXiv:0808.3006 (replaced) [ps, pdf, other]
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Title: Perturbation Method for Classical Spinning Particle Motion: II. Vaidya Space-TimeAuthors: Dinesh SinghComments: 31 pages; REVTeX file; 9 figures; minor typos corrected; Accepted for publication in Phys. Rev. DSubjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph)
- [48] arXiv:0808.3683 (replaced) [ps, pdf, other]
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Title: Constraints on the star formation histories of galaxies from z~1 to z~0Authors: Yan-Mei Chen, Vivienne Wild, Guinevere Kauffmann, Jeremy Blaizot, Marc Davis, Kai Noeske, Jian-Min Wang, Christopher WillmerComments: 14 pages, 11 figures, accepted by MNRASSubjects: Astrophysics (astro-ph)
- [49] arXiv:0809.3747 (replaced) [ps, pdf, other]
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Title: System Parameters for the Eclipsing B-Star Binary HD 42401Authors: S. J. WilliamsComments: 20 pages, 8 figures, Added and modified figures and text. Accepted to AJSubjects: Astrophysics (astro-ph)
- [50] arXiv:0810.0597 (replaced) [ps, pdf, other]
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Title: Direct Imaging of Fine Structure in the Chromosphere of a Sunspot UmbraComments: Accepted for publication in ApJSubjects: Astrophysics (astro-ph)
- [51] arXiv:0810.1953 (replaced) [ps, pdf, other]
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Title: Structural Properties of Pseudo-Bulges, Classical Bulges and Elliptical Galaxies: an SDSS PerspectiveAuthors: Dimitri A. Gadotti (Max Planck Institute for Astrophysics)Comments: Accepted for publication in MNRAS after minor revision; 24 pages, 21 figures, 4 tables; new Appendix A describes tests to fits' robustness; high resolution version available as PDF file at this http URLSubjects: Astrophysics (astro-ph)
- [52] arXiv:0810.3395 (replaced) [ps, pdf, other]
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Title: Spinodal instabilities and the distillation effect in nuclear matter under strong magnetic fieldsComments: 16 pages, 13 figures, 3 tables, revised version submitted to Phys. Rev. CSubjects: Nuclear Theory (nucl-th); Astrophysics (astro-ph)
- [53] arXiv:0811.0006 (replaced) [ps, pdf, other]
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Title: Atmospheric Escape from Hot JupitersComments: Accepted for publication in ApJ, 22 pages, 24 figures. Added additional references--in particular, we now discuss charge-exchange as a potential source of high-velocity neutralsSubjects: Astrophysics (astro-ph)
- [54] arXiv:0811.1985 (replaced) [ps, pdf, other]
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Title: Fomalhaut's Debris Disk and Planet: Constraining the Mass of Fomalhaut b From Disk MorphologyAuthors: E. Chiang (UCB), E. Kite (UCB), P. Kalas (UCB), J. R. Graham (UCB), M. Clampin (NASA Goddard Space Flight Center)Comments: This version 2 should be the final version for the ApJ proofs. Emphasizes that astrometric uncertainties are hard to quantify and that apsidal alignment, though not preferred by the observations, might still be viable, confirming predictions by Quillen (2006) and Wyatt et al. (1999). See the movie at this http URLSubjects: Astrophysics (astro-ph)
- [55] arXiv:0811.2458 (replaced) [ps, pdf, other]
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Title: Fundamental vibrational mode in a highly inhomogeneous starSubjects: Astrophysics (astro-ph)
- [56] arXiv:0811.2534 (replaced) [ps, pdf, other]
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Title: Tuned Finite-Difference Diffusion OperatorsComments: 13 pages, 3 figuresSubjects: Astrophysics (astro-ph)
- [57] arXiv:0811.2975 (replaced) [ps, pdf, other]
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Title: Exoplanets from the CHEPS: Discovery of the Double Planet System HD191760Comments: 8 pages, 6 figures, 4 tables, submitted to MNRASSubjects: Astrophysics (astro-ph)
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