We present a dataset of high resolution spectra of the Sun and ten bright stars of the domains [6297-6303] and [6361-6367] Angtr{ö}m. Solar spectra were obtained in the quiet Sun at various distances from disk centre with the ground based Meudon Solar Tower and Themis telescope (12 mÅ resolution) and with the Solar Optical Telescope (SOT) onboard the Hinode satellite (21 mÅ resolution). Spectra of 10 bright stars (magnitude \< 2) were also got with Themis at 12 mÅ resolution. These spectral domains contain the faint and forbidden OI lines (6300.31 Å and 6363.79 Å) that are useful for the research of Oxygen abundance. The spectra shown here are freely available in FITS format to the research community.
A nucleossíntese primordial é o tema central deste artigo que descreve a evolução do universo desde a sua origem até os 3 primeiros minutos após o big bang. O universo é caracterizado como um caldeirão de partículas. À medida em que o universo se expande e a temperatura diminui, ocorre uma competição entre a criação e a aniquilação das partículas, levando à formação dos primeiros núcleos leves, como hidrogênio, deutério, trítio, lítio, berílio e boro. A formação destes núcleos de massas leves é apresentada sob o ponto de vista da Física Nuclear.
Uma das ideias fundadoras da física quântica, a quantização da energia, foi exposta por Max Planck em 1900, durante uma reunião da Sociedade Alemã de Física. A publicação originada daquele seminário é apresentada nessa tradução direta do alemão para o português.
In this study, the structural and basic astrophysical parameters of the poorly studied open cluster Berkeley 6 are calculated. Analyses of the cluster are carried out using the third photometric, spectroscopic, and astrometric data release of Gaia (Gaia DR3). The membership probabilities of stars located in the direction of the cluster region are calculated by considering their astrometric data. Thus, we identified 119 physical members for Berkeley 6. The colour excess, distance, and age of the cluster are determined simultaneously on the colour-magnitude diagram. We fitted solar metallicity PARSEC isochrones to the colour-magnitude diagram by considering the most probable member stars and obtained $E(G_{\rm BP}-G_{\rm RP})$ colour excess as 0.918$\pm$0.145 mag. The distance and age of the cluster are determined as $d=2625\pm337$ pc and $t=350\pm50$ Myr, respectively.
Apresentamos uma tradução do inglês para o português brasileiro do importante artigo de Sir Robert Penrose sobre buracos negros, mais especificamente sobre a matemática da singularidade física.
Xiaofan Wang, Mikhail Leonidovich Demidov, Yuanyong Deng
et al.
In this article, we discuss an observation phenomenon where the total amount of photons in the full passband of the Birefringent lter is a constant number that is considered by removing the spectrum of the light source irrespective of the instrument transmittance. This conclusion is only noticed and considered to be correct in Huairou Solar Observing Station since 1980s. This article will give a further discussion to the question that had been proposed by the previous researchers. The article structure is organized as history (Sec. 1), experiment (Sec. 2), math (Sec. 3), and discussion (Sec. 4). This issue should be the Paseval-Theorem manifesting itself in astronomical measurement, even though we rigorously demonstrate that this photons conservation has its mathematical generality in Sec. 3.
We measured the proper motion of a $γ$-ray radio-quiet pulsar J0633+0632 using Chandra observations performed in 2009 and 2017. The measured proper motion is $53\pm15$~mas~yr$^{-1}$. We found that the proper motion direction does not follow the extension of the J0633+0632 pulsar wind nebula. The J0633+0632 pulsar wind nebula therefore can be a jet-like feature or a misaligned outflow. We also discuss a possible birth cite of the pulsar.
I explore the origin of an asymmetry of the H$α$ emission from a circumstellar (CS) shell around type IIP supernova SN 2013fs in the spectrum taken 10.3\,h after the shock breakout. A spherical model of the H$α$ emission from the CS shell that takes into account a preshock gas acceleration by the supernova radiation permits us to successfully reproduce the \ha H$α$ profile. Principal factors responsible for the H$α$ asymmetry are the high velocity of the accelerated CS preshock gas ($\sim 3000$\,km s$^{-1}$) and a low H$α$ Sobolev optical depth in a combination with an occultation of the H$α$ emission by the photosphere.
Force on proton vortices in superfluid and superconducting matter of neutron stars is calculated at vanishing stellar temperature. Both longitudinal (dissipative) and transverse (Lorentz-type) components of the force are derived in a coherent way and compared in detail with the corresponding expressions available in the literature. This allows us to resolve a controversy about the form of the Lorentz-type force component acting on proton vortices. The calculated force is a key ingredient in magnetohydrodynamics of superconducting neutron stars and is important for modeling the evolution of stellar magnetic field.
Ayushi Singh, Christopher D. Matzner, Peter H. Jumper
The virial ratio between kinetic and gravitational terms provides key insight into the balance of forces that confine a molecular cloud, but the clumpy and filamentary structures of resolved clouds make it difficult to evaluate this ratio in a consistent way. For clouds with resolved maps of column density as well as a line tracer, we demonstrate that the gravitational energy can be estimated directly from observations in a manner similar to the kinetic energy. This offers improved diagnostic power and consistency. Disentangling a cloud from foreground and background materials is a persistent challenge, for which we introduce a strategy based on Abel's transform. We provide proofs of principle using simulated clouds.
I summarize our recent calculations on quark stars (QSs), for the purpose of explaining some short gamma-ray bursts characterized by internal plateau in their early X-ray afterglow. According to the present plateau sample, the QS central engine model is demonstrated to more preferred than the original neutron star (NS) one. New QS equation of states (PMQS1, PMQS2, PMQS3) are then proposed, respecting fully the observed burst data and the mass distribution of the Galactic NS-NS systems.
Exoplanet properties depend on how well the host star is characterized. For instance, the stellar atmospheric parameters (i.e., effective temperature, surface gravity and overall metallicity) are needed to derive the stellar mass and radius by using evolutionary stellar models or empirical calibrations. I studied how the stellar uncertainties impact the determination of planetary characteristics. By using high-resolution spectra and iSpec, I evaluated how discrepancies between two different spectroscopic approaches (the equivalent method and the synthetic spectral fitting technique) can significantly affect the stellar radius estimation, hence, the exoplanet radius and its possible chemical composition.
We predict the number of black holes with stellar companions that are potentially detectable with Gaia astrometry over the course of its five-year mission. Our model estimates that nearly 2$\times$10$^5$ astrometric binaries hosting black holes and stellar companions brighter than Gaia's detection threshold, G $\sim$ 20, should be discovered with 5$σ$ sensitivity. Among these detectable binaries, systems with longer orbital periods are favored, and black hole and stellar companion masses in the range M$_{BH} \sim$ 6-10 M$_\odot$ and M$_* \sim$ 1-2 M$_\odot$, respectively, are expected to dominate.
It is understood that strong magnetic fields affect the structure of neutron stars. Nevertheless, many calculations for magnetized neutron stars are still being performed using symmetric solutions of Einstein's equations. In this conference proceeding, we review why this is not the correct procedure and we also discuss the effects of magnetic fields on the stellar population and temperature profiles.
Manuel Peimbert, Antonio Peimbert, Gloria Delgado-Inglada
We present a tutorial on the determination of the physical conditions and chemical abundances in gaseous nebulae. We also include a brief review of recent results on the study of gaseous nebulae, their relevance for the study of stellar evolution, galactic chemical evolution, and the evolution of the universe. One of the most important problems in abundance determinations is the existence of a discrepancy between the abundances determined with collisionally excited lines and those determined by recombination lines, this is called the ADF (abundance discrepancy factor) problem; we review results related to this problem. Finally, we discuss possible reasons for the large t$^2$ values observed in gaseous nebulae.
Danica Drašković, Quentin A. Parker, Warren A. Reid
et al.
We present six new planetary nebulae (PNe) discovered in the Small Magellanic Cloud (SMC) from deep UK Schmidt telescope (UKST) narrow band Halpha and broad-band short-red "SR" continuum images and confirmed spectroscopically. These 6 preliminary discoveries provide a 6% increase to the previously known SMC PN population of ~100. Once spectroscopic follow-up of all our newly identified candidates is complete, we expect to increase the total number of known SMC PNe by up to 50%. This will permit a significant improvement to determination of the SMC PN luminosity function (PNLF) and enable further insights into the chemical evolution and kinematics of the SMC PN population.
AbstractWe study the “angular momentum catastrophe” in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009) model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001), and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the “angular momentum catastrophe” can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.
We determine the oxygen density in the central zone of nine type IIP supernovae (SN~IIP) at the nebular stage using oxygen doublet [O I] 6300, 6364 Å. Combined with two available estimates these data indicate that oxygen densities on day 300 are distributed in rather narrow range $(2.3\pm1)\times10^9$ cm$^{-3}$. The result does not depend on the distance, extinction, or model assumptions. We demonstrate that the found density distribution suggests that the explosion energy of SN~IIP increases with the stellar mass.