The companion candidate near Fomalhaut - a background neutron star?

Stars and planetary systemsHigh Energy Astrophysic

Presupernova Structure of Massive Stars

Issues concerning the structure and evolution of core collapse progenitor stars are discussed with an emphasis on interior evolution. We describe a program designed to investigate the transport and mixing processes associated with stellar turbulence, arguably the greatest source of uncertainty in progenitor structure, besides mass loss, at the time of core collapse. An effort to use precision observations of stellar parameters to constrain theoretical modeling is also described.Comment: Proceedings for invited talk at High Energy Density Laboratory Astrophysics conference, Caltech, March 2010. Special issue of Astrophysics and Space Science, submitted for peer review: 7 pages, 3 figure

Updated phase coherent timing solution of the isolated neutron star RX J0720.4-3125 using recent XMM-Newton and Chandra observations

Aims. Since the last phase coherent timing solution of the nearby radio-quiet isolated neutron star RXJ0720.4−3125 six new XMM-Newton and three Chandra observations were carried out. The phase coherent timing solutions from previous authors were performed without restricting to a fixed energy band. However, we recently showed that the phase residuals are energy dependent, and thus phase coherent solutions must be computed referring always to the same energy band. Methods. We updated the phase coherent timing solution for RXJ0720.4−3125 by including the recent XMM-Newton EPIC-pn, MOS1, MOS2 and Chandra ACIS data in the energy range 400–1000 eV. Altogether these observations cover a time span of almost 10 yrs. A further timing solution was obtained including the ROSAT pointed data. In this case, observations cover a time span of ≈16 yrs. To illustrate the timing differences between the soft band (120–400 eV) and the hard band (400–1000 eV) a timing solution for the soft band is also presented and the results are verified using a Z2 n test. Results. In contrast to previous work, we obtain almost identical solutions whether or not we include the ROSAT or Chandra data. Thanks to the restriction to the hard band, the data points from EPIC-pn are in better agreement with those from MOS1, MOS2 and Chandra than in previous works. In general the phase residuals are still large and vary with time. In particular, the latest XMM-Newton and Chandra data show that the phase residuals have attained relatively large and negative values. Using this and previous timing solutions, the residuals indicate a cyclic behaviour with a period ≈7–9 yrs if the variations follow a sinusoid, or twice this value in case the residuals are modulated by an abs(sine) probably approaching a new minimum around MJD = 55 240 days (February 2010). As an alternative interpretation, the phase residuals can be fitted with a glitch that occured around MJD = 53 000 days

Observations of planetary transits at the University Observatory Jena

We report on observations of transit events of the transiting planets XO-1b, TrES-1 and TrES-2 with a 25 cm telescope of the University Observatory Jena. With the help of all available transit times from literature including our own photometry our measurements allowed us to refine the estimate of the orbital period of all three transiting planets observed by us

Transit timing, depth, and duration variation in exoplanet TrES-2?

We report on our ongoing search for timing, duration, and depth variations in the exoplanet TrES-2. In Raetz et al. (2009) we already presented ten different transits obtained at the University Observatory Jena. Between November 2008 and August 2010 twelve additional transits could be observed. The timing, depth and duration of each individual event was analyzed and is presented here

Transit timing, depth, and duration variation in exoplanet TrES-2?

We report on our ongoing search for timing, duration, and depth variations in the exoplanet TrES-2. In Raetz et al. (2009) we already presented ten different transits obtained at the University Observatory Jena. Between November 2008 and August 2010 twelve additional transits could be observed. The timing, depth and duration of each individual event was analyzed and is presented here