The SMC X-ray transient XTE J0111.2-7317 : a Be/X-ray binary in a SNR?

We report observations which confirm the identity of the optical/IR counterpart to the Rossi X-ray Timing Explorer transient source XTE J0111.2-7317. The counterpart is suggested to be a B0-B2 star (luminosity class III--V) showing an IR excess and strong Balmer emission lines. The distance derived from reddening and systemic velocity measurements puts the source in the SMC. Unusually, the source exhibits an extended asymetric H alpha structure.Comment: 5 pages, 3 figs, accepted by MNRA

Sobre la posición sistemática del género Placogyropsis Alloiteau, 1957. (Scleractinia cretácica)

Utilizando varios topotipos de la especie tipo, se estudia el género Placogyropsis Alloiteau, 1957, inscrito por el propio Alloiteau en la familia Dendrogyriidae Alloiteau, 1952. Se sugiere que no pertenece a esta familia, sino a la familia Latomeandriidae y se propone una diagnosis del género

Sobre la posición sistemática del género Placogyropsis Alloiteau, 1957. (Scleractinia cretácica)

Utilizando varios topotipos de la especie tipo, se estudia el género Placogyropsis Alloiteau, 1957, inscrito por el propio Alloiteau en la familia Dendrogyriidae Alloiteau, 1952. Se sugiere que no pertenece a esta familia, sino a la familia Latomeandriidae y se propone una diagnosis del género

Bound-state dark matter with Majorana neutrinos

We propose a simple scenario in which dark matter (DM) emerges as a stable neutral hadronic thermal relics, its stability following from an exact $\operatorname{U}(1)_D$ symmetry. Neutrinos pick up radiatively induced Majorana masses from the exchange of colored DM constituents. There is a common origin for both dark matter and neutrino mass, with a lower bound for neutrinoless double beta decay. Direct DM searches at nuclear recoil experiments will test the proposal, which may also lead to other phenomenological signals at future hadron collider and lepton flavour violation experiments.Comment: 9 pages, 4 figures. arXiv admin note: text overlap with arXiv:1803.0852

A 0535+26: Back in business

In May/June 2005, after 10 years of inactivity, the Be/X-ray binary system A 0535+26 underwent a major X-ray outburst. In this paper data are presented from 10 years of optical, IR and X-ray monitoring showing the behaviour of the system during the quiescent epoch and the lead up to the new outburst. The results show the system going through a period when the Be star in the system had a minimal circumstellar disk and then a dramatic disk recovery leading, presumably, to the latest flare up of X-ray emission. The data are interpreted in terms of the state of the disk and its interaction with the neutron star companion.Comment: Accepted for publication in MNRA

El Laboratori de física i química de l'Institut «Joan Brudieu» de la Seu d'Urgell : una perspectiva històrica

Research in a secondary school about old materials, apparatus and methods of experimental work and teaching. This research was made by two pupils before go to the University