The Stellar Population of the M31 Spiral Arm Around OB Association A24

A study of the stellar population of the M31 spiral arm around OB association A24 was carried out based on the photometric data obtained from deep V and JHK imaging. The luminosity function was obtained for -7 <~ Mbol <~ -3.5 by applying the extinction correction corresponding to Av=1 and the bolometric correction BC(K) as an empirical function of (J-K)o. In comparing the observed color-luminosity diagrams with semitheoretical isochrones modified for the dust-shell effects, we found the young population of t <~ 30 Myr with supergiants of Mbol <~ -5, the bulk of the intermediate-age population of t ~ 0.2 - 2.5 Gyr with bright asymptotic giant branch (AGB) stars of -5 <~ Mbol <~ -4, and old populations of t ~> 3 Gyr with AGB and red giant branch (RGB) stars of Mbol ~> -4. The average star formation rate was estimated to be ~1.8x10^4 M_o/Myr and ~0.7x10^4 M_o/Myr per deprojected disk area of 1 kpc^2 from the number density of B0 V stars around Mv=-4.0 (age ~10 Myr) and the number density of bright AGB stars around Mbol = -4.3 (age ~1 Gyr), respectively. A study of the local variation in the V and the J and H luminosity functions revealed a kind of anticorrelation between the population of the young component and that of the intermediate-age component when subdomains of ~100 pc scales were concerned. This finding suggests that the disk domain around the A24 area experienced a series of star formation episodes alternatively among different subdomains with a timescale of a few spiral passage periods. Brief discussions are given about the interstellar extinction and about the lifetimes of bright AGB stars and the highly red objects (HROs) in the same area.Comment: 27 pages, 11 figures, accepted: ApJ, July 1, 199

Analysis of the finite-source multiclass priority queue with an unreliable server and setup time

In this article, we study a queueing system serving multiple classes of customers. Each class has a finite-calling population. The customers are served according to the preemptive-resume priority policy. We assume general distributions for the service times. For each priority class, we derive the steady-state system size distributions at departure/arrival and arbitrary time epochs. We introduce the residual augmented process completion times conditioned on the number of customers in the system to obtain the system time distribution. We then extend the model by assuming that the server is subject to operation-independent failures upon which a repair process with random duration starts immediately. We also demonstrate how setup times, which may be required before resuming interrupted service or picking up a new customer, can be incorporated in the model

On the impact of Helium abundance on the Cepheid Period-Luminosity and Wesenheit relations and the Distance Ladder

This work analyses the effect of the Helium content on synthetic Period-Luminosity Relations (PLRs) and Period-Wesenheit Relations (PWRs) of Cepheids and the systematic uncertainties on the derived distances that a hidden population of He-enhanced Cepheids may generate. We use new stellar and pulsation models to build a homogeneous and consistent framework to derive the Cepheid features. The Cepheid populations expected in synthetic color-magnitude diagrams of young stellar systems (from 20 Myr to 250 Myr) are computed in several photometric bands for Y = 0.25 and Y = 0.35, at a fixed metallicity (Z = 0.008). The PLRs appear to be very similar in the two cases, with negligible effects (few %) on distances, while PWRs differ somewhat, with systematic uncertainties in deriving distances as high as about 7% at log P < 1.5. Statistical effects due to the number of variables used to determine the relations contribute to a distance systematic error of the order of few percent, with values decreasing from optical to near-infrared bands. The empirical PWRs derived from multi-wavelength datasets for the Large Magellanic Cloud (LMC) is in a very good agreement with our theoretical PWRs obtained with a standard He content, supporting the evidence that LMC Cepheids do not show any He effect

Super-exponential extinction time of the contact process on random geometric graphs

In this paper, we prove lower and upper bounds for the extinction time of the contact process on random geometric graphs with connecting radius tending to infinity. We obtain that for any infection rate $\lambda >0$, the contact process on these graphs survives a time super-exponential in the number of vertices.Comment: Accepted for publication in Combinatorics, Probability and Computin

Essential spectrum and Weyl asymptotics for discrete Laplacians

In this paper, we investigate spectral properties of discrete Laplacians. Our study is based on the Hardy inequality and the use of super-harmonic functions. We recover and improve lower bounds for the bottom of the spectrum and of the essential spectrum. In some situation, we obtain Weyl asymptotics for the eigenvalues. We also provide a probabilistic representation of super-harmonic functions. Using coupling arguments, we set comparison results for the bottom of the spectrum, the bottom of the essential spectrum and the stochastic completeness of different discrete Laplacians. The class of weakly spherically symmetric graphs is also studied in full detail

Experimental bilocality violation without shared reference frames

Non-classical correlations arising in complex quantum networks are attracting growing interest, both from a fundamental perspective and for potential applications in information processing. In particular, in an entanglement swapping scenario a new kind of correlations arise, the so-called nonbilocal correlations that are incompatible with local realism augmented with the assumption that the sources of states used in the experiment are independent. In practice, however, bilocality tests impose strict constraints on the experimental setup and in particular to presence of shared reference frames between the parties. Here, we experimentally address this point showing that false positive nonbilocal quantum correlations can be observed even though the sources of states are independent. To overcome this problem, we propose and demonstrate a new scheme for the violation of bilocality that does not require shared reference frames and thus constitute an important building block for future investigations of quantum correlations in complex networks.Comment: 10 page

Radial Velocity Curves of Ellipsoidal Red Giant Binaries in the Large Magellanic Cloud

Ellipsoidal red giant binaries are close binary systems where an unseen, relatively close companion distorts the red giant, leading to light variations as the red giant moves around its orbit. These binaries are likely to be the immediate evolutionary precursors of close binary planetary nebula and post-asymptotic giant branch and post-red giant branch stars. Due to the MACHO and OGLE photometric monitoring projects, the light variability nature of these ellipsoidal variables has been well studied. However, due to the lack of radial velocity curves, the nature of their masses, separations, and other orbital details has so far remained largely unknown. In order to improve this situation, we have carried out spectral monitoring observations of a large sample of 80 ellipsoidal variables in the Large Magellanic Cloud and we have derived radial velocity curves. At least 12 radial velocity points with good quality were obtained for most of the ellipsoidal variables. The radial velocity data are provided with this paper. Combining the photometric and radial velocity data, we present some statistical results related to the binary properties of these ellipsoidal variables.Comment: 10 pages, 8 figures, 3 table