Follow-up Studies of the Pulsating Magnetic White Dwarf SDSS J142625.71+575218.3

We present a follow-up analysis of the unique magnetic luminosity-variable carbon-atmosphere white dwarf SDSS J142625.71+575218.3. This includes the results of some 106.4 h of integrated light photometry which have revealed, among other things, the presence of a new periodicity at 319.720 s which is not harmonically related to the dominant oscillation (417.707 s) previously known in that star. Using our photometry and available spectroscopy, we consider the suggestion made by Montgomery et al. (2008) that the luminosity variations in SDSS J142625.71+575218.3 may not be caused by pulsational instabilities, but rather by photometric activity in a carbon-transferring analog of AM CVn. This includes a detailed search for possible radial velocity variations due to rapid orbital motion on the basis of MMT spectroscopy. At the end of the exercise, we unequivocally rule out the interacting binary hypothesis and conclude instead that, indeed, the luminosity variations are caused by g-mode pulsations as in other pulsating white dwarfs. This is in line with the preferred possibility put forward by Montgomery et al. (2008).Comment: 11 pages in emulateApJ, 12 figures, accepted for publication in Ap

FLT3 Length Mutations as Marker for Follow-Up Studies in Acute Myeloid Leukaemia

Length mutations within the FLT3 gene (FLT3-LM) can be found in 23% of acute myeloid leukaemia (AML) and thus are the most frequent mutations in AML. FLT3-LM are highly correlated with AML with normal karyotype and other cytogenetic aberrations of the prognostically intermediate group. This group is supposed to be a mixed group of AML with differences in the underlying pathogenesis. For more individualized treatment options it would be helpful to better characterize this large AML group not only by molecular mutations but also use these markers for the definition of minimal residual disease (MRD). However, so far the cytogenetically intermediate AML has been lacking suitable markers for PCR-based MRD detection like the fusion genes in the prognostically favourable subgroups. The suitability of the FLT3-LM as a target for PCR-based MRD was discussed controversially as it seemed to be a rather unstable marker. Thus, we aimed at the evaluation of FLT3-LM as a marker for residual disease in a large cohort of AML. Paired samples of 97 patients with AML at diagnosis and at relapse were analyzed. It could be shown that in only four cases a loss of the length mutation was detected. This is in the range of other well-characterized AML relapsing with a different geno- and/or phenotype. In contrast, a change in the ratio of the mutated allele in comparison to the wild-type allele was frequently observed. In detail, the FLT3-LM showed a tendency to accumulate during disease progression and was found more frequently at relapse than at diagnosis. In addition, 45 patients were analyzed at different time points during and after therapy. Using conventional PCR it clearly could be shown that for most of the patients positive at presentation FLT3-LM is a reliable PCR marker for monitoring treatment response. Even an early detection of relapse was possible in some cases. Copyright (C) 2004 S. Karger AG, Basel

Gamma-ray follow-up studies on Eta Carinae

Observations of high energy gamma rays recently revealed a persistent source in spatial coincidence with the binary system Eta Carinae. Since modulation of the observed gamma-ray flux on orbital time scales has not been reported so far, an unambiguous identification was hitherto not possible. Particularly the observations made by the Fermi Large Area Telescope (LAT) posed additional questions regarding the actual emission scenario owing to the existence of two energetically distinct components in the gamma-ray spectrum of this source, best described by an exponentially cutoff power-law function (CPL) at energies below 10 GeV and a power-law (PL) component dominant at higher energies. The increased exposure in conjunction with the improved instrumental response functions of the LAT now allow us to perform a more detailed investigation of location, spectral shape, and flux time history of the observed gamma-ray emission. For the first time, we are able to report a weak but regular flux decrease over time. This can be understood and interpreted in a colliding-wind binary scenario for orbital modulation of the gamma-ray emission. We find the spectral shape of the gamma-ray signal in agreement with a single emitting particle population in combination with significant absorption by gamma-gamma pair production. Studying the correlation of the flux decrease with the orbital separation of the binary components allows us to predict the behaviour up to the next periastron passage in 2014.Comment: 11 pages, 9 figure

Detailed follow up studies of three ultracompact sdB binaries

We present follow-up studies of three ultracompact hot subdwarf binaries. Using data from the Zwicky Transient Facility, we find orbital periods of 33.6, 37.3, and 36.9 minutes for ZTF 1946+3203, ZTF 0640+1738, and ZTF 0643+0318 respectively. The light curves show ellipsoidal variability of the hot subdwarf star with potential eclipses of an accretion disc. Phase-resolved spectroscopic observations with Keck were used to measure a radial velocity curve and atmospheric parameters of the hot subdwarf stars. ZTF J0643 shows evidence of accretion disc emission lines in the average spectrum. Combining light curve and spectroscopic fits will allow us to measure precise system properties such as masses, to determine the evolutionary history and future evolution of the system.Comment: Accepted for publication in Bulletin de la Soci\'et\'e Royale des Sciences de Li\`ege, proceedings for the sdOB10 conference, 10 pages, 1 figur