Discovery of a Quasi-Periodic Oscillation in the Ultraluminous X-ray Source IC 342 X-1: XMM-Newton Results

We report the discovery of a quasi-periodic oscillation (QPO) at 642 mHz in an {\it XMM-Newton} observation of the ultraluminous X-ray source (ULX) IC 342 X-1. The QPO has a centroid at $\nu_{QPO} = 642 \pm 20$ mHz, a coherence factor of $Q = 11.6$, and an amplitude (rms) of 4.1\% with significance of $3.6\sigma$. The energy dependence study shows that the QPO is stronger in the energy range 0.3 - 5.0 keV. A subsequent observation (6 days later) does not show any signature of the QPO in the power density spectrum. The broadband energy spectra (0.3 - 40.0 keV) obtained by quasi-simultaneous observations of {\it XMM-Newton} and {\it NuSTAR} can be well described by an absorbed {\it diskbb} plus {\it cutoffpl} model. The best fitted spectral parameters are power-law index ($\Gamma$) $\sim$ 1.1, cutoff energy ($E_c$) $\sim$ 7.9 keV and disc temperature ($kT_{in}$) $\sim$ 0.33 keV, where the QPO is detected. The unabsorbed bolometric luminosity is $\sim$ 5.34$\times$ 10$^{39}$ erg~s$^{-1}$. Comparing with the well known X-ray binary GRS 1915+105, our results are consistent with the mass of the compact object in IC 342 X-1 being in the range $\sim 20 - 65 ~ M_\odot$. We discuss the possible implications of our results.Comment: 7 pages, 3 figures (2 colour), in press (MNRAS

Constraining the mixing matrix for Standard Model with four generations: time dependent and semi-leptonic CP asymmetries in Bd0B_d^0, BsB_s and D0D^0

Using existing experimental information from K, B and D decays as well as electroweak precision tests and oblique parameters, we provide constraints and correlations on the parameters of the 4X4 mixing matrix for the Standard Model with four generations (SM4). We emphasize that some correlations amongst the parameters have important repercussions for key observables. We work with a particular representation of this matrix which is highly suited for extracting information from B-decays. Implications of the resulting constraints for time dependent and semileptonic CP asymmetries for $D^0$, $B^0$ and for $B_s$ are also given. While we show that the semi-leptonic asymmetries may be significantly enhanced in SM4 over the SM, there are important constraints and correlations with other observables. In this context we suggest that existing data from B-factories taken on $\Upsilon (4S)$ and $\Upsilon (5S)$, and in the relevant continuum be used to constrain the semi-leptonic asymmetries for $B_d$, $B_s$ as well as their linear combination. Of course, the data from the Tevatron and LHCb experiments can provide non-trivial tests of SM4 as well.Comment: 20 pages, 22 figures, few references and a footnote adde

Observational evidence for mass ejection during soft X-ray dips in GRS1915+105

We investigate the connection between the X-ray and radio properties of the Galactic microquasar GRS1915+105, by analyzing the X-ray data observed with RXTE, during the presence of a huge radio flare (~450 mJy). The X-ray lightcurve shows two dips of ~100 second duration. Detailed time resolved spectral analysis shows the existence of three spectral components: a multicolor disk-blackbody, a Comptonized component due to hot plasma and a power-law. We find that the Comptonized component is very weak during the dip. This is further confirmed by the PHA ratio of the raw data and ratio of the lightcurves in different energy bands. These results, combined with the fact that the 0.5 -- 10 Hz QPO disappears during the dip and that the Comptonized component is responsible for the QPO lead to the conclusion that during the dips the matter emitting Comptonized spectrum is ejected away. This establishes a direct connection between the X-ray and radio properties of the source.Comment: Replaced with some minor changes, corrected typos. Added Journal Re

Comments on "New Brans-Dicke Wormholes"

It is shown that the recently claimed two new Brans-Dicke wormhole solutions [F. He and S-W. Kim, Phys. Rev. D{\bf 65}, 084022 (2002)] are not really new solutions. They are just the well known Brans-Dicke solutions of Class I and II in a different conformal gauge.Comment: 4 page