A Luminous Companion to SGR 1806-20

We have obtained infrared spectra of the star suggested to be the counterpart of the soft gamma-ray repeater (SGR) 1806-20. We found strong emission lines similar to those seen in the spectra of the rare Luminous Blue Variables and B[e] stars. A He I absorption line is also seen, from which we infer a spectral type O9--B2. This classification, in combination with the minimum distance of \simgt6 kpc inferred from its extinction, makes the star one of the most luminous in the Galaxy. We infer that it is a companion to SGR 1806-20, and suggest that the presence of a companion is somehow related to the SGR phenomenon.Comment: 5 pages, AASTEX text+table and 2 PostScript figures (needs LaTeX style files aaspptwo.sty, epsf.sty and rotate.sty). In case of problems, contact [email protected]. Postscript file of complete article available on request. (Replaced because first version had one wrong reference in it

Constraints on the evolution of the relationship between H i mass and halo mass in the last 12 Gyr

The neutral hydrogen (H I) content of dark matter haloes forms an intermediate state in the baryon cycle that connects the hot shock-heated gas and cold star-forming gas in haloes. Measurement of the relationship between H I mass and halo mass therefore puts important constraints on galaxy formation models. We combine radio observations of H I in emission at low redshift (z ∼ 0) with optical/UV observations of H I in absorption at high redshift (1 < z < 4) to derive constraints on the evolution of the H I-mass–halo-mass (HIHM) relation from redshift z = 4 to 0. We find that one can model the HIHM relation similar to the stellar-mass–halo-mass (SHM) relation at z ∼ 0. At z = 0, haloes with mass 1011.7 M⊙ have the highest H I mass fraction (∼1 per cent), which is about four times smaller than their stellar-mass fraction. We model the evolution of the HIHM relation in a manner similar to that of the SHM relation. Combining this parametrization with a redshift- and mass-dependent modified Navarro–Frenk–White profile for the H I density within a halo, we draw constraints on the evolution of the HIHM relation from the observed H I column density, incidence rate and clustering bias at high redshift. We compare these findings with results from hydrodynamical simulations and other approaches in the literature and find the models to be consistent with each other at the 68 per cent confidence level

On the denseness of minimum attaining operators

Let H1,H2 be complex Hilbert spaces and T be a densely defined closed linear operator (not necessarily bounded). It is proved that for each ϵ>0, there exists a bounded operator S with ∥S∥≤ϵ such that T+S is minimum attaining. Further, if T is bounded below, then S can be chosen to be rank one

Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics

Peer reviewedPublisher PD

On associating Fast Radio Bursts with afterglows

A radio source that faded over six days, with a redshift of $z\approx0.5$ host, has been identified by Keane et al. (2016) as the transient afterglow to a fast radio burst (FRB 150418). We report follow-up radio and optical observations of the afterglow candidate and find a source that is consistent with an active galactic nucleus. If the afterglow candidate is nonetheless a prototypical FRB afterglow, existing slow-transient surveys limit the fraction of FRBs that produce afterglows to 0.25 for afterglows with fractional variation, $m=2|S_1-S_2|/(S_1+S_2)\geq0.7$, and 0.07 for $m\geq1$, at 95% confidence. In anticipation of a barrage of bursts expected from future FRB surveys, we provide a simple framework for statistical association of FRBs with afterglows. Our framework properly accounts for statistical uncertainties, and ensures consistency with limits set by slow-transient surveys.Comment: Accepted version (ApJL

Occurrence of wahoo, oriental bonito and bigeye tuna off Karwar

The occurrence of the species Wahoo, Acanthocybium solandri,landed by purse siene, was observed ffirst time in the inshore waters of the west coast other than at Vizhinjam and Colachel situated at the extreme southwest coast of India showing a northern extenision of along the west coast.The pursesiene landing of Oriental bonito, Sarda orientalis and bigeye tuna, Thunnus obesus were also monitored and illustrated

Superconductivity in 2-2-3 system Y2Ba2Cu2O(8+delta)

Researchers synthesized a new high T(sub c) 2-2-3 superconductor Y2Ba2Cu3O(8+delta) by a special preparation technique and characterized it by ac-susceptibility measurements. Diamagnetism and Meissner effect sets in at low fields and superconducting transition onsets at 90 K. The systematic investigation of the real and imaginary components of ac-susceptibility as a function of temperature and applied ac magnetic field reveals that the magnetic behavior is that of a granular type superconductor