Astronomy & Astrophysics最新文献

{"title":"Methane precipitation in ice giant atmospheres","authors":"D. Toledo, P. Rannou, P. Irwin, B. de Batz de Trenquelléon, M. Roman, V. Apestigue, I. Arruego, M. Yela","doi":"10.1051/0004-6361/202452521","DOIUrl":"https://doi.org/10.1051/0004-6361/202452521","url":null,"abstract":"<i>Context<i/>. Voyager-2 radio occultation measurements have revealed changes in the atmospheric refractivity within a 2–4 km layer near the 1.2-bar level in Uranus and the 1.6-bar level in Neptune. These changes were attributed to the presence of a methane cloud, consistent with the observation that methane concentration decreases with altitude above these levels, closely following the saturation vapor pressure. However, no clear spectral signatures of such a cloud have been detected thus far in the spectra acquired from both planets.<i>Aims<i/>. We examine methane cloud properties in the atmospheres of the ice giants, including vertical ice distribution, droplet radius, precipitation rates, timescales, and total opacity, employing microphysical simulations under different scenarios.<i>Methods<i/>. We used a one-dimensional (1D) cloud microphysical model to simulate the formation of methane clouds in the ice giants. The simulations include the processes of nucleation, condensation, coagulation, evaporation, and precipitation, with vertical mixing simulated using an eddy-diffusion profile (<i>K<i/><sub>eddy<sub/>).<i>Results<i/>. Our simulations show cloud bases close to 1.24 bars in Uranus and 1.64 bars in Neptune, with droplets up to 100 µm causing high settling velocities and precipitation rates (∼370 mm per Earth year). The high settling velocities limit the total cloud opacity, yielding values at 0.8 µm of ∼0.19 for Uranus and ∼0.35 for Neptune, using <i>K<i/><sub>eddy<sub/> = 0.5 m<sup>2<sup/> s<sup>−1<sup/> and a deep methane mole fraction (<i>μ<i/><sub>CH<sub>4<sub/><sub/>) of 0.04. In addition, lower <i>K<i/><sub>eddy<sub/> or <i>μ<i/><sub>CH<sub>4<sub/><sub/> values result in smaller opacities. Methane supersaturation is promptly removed by condensation, controlling the decline in <i>μ<i/><sub>CH<sub>4<sub/><sub/> with altitude in the troposphere. However, the high settling velocities prevent the formation of a permanent thick cloud. Stratospheric hazes made of ethane or acetylene ice are expected to evaporate completely before reaching the methane condensation level. Since hazes are required for methane heterogeneous nucleation, this suggests either a change in the solid phase properties of the haze particles, inhibiting evaporation, or the presence of photochemical hazes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124712","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":"MOA-2022-BLG-033Lb, KMT-2023-BLG-0119Lb, and KMT-2023-BLG-1896Lb: Three low mass-ratio microlensing planets detected through dip signals","authors":"Cheongho Han, Ian A. Bond, Youn Kil Jung, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Kyu-Ha Hwang, Chung-Uk Lee, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Hongjing Yang, Weicheng Zang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Hirosame Fujii, Akihiko Fukui, Ryusei Hamada, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Rintaro Kirikawa, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Takahiro Sumi, Daisuke Suzuki, Mio Tomoyoshi, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama, Kansuke Yamashita","doi":"10.1051/0004-6361/202452027","DOIUrl":"https://doi.org/10.1051/0004-6361/202452027","url":null,"abstract":"<i>Aims<i/>. We examined the anomalies in the light curves of the lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT- 2023-BLG-1896. These anomalies share similar traits: they occur near the peak of moderately to highly magnified events and display a distinct short-term dip feature.<i>Methods<i/>. We conducted detailed modeling of the light curves to uncover the nature of the anomalies. This modeling revealed that all signals originated from planetary companions to the primary lens. The planet-to-host mass ratios are very low: <i>q<i/> ~ 7.5 × 10<sup>−5<sup/> for MOA-2022-BLG-033, <i>q<i/> ~ 3.6 × 10<sup>−4<sup/> for KMT-2023-BLG-0119, and <i>q<i/> ~ 6.9 × 10<sup>−5<sup/> for KMT-2023-BLG-1896. The anomalies occurred as the source passed through the negative deviation region behind the central caustic along the planet-host axis. The solutions are subject to a common inner-outer degeneracy, which results in varying estimations of the projected planet-host separation. For KMT-2023-BLG-1896, although the planetary scenario provides the best explanation for the anomaly, the binary companion scenario is possible.<i>Results<i/>. We estimated the physical parameters of the planetary systems through Bayesian analyses based on the lensing observables. While the event timescale was measured for all events, the angular Einstein radius was not measured for any. Additionally, the microlens parallax was measured for MOA-2022-BLG-033. The analysis identifies MOA-2022-BLG-033L as a planetary system with an ice giant with a mass of approximately 12 times that of Earth orbiting an early M dwarf star. The companion of KMT-2023-BLG-1896L is also an ice giant, with a mass of around 16 Earth masses, orbiting a mid-K-type main-sequence star. The companion of KMT-2023-BLG- 0119L, which has a mass around that of Saturn, orbits a mid-K-type dwarf star. The lens for MOA-2022-BLG-033 is highly likely to be located in the disk, whereas for the other events the probabilities of the lens being in the disk or the bulge are roughly equal.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"85 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124859","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":"CO2-rich protoplanetary discs as a probe of dust radial drift and trapping","authors":"Andrew D. Sellek, Marissa Vlasblom, Ewine F. van Dishoeck","doi":"10.1051/0004-6361/202451137","DOIUrl":"https://doi.org/10.1051/0004-6361/202451137","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. Mid-infrared spectra indicate considerable chemical diversity in the inner regions of protoplanetary discs, with some being H&lt;sub&gt;2&lt;sub/&gt;O-dominated and others CO&lt;sub&gt;2&lt;sub/&gt;-dominated. Sublimating ices from radially drifting dust grains are often invoked to explain some of this diversity, particularly with regards to H&lt;sub&gt;2&lt;sub/&gt;O-rich discs.&lt;i&gt;Aims&lt;i/&gt;. We model the contribution made by radially drifting dust grains to the chemical diversity of the inner regions of protoplanetary discs. These grains transport ices – including those of H&lt;sub&gt;2&lt;sub/&gt;O and CO&lt;sub&gt;2&lt;sub/&gt; – inwards to snow lines, thus redistributing the molecular content of the disc. As radial drift can be impeded by dust trapping in pressure maxima, we also explore the difference between smooth discs and those with dust traps due to gas gaps, quantifying the effects of gap location and formation time.&lt;i&gt;Methods&lt;i/&gt;. We used a 1D protoplanetary disc evolution code to model the chemical evolution of the inner disc resulting from gas viscous evolution and dust radial drift. We post-processed these models to produce synthetic spectra, which we analyse with 0D LTE slab models to understand how this evolution may be expressed observationally.&lt;i&gt;Results&lt;i/&gt;. Discs evolve through an initial H&lt;sub&gt;2&lt;sub/&gt;O-rich phase as a result of sublimating ices, followed by a CO&lt;sub&gt;2&lt;sub/&gt; -rich phase as H&lt;sub&gt;2&lt;sub/&gt;O vapour is advected onto the star and CO&lt;sub&gt;2&lt;sub/&gt; is advected into the inner disc from its snow line. The introduction of traps hastens the transition between the phases, temporarily raising the CO&lt;sub&gt;2&lt;sub/&gt;/H&lt;sub&gt;2&lt;sub/&gt;O ratio. However, whether or not this evolution can be traced in observations depends on the contribution of dust grains to the optical depth. If the dust grains become coupled to the gas after crossing the H&lt;sub&gt;2&lt;sub/&gt;O snow line – for example if bare grains fragment more easily than icy grains – then the dust that delivers the H&lt;sub&gt;2&lt;sub/&gt;O adds to the continuum optical depth and obscures the H&lt;sub&gt;2&lt;sub/&gt;O, preventing any evolution in its visible column density. However, the CO&lt;sub&gt;2&lt;sub/&gt;/H&lt;sub&gt;2&lt;sub/&gt;O visible column density ratio is only weakly sensitive to assumptions about the dust continuum obscuration, making it a more suitable tracer of the impact of transport on chemistry than either individual column density. This can be investigated with spectra that show weak features that probe deep enough into the disc. The least effective gaps are those that open close to the star on timescales competitive with dust growth and drift as they block too much CO&lt;sub&gt;2&lt;sub/&gt;; gaps opened later or further out lead to higher CO&lt;sub&gt;2&lt;sub/&gt;/H&lt;sub&gt;2&lt;sub/&gt;O. This leads to a potential correlation between CO&lt;sub&gt;2&lt;sub/&gt;/H&lt;sub&gt;2&lt;sub/&gt;O and gap location that occurs on million-year timescales for fiducial parameters.&lt;i&gt;Conclusions&lt;i/&gt;. Radial drift, especially when combined with dust trapping, produces CO&lt;sub&gt;2&lt;sub/&gt; -rich discs on timescales longer than the vi","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"15 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124654","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":"Deep high-resolution L band spectroscopy in the β Pictoris planetary system★","authors":"Markus Janson, Jonas Wehrung-Montpezat, Ansgar Wehrhahn, Alexis Brandeker, Gayathri Viswanath, Paul Mollière, Thomas Stolker","doi":"10.1051/0004-6361/202452411","DOIUrl":"https://doi.org/10.1051/0004-6361/202452411","url":null,"abstract":"The <i>β<i/> Pictoris system, with its two directly imaged planets <i>β<i/> Pic b and <i>β<i/> Pic c and its well characterised debris disk, is a prime target for detailed characterisation of young planetary systems. Here, we present high-resolution and high-contrast LM band spectroscopy with CRIRES+ of the system, primarily for the purpose of atmospheric characterisation of <i>β<i/> Pic b. We developed methods for determining slit geometry and wavelength calibration based on telluric absorption and emission lines, as well as methods for point spread function (PSF) modelling and subtraction, and artificial planet injection, in order to extract and characterise planet spectra at a high signal-to-noise ratio (<i>S<i/>/<i>N<i/>) and spectral fidelity. Through cross-correlation with model spectra, we detected H<sub>2<sub/>O absorption for planet b in each of the 13 individual observations spanning four different spectral settings. This provides a clear confirmation of previously detected water absorption, and allowed us to derive an exquisite precision on the rotational velocity of <i>β<i/> Pic b, <i>υ<i/><sub>rot<sub/> = 20.36 ± 0.31 km/s, which is consistent within error bars with previous determinations. We also observed a tentative H<sub>2<sub/>O cross-correlation peak at the expected position and velocity of planet c; the feature is however not at a statistically significant level. Despite a higher sensitivity to SiO than earlier studies, we do not confirm a tentative SiO feature previously reported for planet b. When combining data from different epochs and different observing modes for the strong H<sub>2<sub/>O feature of planet b, we find that the <i>S<i/>/<i>N<i/> grows considerably faster when sets of different spectral settings are combined, compared to when multiple data sets of the same spectral setting are combined. This implies that maximising spectral coverage is often more important than maximising integration depth when investigating exoplanetary atmospheres using cross-correlation techniques.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"63 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124657","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":"Surface brightness-colour relations of dwarf stars from detached eclipsing binaries","authors":"D. Graczyk, G. Pietrzyński, C. Galan, N. Miller, W. Gieren, B. Zgirski, G. Hajdu, M. Kałuszyński, R. Chini, A. Gallenne, M. Górski, P. Karczmarek, P. Kervella, M. Kicia, P. F. L. Maxted, N. Nardetto, W. Narloch, B. Pilecki, W. Pych, G. Rojas García, R. Smolec, K. Suchomska, M. Taormina, P. Wielgórski","doi":"10.1051/0004-6361/202452065","DOIUrl":"https://doi.org/10.1051/0004-6361/202452065","url":null,"abstract":"<i>Aims<i/>. Surface brightness-colour relations (SBCRs) are useful tools for predicting the angular diameters of stars. They offer the possibility to calculate precise spectrophotometric distances based on the eclipsing binary method or the Baade–Wesselink method. Double-lined detached eclipsing binary stars (SB2 DEBs), with precisely known trigonometric parallaxes, allow us to calibrate SBCRs with a high level of precision. To improve such calibrations, it is important to supplement the sample of suitable eclipsing binaries with precisely determined physical parameters.<i>Methods<i/>. We selected ten SB2 DEBs within 0.8 kpc of the Sun, which feature components of spectral types ranging from B9 to K3. We analysed their TESS and <i>Kepler<i/> K2 space-based photometry simultaneously with the radial velocities derived from HARPS spectra using the Wilson–Devinney code. The disentangled spectra of DEBs were used to derive atmospheric parameters of their components by applying the GSSP code. The direct effective temperatures were also calculated using spectral energy distribution analysis. The O–C diagrams of the minima times were investigated to detect long-term period changes or apsidal motions.<i>Results<i/>. Most of the systems are composed of significantly unequal components, with mass ratios as low as ~0.5. We derived precise masses, radii, and surface temperatures for them, along with their metallicities. The average precision of mass and radii determinations is 0.3% and 1.4%, respectively, for the surface temperature. The spectroscopic and photometric temperatures of the components are usually consistent to within 100 K, but in some systems, the difference is much larger. The components of HD 149946 show the highest difference (up to 400 K), while the atmospheric models favour different surface metallicities. We also provide an updated calibration of the equivalent width of the interstellar sodium D1 line and the reddening E(<i>B<i/>–<i>V<i/>).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"55 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124650","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":"Signs of ‘Everything Everywhere All at Once’ formation in low-surface-brightness globular-cluster-rich dwarf galaxies","authors":"A. Ferré-Mateu, J. Gannon, D. A. Forbes, A. J. Romanowsky, M. L. Buzzo, J. P. Brodie","doi":"10.1051/0004-6361/202453393","DOIUrl":"https://doi.org/10.1051/0004-6361/202453393","url":null,"abstract":"<i>Context.<i/> Only two ultra-diffuse galaxies (UDGs) have spatially resolved stellar population properties, showing flat to rising metallicity profiles, indicative of a different formation pathway than most dwarf galaxies. The scarcity of other low-surface-brightness (LSB) dwarfs with a similar analysis prevents a deeper understanding of this behaviour.<i>Aims.<i/> We investigated the radial profiles of the ages, metallicities, and star formation histories of four globular cluster (GC)-rich LSB dwarfs, newly observed as part of the ‘Analysis of Galaxies At The Extremes’ (AGATE) collaboration. DFX1 and DF07 are bona fide UDGs, while PUDG-R27 and VCC 1448 are ‘nearly UDGs’. Comparing their and DF44’s properties to simulations, we aim to reveal their formation pathways.<i>Methods.<i/> We used the full-spectral-fitting code pPXF to fit different spectra extracted in annular apertures in a bid to recover the stellar population properties and compute their gradients. We compared these results with a sample of literature classical dwarfs and simulations, in particular simulated UDGs.<i>Results.<i/> Our five LSB dwarfs have flat age and flat to rising metallicity profiles. Such age gradients are compatible with those of classical dwarfs (observed and from cosmological simulations), but the metallicity gradient diverges. All of our LSB dwarfs (except for PUDG-R27, which shows a pronounced increasing metallicity) are compatible with being on the extreme tail of the age–metallicity gradient relation, suggesting a coeval formation, forming the galaxy all at once.<i>Conclusions.<i/> This sample of GC-rich LSB dwarfs with spatially resolved properties provides further evidence that they follow a different formation path than classical dwarfs. However, larger samples with higher-S/N spectra and varying amounts of GC richness are required to set robust constraints on the formation pathways of LSB dwarf galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"40 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124653","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":"The 4 m International Liquid Mirror Telescope: Construction, operation, and science","authors":"J. Surdej, P. Hickson, K. Misra, D. Banerjee, B. Ailawadhi, T. Akhunov, E. Borra, M. Dubey, N. Dukiya, S. Filali, J. Hellemeier, M. Kharayat, B. Kumar, H. Kumar, M. Kumar, T. S. Kumar, P. Kumari, V. Negi, A. Pospieszalska-Surdej, S. Prabhavu, B. Pradhan, K. Pranshu, H. Rawat, B. K. Reddy, A. Sasidharan Pillai, K. Singh, S. Tremblay, S. Turakhia, S. Vijay","doi":"10.1051/0004-6361/202452667","DOIUrl":"https://doi.org/10.1051/0004-6361/202452667","url":null,"abstract":"The International Liquid Mirror Telescope (ILMT) project was motivated by the need for an inexpensive 4 metre diameter optical telescope that could be devoted entirely to astronomical surveys. Its scientific programmes include the detection and study of transients, variable objects, asteroids, comets, space debris and low surface brightness galaxies. To this end, a collaboration was formed between the Institute of Astrophysics and Geophysics (Liège University, Belgium), several Canadian universities (University of British Columbia, Laval University, University of Montreal, University of Toronto, York University, University of Victoria) and the Aryabhatta Research Institute of Observational Sciences (ARIES, India). After several years of design work in Belgium and construction in India on the ARIES Devasthal site, the telescope saw its first light on 29 April 2022. Its commissioning phase lasted from May 2022 until June 2023 (beginning of the monsoon). The ILMT was inaugurated on 21 March 2023 and has been in regular operation since October 2023. The telescope continuously observes the sky passing at the zenith using the SDSS <i>ɡ<i/>′, <i>r<i/>′, and <i>i<i/>′ filters. This paper describes the ILMT, its operation, performance and shows some initial results.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"134 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124862","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":"Dipolar fluence distribution of statistically isotropic FERMI gamma-ray bursts","authors":"Maria Lopes, Armando Bernui, Wiliam S. Hipólito-Ricaldi, Camila Franco, Felipe Avila","doi":"10.1051/0004-6361/202452181","DOIUrl":"https://doi.org/10.1051/0004-6361/202452181","url":null,"abstract":"<i>Aims.<i/> We investigated the large-angle distribution of the gamma-ray bursts (GRBs) from the updated FERMI/GBM catalog to probe the statistical isotropy of these astrophysical transient events. We also studied the angular distribution of the GRB fluence as a way to explore whether this radiative feature shows some preferred direction on the sky that suggest their origin.<i>Methods.<i/> Our model-independent approach performed a directional analysis of the updated FERMI/GBM catalog. The statistical significance of our results is obtained by comparison with a large set of statistically isotropic samples of cosmic objects, with the same features of the FERMI data.<i>Results.<i/> Our analyses confirm that the angular distribution of the FERMIGRB is statistically isotropic on the celestial sphere. Moreover, analyzing the directional distribution of the FERMIGRB fluence, that is, the median GRB fluence in a set of directions that scans the celestial sphere, we found that this astrophysical property exhibits a net dipolar structure with a directional preference for latitudes near the Galactic plane. However, additional studies show that this directional preference is not correlated with the Milky Way Galactic plane, which suggests that the GRB dataset, and its fluence dipolar structure, are extra-Galactic in origin. Interestingly, the analyses of the BATSE Channel 4 fluence data, that is, those GRBs from BATSE with energy > 300 keV, reveal that its dipole direction is very well aligned with the cosmic microwave background dipole.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124648","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":"Polycyclic aromatic hydrocarbon and the ultraviolet extinction bump at the cosmic dawn","authors":"Qi Lin, Xuejuan Yang, Aigen Li, Joris Witstok","doi":"10.1051/0004-6361/202452372","DOIUrl":"https://doi.org/10.1051/0004-6361/202452372","url":null,"abstract":"<i>Context<i/>. First detected in 1965, the mysterious ultraviolet (UV) extinction bump at 2175 Å is the most prominent spectroscopic feature superimposed on the interstellar extinction curve. Its carrier has remained unidentified over the six decades since its first detection, although many candidate materials have been proposed.<i>Aims<i/>. Widely seen in the interstellar medium of the Milky Way as well as several nearby galaxies, this bump was recently also detected by the <i>James Webb<i/> Space Telescope (JWST) at the cosmic dawn in JADES-GS-z6-0, a distant galaxy at redshift <i>z<i/> ≈ 6.71, corresponding to a cosmic age of just 800 million years after the big bang. Differing from that of the known Galactic and extragalactic interstellar sightlines, which always peak at ~2175 Å, the bump seen at <i>z<i/> ≈ 6.71 peaks at an appreciably longer wavelength of ~2263 Å and is the narrowest among all known Galactic and extragalactic extinction bumps.<i>Methods<i/>. Here we show that the combined electronic absorption spectra quantum chemically computed for a number of polycyclic aromatic hydrocarbon (PAH) molecules closely reproduce the bump detected by JWST in JADES-GS-z6-0.<i>Results<i/>. This suggests that PAH molecules had already been pervasive in the Universe at an epoch when asymptotic giant branch stars had not yet evolved to make dust.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"77 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124656","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-cadence stellar variability studies of RR Lyrae stars with DECam: New multiband templates","authors":"K. Baeza-Villagra, N. Rodríguez-Segovia, M. Catelan, A. Rest, A. Papageorgiou, C. E. Martínez-Vázquez, A. A. R. Valcarce, C. E. Ferreira Lopes, F. B. Bianco","doi":"10.1051/0004-6361/202453129","DOIUrl":"https://doi.org/10.1051/0004-6361/202453129","url":null,"abstract":"We present the most extensive set to date of high-quality RR Lyrae light curve templates in the <i>ɡriz<i/> bands, based on time-series observations of the Dark Energy Camera Plane Survey (DECaPS) East field, located in the Galactic bulge at coordinates (RA, Dec)(J2000) = (18:03:34, −29:32:02), obtained with the Dark Energy Camera (DECam) on the 4-m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO). Our templates, which cover both fundamental-mode (RRab) and first-overtone (RRc) pulsators, can be especially useful when there is insufficient data for accurately calculating the average magnitudes and colors, hence distances, as well as to inform multiband light curve classifiers, as will be required in the case of the <i>Vera C. Rubin<i/> Observatory’s Legacy Survey of Space and Time (LSST). In this paper, we describe in detail the procedures that were adopted in producing these templates, including a novel approach to account for the presence of outliers in photometry. Our final sample comprises 136 RRab and 144 RRc templates, all of which are publicly available. Lastly, in this paper we study the inferred Fourier parameters and other light curve descriptors, including rise time, skewness, and kurtosis, as well as their correlations with the pulsation mode, period, and effective wavelength.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124658","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}