Discovery of a new Transient X-ray Pulsar in the Small Magellanic Cloud

Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have revealed a previously unknown transient X-ray pulsar with a pulse period of 95s. Provisionally designated XTE SMC95, the pulsar was detected in three Proportional Counter Array observations during an outburst spanning 4 weeks in March/April 1999. The pulse profile is double peaked reaching a pulse fraction \~0.8. The source is proposed as a Be/neutron star system on the basis of its pulsations, transient nature and characteristically hard X-ray spectrum. The 2-10 keV X-ray luminosity implied by our observations is > 2x10^37 erg/s which is consistent with that of normal outbursts seen in Galactic systems. This discovery adds to the emerging picture of the SMC as containing an extremely dense population of transient high mass X-ray binaries.Comment: Accepted by A&A. 7 pages, 6 figure

Looking for Stars and Finding the Moon: Effects of Lunar Gamma-ray Emission on Fermi LAT Light Curves

We are conducting a search for new gamma-ray binaries by making high signal-to-noise light curves of all cataloged Fermi LAT sources and searching for periodic variability using appropriately weighted power spectra. The light curves are created using a variant of aperture photometry where photons are weighted by the probability that they came from the source of interest. From this analysis we find that the light curves of a number of sources near the ecliptic plane are contaminated by gamma-ray emission from the Moon. This shows itself as modulation on the Moon's sidereal period in the power spectra. We demonstrate that this contamination can be removed by excluding times when the Moon was too close to a source. We advocate that this data screening should generally be used when analyzing LAT data from a source located close to the path of the Moon.Comment: 2012 Fermi Symposium proceedings - eConf C12102

Rossi X-ray Timing Explorer Observations of the X-ray Pulsar EXO 1722-363 - a Candidate Eclipsing Supergiant System

Observations made of the X-ray pulsar EXO 1722-363 using the Proportional Counter Array and All Sky Monitor on board the Rossi X-ray Timing Explorer reveal the orbital period of this system to be 9.741 +/- 0.004 d from periodic changes in the source flux. The detection of eclipses, together with the values of the pulse and orbital periods, suggest that this source consists of a neutron star accreting from the stellar wind of an early spectral type supergiant companion. Pulse timing measurements were also obtained but do not strongly constrain the system parameters. The X-ray spectra can be well fitted with a model consisting of a power law with a high energy cutoff and, for some spectra, a blackbody component with a temperature of approximately 0.85 keV.Comment: Accepted for publication in The Astrophysical Journal. 27 pages including 10 figure

Asymmetric mean reversion of Bitcoin price returns

© 2018 Elsevier Inc. Non-linearity is characterised by an asymmetric mean-reverting property, which has been found to be inherent in the short-term return dynamics of stocks. In this paper, we explore as to whether cryptocurrency returns, as represented by Bitcoin, exhibit similar asymmetric reverting patterns for minutely, hourly, daily and weekly returns between June 2010 and February 2018. We identify several differences in the behaviour of Bitcoin price returns in the pre- and post-$1000 sub-periods and evidence of asymmetric reverting patterns in the Bitcoin price returns under all the ANAR models employed, regardless of the data frequency considered. We also present evidence indicating stronger reverting behaviour of negative price returns in terms of both reverting speed and magnitude compared to positive returns and evidence of positive serial correlation with prior positive price returns. Finally, we also investigated asymmetries in Bitcoin price return series’ persistence by employing higher order ANAR models, finding evidence of a higher persistence of positive returns than negative returns, a result that further supports the existence of asymmetric reverting behaviour in the Bitcoin price returns

4U2206+54 - an Unusual High Mass X-ray Binary with a 9.6 Day Orbital Period but No Strong Pulsations

Rossi X-ray Timing Explorer All-Sky Monitor observations of the X-ray source 4U2206+54, previously proposed to be a Be star system, show the X-ray flux to be modulated with a period of approximately 9.6 days. If the modulation is due to orbital variability then this would be one of the shortest orbital periods known for a Be star X-ray source. However, the X-ray luminosity is relatively modest whereas a high luminosity would be predicted if the system contains a neutron star accreting from the denser inner regions of a Be star envelope. Although a 392s pulse period was previously reported from EXOSAT observations, a reexamination of the EXOSAT light curves does not show this or any other periodicity. An analysis of archival RXTE Proportional Counter Array observations also fails to show any X-ray pulsations. We consider possible models that may explain the properties of this source including a neutron star with accretion halted at the magnetosphere and an accreting white dwarf.Comment: Accepted for publication in the Astrophysical Journa

Natural Hosts of Mosquitoes in Northern Ellesmere Island

Aedes impiger and A. nigripes, near Lake Hazen, were observed to take blood from musk-oxen, birds(mainly the eider ducks), and man. Precipitin tests showed several specimens contained blood of two kinds. The reaction of the host to harassment by mosquitos appears to determine which hosts are fed on successfully.Les Hôtes naturels des moustiques dans le nord de l'île d'Ellesmere. Près du lac Hazen, T. du N.-O. (81°49'N., 71°18'O.), les auteurs ont effectué des observations sur l'alimentation en sang et des tests à la précipitine sur des femelles gorgées d'Aedes impiger et A. nigripes. On donne une liste des vertébrés terrestres mentionnés pour la région. Dans la nature, les deux espèces de moustiques soutirent du sang des bœufs musqués et des oiseaux (également des humains); plusieurs spécimens contiennent du sang des deux espèces (déterminations par les tests à la précipitine). La réaction de l'hôte au harassement par les moustiques est évidemment le facteur majeur qui détermine lequel des hôtes possibles sera attaqué avec succès. D'après leur comportement et leur situation, on estime que les bœufs musqués et les oiseaux nichés dans des sites aquatiques sont les plus susceptibles de fournir du sang. Les auteurs discutent brièvement des méthodes servant à déterminer les préférences envers les hôtes dans l'Arctique

Platelet rich plasma in the treatment of periodontal intrabony defects

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Monitoring and Discovering X-ray Pulsars in the Small Magellanic Cloud

Regular monitoring of the SMC with RXTE has revealed a huge number of X-ray pulsars. Together with discoveries from other satellites at least 45 SMC pulsars are now known. One of these sources, a pulsar with a period of approximately 7.8 seconds, was first detected in early 2002 and since discovery it has been found to be in outburst nine times. The outburst pattern clearly shows a period of 45.1 +/- 0.4 d which is thought to be the orbital period of this system. Candidate outburst periods have also been obtained for nine other pulsars and continued monitoring will enable us to confirm these. This large number of pulsars, all located at approximately the same distance, enables a wealth of comparative studies. In addition, the large number of pulsars found (which vastly exceeds the number expected simply by scaling the relative mass of the SMC and the Galaxy) reveals the recent star formation history of the SMC which has been influenced by encounters with both the LMC and the Galaxy.Comment: 5 pages, 4 figures, AIP conference proceedings format. Contribution to "X-ray Timing 2003: Rossi and Beyond." meeting held in Cambridge, MA, November, 200