Bell inequality violation by entangled single photon states generated from a laser, a LED or a Halogen lamp

In single-particle or intraparticle entanglement, two degrees of freedom of a single particle, e.g., momentum and polarization of a single photon, are entangled. Single-particle entanglement (SPE) provides a source of non classical correlations which can be exploited both in quantum communication protocols and in experimental tests of noncontextuality based on the Kochen-Specker theorem. Furthermore, SPE is robust under decoherence phenomena. Here, we show that single-particle entangled states of single photons can be produced from attenuated sources of light, even classical ones. To experimentally certify the entanglement, we perform a Bell test, observing a violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality. On the one hand, we show that this entanglement can be achieved even in a classical light beam, provided that first-order coherence is maintained between the degrees of freedom involved in the entanglement. On the other hand, we prove that filtered and attenuated light sources provide a flux of independent SPE photons that, from a statistical point of view, are indistinguishable from those generated by a single photon source. This has important consequences, since it demonstrates that cheap, compact, and low power entangled photon sources can be used for a range of quantum technology applications

Evidence of Asymmetry in SN 2007rt, a Type IIn Supernova

An optical photometric and spectroscopic analysis of the slowly-evolving Type IIn SN2007rt is presented, covering a duration of 481 days after discovery. Its earliest spectrum, taken approximately 100 days after the explosion epoch, indicates the presence of a dense circumstellar medium, with which the supernova ejecta is interacting. This is supported by the slowly-evolving light curve. A notable feature in the spectrum of SN 2007rt is the presence of a broad He I 5875 line, not usually detected in Type IIn supernovae. This may imply that the progenitor star has a high He/H ratio, having shed a significant portion of its hydrogen shell via mass-loss. An intermediate resolution spectrum reveals a narrow Halpha P-Cygni profile, the absorption component of which has a width of 128 km/s. This slow velocity suggests that the progenitor of SN 2007rt recently underwent mass-loss with wind speeds comparable to the lower limits of those detected in luminous blue variables. Asymmetries in the line profiles of H and He at early phases bears some resemblance to double-peaked features observed in a number of Ib/c spectra. These asymmetries may be indicative of an asymmetric or bipolar outflow or alternatively dust formation in the fast expanding ejecta. In addition, the late time spectrum, at over 240 days post-explosion, shows clear evidence for the presence of newly formed dust.Comment: Submitted to A&A on 4/2/2009. Accepted by A&A on 17/5/2009.15 pages plus 3 pages of online materia

A very faint core-collapse supernova in M85

An anomalous transient in the early Hubble-type (S0) galaxy Messier 85 (M85) in the Virgo cluster was discovered by Kulkarni et al. (2007) on 7 January 2006 that had very low luminosity (peak absolute R-band magnitude MR of about -12) that was constant over more than 80 days, red colour and narrow spectral lines, which seem inconsistent with those observed in any known class of transient events. Kulkarni et al. (2007) suggest an exotic stellar merger as the possible origin. An alternative explanation is that the transient in M85 was a type II-plateau supernova of extremely low luminosity, exploding in a lenticular galaxy with residual star-forming activity. This intriguing transient might be the faintest supernova that has ever been discovered.Comment: 7 pages, 2 figures. Submitted to Nature "Brief Communication Arising" on 18 July 2007, Accepted on 17 August 2007. Arising from: Kulkarni et al. 2007, Nature, 447, 458-46

SN 1999ga: a low-luminosity linear type II supernova?

Type II-linear supernovae are thought to arise from progenitors that have lost most of their H envelope by the time of the explosion, and they are poorly understood because they are only occasionally discovered. It is possible that they are intrinsically rare, but selection effects due to their rapid luminosity evolution may also play an important role in limiting the number of detections. In this context, the discovery of a subluminous type II-linear event is even more interesting. We investigate the physical properties and characterise the explosion site of the type II SN 1999ga, which exploded in the nearby spiral galaxy NGC 2442. Spectroscopic and photometric observations of SN 1999ga allow us to constrain the energetics of the explosion and to estimate the mass of the ejected material, shedding light on the nature of the progenitor star in the final stages of its life. The study of the environment in the vicinity of the explosion site provides information on a possible relation between these unusual supernovae and the properties of the galaxies hosting them. Despite the lack of early-time observations, we provide reasonable evidence that SN 1999ga was probably a type II-linear supernova that ejected a few solar masses of material, with a very small amount of radioactive elements of the order of 0.01 solar masses.Comment: 11 pages, 9 figures. Accepted for publication in A&A (March 28, 2009

On the nature of the progenitors of three type II-P supernovae: 2004et, 2006my and 2006ov

The pre-explosion observations of the type II-P supernovae 2006my, 2006ov and 2004et, are re-analysed. In the cases of supernovae 2006my and 2006ov we argue that the published candidate progenitors are not coincident with their respective supernova sites in pre-explosion Hubble Space Telescope observations. We therefore derive upper luminosity and mass limits for the unseen progenitors of both these supernovae, assuming they are red supergiants: 2006my (log L/Lsun = 4.51; mass < 13Msun) and 2006ov (log L/Lsun = 4.29; mass < 10Msun). In the case of supernova 2004et we show that the yellow-supergiant progenitor candidate, originally identified in Canada France Hawaii Telescope images, is still visible ~3 years post-explosion in observations from the William Herschel Telescope. High-resolution Hubble Space Telescope and Gemini (North) adaptive optics late-time imagery reveal that this source is not a single yellow supergiant star, but rather is resolved into at least three distinct sources. We report the discovery of the unresolved progenitor as an excess of flux in pre-explosion Isaac Newton Telescope i'-band imaging. Accounting for the late-time contribution of the supernova using published optical spectra, we calculate the progenitor photometry as the difference between the pre- and post-explosion, ground-based observations. We find the progenitor was most likely a late K to late M-type supergiant of 8 +5/-1 Msun. In all cases we conclude that future, high-resolution observations of the supernova sites will be required to confirm these results.Comment: 43 pages (pre-print format), 12 figures, 10 tables. Significant revision following referee's comments. Accepted for publication in MNRA

Importance of activity data for improving the residential wood combustion emission inventory at regional level

The contribution of residential wood combustion (RWC) to emission inventory at local level was estimated using a bottomeup approach for the Lombardy Region of North Italy. A survey, based on the CATI (Computer Assisted Telephone Interviewing) method, has been undertaken through 18,000 interviews. The interviews had the objective to characterize the RWC use in this region, in term of both total and municipal wood consumption. Details on the type of appliances used in RWC were also gathered. The results of the survey were then statistically analyzed in order to allow an estimate of RWC with high spatial resolution (i.e., at municipal level) in relation to the size and altitude of the territory. The work provides new evidence of the importance of wood combustion as a key source for PM and NMVOC emissions at local level, and thus highlights the importance of technological improvements and new policies aimed at emission reduction in this sector. Considering the great differences in average PM emission factors between low efficiency appliances (fireplaces, old stoves) and high efficiency ones (new stoves, pellet burners), this work emphasizes the importance of obtaining more detailed information on the types of wood appliances used for arriving at a reliable PM emission inventory for RWC

A low energy core-collapse supernova without a hydrogen envelope

The final fate of massive stars depends on many factors, including mass, rotation rate, magnetic fields and metallicity. Theory suggests that some massive stars (initially greater than 25-30 solar masses) end up as Wolf-Rayet stars which are deficient in hydrogen because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion produces ejecta of low kinetic energy, a faint optical display and a small mass fraction of radioactive nickel(1,2,3). An alternative origin for low energy supernovae is the collapse of the oxygen-neon core of a relatively lowmass star (7-9 solar masses) through electron capture(4,5). However no weak, hydrogen deficient, core-collapse supernovae are known. Here we report that such faint, low energy core-collapse supernovae do exist, and show that SN2008ha is the faintest hydrogen poor supernova ever observed. We propose that other similar events have been observed but they have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN2002cx-like events(6)). This discovery could link these faint supernovae to some long duration gamma-ray bursts. Extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce those long gamma-ray bursts whose afterglows do not show evidence of association with supernovae (7,8,9).Comment: Submitted 12 January 2009 - Accepted 24 March 200

SN 2013df, a double-peaked IIb supernova from a compact progenitor and an extended H envelope

Optical observations of the type IIb SN 2013df from a few days to about 250 days after explosion are presented. These observations are complemented with UV photometry taken by \textit{SWIFT} up to 60 days post-explosion. The double-peak optical light curve is similar to those of SNe 1993J and 2011fu although with different decline and rise rates. From the modelling of the bolometric light curve, we have estimated that the total mass of synthesised $^{56}$Ni in the explosion is $\sim0.1$ M$_{\odot}$, while the ejecta mass is $0.8-1.4$ M$_{\odot}$ and the explosion energy $0.4-1.2 \times 10^{51}$erg. In addition, we have estimated a lower limit to the progenitor radius ranging from $64-169$ $R_{\odot}$. The spectral evolution indicates that SN 2013df had a hydrogen envelope similar to SN 1993J ($\sim 0.2$ M$_{\odot}$). The line profiles in nebular spectra suggest that the explosion was asymmetric with the presence of clumps in the ejecta, while the [O\,{\sc i}] $\lambda$$\lambda$$6300$, $6364$ luminosities, may indicate that the progenitor of SN 2013df was a relatively low mass star ( $\sim 12-13$ M$_{\odot}$).Comment: 18 pages, 11 figures, 9 tables, accepted for publication in MNRA