Infrared excesses in stars with and without planets using revised WISE{\it WISE} photometry

We present an analysis on the potential prevalence of mid infrared excesses in stars with and without planetary companions. Based on an extended database of stars detected with the ${\it WISE}$ satellite, we studied two stellar samples: one with 236 planet hosts and another with 986 objects for which planets have been searched but not found. We determined the presence of an excess over the photosphere by comparing the observed flux ratio at 22 $\mu$m and 12 $\mu$m ($f_{22}/f_{12}$) with the corresponding synthetic value, derived from results of classical model photospheres. We found a detection rate of 0.85$\%$ at 22 $\mu$m (2 excesses) in the sample of stars with planets and 0.1$\%$ (1 detection) for the stars without planets. The difference of the detection rate between the two samples is not statistically significant, a result that is independent of the different approaches found in the literature to define an excess in the wavelength range covered by ${\it WISE}$ observations. As an additional result, we found that the ${\it WISE}$ fluxes required a normalisation procedure to make them compatible with synthetic data, probably pointing out a revision of the ${\it WISE}$ data calibration.Comment: 10 pages, 6 figures, 3 tables. Accepted for publication in MNRA

New insights into Capsicum spp relatedness and the diversification process of Capsicum annuum in Spain

The successful exploitation of germplasm banks, harbouring plant genetic resources indispensable for plant breeding, will depend on our ability to characterize their genetic diversity. The Vegetable Germplasm Bank of Zaragoza (BGHZ) (Spain) holds an important Capsicum annuum collection, where most of the Spanish pepper variability is represented, as well as several accessions of other domesticated and non-domesticated Capsicum spp from all over the five continents. In the present work, a total of 51 C. annuum landraces (mainly from Spain) and 51 accessions from nine Capsicum species maintained at the BGHZ were evaluated using 39 microsatellite (SSR) markers spanning the whole genome. The 39 polymorphic markers allowed the detection of 381 alleles, with an average of 9.8 alleles per locus. A sizeable proportion of alleles (41.2%) were recorded as specific alleles and the majority of these were present at very low frequencies (rare alleles). Multivariate and model-based analyses partitioned the collection in seven clusters comprising the ten different Capsicum spp analysed: C. annuum, C. chinense, C. frutescens, C. pubescens, C. bacatum, C. chacoense and C. eximium. The data clearly showed the close relationships between C. chinense and C. frutescens. C. cardenasii and C. eximium were indistinguishable as a single, morphologically variable species. Moreover, C. chacoense was placed between C. baccatum and C. pubescens complexes. The C. annuum group was structured into three main clusters, mostly according to the pepper fruit shape, size and potential pungency. Results suggest that the diversification of C. annuum in Spain may occur from a rather limited gene pool, still represented by few landraces with ancestral traits. This ancient population would suffer from local selection at the distinct geographical regions of Spain, giving way to pungent and elongated fruited peppers in the South and Center, while sweet blocky and triangular types in Northern Spain

The disk of the eruptive protostar V900 Mon; a MATISSE/VLTI and MUSE/VLT perspective

In this work, we study the silicate dust content in the disk of one of the youngest eruptive stars, V900 Mon, at the highest angular resolution probing down to the inner 10 au of said disk, and study the historical evolution of the system traced in part by a newly discovered emission clump. We performed high-angular resolution mid-infrared interferometric observations of V900 Mon with MATISSE/VLTI with a spatial coverage ranging from 38-m to 130-m baselines, and compared them to archival MIDI/VLTI data. We also mined and re-analyzed archival optical and infrared photometry of the star to study its long-term evolution since its eruption in the 1990s. We complemented our findings with integral field spectroscopy data from MUSE/VLT. The MATISSE/VLTI data suggest a radial variation of the silicate feature in the dusty disk, whereby at large spatial scales ($\geq10$ au) the protostellar disk's emission is dominated by large-sized ($\geq1\,\mu m$) silicate grains, while at smaller spatial scales and closer to the star ($\leq5$ au), silicate emission is absent suggesting self-shielding. We propose that the self-shielding may be the result of small dust grains at the base of the collimated CO outflow previously detected by ALMA. A newly discovered knot in the MUSE/VLT data, located at a projected distance approximately 27,000 au from the star, is co-aligned with the molecular gas outflow at a P.A. of $250^o$ ($\pm5^o$) consistent with the position angle and inclination of the disk. The knot is seen in emission in H$\alpha$, [N II], and the [S II] doublet and its kinematic age is about 5150 years. This ejected material could originate from a previous eruption.Comment: 18 pages, 16 figures, accepted for publication by Astronomy & Astrophysic

Gaia23bab: a new EXor

© 2024 The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/On March 6 2023, the Gaia telescope has alerted a 2-magnitude burst from Gaia23bab, a Young Stellar Object in the Galactic plane. We observed Gaia23bab with the Large Binocular Telescope obtaining optical and near-infrared spectra close in time to the peak of the burst, and collected all public multi-band photometry to reconstruct the historical light curve. This latter shows three bursts in ten years (2013, 2017 and 2023), whose duration and amplitude are typical of EXor variables. We estimate that, due to the bursts, the mass accumulated on the star is about twice greater than if the source had remained quiescent for the same period of time. Photometric analysis indicates that Gaia23bab is a Class,II source with age < 1 Myr, spectral type G3-K0, stellar luminosity 4.0 L_sun, and mass 1.6 M_sun. The optical/near infrared spectrum is rich in emission lines. From the analysis of these lines we measured the accretion luminosity and the mass accretion rate L_acc(burst)=3.7 L_sun, M_acc(burst) 2.0 10 $^(-7) M_sun/yr, consistent with those of EXors. More generally, we derive the relationships between accretion and stellar parameters in a sample of EXors. We find that, when in burst, the accretion parameters become almost independent of the stellar parameters and that EXors, even in quiescence, are more efficient than classical T Tauri stars in assembling mass.Peer reviewe

The clumpy structure of ϵ\epsilon Eridani's debris disc revisited by ALMA

$\epsilon$ Eridani is the closest star to our Sun known to host a debris disc. Prior observations in the (sub-)millimetre regime have potentially detected clumpy structure in the disc and attributed this to interactions with an (as yet) undetected planet. However, the prior observations were unable to distinguish between structure in the disc and background confusion. Here we present the first ALMA image of the entire disc, which has a resolution of 1.6"$\times$1.2". We clearly detect the star, the main belt and two point sources. The resolution and sensitivity of this data allow us to clearly distinguish background galaxies (that show up as point sources) from the disc emission. We show that the two point sources are consistent with background galaxies. After taking account of these, we find that resolved residuals are still present in the main belt, including two clumps with a $>3\sigma$ significance -- one to the east of the star and the other to the northwest. We perform $n$-body simulations to demonstrate that a migrating planet can form structures similar to those observed by trapping planetesimals in resonances. We find that the observed features can be reproduced by a migrating planet trapping planetesimals in the 2:1 mean motion resonance and the symmetry of the most prominent clumps means that the planet should have a position angle of either ${\sim10^\circ}$ or ${\sim190^\circ}$. Observations over multiple epochs are necessary to test whether the observed features rotate around the star.Comment: 16 pages, 10 figures, accepted for publication in MNRA

The Relation between the Mass Accretion Rate and the Disk Mass in Class I Protostars

Evidence of a relation between the mass accretion rate and the disk mass is established for young, Class II pre-main-sequence stars. This observational result opened an avenue to test theoretical models and constrain the initial conditions of disk formation, fundamental in the understanding of the emergence of planetary systems. However, it is becoming clear that planet formation starts even before the Class II stage, in disks around Class 0 and I protostars. We show for the first time evidence for a correlation between the mass accretion rate and the disk mass for a large sample of Class I young stars located in nearby (<500 pc) star-forming regions. We fit our sample, finding that the Class I object relation has a slope flatter than Class II stars, and the former have higher mass accretion rates and disk masses. The results are put in context of disk evolution models

Brightness and mass accretion rate evolution during the 2022 burst of EX~Lupi

EX Lupi is the prototype by which EXor-type outbursts were defined. It has experienced multiple accretion-related bursts and outbursts throughout the last decades, whose study have greatly extended our knowledge about the effects of these types of events. This star experienced a new burst in 2022. We used multi-band photometry to create color-color and color-magnitude diagrams to exclude the possibility that the brightening could be explained by a decrease in extinction. We obtained VLT/X-shooter spectra to determine the Lacc and Macc during the peak of the burst and after its return to quiescence using 2 methods: empirical relationships between line luminosity and Lacc, and a slab model of the whole spectrum. We examined the 130 year light curve of EX Lupi to provide statistics on the number of outbursts experienced during this period of time. Our analysis of the data taken during the 2022 burst confirmed that a change in extinction is not responsible for the brightening. Our two approaches in calculating the Macc were in agreement, and resulted in values that are 2 orders of magnitude above what had previously been estimated, thus suggesting that EX Lupi is a strong accretor even when in quiescence. We determined that in 2022 March the Macc increased by a factor of 7 with respect to the quiescent level. We also found hints that even though the Macc had returned to almost its pre-outburst levels, certain physical properties of the gas had not returned to the quiescent values. We found that the mass accreted during this three month event was 0.8 lunar masses, which is approximately half of what is accreted during a year of quiescence. We calculated that if EX Lupi remains as active as it has been for the past 130 years, during which it has experienced at least 3 outbursts and 10 bursts, then it will deplete the mass of its circumstellar material in less than 160000 yr