Resultados de investigación

We study the broadband emission of Mrk 501 using multiwavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi's Large Area Telescope (LAT), NuSTAR, Swift, GASP-WEBT, and the Owens Valley Radio Observatory. Mrk 501 showed an extremely low broadband activity, which may help to unravel its baseline emission. Nonetheless, significant flux variations are detected at all wave bands, with the highest occurring at X-rays and very-high-energy (VHE) {gamma}-rays. A significant correlation (>3{sigma}) between X-rays and VHE {gamma}-rays is measured, supporting leptonic scenarios to explain the variable parts of the emission, also during low activity. This is further supported when we extend our data from 2008 to 2020, and identify, for the first time, significant correlations between the Swift X-Ray Telescope and Fermi-LAT. We additionally find correlations between high-energy {gamma}-rays and radio, with the radio lagging by more than 100 days, placing the {gamma}-ray emission zone upstream of the radio-bright regions in the jet. Furthermore, Mrk 501 showed a historically low activity in X-rays and VHE {gamma}-rays from mid-2017 to mid-2019 with a stable VHE flux (>0.2TeV) of 5% the emission of the Crab Nebula. The broadband spectral energy distribution (SED) of this 2yr long low state, the potential baseline emission of Mrk 501, can be characterized with one-zone leptonic models, and with (lepto)-hadronic models fulfilling neutrino flux constraints from IceCube. We explore the time evolution of the SED toward the low state, revealing that the stable baseline emission may be ascribed to a standing shock, and the variable emission to an additional expanding or traveling shock., This study focuses on the multiwavelength (MWL) data collected from Mrk 501 during the 4yr period spanning from the beginning of the observational period in the year 2017 until the end of the observational period in the year 2020 (MJD 57754 to MJD 59214). The coordinated observations involve a large number of instruments, including FACT, MAGIC, Fermi-LAT, Swift, GLAST-AGILE Support Program (GASP)-Whole Earth Blazar Telescope (WEBT), and OVRO. Additionally, three 10hr long observations with NuSTAR yielded a precise measurement of the falling segment of the low-energy bump, which is expected to be dominated by the highest-energy electrons at the source., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

We present a Spitzer/Herschel focused survey of the Aquila molecular clouds (d~436pc) as part of the eHOPS (extension of the Herschel orion protostar survey, or HOPS, Out to 500 ParSecs) census of nearby protostars. For every source detected in the Herschel/PACS bands, the eHOPS-Aquila catalog contains 1-850{mu}m SEDs assembled from the Two Micron All Sky Survey, Spitzer, Herschel, the Wide-field Infrared Survey Explorer, and James Clerk Maxwell Telescope/SCUBA-2 data. Using a newly developed set of criteria, we classify objects by their SEDs as protostars, pre-main-sequence stars with disks, and galaxies. A total of 172 protostars are found in Aquila, tightly concentrated in the molecular filaments that thread the clouds. Of these, 71 (42%) are Class 0 protostars, 54 (31%) are Class I protostars, 43 (25%) are flat-spectrum protostars, and four (2%) are Class II sources. Ten of the Class 0 protostars are young PACS bright red sources similar to those discovered in Orion. We compare the SEDs to a grid of radiative transfer models to constrain the luminosities, envelope densities, and envelope masses of the protostars. A comparison of the eHOPS-Aquila to the HOPS protostars in Orion finds that the protostellar luminosity functions in the two star-forming regions are statistically indistinguishable, the bolometric temperatures/envelope masses of eHOPS-Aquila protostars are shifted to cooler temperatures/higher masses, and the eHOPS-Aquila protostars do not show the decline in luminosity with evolution found in Orion. We briefly discuss whether these differences are due to biases between the samples, diverging star formation histories, or the influence of environment on protostellar evolution., This paper presents SEDs assembled from photometry and spectra covering a wavelength range of 1-850um. These come from multiple catalogs. The photometry from 1-24um is from the Spitzer Extended Solar Neighborhood Archive (SESNA) catalog compiled by R. Gutermuth et al. (2022, in preparation). The SESNA data products are publicly available through http://bit.ly/sesna2021 We use observations from the Herschel Space Observatory to extract photometry in the 70-500um wavelength region. We obtain the observations from the Herschel Science Archive. We provide the observational details such as observation IDs, observed wavelengths, proposal names, and scan velocities for these observations in Appendix A (Tables 7 and 8). The 850um photometry is from maps made with the Submillimeter Common-User Bolometer Array-2 (SCUBA-2) instrument on the James Clerk Maxwell Telescope (JCMT). We use the 850um flux maps from the JCMT Gould Belt Survey data release repository (Kirk+ 2018ApJS..238....8K ; doi: 10.11570/18.0005). When available, we complement the Spitzer photometry with the spectroscopic measurements from the Infrared Spectrograph (IRS) on Spitzer using the Short-Low (SL; 5.2-14um) and Long-Low (LL; 14-38um) modules, both having a low spectral resolution of about 90. We obtain the IRS observation from the Combined Atlas of Sources with Spitzer IRS Spectra (CASSIS). We also utilize mid-IR photometry from the Wide-field Infrared Survey Explorer (WISE). The WISE photometry is retrieved from the AllWISE catalog (see II/328) in the NASA/IPAC Infrared Science Archive (IRSA). After following the steps from Sections 4.1.2-4.1.6, we find a total of 172 protostars (Table 2), 73 pre-main-sequence (pre-MS) stars with disks (Table 9), 24 reddened pre-MS stars with disks (Table 9), 118 galaxies (Table 10), and 12 candidate protostars (Table 11)., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

One of the most reliable means of studying the stellar interior is through the apsidal motion in double line eclipsing binary systems since these systems present errors in masses, radii, and effective temperatures of only a few per cent. On the other hand, the theoretical values of the apsidal motion to be compared with the observed values depend on the stellar masses of the components and more strongly on their radii (fifth power). The main objective of this work is to make available grids of evolutionary stellar models that, in addition to the traditional parameters (e.g. age, mass, logg, Teff), also contain the necessary parameters for the theoretical study of apsidal motion and tidal evolution. This information is useful for the study of the apsidal motion in eclipsing binaries and their tidal evolution, and can also be used for the same purpose in exoplanetary systems., All models were computed using the MESA package. We consider core overshooting for models with masses >=1.2M_{sun}_. For the amount of core overshooting adopted a recent relationship for mass times core overshooting. We adopted for the mixing-length parameter {alpha}_MLT_ the value 1.84 (the solar-calibrated value). Mass loss was taken into account in two evolutionary phases. The models were followed from the pre-main sequence phase to the white dwarf (WD) stage. The evolutionary models containing age, luminosity, logg, and Teff, as well as the first three harmonics of the internal stellar structure (k_2_, k_3_, and k_4_), the radius of gyration {beta} y, and the dimensionless variable {alpha}, related to gravitational potential energy, are presented in 69 tables covering three chemical compositions: [Fe/H] = -0.50, 0.00, and 0.50. Additional models with different input physics are available., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

The phenomenon of limb-darkening is relevant to many topics in astrophysics, including the analysis of light curves of eclipsing binaries, optical interferometry, measurement of stellar diameters, line profiles of rotating stars, gravitational microlensing, and transits of extrasolar planets. Multiple parametric limb-darkening laws have been presented, and there are many available sources of theoretical limb-darkening coefficients (LDCs) calculated using stellar model atmospheres. The power-2 limb-darkening law allows a very good representation of theoretically predicted intensity profiles, but few LDCs are available for this law from spherically symmetric model atmospheres. We therefore present such coefficients in this work. We computed LDCs for the space missions Gaia, Kepler, TESS, and CHEOPS and for the passbands uvby, UBVRIJHK, and SDSS ugriz, using the PHOENIX-COND spherical models. We adopted two methods to characterise the truncation point, which sets the limb of the star: the first (M1) uses the point where the derivative dI(r)/dr is at its maximum --- where I(r) is the specific intensity as a function of the normalised radius r --- corresponding to {mu}_cri_, and the second (M2) uses the midpoint between the point {mu}_cri_ and the point located at {mu}_cri-1_. The LDCs were computed adopting the Levenberg-Marquardt least-squares minimisation method, with a resolution of 900 equally spaced {mu} points, and covering 823 model atmospheres for a solar metallicity, effective temperatures of 2300 to 12000K, logg values from 0.0 to 6.0, and microturbulent velocities of 2km/s. As our previous calculations of LDCs using spherical models included only 100{mu} points, we also updated the calculations for the four-parameter law for the passbands listed above, and compared them with those from the power-2 law. Comparisons between the quality of the fits provided by the power-2 and four-parameter laws show that the latter presents a lower merit function, chi^2^, than the former for both cases (M1 and M2). This is important when choosing the best approach for a particular science goal., We computed LDCs for the power-2 law using specific intensities from spherical model atmospheres, as such results were only previously available for a small range of stellar parameters. To this end, we used the phoenix-cond models for Te values from 2300K to 12000K, log g values from 0.0 to 6.0, solar metallicity, V_{xi}_=2.0km/s, and with 900 {mu} points. We also computed LDCs for the four-parameter law, which supersede our previous calculations based on only 100 {mu} points. For both laws, we computed coefficients for the uvby, UBVRIJHK; and SDSS ugriz passbands, and for the Gaia, Kepler, TESS, and CHEOPS photometric systems., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

Radial velocities (RVs) measured from high-resolution stellar spectra are routinely used to detect and characterise orbiting exoplanet companions. The different lines present in stellar spectra are created by several species, which are non-uniformly affected by stellar variability features such as spots or faculae. Stellar variability distorts the shape of the spectral absorption lines from which precise RVs are measured, posing one of the main problems in the study of exoplanets. In this work we aim to study how the spectral lines present in M dwarfs are independently impacted by stellar activity. We use CARMENES optical spectra of six active early- and mid-type M dwarfs to compute line-by-line RVs and study their correlation with several well-studied proxies of stellar activity. We are able to classify spectral lines based on their sensitivity to activity in five M dwarfs displaying high levels of stellar activity. We further use this line classification to compute RVs with activity-sensitive lines and less sensitive lines, enhancing or mitigating stellar activity effects in the RV time series. For specific sets of the least activity-sensitive lines, the RV scatter decreases by ~2 to 5 times the initial one, depending on the star. Finally, we compare these lines in the different stars analysed, finding the sensitivity to activity to vary from star to star. Despite the high density of lines and blends present in M dwarf stellar spectra, we find that a line-by-line approach is able to deliver precise RVs. Line-by-line RVs are also sensitive to stellar activity effects, and allow for an accurate selection of activity- insensitive lines to mitigate activity effects in RV. However, we find stellar activity effects to vary in the same insensitive lines from star to star., Tables containing information about the sensitivity to activity of the different lines, one table for each of the six stars studied in this work. Each table includes the central wavelength of the line as measured in the spectral template used, the scatter of the line RV, and the Pearson's correlation coefficient R obtained for the correlation between the line RV and the three activity indicators considered (i.e. three different R values, one per indicator). We note that even though we use the term line, these 'lines' correspond to minima in the spectrum and are the result of blends of true atomic lines or features in molecular bands., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf stars destabilized by mass accretion from a companion star, but the nature of their progenitors remains poorly understood. A way to discriminate between progenitor systems is through radio observations; a non-degenerate companion star is expected to lose material through winds or binary interaction before explosion, and the supernova ejecta crashing into this nearby circumstellar material should result in radio synchrotron emission. However, despite extensive efforts, no type Ia supernova (SN Ia) has ever been detected at radio wavelengths, which suggests a clean environment and a companion star that is itself a degenerate white dwarf star. Here we report on the study of SN 2020eyj, a SN Ia showing helium-rich circumstellar material, as demonstrated by its spectral features, infrared emission and, for the first time in a SN Ia to our knowledge, a radio counterpart. On the basis of our modelling, we conclude that the circumstellar material probably originates from a single-degenerate binary system in which a white dwarf accretes material from a helium donor star, an often proposed formation channel for SNe Ia. We describe how comprehensive radio follow-up of SN 2020eyj-like SNe Ia can improve the constraints on their progenitor systems., SN 2020eyj was first detected on 7 March 2020 UT (modified Julian date (MJD) = 58915.12, at RA=11:11:47.19, DE=29:23:06.5 (J2000). The SN was classified as a SN Ia based on a low-resolution spectrum obtained on 2 April 2020, 25 days after the first detection. We present optical photometry of SN 2020eyj in table 1., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

Light from celestial objects interacts with the molecules of the Earth's atmosphere, resulting in the production of telluric absorption lines in ground-based spectral data. Correcting for these lines, which strongly affect red and infrared wavelengths, is often needed in a wide variety of scientific applications. Here we present the template division telluric modeling (TDTM) technique, a method to accurately remove telluric absorption lines in stars that exhibit numerous intrinsic features. Based on the Earth's barycentric motion through the year, our approach is suited to disentangle telluric and stellar spectral components. By fitting a synthetic transmission model, telluric-free spectra are derived. We demonstrate the performance of the TDTM technique in correcting telluric contamination using a high-resolution optical spectral time series of the feature-rich M3.0 dwarf star Wolf 294 obtained with the CARMENES spectrograph. We apply the TDTM approach to the CARMENES survey sample, which consists of 382 targets encompassing 22357 optical and 20314 near-infrared spectra, to correct for telluric absorption. The corrected spectra are co-added to construct template spectra for each of our targets. This library of telluric-free, high signal-to-noise ratio (S/N), high-resolution (R>80000) templates comprises the most comprehensive collection of spectral M dwarf data available to date, both in terms of quantity and quality, and is available at the project's website., In Table C.1, we provide the list of stars included in the spectral template library, which features telluric-free, high S/N optical (VIS) and near-infrared (NIR) CARMENES spectra. The individual observations of each star have been corrected for telluric absorption lines using the TDTM technique. Subsequently, the individual spectra have been coadded to produce a high S/N template spectrum for each star. Details in Table C.1 include the the star identifier, coordinates, spectral type, J magnitude, the number of coadded spectra for each VIS and NIR template, and the S/N of each VIS and NIR template. The template spectra are accessible through the CARMENES GTO Data Archive (http://carmenes.cab.inta-csic.es)., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

We present an adapted version of the code HII-CHI-mistry-UV (Perez-Montero & Amorin, 2017MNRAS.467.1287P) to derive chemical abundances from emission lines in the ultraviolet, for use in narrow line regions (NLR) of Active Galactic Nuclei (AGN). We evaluate different ultraviolet emission line ratios and how different assumptions about the models, including the presence of dust grains, the shape of the incident spectral energy distribution, or the thickness of the gas envelope around the central source, may affect the final estimates as a function of the set of emission lines used. We compare our results with other published recipes for deriving abundances using the same emission lines and show that deriving the carbon-to-oxygen abundance ratio using CIII] {lambda}1909{AA} and OIII] {lambda}1665{AA} emission lines is a robust indicator of the metal content in AGN that is nearly independent of model assumptions, similar to the case of star-forming regions. Moreover, we show that a prior determination of C/O allows for a much more precise determination of the total oxygen abundance using carbon UV lines, as op- posed to assuming an arbitrary relationship between O/H and C/O, which can lead to non-negligible discrepancies., Table 2: List of UV fluxes for the sample of AGN and references. Table 3: Chemical abundances estimated from HCm-UV, using the grid of AGN models for alpha(OX)=-1.2 and the stopping criteria of 98% of free electrons. Dust-free or grain-included models are selected based on their C3C4 value., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

Quaoar is a classical trans-Neptunian object (TNO) with an area-equivalent diameter of 1100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations observed between 2018 and 2021, an inhomogeneous ring (Q1R, i.e., Quaoar's first ring) has been detected around this body. A new stellar occultation by Quaoar was observed on August 9, 2022, with the aim of improving Quaoar's shape models and the physical parameters of Q1R, while searching for additional material around the body. The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements). Quaoar's elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of 579.5+/-4.0km, apparent oblateness of 0.12+/-0.01, and area-equivalent radius of 543+/-2km. Quaoar's limb orientation is consistent with Q1R and Weywot orbiting in Quaoar's equatorial plane. The orbital radius of Q1R is refined to a value of 4057+/-6km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of ~5km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of 2520+/-20km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10km and a normal optical depth of ~0.004. Just as Q1R, it also lies outside Quaoar's classical Roche limit., Light flux of the occulted star plus the occulting object during the stellar occultation for each observer, also the best fitted model and their residuals. objects: ------------------------------------------------------------------- Planet Name H i e a mag deg AU ------------------------------------------------------------------- 50000 Quaoar 2.51 7.990425 0.04154574 43.64120180 -------------------------------------------------------------------, Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No

Because of its proximity and the large size of its black hole, M87 is one of the best targets for studying the launching mechanism of active galactic nucleus jets. Currently, magnetic fields are considered to be an essential factor in the launching and accelerating of the jet. However, current observational estimates of the magnetic field strength of the M87 jet are limited to the innermost part of the jet (<~100r_s_) or to HST-1 (~10^5^r_s_). No attempt has yet been made to measure the magnetic field strength in between. We aim to infer the magnetic field strength of the M87 jet out to a distance of several thousand r_s_ by tracking the distance-dependent changes in the synchrotron spectrum of the jet from high-resolution very long baseline interferometry observations. In order to obtain high-quality spectral index maps, quasi-simultaneous observations at 22 and 43GHz were conducted using the KVN and VERA Array (KaVA) and the Very Long Baseline Arra (VLBA). We compared the spectral index distributions obtained from the observations with a model and placed limits on the magnetic field strengths as a function of distance. The overall spectral morphology is broadly consistent over the course of these observations. The observed synchrotron spectrum rapidly steepens from alpha_22-43GHz_~-0.7 at ~2mas to alpha_22-43GHz_~-2.5 at ~6mas. In the KaVA observations, the spectral index remains unchanged until ~10mas, but this trend is unclear in the VLBA observations. A spectral index model in which nonthermal electron injections inside the jet decrease with distance can adequately reproduce the observed trend. This suggests the magnetic field strength of the jet at a distance of 2-10mas (~900r_s_~4500r_s_ in the deprojected distance) has a range of B=(0.3-1.0G)(z/2mas)^-0.73^. Extrapolating to the Event Horizon Telescope scale yields consistent results, suggesting that the majority of the magnetic flux of the jet near the black hole is preserved out to ~4500r_s_ without significant dissipation., VLBI CLEAN images of M87 in FITS format. This is a multi-epoch (Eight epochs for KaVA and five epochs for VLBA) and multi-frequency (22 and 43GHz) data set for reconstructing the spectral index profiles. When creating the FITS images, data within the (u, v) range of 33-170 mega-lambda has been used for KaVA, and 25-685 mega-lambda for VLBA. All images have been restored to the same beam size of 1.2masx1.2mas (for details, see Sect 3.1 of the paper)., Financial support from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033, No