2020, Hansen, C.J., Koch, A., Mashonkina, L., Magg, M., Bergemann, M., Sitnova, T., Gallagher, A.J., Ilyin, I., Caffau, E., Zhang, H.W., Strassmeier, K.G., Klessen, R.S.

A long sought after goal using chemical abundance patterns derived from metal-poor stars is to understand the chemical evolution of the Galaxy and to pin down the nature of the first stars (Pop III). Metal-poor, old, unevolved stars are excellent tracers as they preserve the abundance pattern of the gas from which they were born, and hence they are frequently targeted in chemical tagging studies. Here, we use a sample of 14 metal-poor stars observed with the high-resolution spectrograph called the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) to derive abundances of 32 elements (34 including upper limits). We present well-sampled abundance patterns for all stars obtained using local thermodynamic equilibrium (LTE) radiative transfer codes and one-dimensional (1D) hydrostatic model atmospheres. However, it is currently well-known that the assumptions of 1D and LTE may hide several issues, thereby introducing biases in our interpretation as to the nature of the first stars and the chemical evolution of the Galaxy. Hence, we use non-LTE (NLTE) and correct the abundances using three-dimensional model atmospheres to present a physically more reliable pattern. In order to infer the nature of the first stars, we compare unevolved, cool stars, which have been enriched by a single event (“mono-enriched”), with a set of yield predictions to pin down the mass and energy of the Pop III progenitor. To date, only few bona fide second generation stars that are mono-enriched are known. A simple χ2-fit may bias our inferred mass and energy just as much as the simple 1D LTE abundance pattern, and we therefore carried out our study with an improved fitting technique considering dilution and mixing. Our sample presents Carbon Enhanced Metal-Poor (CEMP) stars, some of which are promising bona fide second generation (mono-enriched) stars. The unevolved, dwarf BD+09_2190 shows a mono-enriched signature which, combined with kinematical data, indicates that it moves in the outer halo and likely has been accreted onto the Milky Way early on. The Pop III progenitor was likely of 25.5 M⊙ and 0.6 foe (0.6 1051 erg) in LTE and 19.2 M⊙ and 1.5 foe in NLTE, respectively. Finally, we explore the predominant donor and formation site of the rapid and slow neutron-capture elements. In BD-10_3742, we find an almost clean r-process trace, as is represented in the star HD20, which is a “metal-poor Sun benchmark” for the r-process, while TYC5481-00786-1 is a promising CEMP-r/-s candidate that may be enriched by an asymptotic giant branch star of an intermediate mass and metallicity.

2021, Hodgkin, S.T., Harrison, D.L., Breedt, E., Wevers, T., Rixon, G., Delgado, A., Yoldas, A., Kostrzewa-Rutkowska, Z., Wyrzykowski, Ł., van Leeuwen, M., Blagorodnova, N., Serraller, I., Steeghs, D., Sullivan, M., Szabados, L., Szegedi-Elek, E., Tisserand, P., Tomasella, L., van Velzen, S., Whitelock, P.A, Wilson, R.W., Campbell, H., Young, D.R., Eappachen, D., Fraser, M., Ihanec, N., Koposov, S.E., Kruszyńska, K., Marton, G., Rybicki, K.A., Brown, A.G.A., Burgess, P. W., Busso, G., Cowell, S., De Angeli, F., Diener, C., Evans, D.W., Gilmore, G., Holland, G., Jonker, P.G., van Leeuwen, F., Mignard, F., Osborne, P.J., Portell, J., Prusti, T., Richards, P.J., Riello, M., Seabroke, G.M., Walton, N.A., Ábrahám, Péter, Altavilla, G., Baker, S.G., Bastian, U., O'Brien, P., de Bruijne, J., Butterley, T., Carrasco, J.M., Castañeda, J., Clark, J.S., Clementini, G., Copperwheat, C.M., Cropper, M., Damljanovic, G., Davidson, M., Davis, C.J., Dennefeld, M., Dhillon, V.S., Dolding, C., Dominik, M., Esquej, P., Eyer, L., Fabricius, C., Fridman, M., Froebrich, D., Garralda, N., Gomboc, A., González-Vidal, J.J., Guerra, R., Hambly, N.C., Hardy, L.K., Holl, B., Hourihane, A., Japelj, J., Kann, D.A., Kiss, C., Knigge, C., Kolb, U., Komossa, S., Kóspál, Á., Kovács, G., Kun, M., Leto, G., Lewis, F., Littlefair, S.P., Mahabal, A.A., Mundell, C.G., Nagy, Z., Padeletti, D., Palaversa, L., Pigulski, A., Pretorius, M.L., van Reeven, W., Ribeiro, V.A.R.M., Roelens, M., Rowell, N., Schartel, N., Scholz, A., Schwope, A., Sipőcz, B.M., Smartt, S.J., Smith, M.D.

Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky. Aims. We present the Gaia Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and publication of transient photometric events as seen by Gaia. Methods. We outline the data handling, timings, and performances, and we describe the transient detection algorithms and filtering procedures needed to manage the high false alarm rate. We identify two classes of events: (1) sources which are new to Gaia and (2) Gaia sources which have undergone a significant brightening or fading. Validation of the Gaia transit astrometry and photometry was performed, followed by testing of the source environment to minimise contamination from Solar System objects, bright stars, and fainter near-neighbours. Results. We show that the Gaia Science Alerts project suffers from very low contamination, that is there are very few false-positives. We find that the external completeness for supernovae, CE = 0.46, is dominated by the Gaia scanning law and the requirement of detections from both fields-of-view. Where we have two or more scans the internal completeness is CI = 0.79 at 3 arcsec or larger from the centres of galaxies, but it drops closer in, especially within 1 arcsec. Conclusions. The per-Transit photometry for Gaia transients is precise to 1% at G = 13, and 3% at G = 19. The per-Transit astrometry is accurate to 55 mas when compared to Gaia DR2. The Gaia Science Alerts project is one of the most homogeneous and productive transient surveys in operation, and it is the only survey which covers the whole sky at high spatial resolution (subarcsecond), including the Galactic plane and bulge. © S. T. Hodgkin et al. 2021.

2020, Breuval, Louise, Kervella, Pierre, Anderson, Richard I., Riess, Adam G., Arenou, Frédéric, Trahin, Boris, Mérand, Antoine, Gallenne, Alexandre, Gieren, Wolfgang, Storm, Jesper, Bono, Giuseppe, Pietrzynski, Grzegorz, Nardetto, Nicolas, Javanmardi, Behnam, Hocdé, Vincent

Aims. Classical Cepheids provide the foundation for the empirical extragalactic distance ladder. Milky Way Cepheids are the only stars in this class accessible to trigonometric parallax measurements. However, the parallaxes of Cepheids from the second Gaia data release (GDR2) are affected by systematics because of the absence of chromaticity correction, and occasionally by saturation. Methods. As a proxy for the parallaxes of 36 Galactic Cepheids, we adopt either the GDR2 parallaxes of their spatially resolved companions or the GDR2 parallax of their host open cluster. This novel approach allows us to bypass the systematics on the GDR2 Cepheids parallaxes that is induced by saturation and variability. We adopt a GDR2 parallax zero-point (ZP) of −0.046 mas with an uncertainty of 0.015 mas that covers most of the recent estimates. Results. We present new Galactic calibrations of the Leavitt law in the V, J, H, KS, and Wesenheit WH bands. We compare our results with previous calibrations based on non-Gaia measurements and compute a revised value for the Hubble constant anchored to Milky Way Cepheids. Conclusions. From an initial Hubble constant of 76.18 ± 2.37 km s−1 Mpc−1 based on parallax measurements without Gaia, we derive a revised value by adopting companion and average cluster parallaxes in place of direct Cepheid parallaxes, and we find H0 = 72.8 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 when all Cepheids are considered and H0 = 73.0 ± 1.9 (statistical + systematics) ±1.9 (ZP) km s−1 Mpc−1 for fundamental mode pulsators only.

2020, Solanki, S.K., del Toro Iniesta, J.C., Woch, J., Gandorfer, A., Hirzberger, J., Alvarez-Herrero, A., Appourchaux, T., Martínez Pillet, V., Pérez-Grande, I., Sanchis Kilders, E., Schmidt, W., Garranzo-García, D., Laguna, H., Martín, J.A., Navarro, R., Villanueva, J., Núñez Peral, A., Royo, M., Sánchez, A., Silva-López, M., Fourmond, J.-J., Berkefeld, Th., Ruiz de Galarreta, C., Bouzit, M., Hervier, V., Le Clec'h, J.C., Szwec, N., Chaigneau, M., Buttice, V., Volkmer, R., Dominguez-Tagle, C., Philippon, A., Baumgartner, J., Boumier, P., Le Cocguen, R., Baranjuk, G., Bell, A., Heidecke, F., Maue, T., Blanco Rodríguez, J., Nakai, E., Scheiffelen, T., Sigwarth, M., Soltau, D., Domingo, V., Fiethe, B., Ferreres Sabater, A., Gasent Blesa, J.L., Rodríguez Martínez, P., Osorno Caudel, D., Bosch, J., Casas, A., Carmona, M., Gómez Cama, J.M., Herms, A., Roma, D., Guan, Y., Alonso, G., Gómez-Sanjuan, A., Piqueras, J., Torralbo, I., Lange, T., Michel, H., Michalik, H., Bonet, J.A., Fahmy, S., Müller, D., Zouganelis, I., Deutsch, W., Busse, D., Fernandez-Rico, G., Grauf, B., Gizon, L., Heerlein, K., Kolleck, M., Lagg, A., Meller, R., Müller, R., Schühle, U., Staub, J., Enge, R., Albert, K., Alvarez Copano, M., Beckmann, U., Bischoff, J., Frahm, S., Germerott, D., Guerrero, L., Löptien, B., Meierdierks, T., Oberdorfer, D., Papagiannaki, I., Ramanath, S., Bellot Rubio, L.R., Schou, J., Werner, S., Yang, D., Zerr, A., Bergmann, M., Bochmann, J., Heinrichs, J., Meyer, S., Monecke, M., Müller, M.-F., Cobos Carracosa, J.P., Sperling, M., Álvarez García, D., Aparicio, B., Balaguer Jiménez, M., Girela, F., Hernández Expósito, D., Herranz, M., Labrousse, P., López Jiménez, A., Orozco Suárez, D., Ramos, J.L., Barandiarán, J., Vera, I., Bastide, L., Campuzano, C., Cebollero, M., Dávila, B., Fernández-Medina, A., García Parejo, P.

This paper describes the Polarimetric and Helioseismic Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and helioseismology instrument to observe the Sun from outside the Sun-Earth line. It is the key instrument meant to address the top-level science question: How does the solar dynamo work and drive connections between the Sun and the heliosphere? SO/PHI will also play an important role in answering the other top-level science questions of Solar Orbiter, as well as hosting the potential of a rich return in further science. SO/PHI measures the Zeeman effect and the Doppler shift in the FeI 617.3nm spectral line. To this end, the instrument carries out narrow-band imaging spectro-polarimetry using a tunable LiNbO_3 Fabry-Perot etalon, while the polarisation modulation is done with liquid crystal variable retarders (LCVRs). The line and the nearby continuum are sampled at six wavelength points and the data are recorded by a 2kx2k CMOS detector. To save valuable telemetry, the raw data are reduced on board, including being inverted under the assumption of a Milne-Eddington atmosphere, although simpler reduction methods are also available on board. SO/PHI is composed of two telescopes; one, the Full Disc Telescope (FDT), covers the full solar disc at all phases of the orbit, while the other, the High Resolution Telescope (HRT), can resolve structures as small as 200km on the Sun at closest perihelion. The high heat load generated through proximity to the Sun is greatly reduced by the multilayer-coated entrance windows to the two telescopes that allow less than 4% of the total sunlight to enter the instrument, most of it in a narrow wavelength band around the chosen spectral line.

2021, Matas Pinto, A. M., Spite, M., Caffau, E., Bonifacio, P., Sbordone, L., Sivarani, T., Steffen, M., Spite, F., François, P., Di Matteo, P.

Context. The study of old, metal-poor stars deepens our knowledge on the early stages of the universe. In particular, the study of these stars gives us a valuable insight into the masses of the first massive stars and their emission of ionising photons. Aims. We present a detailed chemical analysis and determination of the kinematic and orbital properties of a sample of 11 dwarf stars. These are metal-poor stars, and a few of them present a low lithium content. We inspected whether the other elements also present anomalies. Methods. We analysed the high-resolution UVES spectra of a few metal-poor stars using the Turbospectrum code to synthesise spectral lines profiles. This allowed us to derive a detailed chemical analysis of Fe, C, Li, Na, Mg, Al, Si, CaI, CaII, ScII, TiII, Cr, Mn, Co, Ni, Sr, and Ba. Results. We find excellent coherence with the reference metal-poor First Stars sample. The lithium-poor stars do not present any anomaly of the abundance of the elements other than lithium. Among the Li-poor stars, we show that CS 22882-027 is very probably a blue-straggler. The star CS 30302-145, which has a Li abundance compatible with the plateau, has a very low Si abundance and a high Mn abundance. In many aspects, it is similar to the α-poor star HE 1424-0241, but it is less extreme. It could have been formed in a satellite galaxy and later been accreted by our Galaxy. This hypothesis is also supported by its kinematics.

2021, Ellwarth, M., Fischer, C.E., Vitas, N., Schmiz, S., Schmidt, W.

Context. Exploding granules have drawn renewed interest because of their interaction with the magnetic field (either emerging or already present). Especially the newly forming downflow lanes developing in their centre seem to be eligible candidates for the intensification of magnetic fields. We analyse spectroscopic data from two different instruments in order to study the intricate velocity pattern within the newly forming downflow lanes in detail. Aims. We aim to examine general properties of a number of exploding granules, such as their lifetime and extend. To gain a better understanding of the formation process of the developing intergranular lane in exploding granules, we study the temporal evolution and height dependence of the line-of-sight velocities at their formation location. Additionally, we search for evidence that exploding granules act as acoustic sources. Methods. We investigated the evolution of several exploding granules using data taken with the Interferometric Bidimensional Spectrometer and the Imaging Magnetograph eXperiment. Velocities for different heights of the solar atmosphere were determined by computing bisectors of the Fe I 6173.0 Å and the Fe I 5250.2 Å lines. We performed a wavelet analysis to study the intensity and velocity oscillations within and around exploding granules. We also compared our observational findings with predictions of numerical simulations. Results. Exploding granules have significantly longer lifetimes (10 to 15 min) than regular granules. Exploding granules larger than 3.8″ form an independent intergranular lane during their decay phase, while smaller granules usually fade away or disappear into the intergranular area (we find only one exception of a smaller exploding granule that also forms an intergranular lane). For all exploding granules that form a new intergranular downflow lane, we find a temporal height-dependent shift with respect to the maximum of the downflow velocity. Our suggestion that this results from a complex atmospheric structure within the newly forming downflow lane is supported by the comparison with synthesised profiles inferred from the simulations. We found an enhanced wavelet power with periods between 120 s to 190 s seen in the intensity and velocity oscillations of high photospheric or chromospheric spectral lines in the region of the dark core of an exploding granule. © M. Ellwarth et al. 2021.

2020, Webb, N.A., Coriat, M., Traulsen, I., Ballet, J., Motch, C., Carrera, F.J., Koliopanos, F., Authier, J., de la Calle, I., Ceballos, M.T., Colomo, E., Chuard, D., Freyberg, M., Garcia, T., Kolehmainen, M., Lamer, G., Lin, D., Maggi, P., Michel, L., Page, C.G., Page, M.J., Perea-Calderon, J.V., Pineau, F.-X., Rodriguez, P., Rosen, S.R., Santos Lleo, M., Saxton, R.D., Schwope, A., Tomás, L., Watson, M.G., Zakardjian, A.

Context. Sky surveys produce enormous quantities of data on extensive regions of the sky. The easiest way to access this information is through catalogues of standardised data products. XMM-Newton has been surveying the sky in the X-ray, ultra-violet, and optical bands for 20 years. Aims. The XMM-Newton Survey Science Centre has been producing standardised data products and catalogues to facilitate access to the serendipitous X-ray sky. Methods. Using improved calibration and enhanced software, we re-reduced all of the 14 041 XMM-Newton X-ray observations, of which 11 204 observations contained data with at least one detection and with these we created a new, high quality version of the XMM-Newton serendipitous source catalogue, 4XMM-DR9. Results. 4XMM-DR9 contains 810 795 detections down to a detection significance of 3σ, of which 550 124 are unique sources, which cover 1152 degrees2 (2.85%) of the sky. Filtering 4XMM-DR9 to retain only the cleanest sources with at least a 5σ detection significance leaves 433 612 detections. Of these detections, 99.6% have no pileup. Furthermore, 336 columns of information on each detection are provided, along with images. The quality of the source detection is shown to have improved significantly with respect to previous versions of the catalogues. Spectra and lightcurves are also made available for more than 288 000 of the brightest sources (36% of all detections).

2021, Predehl, P., Andritschke, R., Arefiev, V., Babyshkin, V., Batanov, O., Becker, W., Böhringer, H., Bogomolov, A., Boller, T., Borm, K., Bornemann, W., Bräuninger, H., Brüggen, M., Brunner, H., Brusa, M., Bulbul, E., Buntov, M., Burwitz, V., Burkert, W., Clerc, N., Churazov, E., Coutinho, D., Dauser, T., Dennerl, K., Doroshenko, V., Eder, J., Emberger, V., Eraerds, T., Finoguenov, A., Freyberg, M., Friedrich, P., Friedrich, S., Fürmetz, M., Georgakakis, A., Gilfanov, M., Granato, S., Grossberger, C., Gueguen, A., Gureev, P., Haberl, F., Hälker, O., Hartner, G., Hasinger, G., Huber, H., Ji, L., Kienlin, A. v., Kink, W., Korotkov, F., Kreykenbohm, I., Lamer, G., Lomakin, I., Lapshov, I., Liu, T., Maitra, C., Meidinger, N., Menz, B., Merloni, A., Mernik, T., Mican, B., Mohr, J., Müller, S., Nandra, K., Nazarov, V., Pacaud, F., Pavlinsky, M., Perinati, E., Pfeffermann, E., Pietschner, D., Ramos-Ceja, M. E., Rau, A., Reiffers, J., Reiprich, T. H., Robrade, J., Salvato, M., Sanders, J., Santangelo, A., Sasaki, M., Scheuerle, H., Schmid, C., Schmitt, J., Schwope, A., Shirshakov, A., Steinmetz, M., Stewart, I., Strüder, L., Sunyaev, R., Tenzer, C., Tiedemann, L., Trümper, J., Voron, V., Weber, P., Wilms, J., Yaroshenko, V.

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2-2.3 keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3-8 keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements.

2021, Casamiquela, L., Soubiran, C., Jofré, P., Chiappini, C., Lagarde, N., Tarricq, Y., Carrera, R., Jordi, C., Balaguer-Núñez, L., Carbajo-Hijarrubia, J., Blanco-Cuaresma, S.

Context. Precise chemical abundances coupled with reliable ages are key ingredients to understanding the chemical history of our Galaxy. Open clusters (OCs) are useful for this purpose because they provide ages with good precision. Aims. The aim of this work is to investigate the relation between different chemical abundance ratios and age traced by red clump (RC) stars in OCs. Methods. We analyzed a large sample of 209 reliable members in 47 OCs with available high-resolution spectroscopy. We applied a differential line-by-line analysis, performing a comprehensive chemical study of 25 chemical species. This sample is among the largest samples of OCs homogeneously characterized in terms of atmospheric parameters, detailed chemistry, and age. Results. In our metallicity range (-0.2 < [M/H] < +0.2) we find that while most Fe-peak and α elements show a flat dependence on age, the s-process elements show a decreasing trend with increasing age with a remarkable knee at 1 Gyr. For Ba, Ce, Y, Mo, and Zr, we find a plateau at young ages (< 1 Gyr). We investigate the relations between all possible combinations among the computed chemical species and age. We find 19 combinations with significant slopes, including [Y/Mg] and [Y/Al]. The ratio [Ba/α] shows the most significant correlation. Conclusions. We find that the [Y/Mg] relation found in the literature using solar twins is compatible with the one found here in the solar neighborhood. The age-abundance relations in clusters at large distances(d > 1 kpc) show larger scatter than those in clusters in the solar neighborhood, particularly in the outer disk. We conclude that, in addition to pure nucleosynthetic arguments, the complexity of the chemical space introduced by the Galactic dynamics must be taken into account in order to understand these relations, especially outside of the local bubble. © L. Casamiquela et al. 2021.

2021, Müller, Oliver, Pawlowski, Marcel S., Lelli, Federico, Fahrion, Katja, Rejkuba, Marina, Hilker, Michael, Kanehisa, Jamie, Libeskind, Noam, Jerjen, Helmut

The plane-of-satellites problem is one of the most severe small-scale challenges for the standard Λ cold dark matter (ΛCDM) cosmological model: Several dwarf galaxies around the Milky Way and Andromeda co-orbit in thin, planar structures. A similar case has been identified around the nearby elliptical galaxy Centaurus A (Cen A). In this Letter, we study the satellite system of Cen A, adding twelve new galaxies with line-of-sight velocities from VLT/MUSE observations. We find that 21 out of 28 dwarf galaxies with measured velocities share a coherent motion. Similarly, flattened and coherently moving structures are found only in 0.2% of Cen A analogs in the Illustris-TNG100 cosmological simulation, independently of whether we use its dark-matter-only or hydrodynamical run. These analogs are not co-orbiting, and they arise only by chance projection, thus they are short-lived structures in such simulations. Our findings indicate that the observed co-rotating planes of satellites are a persistent challenge for ΛCDM, which is largely independent from baryon physics. © O. Müller et al. 2021.