A particle dark matter footprint on the first generation of stars

Dark matter particles with properties identical to dark matter candidates that are hinted at by several international collaborations dedicated to experimental detection of dark matter (DAMA, COGENT, CRESST and CDMS-II, although not, most notably, by LUX), and which also have a dark matter asymmetry identical to the observed baryon asymmetry (Planck and Wilkinson Microwave Anisotropy Probe), may produce a significant impact on the evolution of the first generation of low-metallicity stars. The lifetimes of these stars in different phases of stellar evolution are significantly extended, namely, in the pre-main sequence, main sequence, and red giant phases. In particular, intermediate-mass stars in the red giant phase experience significant changes in their luminosity and chemical composition. The annihilations of dark matter particles affect the interior of the star in such a way that the $3\alpha-$reaction becomes less efficient in the production of carbon and oxygen. This dark matter effect contradicts the excess of carbon and other metals observed today in stars of low mass and low metallicity. Hence, we can impose an upper limit on the dark matter halo density, and therefore on the redshift, at which the first generation of low-metallicity stars formed.Comment: 8 pages; 5 figures ; The article's link: http://iopscience.iop.org/0004-637X/786/1/25

Helioseismology and Asteroseismology: Looking for Gravitational Waves in acoustic oscillations

Current helioseismology observations allow the determination of the frequencies and surface velocity amplitudes of solar acoustic modes with exceptionally high precision. In some cases, the frequency accuracy is better than one part in a million. We show that there is a distinct possibility that the quadrupole acoustic modes of low order could be excited by gravitational waves (GWs), if the GWs have a strain amplitude in the range $10^{-20}h_{-20}$ with $h_{-20}\sim 1$ or $h_{-20}\sim 10^{3}$, as predicted by several types of GW sources, such as galactic ultracompact binaries or extreme mass ratio inspirals and coalescence of black holes. If the damping rate at low order is $10^{-3}\eta_N$ $\mu{\rm Hz}$, with $\eta_N\sim 10^{-3}$ - $1,$ as inferred from the theory of stellar pulsations, then GW radiation will lead to a maximum rms surface velocity amplitude of quadrupole modes of the order of $h_{-20}\eta_N^{-1}\sim$ $10^{-9}$ - $10^{-3}$ ${\rm cm\; s^{-1}}$, on the verge of what is currently detectable via helioseismology. The frequency and sensitivity range probed by helioseismological acoustic modes overlap with, and complement, the capabilities of eLISA for the brightest resolved ultracompact galactic binaries.Comment: 8 pages, 1 table and 4 figures, updated bibliography. The article was reviewed following the comments and suggestions made by several colleague

Gravitational Waves from Stellar Black Hole Binaries and the Impact on Nearby Sun-like Stars

We investigate the impact of resonant gravitational waves on quadrupole acoustic modes of Sun-like stars located nearby stellar black hole binary systems (such as GW150914 and GW151226). We find that the stimulation of the low-overtone modes by gravitational radiation can lead to sizeable photometric amplitude variations, much larger than the predictions for amplitudes driven by turbulent convection, which in turn are consistent with the photometric amplitudes observed in most Sun-like stars. For accurate stellar evolution models, using up-to-date stellar physics, we predict photometric amplitude variations of $1$ -- $10^3$ ppm for a solar mass star located at a distance between 1 au and 10 au from the black hole binary, and belonging to the same multi-star system. The observation of such a phenomenon will be within the reach of the Plato mission because telescope will observe several portions of the Milky Way, many of which are regions of high stellar density with a substantial mixed population of Sun-like stars and black hole binaries.Comment: 7 pages, 2 figures. ApJ, in pres

Solar neutrino physics: Sensitivity to light dark matter particles

Neutrinos are produced in several neutrino nuclear reactions of the proton-proton chain and carbon-nitrogen-oxygen cycle that take place at different radius of the Sun's core. Hence, measurements of solar neutrino fluxes provide a precise determination of the local temperature. The accumulation of non-annihilating light dark matter particles (with masses between 5 GeV and 16 GeV in the Sun produces a change in the local solar structure, namely, a decrease in the central temperature of a few percent. This variation depends on the properties of the dark matter particles, such as the mass of the particle and its spin-independent scattering cross-section on baryon-nuclei, specifically, the scattering with helium, oxygen, and nitrogen among other heavy elements. This temperature effect can be measured in almost all solar neutrino fluxes. In particular, by comparing the neutrino fluxes generated by stellar models with current observations, namely 8B neutrino fluxes, we find that non-annihilating dark matter particles with a mass smaller than 10 GeV and a spin-independent scattering cross-section with heavy baryon-nuclei larger than 3 x 10^{-37} cm^-2 produce a variation in the 8B neutrino fluxes that would be in conflict with current measurements.Comment: The article was originally published in the Astrophysical Journal. 7 pages and 4 figures http://adsabs.harvard.edu/abs/2012ApJ...752..129

Planetary influence on the young Sun's evolution: the solar neutrino probe

Recent observations of solar twin stars with planetary systems like the Sun, have uncovered that these present a peculiar surface chemical composition. This is believed to be related to the formation of earth-like planets. This suggests that twin stars have a radiative interior that is richer in heavy elements than their envelopes. Moreover, the current standard solar model does not fully agree with the helioseismology data and solar neutrino flux measurements. In this work, we find that this agreement can improve if the Sun has mass loss during the pre-main sequence, as was previously shown by other groups. Despite this better agreement, the internal composition of the Sun is still uncertain, especially for elements heavier than helium. With the goal of inferring the chemical abundance of the solar interior, we tested several chemical compositions. We found that heavy element abundances influence the sound speed and solar neutrinos equally. Nevertheless, the carbon-nitrogen-oxygen (CNO;13N, 15O and 17F) neutrino fluxes are the most affected; this is due to the fact that contrarily to proton-proton (pp, pep, 8B and 7Be) neutrino fluxes, the CNO neutrino fluxes are less dependent on the total luminosity of the star. Furthermore, if the central solar metallicity increases by 30%, as hinted by the solar twin stars observations, this new solar model predicts that 13N, 15O and 17F neutrino fluxes increase by 25%-80% relative to the standard solar model. Finally, we highlight that the next generation of solar neutrino experiments will not only put constraints on the abundances of carbon, oxygen and nitrogen, but will also give some information about their radial distribution.Comment: 8 pages, 5 Figures http://adsabs.harvard.edu/doi/10.1093/mnras/stt142

Solar constraints on asymmetric dark matter

The dark matter content of the Universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the Universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freeze-out depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels). In these \eta-parametrised asymmetric dark matter models (\eta-ADM), the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of \eta-dark matter asymmetry close to the baryon asymmetry \eta_B. Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT and CRESST experiments. Here, we constrain \eta-ADM models by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an \eta-dark matter asymmetry with a value in the interval 10^{-12}-10^{-10}, would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological \eta-asymmetric dark matter scenarios that we discuss are in agreement with the current WMAP measured values.Comment: 9 pages, 3 figure

Nearby stars as gravitational wave detectors

Sun-like stellar oscillations are excited by turbulent convection and have been discovered in some 500 main sequence and sub-giant stars and in more than 12,000 red giant stars. When such stars are near gravitational wave sources, low-order quadrupole acoustic modes are also excited above the experimental threshold of detectability, and they can be observed, in principle, in the acoustic spectra of these stars. Such stars form a set of natural detectors to search for gravitational waves over a large spectral frequency range, from $10^{-7}$ Hz to $10^{-2}$ Hz. In particular, these stars can probe the $10^{-6}$ Hz -- $10^{-4}$ Hz spectral window which cannot be probed by current conventional gravitational wave detectors, such as SKA and eLISA. The PLATO stellar seismic mission will achieve photospheric velocity amplitude accuracy of $~ {\rm cm/s}$. For a gravitational wave search, we will need to achieve accuracies of the order of $10^{-2}{\rm cm/s}$, i.e., at least one generation beyond PLATO. However, we have found that multi-body stellar systems have the ideal setup for this type of gravitational wave search. This is the case for triple stellar systems formed by a compact binary and an oscillating star. Continuous monitoring of the oscillation spectra of these stars to a distance of up to a kpc could lead to the discovery of gravitational waves originating in our galaxy or even elsewhere in the universe. Moreover, unlike experimental detectors, this observational network of stars will allow us to study the progression of gravitational waves throughout space.Comment: 10 pages, 2 figures and 1 table. Published in The Astrophysical Journa

Helioseismology with long range dark matter-baryon interactions

Assuming the existence of a primordial asymmetry in the dark sector, we study how DM-baryon long-range interactions, induced by the kinetic mixing of a new $U(1)$ gauge boson and the photon, affects the evolution of the Sun and in turn the sound speed profile obtained from helioseismology. Thanks to the explicit dependence on the exchanged momenta in the differential cross section (Rutherford-like scattering), we find that dark matter particles with a mass of $\sim 10\;{\rm GeV}$, kinetic mixing parameter of the order of $10^{-9}$ and a mediator with a mass smaller than a few MeV improve the agreement between the best solar model and the helioseismic data without being excluded by direct detection experiments. In particular, the \LUX\ detector will soon be able to either constrain or confirm our best fit solar model in the presence of a dark sector with long-range interactions that reconcile helioseismology with thermal neutrino results.Comment: v2: new section on the importance of the self-interaction added, discussion on its magnitude added, some clarifications and some references added, few typos corrected, results slightly modified; matches version published on ApJ ; article with 12 pages and 4 figure