Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Cornelis Tevel made sunspot observations during the period 1816–1836, including the Dalton Minimum. In this work, the first revision of these observations since Wolf incorporated them into his database is presented. On the one hand, the number of individual sunspots from Tevel’s drawings was counted. This is of special interest for the sunspot number reconstruction because this kind of information is not as common in historical sunspot records as the number of groups. Thus, Tevel could be considered for the future reconstruction of the sunspot number index. On the other hand, the number of groups counted according to modern sunspot group classifications finding significant misinterpretations with the number of groups assigned to Tevel in the existing databases. Tevel was a relevant sunspot observer in the Dalton Minimum. In fact, he was the observer with the highest number of groups observed in Solar Cycles 6 and 7 according to the existing sunspot group number databases. According to the raw group number recount in this work, the maximum amplitudes for Solar Cycles 6 and 7 are, respectively, 27% and 7% lower than those previously determined. Moreover, Solar Cycle 6 is the weakest solar cycle since the Maunder Minimum after applying these new counts. Group counts from Tevel’s observations were compared with those from relevant contemporary astronomers, demonstrating that Schwabe and Tevel systematically recorded a higher number of groups than Flaugergues and Derfflinger. In addition, sunspot areas and positions recorded by Tevel should be used with caution for scientific purposes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Measurements of cosmic flows enable us to test whether cosmological models can accurately describe the evolution of the density field in the nearby universe. In this paper, we measure the low-order kinematic moments of the cosmic flow field, namely bulk flow and shear moments, using the Cosmicflows-4 Tully−Fisher catalog (CF4TF). To make accurate cosmological inferences with the CF4TF sample, it is important to make realistic mock catalogs. We present the mock sampling algorithm of CF4TF. These mocks can accurately realize the survey geometry and luminosity selection function, enabling researchers to explore how these systematics affect the measurements. These mocks can also be further used to estimate the covariance matrix and errors of the power spectrum and two-point correlation function in future work. In this paper, we use the mocks to test the cosmic flow estimator and find that the measurements are unbiased. The measured bulk flow in the local universe is 376 ± 23 (error) ± 183 (cosmic variance) km s<jats:sup>−1</jats:sup> at depth <jats:italic>d</jats:italic> <jats:sub>MLE</jats:sub> = 35 Mpc <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup>, to the Galactic direction of (<jats:italic>l</jats:italic>, <jats:italic>b</jats:italic>) = (298° ± 3°, −6° ± 3°). Both the measured bulk and shear moments are consistent with the concordance Λ Cold Dark Matter cosmological model predictions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We simulate transverse oscillations in radiatively cooling coronal loops and forward-model their spectroscopic and imaging signatures, paying attention to the influence of background emission. The transverse oscillations are driven at one footpoint by a periodic velocity driver. A standing kink wave is subsequently formed and the loop cross section is deformed due to the Kelvin–Helmholtz instability, resulting in energy dissipation and heating at small scales. Besides the transverse motions, a long-period longitudinal flow is also generated due to the ponderomotive force induced slow wave. We then transform the simulated straight loop to a semi-torus loop and forward-model their spectrometer and imaging emissions, mimicking observations of Hinode/EIS and SDO/AIA. We find that the oscillation amplitudes of the intensity are different at different slit positions, but are roughly the same in different spectral lines or channels. X-t diagrams of both the Doppler velocity and the Doppler width show periodic signals. We also find that the background emission dramatically decreases the Doppler velocity, making the estimated kinetic energy two orders of magnitude smaller than the real value. Our results show that background subtraction can help recover the real oscillation velocity. These results are helpful for further understanding transverse oscillations in coronal loops and their observational signatures. However, they cast doubt on the spectroscopically estimated energy content of transverse waves using the Doppler velocity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use the stellar evolution code <jats:sc>MESA</jats:sc> to study the negative jet feedback mechanism in common envelope jet supernovae (CEJSNe), in which a neutron star (NS) launches jets in the envelope of a red supergiant (RSG). We find that the feedback reduces the mass accretion rate to be <jats:italic>χ</jats:italic> <jats:sub>j</jats:sub> ≃ 0.04–0.3 times the mass accretion rate without the operation of jets. We mimic the effect of the jets on the RSG envelope by depositing the energy that the jets carry into the envelope zones outside the NS orbit. The energy deposition inflates the envelope, therefore reducing the density in the NS vicinity, which in turn reduces the mass accretion rate in a negative feedback cycle. In calculating the above values for the negative jet feedback coefficient (the further reduction in the accretion rate) <jats:italic>χ</jats:italic> <jats:sub>j</jats:sub>, we adopt the canonical ratio of jet power to actual accretion power of 0.1, and the results of numerical simulations that show the actual mass accretion rate to be a fraction of 0.1–0.5 of the Bondi–Hoyle–Lyttleton mass accretion rate.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the first detection of the molecule cyanomethyl, CH<jats:sub>2</jats:sub>CN, in a protoplanetary disk. Until now, CH<jats:sub>2</jats:sub>CN had only been observed at earlier evolutionary stages, in the molecular clouds TMC-1, Sgr2, and L483, in the prestellar core L1544, and toward the protostar L1527. We detect six transitions of ortho-CH<jats:sub>2</jats:sub>CN toward the disk around nearby T Tauri star TW Hya. An excitation analysis reveals that the disk-averaged column density, <jats:bold> <jats:italic>N</jats:italic> </jats:bold>, for ortho-CH<jats:sub>2</jats:sub>CN is (6.3 ± 0.5) × 10<jats:sup>12</jats:sup> cm<jats:sup>−2</jats:sup>, which is rescaled to reflect a 3:1 ortho-para ratio, resulting in a total column density, <jats:bold> <jats:italic>N</jats:italic> </jats:bold> <jats:sub>tot</jats:sub>, of (8.4 ± 0.7) × 10<jats:sup>12</jats:sup> cm<jats:sup>−2</jats:sup>. We calculate a disk-average rotational temperature, <jats:bold> <jats:italic>T</jats:italic> </jats:bold> <jats:sub>rot</jats:sub> = 40 ± 5 K, while a radially resolved analysis shows that <jats:bold> <jats:italic>T</jats:italic> </jats:bold> <jats:sub>rot</jats:sub> remains relatively constant across the radius of the disk. This high rotation temperature suggests that in a static disk and if vertical mixing can be neglected, CH<jats:sub>2</jats:sub>CN is largely formed through gas-phase reactions in the upper layers of the disk, rather than solid-state reactions on the surface of grains in the disk midplane. The integrated intensity radial profiles show a ring structure consistent with molecules such as CN and DCN. We note that this is also consistent with previous lower-resolution observations of centrally peaked CH<jats:sub>3</jats:sub>CN emission toward the TW Hya disks, since the observed emission gap disappears when convolving our observations with a larger beam size. We obtain a CH<jats:sub>2</jats:sub>CN/CH<jats:sub>3</jats:sub>CN ratio ranging between 4 and 10. This high CH<jats:sub>2</jats:sub>CN/CH<jats:sub>3</jats:sub>CN is reproduced in a representative chemical model of the TW Hya disk that employs standard static disk chemistry model assumptions, i.e., without any additional tuning.</jats:p>