Pub Date : 2021-09-01DOI: 10.1051/0004-6361/202141167
H. Kaplan, Amy Simon, V. Hamilton, M. Thompson, S. Sandford, M. Barucci, E. Cloutis, J. Brucato, D. Reuter, D. Glavin, B. Clark, J. Dworkin, H. Campins, J. Emery, S. Fornasier, X. Zou, D. Lauretta
Context. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission detected an infrared absorption at 3.4 μm on near-Earth asteroid (101955) Bennu. This absorption is indicative of carbon species, including organics, on the surface. Aims. We aim to describe the composition of the organic matter on Bennu by investigating the spectral features in detail. Methods. We use a curated set of spectra acquired by the OSIRIS-REx Visible and InfraRed Spectrometer that have features near 3.4 μm (3.2 to 3.6 μm) attributed to organics. We assess the shapes and strengths of these absorptions in the context of laboratory spectra of extraterrestrial organics and analogs. Results. We find spectral evidence of aromatic and aliphatic CH bonds. The absorptions are broadly consistent in shape and depth with those associated with insoluble organic matter in meteorites. Given the thermal and space weathering environments on Bennu, it is likely that the organics have not been exposed for long enough to substantially decrease the H/C and destroy all aliphatic molecules.
{"title":"Composition of organics on asteroid (101955) Bennu","authors":"H. Kaplan, Amy Simon, V. Hamilton, M. Thompson, S. Sandford, M. Barucci, E. Cloutis, J. Brucato, D. Reuter, D. Glavin, B. Clark, J. Dworkin, H. Campins, J. Emery, S. Fornasier, X. Zou, D. Lauretta","doi":"10.1051/0004-6361/202141167","DOIUrl":"https://doi.org/10.1051/0004-6361/202141167","url":null,"abstract":"Context. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission detected an infrared absorption at 3.4 μm on near-Earth asteroid (101955) Bennu. This absorption is indicative of carbon species, including organics, on the surface. Aims. We aim to describe the composition of the organic matter on Bennu by investigating the spectral features in detail. Methods. We use a curated set of spectra acquired by the OSIRIS-REx Visible and InfraRed Spectrometer that have features near 3.4 μm (3.2 to 3.6 μm) attributed to organics. We assess the shapes and strengths of these absorptions in the context of laboratory spectra of extraterrestrial organics and analogs. Results. We find spectral evidence of aromatic and aliphatic CH bonds. The absorptions are broadly consistent in shape and depth with those associated with insoluble organic matter in meteorites. Given the thermal and space weathering environments on Bennu, it is likely that the organics have not been exposed for long enough to substantially decrease the H/C and destroy all aliphatic molecules.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"3 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84733934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01DOI: 10.1051/0004-6361/202140782
M. Rachid, N. Brunken, D. Boe, G. Fedoseev, A. Boogert, H. Linnartz
Context. In the near future, high spatial and spectral infrared (IR) data of star-forming regions obtained by the James Webb Space Telescope may reveal new solid-state features of various species, including more intriguing classes of chemical compounds. The identification of complex organic molecules (COMs) in the upcoming data will only be possible when laboratory IR ice spectra of these species under astronomically relevant conditions are available for comparison. For this purpose, systematic series of laboratory measurements are performed, providing high-resolution IR spectra of COMs. Here, spectra of pure methylamine (CH3NH2) and methylamine-containing ices are discussed. Aims. The work is aimed at characterizing the mid-IR (500–4000 cm−1, 20–2.5 μm) spectra of methylamine in pure and mixed ices to provide accurate spectroscopic data of vibrational bands that are most suited to trace this species in interstellar ices. Methods. Fourier transform infrared spectroscopy is used to record spectra of CH3NH2 in the pure form and mixed with H2O, CH4, and NH3, for temperatures ranging from 15 to 160 K. The IR spectra in combination with HeNe laser (632.8 nm) interference data of pure CH3NH2 ice was used to derive the IR band strengths of methylamine in pure and mixed ices. Results. The refractive index of amorphous methylamine ice at 15 K was determined as being 1.30± 0.01. Accurate spectroscopic information and band strength values are systematically presented for a large set of methylamine-containing ices and different temperatures. Selected bands are characterized and their use as methylamine tracers is discussed. The selected bands include the following: the CH3 antisymmetric stretch band at 2881.3 cm−1 (3.471 μm), the CH3 symmetric stretch band at 2791.9 cm−1 (3.582 μm), the CH3 antisymmetric deformation bands, at 1455.0 and 1478.6 cm−1 (6.873 and 6.761 μm), the CH3 symmetric deformation band at 1420.3 cm−1 (7.042 μm), and the CH3 rock at 1159.2 cm−1 (8.621 μm). Using the laboratory data recorded in this work and ground-based spectra of ices toward YSOs (Young Stellar Objects), upper-limits for the methylamine ice abundances are derived. In some of these YSOs, the methylamine abundance is less than 4% relative to H2O.
{"title":"Infrared spectra of complex organic molecules in astronomically relevant ice mixtures: IV. Methylamine","authors":"M. Rachid, N. Brunken, D. Boe, G. Fedoseev, A. Boogert, H. Linnartz","doi":"10.1051/0004-6361/202140782","DOIUrl":"https://doi.org/10.1051/0004-6361/202140782","url":null,"abstract":"Context. In the near future, high spatial and spectral infrared (IR) data of star-forming regions obtained by the James Webb Space Telescope may reveal new solid-state features of various species, including more intriguing classes of chemical compounds. The identification of complex organic molecules (COMs) in the upcoming data will only be possible when laboratory IR ice spectra of these species under astronomically relevant conditions are available for comparison. For this purpose, systematic series of laboratory measurements are performed, providing high-resolution IR spectra of COMs. Here, spectra of pure methylamine (CH3NH2) and methylamine-containing ices are discussed. Aims. The work is aimed at characterizing the mid-IR (500–4000 cm−1, 20–2.5 μm) spectra of methylamine in pure and mixed ices to provide accurate spectroscopic data of vibrational bands that are most suited to trace this species in interstellar ices. Methods. Fourier transform infrared spectroscopy is used to record spectra of CH3NH2 in the pure form and mixed with H2O, CH4, and NH3, for temperatures ranging from 15 to 160 K. The IR spectra in combination with HeNe laser (632.8 nm) interference data of pure CH3NH2 ice was used to derive the IR band strengths of methylamine in pure and mixed ices. Results. The refractive index of amorphous methylamine ice at 15 K was determined as being 1.30± 0.01. Accurate spectroscopic information and band strength values are systematically presented for a large set of methylamine-containing ices and different temperatures. Selected bands are characterized and their use as methylamine tracers is discussed. The selected bands include the following: the CH3 antisymmetric stretch band at 2881.3 cm−1 (3.471 μm), the CH3 symmetric stretch band at 2791.9 cm−1 (3.582 μm), the CH3 antisymmetric deformation bands, at 1455.0 and 1478.6 cm−1 (6.873 and 6.761 μm), the CH3 symmetric deformation band at 1420.3 cm−1 (7.042 μm), and the CH3 rock at 1159.2 cm−1 (8.621 μm). Using the laboratory data recorded in this work and ground-based spectra of ices toward YSOs (Young Stellar Objects), upper-limits for the methylamine ice abundances are derived. In some of these YSOs, the methylamine abundance is less than 4% relative to H2O.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"156 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74750103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-09-01DOI: 10.1051/0004-6361/202039203
L. Xing, Yuanzhi Li, L. Chang, Chuan-jun Wang, J. Bai
Context. Observations of young, low-mass, main-sequence, and zero-age main-sequence stars show evidence of a correlation between lithium abundance and chromospheric activity, albeit with a very large scatter. Fast rotation stars (including T Tauri stars, RS CVn, and BY Dra systems) show the Li I doublet at 6707.8Å in their spectra. The lithium depletion is probably related to the rotation (turbulent diffusion induced by rotation). Because the flare activity of stars increases with decreasing rotation period, a correlation can be expected between lithium abundance and chromospheric activity for active stars. Aims. The aim of this paper is to investigate the relation between lithium abundance and the Ca II H and K emission index ( R (cid:48) HK = L HK / L bol ) for a sample of active stars. Methods. Based on the high-resolution spectroscopic observations, we calculated lithium abundance for 14 chromospherically active late-type stars using the comparison of the measured Li I λ 670.8nm equivalent width with curve of growth calculations in non-local- thermodynamic-equilibrium conditions. We also searched the correlation between lithium abundance and the Ca II H & K emission index (log R (cid:48) HK ) for the 14 chromospherically active late-type stars. Results. The study of the relationship between lithium abundance and the Ca II H & K emission index (log R (cid:48) HK ) found that the activ- ity of sample stars increases with increasing lithium abundance. Next, the lithium abundance analogs progressively decrease as the rotation periods increase (rotation becomes slow) and the large values of the log R (cid:48) HK along with small values of Rossby numbers for the sample of chromospherically active stars. Conclusions. The lithium abundance (log N (Li)) versus the chromospheric activity and log N (Li) against the rotation period both indicate that the lithium abundance analogs progressively increase as the chromospheric activity index increases and/or the rotation velocity increase (rotation period becomes small) for our sample of active stars. On the other hand, the log R (cid:48) HK against the Rossby number R O shows that there is a clear trend of increasing activity with increasing rotation velocity for these active stars. Considering that the lithium abundance decreases with increasing stellar age in late-type stars, we can deduce that the chromospheric activity and the rotation velocity both decrease with the increase of stellar age for our sample active stars.
上下文。对年轻的、低质量的、主序星和零年龄的主序星的观测显示了锂丰度和色球活动之间的相关性，尽管存在很大的分散。快速旋转的恒星(包括金牛座T星，RS CVn和BY Dra系统)在其光谱中显示Li I双重态6707.8Å。锂耗尽可能与旋转(由旋转引起的湍流扩散)有关。由于恒星的耀斑活动随着旋转周期的减小而增加，因此可以预期活跃恒星的锂丰度与色球活动之间存在相关性。目标本文的目的是研究活性恒星样品中锂丰度与Ca II H和K发射指数(R (cid:48) HK = L HK / L bol)之间的关系。方法。在高分辨率光谱观测的基础上，利用Li I λ 670.8nm等效宽度与非局域热力学平衡条件下的生长曲线计算，计算了14颗色球活动晚型恒星的锂丰度。我们还研究了14颗色球活动的晚型恒星的锂丰度与Ca II H & K发射指数(log R (cid:48) HK)的相关性。结果。对锂丰度与Ca II H & K发射指数(log R (cid:48) HK)关系的研究发现，样品恒星的活性随着锂丰度的增加而增加。接下来，随着旋转周期的增加(旋转变得缓慢)，锂丰度类似物逐渐减少，并且对于色球活跃恒星的样本，log R (cid:48) HK的大值以及Rossby数的小值。结论。锂丰度(log N (Li))与色球活动的关系和log N (Li)与旋转周期的关系都表明，随着色球活动指数的增加和/或旋转速度的增加(旋转周期变小)，我们的活性恒星样本的锂丰度类似物逐渐增加。另一方面，对数R (cid:48) HK与Rossby数R O的比值表明，随着旋转速度的增加，这些活跃恒星的活动有明显的增加趋势。考虑到晚型恒星的锂丰度随恒星年龄的增加而降低，我们可以推断，对于我们的样品活性恒星，色球活动和旋转速度都随着恒星年龄的增加而降低。
{"title":"Lithium abundance in a sample of active stars: High-resolution spectrograph observation with the 1.8 m telescope","authors":"L. Xing, Yuanzhi Li, L. Chang, Chuan-jun Wang, J. Bai","doi":"10.1051/0004-6361/202039203","DOIUrl":"https://doi.org/10.1051/0004-6361/202039203","url":null,"abstract":"Context. Observations of young, low-mass, main-sequence, and zero-age main-sequence stars show evidence of a correlation between lithium abundance and chromospheric activity, albeit with a very large scatter. Fast rotation stars (including T Tauri stars, RS CVn, and BY Dra systems) show the Li I doublet at 6707.8Å in their spectra. The lithium depletion is probably related to the rotation (turbulent diffusion induced by rotation). Because the flare activity of stars increases with decreasing rotation period, a correlation can be expected between lithium abundance and chromospheric activity for active stars. Aims. The aim of this paper is to investigate the relation between lithium abundance and the Ca II H and K emission index ( R (cid:48) HK = L HK / L bol ) for a sample of active stars. Methods. Based on the high-resolution spectroscopic observations, we calculated lithium abundance for 14 chromospherically active late-type stars using the comparison of the measured Li I λ 670.8nm equivalent width with curve of growth calculations in non-local- thermodynamic-equilibrium conditions. We also searched the correlation between lithium abundance and the Ca II H & K emission index (log R (cid:48) HK ) for the 14 chromospherically active late-type stars. Results. The study of the relationship between lithium abundance and the Ca II H & K emission index (log R (cid:48) HK ) found that the activ- ity of sample stars increases with increasing lithium abundance. Next, the lithium abundance analogs progressively decrease as the rotation periods increase (rotation becomes slow) and the large values of the log R (cid:48) HK along with small values of Rossby numbers for the sample of chromospherically active stars. Conclusions. The lithium abundance (log N (Li)) versus the chromospheric activity and log N (Li) against the rotation period both indicate that the lithium abundance analogs progressively increase as the chromospheric activity index increases and/or the rotation velocity increase (rotation period becomes small) for our sample of active stars. On the other hand, the log R (cid:48) HK against the Rossby number R O shows that there is a clear trend of increasing activity with increasing rotation velocity for these active stars. Considering that the lithium abundance decreases with increasing stellar age in late-type stars, we can deduce that the chromospheric activity and the rotation velocity both decrease with the increase of stellar age for our sample active stars.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"3 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78464725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-30DOI: 10.1051/0004-6361/202141128
H. Zhao, M. Schultheis, Á. Rojas-Arriagada, A. Recio-Blanco, P. Laverny, G. Kordopatis, F. Surot
Context. Diffuse interstellar bands (DIBs) are important interstellar absorption features of which the origin is still debated. With the large data sets from modern spectroscopic surveys, background stars are widely used to show how the integrated columns of DIB carriers accumulate from the Sun to great distances. To date, studies on the kinematics of the DIB carriers are still rare. Aims. We aim to make use of the measurements from the Giraffe Inner Bulge Survey (GIBS) and the Gaia–ESO survey (GES) to study the kinematics and distance of the carrier of DIB λ8620, as well as other properties. Methods. The DIBs were detected and measured following the same procedures as in Zhao et al. (2021, A&A, 645, A14; hereafter Paper I), assuming a Gaussian profile. The median radial velocities of the DIB carriers in 38 GIBS and GES fields were used to trace their kinematics, and the median distances of the carriers in each field were estimated by the median radial velocities and two applied Galactic rotation models. Results. We successfully detected and measured DIB λ8620 in 760 of 4117 GES spectra with |b|6 10◦ and signal-to-noise ratio (S/N) > 50. Combined with the DIBs measured in GIBS spectra (Paper I), we confirmed a tight relation between EW and E(J −KS) as well as AV, with similar fitting coefficients to those found by previous works. With a more accurate sample and the consideration of the solar motion, the rest-frame wavelength of DIB λ8620 was redetermined as 8620.83 Å, with a mean fit error of 0.36 Å. We studied the kinematics of the DIB carriers by tracing their median radial velocities in each field in the local standard of rest (VLSR) and into the galactocentric frame (VGC), respectively, as a function of the Galactic longitudes. Based on the median VLSR and two Galactic rotation models, we obtained valid kinematic distances of the DIB carriers for nine GIBS and ten GES fields. We also found a linear relation between the DIB λ8620 measured in this work and the near-infrared DIB in APOGEE spectra at 1.5273μm, and we estimated the carrier abundance to be slightly lower compared to the DIB λ15273. Conclusions. We demonstrate that the DIB carriers can be located much closer to the observer than the background stars based on the following arguments: (i) qualitatively, the carriers occupy in the Galactic longitude–velocity diagram typical rotation velocities of stars in the local Galactic disk, while the background stars in the GIBS survey are mainly located in the Galactic bulge; (ii) quantitatively, all the derived kinematic distances of the DIB carriers are smaller than the median distances to background stars in each field. A linear correlation between DIB λ8620 and DIB λ15273 has been established, showing similar carrier abundances and making them both attractive for future studies of the interstellar environments.
{"title":"The diffuse interstellar band around 8620 Å. II. Kinematics and distance of the DIB carrier","authors":"H. Zhao, M. Schultheis, Á. Rojas-Arriagada, A. Recio-Blanco, P. Laverny, G. Kordopatis, F. Surot","doi":"10.1051/0004-6361/202141128","DOIUrl":"https://doi.org/10.1051/0004-6361/202141128","url":null,"abstract":"Context. Diffuse interstellar bands (DIBs) are important interstellar absorption features of which the origin is still debated. With the large data sets from modern spectroscopic surveys, background stars are widely used to show how the integrated columns of DIB carriers accumulate from the Sun to great distances. To date, studies on the kinematics of the DIB carriers are still rare. Aims. We aim to make use of the measurements from the Giraffe Inner Bulge Survey (GIBS) and the Gaia–ESO survey (GES) to study the kinematics and distance of the carrier of DIB λ8620, as well as other properties. Methods. The DIBs were detected and measured following the same procedures as in Zhao et al. (2021, A&A, 645, A14; hereafter Paper I), assuming a Gaussian profile. The median radial velocities of the DIB carriers in 38 GIBS and GES fields were used to trace their kinematics, and the median distances of the carriers in each field were estimated by the median radial velocities and two applied Galactic rotation models. Results. We successfully detected and measured DIB λ8620 in 760 of 4117 GES spectra with |b|6 10◦ and signal-to-noise ratio (S/N) > 50. Combined with the DIBs measured in GIBS spectra (Paper I), we confirmed a tight relation between EW and E(J −KS) as well as AV, with similar fitting coefficients to those found by previous works. With a more accurate sample and the consideration of the solar motion, the rest-frame wavelength of DIB λ8620 was redetermined as 8620.83 Å, with a mean fit error of 0.36 Å. We studied the kinematics of the DIB carriers by tracing their median radial velocities in each field in the local standard of rest (VLSR) and into the galactocentric frame (VGC), respectively, as a function of the Galactic longitudes. Based on the median VLSR and two Galactic rotation models, we obtained valid kinematic distances of the DIB carriers for nine GIBS and ten GES fields. We also found a linear relation between the DIB λ8620 measured in this work and the near-infrared DIB in APOGEE spectra at 1.5273μm, and we estimated the carrier abundance to be slightly lower compared to the DIB λ15273. Conclusions. We demonstrate that the DIB carriers can be located much closer to the observer than the background stars based on the following arguments: (i) qualitatively, the carriers occupy in the Galactic longitude–velocity diagram typical rotation velocities of stars in the local Galactic disk, while the background stars in the GIBS survey are mainly located in the Galactic bulge; (ii) quantitatively, all the derived kinematic distances of the DIB carriers are smaller than the median distances to background stars in each field. A linear correlation between DIB λ8620 and DIB λ15273 has been established, showing similar carrier abundances and making them both attractive for future studies of the interstellar environments.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"5 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76384997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-27DOI: 10.1007/s00159-021-00133-8
Francesca Matteucci
In this review, I will discuss the comparison between model results and observational data for the Milky Way, the predictive power of such models as well as their limits. Such a comparison, known as Galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various Galactic components (halo, bulge, thick disk and thin disk).
{"title":"Modelling the chemical evolution of the Milky Way","authors":"Francesca Matteucci","doi":"10.1007/s00159-021-00133-8","DOIUrl":"10.1007/s00159-021-00133-8","url":null,"abstract":"<div><p>In this review, I will discuss the comparison between model results and observational data for the Milky Way, the predictive power of such models as well as their limits. Such a comparison, known as Galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various Galactic components (halo, bulge, thick disk and thin disk).</p></div>","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"29 1","pages":""},"PeriodicalIF":27.8,"publicationDate":"2021-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00159-021-00133-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138514252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-25DOI: 10.1051/0004-6361/202141243
J. Dyks
Radio pulsars exhibit an enormous diversity of single pulse behaviour that involves sudden changes in pulsation mode and nulling occurring on timescales of tens or hundreds of spin periods. The pulsations appear both chaotic and quasi-regular, which has hampered their interpretation for decades. Here I show that the pseudo-chaotic complexity of single pulses is caused by the viewing of a relatively simple radio beam that has a sector structure traceable to the magnetospheric charge distribution. The slow ExB drift of the sector beam, when sampled by the line of sight, produces the classical drift-period-folded patterns known from observations. The drifting azimuthal zones of the beam produce the changes in pulsation modes and both the intermodal and sporadic nulling at timescales of beating between the drift and the star spin. The axially symmetric conal beams are thus a superficial geometric illusion, and the standard carousel model of pulsar radio beams does not apply. The beam suggests a particle flow structure that involves inward motions with possible inward emission.
{"title":"Geometry of radio pulsar signals: The origin of pulsation modes and nulling","authors":"J. Dyks","doi":"10.1051/0004-6361/202141243","DOIUrl":"https://doi.org/10.1051/0004-6361/202141243","url":null,"abstract":"Radio pulsars exhibit an enormous diversity of single pulse behaviour that involves sudden changes in pulsation mode and nulling occurring on timescales of tens or hundreds of spin periods. The pulsations appear both chaotic and quasi-regular, which has hampered their interpretation for decades. Here I show that the pseudo-chaotic complexity of single pulses is caused by the viewing of a relatively simple radio beam that has a sector structure traceable to the magnetospheric charge distribution. The slow ExB drift of the sector beam, when sampled by the line of sight, produces the classical drift-period-folded patterns known from observations. The drifting azimuthal zones of the beam produce the changes in pulsation modes and both the intermodal and sporadic nulling at timescales of beating between the drift and the star spin. The axially symmetric conal beams are thus a superficial geometric illusion, and the standard carousel model of pulsar radio beams does not apply. The beam suggests a particle flow structure that involves inward motions with possible inward emission.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"5 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89629261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-08-01DOI: 10.1051/0004-6361/202040028E
R. J. Campbell, M. Mathioudakis, M. Collados, P. Keys, A. Ramos, C. Nelson, D. Kuridze, A. Reid
We correct a typographical error in the original paper. Figures 10, 12, 14, 15, and 16 contain a table in the top right panel with four columns and four rows of values. The line of sight velocity, vLOS, values for scheme 1 inversions (in the fourth row, first column and second column) are inserted the wrong way around. The values themselves are correct, but printed in the wrong column. All other values in the tables remain unaffected, and none of the paper's discussions or conclusions are impacted. We provide corrected versions of Figs. 10, 12, 14, 15, and 16 in Figs. 1, 2, 3, 4, and 5, respectively.
{"title":"Erratum: Temporal evolution of small-scale internetwork magnetic fields in the solar photosphere (A&A (2021) 647 (A182) DOI: 10.1051/0004-6361/202040028)","authors":"R. J. Campbell, M. Mathioudakis, M. Collados, P. Keys, A. Ramos, C. Nelson, D. Kuridze, A. Reid","doi":"10.1051/0004-6361/202040028E","DOIUrl":"https://doi.org/10.1051/0004-6361/202040028E","url":null,"abstract":"We correct a typographical error in the original paper. Figures 10, 12, 14, 15, and 16 contain a table in the top right panel with four columns and four rows of values. The line of sight velocity, vLOS, values for scheme 1 inversions (in the fourth row, first column and second column) are inserted the wrong way around. The values themselves are correct, but printed in the wrong column. All other values in the tables remain unaffected, and none of the paper's discussions or conclusions are impacted. We provide corrected versions of Figs. 10, 12, 14, 15, and 16 in Figs. 1, 2, 3, 4, and 5, respectively.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"57 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73266724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-21DOI: 10.1051/0004-6361/202141157
M. Bouvier, A. L'opez-Sepulcre, C. Ceccarelli, N. Sakai, S. Yamamoto, Y.-L. Yang
The spectral energy distribution (SED) in the millimetre (mm) to centimetre (cm) range is a useful tool for characterising the dust in protostellar envelopes as well as free-free emission from the protostar and outflow. While many studies have been carried out towards low- and high-mass protostars, little exists so far about solar-type protostars in high-mass star-forming regions, which are likely to be representatives of the conditions where the Solar System was born. We focus here on the OMC-2/3 solar-type protostars, which are bounded by nearby HII regions and which are, therefore, potentially affected by the high-UV illumination. We aim to understand whether the small-scale structure ($leq$1000 au) and the evolutionary status of these solar-type protostars are affected by the nearby HII regions, as is the case for the large-scale ($leq$10$^4$ au) gas chemical composition. We used ALMA in the 1.3 mm band (246.2 GHz) to image the continuum of 16 OMC-2/3 solar-type protostars, with an angular resolution of 0.25$''$ (100 au). We completed our data with archival data from the VANDAM survey of Orion Protostars at 333 and 32.9 GHz, respectively, to construct the dust SED, extract several dust parameters and to assess whether free-free emission is contaminating their dust SED in the cm range. From the mm to cm range dust SED, we found low dust emissivity spectral indexes ($beta < 1$) for the majority of our source sample and free-free emission towards only 5 of the 16 sample sources. We were also able to confirm or correct the evolutionary status of the source sample. Finally, we did not find any dependence of the source dust parameters on their location in the OMC-2/3 filament. Our results show that the small-scale dust properties of the OMC-2/3 protostars are not affected by the high- UV illumination from the nearby HII regions.
{"title":"ORion Alma New GEneration Survey (ORANGES). I. Dust continuum and free-free emission of OMC-2/3 filament protostars","authors":"M. Bouvier, A. L'opez-Sepulcre, C. Ceccarelli, N. Sakai, S. Yamamoto, Y.-L. Yang","doi":"10.1051/0004-6361/202141157","DOIUrl":"https://doi.org/10.1051/0004-6361/202141157","url":null,"abstract":"The spectral energy distribution (SED) in the millimetre (mm) to centimetre (cm) range is a useful tool for characterising the dust in protostellar envelopes as well as free-free emission from the protostar and outflow. While many studies have been carried out towards low- and high-mass protostars, little exists so far about solar-type protostars in high-mass star-forming regions, which are likely to be representatives of the conditions where the Solar System was born. We focus here on the OMC-2/3 solar-type protostars, which are bounded by nearby HII regions and which are, therefore, potentially affected by the high-UV illumination. We aim to understand whether the small-scale structure ($leq$1000 au) and the evolutionary status of these solar-type protostars are affected by the nearby HII regions, as is the case for the large-scale ($leq$10$^4$ au) gas chemical composition. We used ALMA in the 1.3 mm band (246.2 GHz) to image the continuum of 16 OMC-2/3 solar-type protostars, with an angular resolution of 0.25$''$ (100 au). We completed our data with archival data from the VANDAM survey of Orion Protostars at 333 and 32.9 GHz, respectively, to construct the dust SED, extract several dust parameters and to assess whether free-free emission is contaminating their dust SED in the cm range. From the mm to cm range dust SED, we found low dust emissivity spectral indexes ($beta < 1$) for the majority of our source sample and free-free emission towards only 5 of the 16 sample sources. We were also able to confirm or correct the evolutionary status of the source sample. Finally, we did not find any dependence of the source dust parameters on their location in the OMC-2/3 filament. Our results show that the small-scale dust properties of the OMC-2/3 protostars are not affected by the high- UV illumination from the nearby HII regions.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"32 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76017475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-20DOI: 10.1051/0004-6361/202141591
M. Gelder, B. Tabone, E. Dishoeck, B. Godard
As material from an infalling protostellar envelope hits the forming disk, an accretion shock may develop which could (partially) alter the envelope material entering the disk. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate that emission originating from warm SO and SO$_2$ might be good tracers of such accretion shocks. The goal of this work is to test under what shock conditions the abundances of gas-phase SO and SO$_2$ increase in an accretion shock at the disk-envelope interface. Detailed shock models including gas dynamics are computed using the Paris-Durham shock code for non-magnetized J-type accretion shocks in typical inner envelope conditions. The effect of pre-shock density, shock velocity, and strength of the ultraviolet (UV) radiation field on the abundance of warm SO and SO$_2$ is explored. Warm gas-phase chemistry is efficient in forming SO under most J-type shock conditions considered. In lower-velocity (~3 km/s) shocks, the abundance of SO is increased through subsequent reactions starting from thermally desorbed CH$_4$ toward H$_2$CO and finally SO. In higher velocity (>4 km/s) shocks, both SO and SO$_2$ are formed through reactions of OH and atomic S. The strength of the UV radiation field is crucial for SO and in particular SO$_2$ formation through the photodissociation of H$_2$O. Thermal desorption of SO and SO$_2$ ice is only relevant in high-velocity (>5 km/s) shocks at high densities ($>10^7$ cm$^{-3}$). Warm emission from SO and SO$_2$ is a possible tracer of accretion shocks at the disk-envelope interface as long as a local UV field is present. Additional observations with ALMA at high-angular resolution could provide further constraints. Moreover, the James Webb Space Telescope will give access to other possible slow, dense shock tracers such as H$_2$, H$_2$O, and [S I] 25$mu$m.
{"title":"Modeling accretion shocks at the disk-envelope interface. Sulfur chemistry","authors":"M. Gelder, B. Tabone, E. Dishoeck, B. Godard","doi":"10.1051/0004-6361/202141591","DOIUrl":"https://doi.org/10.1051/0004-6361/202141591","url":null,"abstract":"As material from an infalling protostellar envelope hits the forming disk, an accretion shock may develop which could (partially) alter the envelope material entering the disk. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) indicate that emission originating from warm SO and SO$_2$ might be good tracers of such accretion shocks. The goal of this work is to test under what shock conditions the abundances of gas-phase SO and SO$_2$ increase in an accretion shock at the disk-envelope interface. Detailed shock models including gas dynamics are computed using the Paris-Durham shock code for non-magnetized J-type accretion shocks in typical inner envelope conditions. The effect of pre-shock density, shock velocity, and strength of the ultraviolet (UV) radiation field on the abundance of warm SO and SO$_2$ is explored. Warm gas-phase chemistry is efficient in forming SO under most J-type shock conditions considered. In lower-velocity (~3 km/s) shocks, the abundance of SO is increased through subsequent reactions starting from thermally desorbed CH$_4$ toward H$_2$CO and finally SO. In higher velocity (>4 km/s) shocks, both SO and SO$_2$ are formed through reactions of OH and atomic S. The strength of the UV radiation field is crucial for SO and in particular SO$_2$ formation through the photodissociation of H$_2$O. Thermal desorption of SO and SO$_2$ ice is only relevant in high-velocity (>5 km/s) shocks at high densities ($>10^7$ cm$^{-3}$). Warm emission from SO and SO$_2$ is a possible tracer of accretion shocks at the disk-envelope interface as long as a local UV field is present. Additional observations with ALMA at high-angular resolution could provide further constraints. Moreover, the James Webb Space Telescope will give access to other possible slow, dense shock tracers such as H$_2$, H$_2$O, and [S I] 25$mu$m.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"99 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90845480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-16DOI: 10.1051/0004-6361/202141317
M. Farnir, C. Pinçon, M. Dupret, A. Noels, R. Scuflaire
This study is the first of a series of papers that provide a technique to analyse the mixed-modes frequency spectra and characterise the structure of stars on the subgiant and red-giant branches. We define seismic indicators, relevant of the stellar structure and study their evolution on a grid of models. The proposed method, EGGMiMoSA, relies on the asymptotic description of mixed modes, defines initial guesses for the parameters, and uses a Levenberg-Marquardt technique to adjust the mixed-modes pattern efficiently. We follow the evolution of the mixed-modes parameters along a grid of models from the subgiant phase to the RGB bump and extend past works. We show the impact of the mass and composition on their evolution. The evolution of the period spacing $Deltapi_1$, pressure offset $epsilon_p$, gravity offset $epsilon_g$, and coupling factor $q$ as a function of $Deltanu$ is little affected by the chemical composition and it follows two different regimes depending on the evolutionary stage. On the subgiant branch, the models display a moderate core-envelope density contrast. The evolution of $Delta pi_1$, $epsilon_p$, $epsilon_g$, and $q$ thus significantly changes with the mass. Also, we demonstrate that, at fixed Z/X and with proper measurements of $Deltapi_1$ and $Deltanu$, we may unambiguously constrain the mass, radius and age of a subgiant star. Conversely, on the red-giant branch, the core-envelope density contrast becomes very large. Consequently, the evolution of $epsilon_p$, $epsilon_g$ and $q$ as a function of $Deltanu$ becomes independent of the mass. This is also true for $Delta pi_1$ in stars with masses $lesssim 1.8M_odot$ because of core electron degeneracy. This degeneracy is lifted for higher masses, again allowing for a precise measurement of the age. Overall, our computations qualitatively agree with past observed and theoretical studies.
{"title":"Asteroseismology of evolved stars with EGGMiMoSA. I. Theoretical mixed-mode patterns from the subgiant to the RGB phase","authors":"M. Farnir, C. Pinçon, M. Dupret, A. Noels, R. Scuflaire","doi":"10.1051/0004-6361/202141317","DOIUrl":"https://doi.org/10.1051/0004-6361/202141317","url":null,"abstract":"This study is the first of a series of papers that provide a technique to analyse the mixed-modes frequency spectra and characterise the structure of stars on the subgiant and red-giant branches. We define seismic indicators, relevant of the stellar structure and study their evolution on a grid of models. The proposed method, EGGMiMoSA, relies on the asymptotic description of mixed modes, defines initial guesses for the parameters, and uses a Levenberg-Marquardt technique to adjust the mixed-modes pattern efficiently. We follow the evolution of the mixed-modes parameters along a grid of models from the subgiant phase to the RGB bump and extend past works. We show the impact of the mass and composition on their evolution. The evolution of the period spacing $Deltapi_1$, pressure offset $epsilon_p$, gravity offset $epsilon_g$, and coupling factor $q$ as a function of $Deltanu$ is little affected by the chemical composition and it follows two different regimes depending on the evolutionary stage. On the subgiant branch, the models display a moderate core-envelope density contrast. The evolution of $Delta pi_1$, $epsilon_p$, $epsilon_g$, and $q$ thus significantly changes with the mass. Also, we demonstrate that, at fixed Z/X and with proper measurements of $Deltapi_1$ and $Deltanu$, we may unambiguously constrain the mass, radius and age of a subgiant star. Conversely, on the red-giant branch, the core-envelope density contrast becomes very large. Consequently, the evolution of $epsilon_p$, $epsilon_g$ and $q$ as a function of $Deltanu$ becomes independent of the mass. This is also true for $Delta pi_1$ in stars with masses $lesssim 1.8M_odot$ because of core electron degeneracy. This degeneracy is lifted for higher masses, again allowing for a precise measurement of the age. Overall, our computations qualitatively agree with past observed and theoretical studies.","PeriodicalId":785,"journal":{"name":"The Astronomy and Astrophysics Review","volume":"102 1","pages":""},"PeriodicalIF":25.8,"publicationDate":"2021-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80527269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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