Search results for " branch"

Measurement of the 151Sm n,gamma 152Sm cross section at n_TOF

2005

The 151 Sm(n, γ ) 152 Sm cross section, which is important for the interpretation of the 151 Sm branching as an s -process thermometer, was measured from 1 eV up to 1 MeV at the innovative n_TOF facility at CERN. Based on these data, the Maxwellian-averaged cross section at k T = 30  keV is found to be 3100±160 mb. This value can be used to constrain the thermodynamical conditions in Asymptotic Giant Branch (AGB) stars during He-shell burning.

Update on the b→s anomalies

2019

We present a brief update of our model-independent analyses of the b->s data presented in the articles published in Phys. Rev. D96 (2017) 095034 and Phys. Rev. D98 (2018) 095027 based on new data on R_K by LHCb, on R_{K^*} by Belle, and on B_{s,d}-> mu^+ mu^- by ATLAS.

AMBER observations of the AGB star RS Cap: extended atmosphere and comparison with stellar models

2011

We report on K-band VLTI/AMBER observations at medium spectral resolution ($\sim$1500) of RS Capricorni, an M6/M7III semi-regular AGB star. From the spectrally-dispersed visibilities, we measure the star diameter as a function of observing wavelength from 2.13 to 2.47 microns. We derive a Rosseland angular diameter of $7.95 \pm 0.07$ mas, which corresponds to an effective temperature of $3160 \pm 160$ K. We detect size variations of around 10% in the CO band heads, indicating strong opacity effects of CO in the stellar photosphere. We also detect a linear increase of the size as a function of wavelength, beginning at 2.29 microns. Models of the stellar atmosphere, based on the mass of the s…

A detailed spectroscopy of the carbon-rich star BD +57° 2161

2005

An LTE abundance analysis based on high-resolution spectra is presented for the carbon-rich star BD +57° 2161, whose evolutionary status is unknown. With [C/Fe] = +0.4 dex and a mean s-process overabundance of [s/Fe] ≃ +1.5 dex the peculiar atmospheric composition of BD +57° 2161 is confirmed. The 12 C/ 13 C abundance ratio was found to be about 10. The mild iron deficiency, [Fe/H] = -0.2, supports the idea that BD +57° 2161 could be an old-disk-population object. Radial-velocity measurements confirm the binary nature of the star. Therefore the peculiar chemical composition could be due to the mass transfer from the secondary - AGB star in the past. Orbital parameters are estimated for anot…

Study of Two BeppoSAX Observations of GX 340+0

2006

We present the results of two BeppoSAX broad band (0.1–200 keV) observations of the Z-source GX 340+0 comparing our results to those of a previous observation of the source. From the color–color diagram we selected three zones and extracted the source energy spectrum from each zone. We find that the model, composed by a blackbody plus a Comptonized component, absorbed by an equivalent hydrogen column of ~6 × 10 22 cm −2 , well fits the spectra in the energy range below 30 keV. At higher energies a power law component with photon index of 2.5 is observed. The associated flux decreases going from the horizontal branch to the flaring branch of the Z-track.

Self-Enrichment in Globular Clusters: Is There a Role for the Super-Asymptotic Giant Branch Stars?

2008

In four globular clusters (GCs) a non negligible fraction of stars can be interpreted only as a very helium rich population. The evidence comes from the presence of a "blue" main sequence in $\omega$ Cen and NGC 2808, and from the the very peculiar horizontal branch morphology in NGC 6441 and NGC 6388. Although a general consensus is emerging on the fact that self--enrichment is a common feature among GCs, the helium content required for these stars is Y$\simgt$0.35, and it is difficult to understand how it can be produced without any --or, for $\omega$ Cen, without a considerable--associated metal enhancement. We examine the possible role of super--AGB stars, and show that they may provide…

Radio-ejection and bump-related orbital period gap of millisecond binary pulsars

2005

The monotonic increase of the radius of low mass stars during their ascent on the red giant branch halts when they suffer a temporary contraction. This occurs when the hydrogen burning shell reaches the discontinuity in hydrogen content left from the maximum increase in the convective extension, at the time of the first dredge up, and produces a well known "bump" in the luminosity function of the red giants of globular clusters. If the giant is the mass losing component in a binary in which mass transfer occurs on the nuclear evolution time scale, this event produces a temporary stop in the mass transfer, which we will name "bump related" detachment. If the accreting companion is a neutron …

Lithium in the intermediate age cluster NGC 3680: Following Li evolution along the C-M diagram

2001

We present an analysis of high resolution spectroscopic observations (R 30 000, S=N =6 0 150) of 24 members of the intermediate age (1.5 Gyr) open cluster NGC 3680, covering all regions of the cluster colour-magnitude (C{M) diagram where cluster members are known to exist. These observations represent in many aspects challenges to our understanding of stellar interior and mixing. Four main sequence G stars have, within the errors, the same Li abundance, 0.3 dex lower than similar stars in the1 Gyr younger Hyades but comparable with those observed in the coeval cluster IC 4651. The cluster shows a clear Li-dip located around the turn-o; two stars on the upper part of the turn-o are out of th…

On the irreducibility of Hurwitz spaces of coverings with two special fibers

2012

Single and Double Beta-DecayQValues among the TripletZr96,Nb96, andMo96

2016

The atomic mass relations among the mass triplet ^{96}Zr, ^{96}Nb, and ^{96}Mo have been determined by means of high-precision mass measurements using the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyvaskyla. We report Q values for the ^{96}Zr single and double β decays to ^{96}Nb and ^{96}Mo, as well as the Q value for the ^{96}Nb single β decay to ^{96}Mo, which are Q_{β}(^{96}Zr)=163.96(13), Q_{ββ}(^{96}Zr)=3356.097(86), and Q_{β}(^{96}Nb)=3192.05(16)  keV. Of special importance is the ^{96}Zr single β-decay Q value, which has never been determined directly. The single β decay, whose main branch is fourfold unique forbidden, is an alternative decay path to the…