Astronomy & Astrophysics最新文献

{"title":"Multi-epoch jet outbursts in Abell 496: Synchrotron ageing and buoyant X-ray cavities draped by warm gas filaments","authors":"F. Ubertosi, S. Giacintucci, T. Clarke, M. Markevitch, T. Venturi, E. O’Sullivan, M. Gitti","doi":"10.1051/0004-6361/202451766","DOIUrl":"https://doi.org/10.1051/0004-6361/202451766","url":null,"abstract":"<i>Aims.<i/> The galaxy cluster Abell 496 has been extensively studied in the past for the clear sloshing motion of its hot intracluster medium (ICM) on large scales, but the interplay between the central radio galaxy and the surrounding cluster atmosphere is mostly unexplored. We present a dedicated radio, X-ray, and optical study of Abell 496 with the aim being to investigate this connection.<i>Methods.<i/> We use deep radio images obtained with the Giant Metrewave Radio Telescope (GMRT) at 150, 330, and 617 MHz, the Very Large Array (VLA) at 1.4 and 4.8 GHz, and the VLA Low Band Ionosphere and Transient Experiment (VLITE) at 340 MHz, with angular resolutions ranging from 0.​″5 to 25″. Additionally, we use archival <i>Chandra<i/> and Very Large Telescope (VLT) MUSE observations.<i>Results.<i/> The radio images reveal three distinct periods of jet activity: an ongoing episode on subkiloparsec scales with an inverted radio spectrum; an older episode that produced lobes on scales of ∼20 kpc, which now have a steep spectral index (<i>α<i/> = 2.0 ± 0.1); and an even older episode that produced lobes on scales of ∼50 − 100 kpc with an ultrasteep spectrum (<i>α<i/> = 2.7 ± 0.2). Archival <i>Chandra<i/> X-ray observations show that the older and oldest episodes excavated two generations of cavities in the hot gas of the cluster. The outermost X-ray cavity has a clear mushroom-head shape, likely caused by its buoyant rise in the cluster’s potential. Cooling of the hot gas is ongoing in the innermost 20 kpc, where warm, H<i>α<i/>-bright filaments are visible in VLT-MUSE data. The H<i>α<i/>-filaments are stretched toward the mushroom-head cavity, which may have stimulated ICM cooling in its wake. We conclude by discussing our nondetection of a radio mini-halo in this vigorously sloshing but low-mass galaxy cluster.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"231 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"A survey of extremely metal-poor gas at cosmic noon","authors":"Louise Welsh, Ryan Cooke, Michele Fumagalli, Max Pettini, Gwen C. Rudie","doi":"10.1051/0004-6361/202451147","DOIUrl":"https://doi.org/10.1051/0004-6361/202451147","url":null,"abstract":"<i>Aims.<i/> We aim to study the high-precision chemical abundances of metal-poor gas clouds at cosmic noon (2 < <i>z<i/> < 4) and investigate the associated enrichment histories.<i>Methods.<i/> We analyze the abundances of four newly discovered metal-poor gas clouds utilizing observations conducted with Keck/HIRES and VLT/UVES. These systems are classified as very metal-poor (VMP), with [Fe/H] < −2.57, and one system qualifies as an extremely metal-poor (EMP) Damped Lyman-<i>α<i/> (DLA) system with [Fe/H] = −3.13 ± 0.06. In combination with new high-resolution data of two previously known EMP DLAs and 2 systems reported in the literature, we conduct a comprehensive analysis of eight of the most metal-poor gas clouds currently known. We focus on high-precision abundance measurements using the elements: C, N, O, Al, Si, and Fe.<i>Results.<i/> Our findings indicate increasing evidence of elevated [O/Fe] abundances when [Fe/H] < −3. EMP DLAs are well-modeled with a mean value of [O/Fe]<sub>cen<sub/> = +0.50 ± 0.04 and an intrinsic scatter of σ<sub>int[O/Fe]<sub/> = 0.13<sub>-0.04<sub/><sup>+0.06<sup/>. While VMP DLAs are well-modeled with [O/Fe]<sub>cen<sub/> = +0.40 ± 0.02 and <i>σ<i/><sub>int, [O/Fe]<sub/> = 0.06 ± 0.02. We further find tentative evidence of a redshift evolution of [C/O] across these most metal-poor DLAs with lower redshift systems showing elevated [C/O] ratios. Using the measured abundances, combined with a stochastic chemical enrichment model, we investigate the properties of the stellar population responsible for enriching EMP gas at cosmic noon. We find that the chemistry of these systems is best explained via the enrichment of just two massive progenitors, <i>N<i/><sub>⋆<sub/> = 2 ± 1, that ended their lives as core collapse SNe with a typical explosion energy <i>E<i/><sub>exp<sub/> = (1.6 ± 0.6)×10<sup>51<sup/> erg. These progenitors formed obeying a Salpeter-like power-law IMF, where all stars of mass greater than <i>M<i/><sub>max<sub/> = 32<sub>-4<sub/><sup>+10<sup/>M<sub>⊙<sub/> collapse directly to black holes and do not contribute to the metal enrichment.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"191 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"Connecting integrated red giant branch mass loss from asteroseismology and globular clusters","authors":"K. Brogaard, A. Miglio, W. E. van Rossem, E. Willett, J. S. Thomsen","doi":"10.1051/0004-6361/202452033","DOIUrl":"https://doi.org/10.1051/0004-6361/202452033","url":null,"abstract":"<i>Context.<i/> Asteroseismic investigations of solar-like oscillations in giant stars enable the derivation of their masses and radii. For mono-age mono-metallicity populations of stars, this allows the integrated red giant branch (RGB) mass loss to be estimated by comparing the median mass of the low-luminosity RGB stars to that of the helium-core-burning (HeCB) stars.<i>Aims.<i/> We aim to exploit quasi-mono-age mono-metallicity populations of field stars in the <i>α<i/>-rich sequence of the Milky Way (MW) to derive the integrated mass loss and its dependence on metallicity. By comparison to metal-rich globular clusters (GCs), we wish to determine whether the RGB mass loss differs in the two environments.<i>Methods.<i/> We used catalogues of asteroseismic parameters based on time-series photometry from the <i>Kepler<i/> and K2 missions cross-matched to spectroscopic information from APOGEE-DR17, photometry from 2MASS, parallaxes from Gaia DR3, and reddening maps. We determined the RGB mass loss by comparing mass distributions of RGB and HeCB stars in three metallicity bins. For two GCs, the mass loss is derived from colour–magnitude diagrams.<i>Results.<i/> We find the integrated RGB mass loss to increase with decreasing metallicity and/or mass in the [Fe/H] range from −0.9 to +0.0. At [Fe/H] = −0.50, the RGB mass loss of MW <i>α<i/>-rich field stars is compatible with that in GCs of the same metallicity.<i>Conclusions.<i/> We provide novel empirical determinations of the integrated mass loss connecting field stars and GC stars at comparable metallicities. These show that mass loss cannot be accurately described by a Reimers mass-loss law with a single value of <i>η<i/>. This should encourage further development of the theory underlying processes involved in mass loss.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"JADES: Balmer decrement measurements at redshifts 4 < z < 7","authors":"Lester Sandles, Francesco D’Eugenio, Roberto Maiolino, Tobias J. Looser, Santiago Arribas, William M. Baker, Nina Bonaventura, Andrew J. Bunker, Alex J. Cameron, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Anna de Graaff, Daniel J. Eisenstein, Kevin Hainline, Zhiyuan Ji, Benjamin D. Johnson, Gareth C. Jones, Nimisha Kumari, Erica Nelson, Michele Perna, Tim Rawle, Hans-Walter Rix, Brant Robertson, Bruno Rodríguez Del Pino, Jan Scholtz, Irene Shivaei, Renske Smit, Fengwu Sun, Sandro Tacchella, Hannah Übler, Christina C. Williams, Chris Willott, Joris Witstok","doi":"10.1051/0004-6361/202347119","DOIUrl":"https://doi.org/10.1051/0004-6361/202347119","url":null,"abstract":"We present Balmer decrement, H<i>α<i/>/H<i>β<i/>, measurements for a sample of 51 galaxies at redshifts <i>z<i/> = 4 − 7 observed with the JWST/NIRSpec micro-shutter assembly (MSA), as part of the JWST Advanced Deep Extragalactic Survey (JADES). Leveraging 28-hour long exposures and the efficiency of the prism/clear configuration (but also using information from the medium-resolution gratings), we were able to directly probe the low-mass end of the galaxy population, reaching stellar masses, <i>M<i/><sub>⋆<sub/>, as low as 10<sup>7<sup/> M<sub>⊙<sub/>. We find that the correlation between the Balmer decrement and <i>M<i/><sub>⋆<sub/> is already established at these high redshifts, indicating a rapid buildup of dust in moderately massive galaxies at such early epochs. The lowest-mass galaxies in our sample (<i>M<i/><sub>⋆<sub/> = 1 − 3 × 10<sup>7<sup/> M<sub>⊙<sub/>) display a remarkably low Balmer decrement of 2.88 ± 0.08, consistent with Case B, suggesting very little dust content. However, we warn that such a low observed Balmer decrement may also partly be a consequence of an intrinsically lower H<i>α<i/>/H<i>β<i/> resulting from the extreme conditions of the ionised gas in these primeval and unevolved systems. We further compare the Balmer decrement to continuum-derived star formation rates (SFRs), finding tentative evidence of a correlation, which likely traces the underlying connection between the SFR and the mass of cold gas. However, we note that larger samples are required to distinguish between direct and primary correlations from indirect and secondary dependences at such high redshifts.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"76 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"Collisional damping in debris discs: Only significant if collision velocities are low","authors":"Marija R. Jankovic, Mark C. Wyatt, Torsten Löhne","doi":"10.1051/0004-6361/202451080","DOIUrl":"https://doi.org/10.1051/0004-6361/202451080","url":null,"abstract":"<i>Context<i/>. Dusty debris discs around main sequence stars are observed to vary widely in terms of their vertical thickness. Their vertical structure may be affected by damping in inelastic collisions. Although kinetic models have often been used to study the collisional evolution of debris discs, these models have not yet been used to study the evolution of their vertical structure.<i>Aims<i/>. We extend an existing implementation of a kinetic model of collisional evolution to include the evolution of orbital inclinations and we use this model to study the effects of collisional damping in pre-stirred discs.<i>Methods<i/>. We evolved the number of particles of different masses, eccentricities, and inclinations using the kinetic model and used Monte Carlo simulations to calculate collision rates between particles in the disc. We considered all relevant collisional outcomes including fragmentation, cratering, and growth.<i>Results<i/>. Collisional damping is inefficient if particles can be destroyed by projectiles that are of much lower mass. If that is the case, catastrophic disruptions shape the distributions of eccentricities and inclinations, and their average values evolve slowly and at the same rate for all particle sizes.<i>Conclusions<i/>. The critical projectile-to-target mass ratio (<i>Y<i/><sub>c<sub/>) and the collisional timescale jointly determine the level of collisional damping in debris discs. If <i>Y<i/><sub>c<sub/> is much smaller than unity, a debris disc retains the inclination distribution that it is born with for much longer than the collisional timescale of the largest bodies in the disc. Such a disc should exhibit a vertical thickness that is independent of wavelength even in the absence of other physical processes. Collisional damping is efficient if <i>Y<i/><sub>c<sub/> is of order unity or larger. For millimetre-sized dust grains and common material strength assumptions, this requires collision velocities of lower than ~40 m s<sup>−1<sup/>. We discuss the implications of our findings for exo-Kuiper belts, discs around white dwarfs, and planetary rings.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"197 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"High-resolution transmission spectroscopy of the hot-Saturn HD 149026b","authors":"Federico Biassoni, Francesco Borsa, Francesco Haardt, Monica Rainer","doi":"10.1051/0004-6361/202451750","DOIUrl":"https://doi.org/10.1051/0004-6361/202451750","url":null,"abstract":"Advances in modern technology have enabled the characterization of exoplanetary atmospheres, which can be achieved by exploitation of the transmission spectroscopy technique. We performed visible (VIS) and near-infrared (NIR) high-resolution spectroscopic observations of one transit of HD 149026b, a close-in orbit sub-Saturn exoplanet by using the GIARPS configuration at the Telescopio Nazionale <i>Galileo<i/> (TNG). We first analyzed the radial-velocity data, refining the value of the projected spin-orbit obliquity (<i>λ<i/>). We then performed transmission spectroscopy, looking for absorption signals from the planetary atmosphere. We find no evidence for H<i>α<i/>, Na I D2-D1, Mg I, or Li I in the VIS and metastable helium triplet He I(2<sup>3<sup/>S) in the NIR using a line-by-line approach. The non-detection of HeI is also supported by theoretical simulations. With the use of the cross-correlation technique (CCF), we do not detect Ti I, V I, Cr I, Fe I, or VO in the visible, or indeed CH<sub>4<sub/>, CO<sub>2<sub/>, H<sub>2<sub/>O, HCN, NH<sub>3<sub/>, or VO in the NIR. Our non-detection of Ti I in the planetary atmosphere is in contrast with a previous detection. We performed injection-retrieval tests, finding that our dataset is sensitive to our Ti I model. The non-detection supports the Ti I cold-trap theory, which is valid for planets with <i>T<i/><sub>eq<sub/> < 2200 K, such as HD 149026b. Although we do not attribute it directly to the planet, we find a possibly significant Ti I signal that is highly redshifted (≃+20 km s<sup>−1<sup/> ) with respect to the planetary rest frame. Redshifted signals are also found in the Fe I and Cr I maps. While we can exclude an eccentric orbit as the cause of this redshifted Ti I signal, we investigated the possibility of material accretion falling onto the star – which is possibly supported by the presence of strong Li I in the stellar spectrum - but obtained inconclusive results. The analysis of multiple transits datasets could shed more light on this target.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"252 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"CHANG-ES","authors":"V. Heesen, T. Wiegert, J. Irwin, R. Crocker, A. Kiehn, J.-T. Li, Q. D. Wang, M. Stein, R.-J. Dettmar, M. Soida, R. Henriksen, L. Gajović, Y. Yang, M. Brüggen","doi":"10.1051/0004-6361/202451569","DOIUrl":"https://doi.org/10.1051/0004-6361/202451569","url":null,"abstract":"<i>Context.<i/> Cosmic rays may be dynamically very important in driving large-scale galactic winds. Edge-on galaxies give us an outsider’s view of radio haloes, and of their extra-planar cosmic-ray electrons and magnetic fields.<i>Aims.<i/> We present a new radio continuum imaging study of the nearby edge-on galaxy NGC 4217. We examine the distribution of extra-planar cosmic rays and magnetic fields. We observed it with both the <i>Jansky<i/> Very Large Array (JVLA) in the <i>S<i/> band (2–4 GHz) and the LOw Frequency ARray (LOFAR) at 144 MHz.<i>Methods.<i/> We measured vertical intensity profiles and exponential scale heights. We re-imaged both the JVLA and LOFAR data at matched angular resolution in order to measure radio spectral indices between 144 MHz and 3 GHz. Confusing point-like sources were subtracted prior to imaging. We then fitted intensity profiles with cosmic-ray electron advection models, using an isothermal wind model that is driven by a combination of pressure from the hot gas and cosmic rays.<i>Results.<i/> We discover a large-scale radio halo on the north-western side of the galactic disc. The morphology is reminiscent of a bubble extending up to 20 kpc from the disc. We find spectral ageing in the bubble, which allowed us to measure the advection speeds of the cosmic-ray electrons, which accelerate from 300 to 600 km s<sup>−1<sup/>. Assuming energy equipartition between the cosmic rays and the magnetic field, we estimate the bubble may have been inflated by a modest 10% of the kinetic energy injected by supernovae over its dynamical timescale of 35 Myr. While no active galactic nucleus (AGN) has been detected, such activity in the recent past cannot be ruled out.<i>Conclusions.<i/> Non-thermal bubbles with sizes of tens of kiloparsecs may be a ubiquitous feature of star-forming galaxies, and if so this would demonstrate the influence of feedback. Determining possible contributions by AGN feedback will require deeper observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"New orbital periods of high-inclination dwarf novae based on Gaia Alerts photometry","authors":"C. Sáez-Carvajal, N. Vogt, M. Zorotovic, J. García-Veas, G. Aravena-Rojas, L. Dumond, F. Figueroa-Tapia, Y. López-Bonilla, A. Rodríguez-Jiménez, I. Vega-Manubens, B. Grawe","doi":"10.1051/0004-6361/202451661","DOIUrl":"https://doi.org/10.1051/0004-6361/202451661","url":null,"abstract":"The orbital period of a cataclysmic variable stands as a crucial parameter for investigating the structure and physics of these binary systems, as well as understanding their evolution. We use photometric <i>Gaia<i/> data for dwarf novae (DNe) in the quiescent state – which are available for a number of years – to determine new orbital periods and improve or modify previously suggested period values. Two approaches are implemented for selecting high-inclination targets, either eclipsing or with ellipsoidal variations. We determine new orbital periods for 75 DNe and improve ephemerides for 27 more (three of which change significantly), contributing 9.4% of the known DNe periods of between 0.05 and 2.0 days, and doubling the number of known periods exceeding 0.44 days. Their phase-folded light curves are presented and arranged by orbital period, illustrating the transition from short-period systems, dominated by radiation from the accretion disc and the hot spot, to longer-period DNe, where the Roche-lobe-filling secondary star is the primary visual flux source. This transition – which occurs around the well-known period gap (between ∼2 and 3 hours) – is expected, as DNe with larger orbital periods typically harbour more massive donors, which contribute to the visible flux. However, this transition is not abrupt. Within the same range of periods, we observe systems dominated by ellipsoidal variations, where the companion star is clearly visible, as well as others dominated by the disc and the hot spot. The presence of some DNe with ellipsoidal variations near the lower edge of the period gap is striking, as the companions in these systems are expected to be cool low-mass M-dwarfs not visible in the light curve. This could indicate that we are observing systems where the donor star was originally much more massive and underwent significant nuclear evolution before mass-transfer began, as has been suggested previously for QZ Ser.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"170 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"Temporal and chromatic variation of polarized scattered light in the outer disk of PDS 70⋆","authors":"J. Ma, C. Ginski, R. Tazaki, C. Dominik, H. M. Schmid, F. Ménard","doi":"10.1051/0004-6361/202451614","DOIUrl":"https://doi.org/10.1051/0004-6361/202451614","url":null,"abstract":"<i>Context.<i/> PDS 70 stands out as the only system hosting a protoplanetary disk and two confirmed planets undergoing formation. It is a unique target for characterizing the dust in this type of disk.<i>Aims.<i/> We aim to accurately measure the reflected polarized intensity and quantify the variability and asymmetry for PDS 70 across multiple epochs and wavelengths in the optical and near-infrared. We present new high-contrast polarimetric differential imaging observations of PDS 70, with the <i>N<i/>_<i>R<i/> filter on SPHERE/ZIMPOL.<i>Methods.<i/> We combined the new observation with archival data of the VLT/SPHERE instrument, spanning five wavelengths (<i>N<i/>_<i>R<i/>, <i>V<i/><i>B<i/><i>B<i/>, <i>J<i/>, <i>H<i/>, and <i>K<i/><i>s<i/>) over seven epochs and eight years. For each observational epoch, we corrected the smearing effect due to finite instrument resolution, measured the azimuthal brightness profiles, and derived the intrinsic disk-integrated polarized reflectivity and the intrinsic brightness contrasts.<i>Results.<i/> With our homogeneous analysis of all available optical and near-infrared data sets of the disk around PDS 70, we find significant temporal variability of the integrated polarized reflectivity as well as the azimuthal brightness profile. This indicates variable shadowing on the outer disk by inner disk structures beyond the resolution limit of current imaging instruments. Despite these variabilities, we observe a systematic wavelength-dependent contrast between the near side and the far side of the inclined disk. These results underline the importance of considering both the shadowing effect from the inner disk and the surface geometry of the observed reflecting disk in the analysis and interpretation of observational data.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}

{"title":"Abnormal Stokes V profiles observed by Hinode in a sunspot","authors":"H. Hamedivafa, R. Rezaei","doi":"10.1051/0004-6361/202450625","DOIUrl":"https://doi.org/10.1051/0004-6361/202450625","url":null,"abstract":"<i>Context.<i/> Hidden magnetic components in a sunspot are present as small-scale structures that are absent in low-resolution observations.<i>Aims.<i/> We search for traces of the hidden magnetic components in spectro-polarimetric observations of a mature sunspot close to the disk center recorded by Hinode.<i>Methods.<i/> To find extra humps in the far blue and red lobes of Stokes <i>V<i/>, we examined the sign reversal in the second derivative of the profile in the umbra and penumbra. We also looked for the hump signature in the Stokes <i>I<i/> and the linear polarization profiles.<i>Results.<i/> The amplitudes of the humps are small compared to the main component. More than half of the profiles show one extra hump, while 21% show an extra hump on both the blue and the red lobe of the 630.15 nm line with the same magnetic polarity as the sunspot. The location of the pixels where the extra hump is seen on both lobes has a pseudo-grainy structure in the single wavelength Stokes <i>V<i/> magnetograms. This type of profile is better detected in darker parts of the penumbra, as well as in the umbra-penumbra border toward the umbra. The spectral distance between the two humps averaged over elliptical rings levels off in the umbra, decreases toward the penumbra, and levels off again there. We find no correlations between the wavelength positions of the two humps.<i>Conclusions.<i/> We discuss two scenarios that could potentially produce the simultaneously observed blue and red humps: one in which a single hidden magnetic component is responsible for the two humps, and another in which the two humps emanate from two hidden magnetic components.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}