| 1. |
|
|
| 2. |
|
|
| 3. |
- Bernal, Ximena E., et al.
(författare)
-
Empowering Latina scientists
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 4. |
- Alonso-Albi, T., et al.
(författare)
-
Revisiting the case of R Monocerotis: Is CO removed at R
- 2018
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 617
-
Tidskriftsartikel (refereegranskat)abstract
- Context. To our knowledge, R Mon is the only B0 star in which a gaseous Keplerian disk has been detected. However, there is some controversy about the spectral type of R Mon. Some authors propose that it could be a later B8e star, where disks are more common. Aims. Our goal is to re-evaluate the R Mon spectral type and characterize its protoplanetary disk. Methods. The spectral type of R Mon has been re-evaluated using the available continuum data and UVES emission lines. We used a power-law disk model to fit previous12CO 1 →0 and 2 →1 interferometric observations and the PACS CO data to investigate the disk structure. Interferometric detections of13CO J = 1 →0, HCO+1 →0, and CN 1 →0 lines using the IRAM Plateau de Bure Interferometer (PdBI) are presented. The HCN 1 →0 line was not detected. Results. Our analysis confirms that R Mon is a B0 star. The disk model compatible with the12CO 1 →0 and 2 →1 interferometric observations falls short of predicting the observed fluxes of the 14 < Ju< 31 PACS lines; this is consistent with the scenario in which some contribution to these lines is coming from a warm envelope and/or UV-illuminated outflow walls. More interestingly, the upper limits to the fluxes of the Ju> 31 CO lines suggest the existence of a region empty of CO at R ? 20 au in the protoplanetary disk. The intense emission of the HCO+and CN lines shows the strong influence of UV photons on gas chemistry. Conclusions. The observations gathered in this paper are consistent with the presence of a transition disk with a cavity of Rin≥ 20 au around R Mon. This size is similar to the photoevaporation radius that supports the interpretation that UV photoevaporation is main disk dispersal mechanism in massive stars.
|
|
| 5. |
- Eiroa, C., et al.
(författare)
-
Exocomet signatures around the A-shell star φ Leonis?
- 2016
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 594
-
Tidskriftsartikel (refereegranskat)abstract
- We present an intensive monitoring of high-resolution spectra of the Ca ii K line in the A7IV shell star φ Leo at very short (minutes, hours), short (night to night), and medium (weeks, months) timescales. The spectra show remarkable variable absorptions on timescales of hours, days, and months. The characteristics of these sporadic events are very similar to most that are observed toward the debris disk host star β Pic, which are commonly interpreted as signs of the evaporation of solid, comet-like bodies grazing or falling onto the star. Therefore, our results suggest the presence of solid bodies around φ Leo. To our knowledge, with the exception of β Pic, our monitoring has the best time resolution at the mentioned timescales for a star with events attributed to exocomets. Assuming the cometary scenario and considering the timescales of our monitoring, our results indicate that φ Leo presents the richest environment with comet-like events known to date, second only to β Pic.
|
|
| 6. |
- Olofsson, J., et al.
(författare)
-
Dust production in the debris disk around HR4796 A
- 2019
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 630
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Debris disks are the natural by-products of the planet formation process. Scattered or polarized light observations are mostly sensitive to small dust grains that are released from the grinding down of bigger planetesimals.Aims. High angular resolution observations at optical wavelengths can provide key constraints on the radial and azimuthal distribution of the small dust grains. These constraints can help us better understand where most of the dust grains are released upon collisions.Methods. We present SPHERE/ZIMPOL observations of the debris disk around HR4796A, and we modeled the radial profiles along several azimuthal angles of the disk with a code that accounts for the effect of stellar radiation pressure. This enabled us to derive an appropriate description for the radial and azimuthal distribution of the small dust grains.Results. Even though we only modeled the radial profiles along, or close to, the semi-major axis of the disk, our best-fit model is not only in good agreement with our observations but also with previously published datasets (from near-infrared to sub-mm wavelengths). We find that the reference radius is located at 76.4 +/- 0.4 au, and the disk has an eccentricity of 0.076(-0.010)(+0.016) with the pericenter located on the front side of the disk (north of the star). We find that small dust grains must be preferentially released near the pericenter to explain the observed brightness asymmetry.Conclusions. Even though parent bodies spend more time near the apocenter, the brightness asymmetry implies that collisions happen more frequently near the pericenter of the disk. Our model can successfully reproduce the shape of the outer edge of the disk without requiring an outer planet shaping the debris disk. With a simple treatment for the effect of the radiation pressure, we conclude that the parent planetesimals are located in a narrow ring of about 3.6 au in width.
|
|
| 7. |
- Perez-Rapela, Daniel, et al.
(författare)
-
Comparison of WorldSID to PMHS kinematics in far-side impact
- 2018
-
Ingår i: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI. - 2235-3151. ; 2018-September, s. 630-654
-
Konferensbidrag (refereegranskat)abstract
- Far-side impacts represent 9.5% of all automobile crashes and 8.3% of all MAIS3+ injuries. This type of event generates loads that challenge current restraint systems by setting the occupant on an inward motion. This complex motion, influenced by a number of restraint and impact parameters, often results in a loss of shoulder-to-belt contact. Reducing the negative outcomes of this type of crash requires an ATD capable of correctly representing the kinematics and sensitivity to restraint and impact parameters. The WorldSID is the most advanced ATD for injury evaluation in near-side crashes. However, its suitability for far-side scenarios still needs to be evaluated. This study performed a parametric evaluation of the effect of restraint and impact parameters on WorldSID kinematics. A total of 19 tests in six different test configurations were conducted, matching previously published PMHS tests. The ATD motion was tracked with a 3D high-speed motion-capture system. The parameters varied were: the impact severity and direction; D-ring position; pelvic restraint; and seat belt pretensioning. The ATD response and sensitivity to parameters were evaluated and compared to previously published PMHS data. The results show discrepancies in shoulder-belt engagement, head and torso kinematics and sensitivity to initial conditions.
|
|
| 8. |
- Rebollido, I., et al.
(författare)
-
The co-existence of hot and cold gas in debris discs
- 2018
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 614
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial, protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars. This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. Aims. The goal of this paper is to investigate the presence of hot gas in the immediate surroundings of the cold-gas-bearing debris-disc central stars. Methods. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of β Pic and Fomalhaut, have been obtained from La Palma (Spain), La Silla (Chile), and La Luz (Mexico) observatories. To verify the presence of hot gas around the sample of stars, we have analysed the Ca II H&K and the Na I D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity. Results. Narrow, stable Ca II and/or Na I absorption features have been detected superimposed to the photospheric lines in 10 out of the 15 observed cold-gas-bearing debris-disc stars. Features are found at the radial velocity of the stars, or slightly blue- or red-shifted, and/or at the velocity of the local interstellar medium (ISM). Some stars also present transient variable events or absorptions extended towards red wavelengths (red wings). These are the first detections of such Ca II features in 7 out of the 15 observed stars. Although an ISM origin cannot categorically be excluded, the results suggest that the stable and variable absorptions arise from relatively hot gas located in the CS close-in environment of the stars. This hot gas is detected in at least ~80%, of edge-on cold-gas-bearing debris discs, while in only ~10% of the discs seen close to face-on. We interpret this result as a geometrical effect, and suggest that the non-detection of hot gas absorptions in some face-on systems is due to the disc inclination and likely not to the absence of the hot-gas component. This gas is likely released in physical processes related in some way to the evaporation of exocomets, evaporation of dust grains, or grain-grain collisions close to the central star.
|
|
