@article{11540, abstract = {Observations have revealed that the star formation rate (SFR) and stellar mass (Mstar) of star-forming galaxies follow a tight relation known as the galaxy main sequence. However, what physical information is encoded in this relation is under debate. Here, we use the EAGLE cosmological hydrodynamical simulation to study the mass dependence, evolution, and origin of scatter in the SFR–Mstar relation. At z = 0, we find that the scatter decreases slightly with stellar mass from 0.35 dex at Mstar ≈ 109 M⊙ to 0.30 dex at Mstar ≳ 1010.5 M⊙. The scatter decreases from z = 0 to z = 5 by 0.05 dex at Mstar ≳ 1010 M⊙ and by 0.15 dex for lower masses. We show that the scatter at z = 0.1 originates from a combination of fluctuations on short time-scales (ranging from 0.2–2 Gyr) that are presumably associated with self-regulation from cooling, star formation, and outflows, but is dominated by long time-scale (∼10 Gyr) variations related to differences in halo formation times. Shorter time-scale fluctuations are relatively more important for lower mass galaxies. At high masses, differences in black hole formation efficiency cause additional scatter, but also diminish the scatter caused by different halo formation times. While individual galaxies cross the main sequence multiple times during their evolution, they fluctuate around tracks associated with their halo properties, i.e. galaxies above/below the main sequence at z = 0.1 tend to have been above/below the main sequence for ≫1 Gyr.}, author = {Matthee, Jorryt J and Schaye, Joop}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics : galaxies: evolution, galaxies: formation, galaxies: star formation, cosmology: theory}, number = {1}, pages = {915--932}, publisher = {Oxford University Press}, title = {{The origin of scatter in the star formation rate–stellar mass relation}}, doi = {10.1093/mnras/stz030}, volume = {484}, year = {2019}, } @article{11616, abstract = {We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R⋆ = 2.943 ± 0.064 R⊙), mass (M⋆ = 1.212 ± 0.074 M⊙), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 0.431 ± 0.062 g cm−3). The properties of HD 221416 b show that the host-star metallicity–planet mass correlation found in sub-Saturns (4–8 R⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.}, author = {Huber, Daniel and Chaplin, William J. and Chontos, Ashley and Kjeldsen, Hans and Christensen-Dalsgaard, Jørgen and Bedding, Timothy R. and Ball, Warrick and Brahm, Rafael and Espinoza, Nestor and Henning, Thomas and Jordán, Andrés and Sarkis, Paula and Knudstrup, Emil and Albrecht, Simon and Grundahl, Frank and Andersen, Mads Fredslund and Pallé, Pere L. and Crossfield, Ian and Fulton, Benjamin and Howard, Andrew W. and Isaacson, Howard T. and Weiss, Lauren M. and Handberg, Rasmus and Lund, Mikkel N. and Serenelli, Aldo M. and Rørsted Mosumgaard, Jakob and Stokholm, Amalie and Bieryla, Allyson and Buchhave, Lars A. and Latham, David W. and Quinn, Samuel N. and Gaidos, Eric and Hirano, Teruyuki and Ricker, George R. and Vanderspek, Roland K. and Seager, Sara and Jenkins, Jon M. and Winn, Joshua N. and Antia, H. M. and Appourchaux, Thierry and Basu, Sarbani and Bell, Keaton J. and Benomar, Othman and Bonanno, Alfio and Buzasi, Derek L. and Campante, Tiago L. and Çelik Orhan, Z. and Corsaro, Enrico and Cunha, Margarida S. and Davies, Guy R. and Deheuvels, Sebastien and Grunblatt, Samuel K. and Hasanzadeh, Amir and Di Mauro, Maria Pia and A. García, Rafael and Gaulme, Patrick and Girardi, Léo and Guzik, Joyce A. and Hon, Marc and Jiang, Chen and Kallinger, Thomas and Kawaler, Steven D. and Kuszlewicz, James S. and Lebreton, Yveline and Li, Tanda and Lucas, Miles and Lundkvist, Mia S. and Mann, Andrew W. and Mathis, Stéphane and Mathur, Savita and Mazumdar, Anwesh and Metcalfe, Travis S. and Miglio, Andrea and F. G. Monteiro, Mário J. P. and Mosser, Benoit and Noll, Anthony and Nsamba, Benard and Joel Ong, Jia Mian and Örtel, S. and Pereira, Filipe and Ranadive, Pritesh and Régulo, Clara and Rodrigues, Thaíse S. and Roxburgh, Ian W. and Aguirre, Victor Silva and Smalley, Barry and Schofield, Mathew and Sousa, Sérgio G. and Stassun, Keivan G. and Stello, Dennis and Tayar, Jamie and White, Timothy R. and Verma, Kuldeep and Vrard, Mathieu and Yıldız, M. and Baker, David and Bazot, Michaël and Beichmann, Charles and Bergmann, Christoph and Bugnet, Lisa Annabelle and Cale, Bryson and Carlino, Roberto and Cartwright, Scott M. and Christiansen, Jessie L. and Ciardi, David R. and Creevey, Orlagh and Dittmann, Jason A. and Nascimento, Jose-Dias Do and Eylen, Vincent Van and Fürész, Gabor and Gagné, Jonathan and Gao, Peter and Gazeas, Kosmas and Giddens, Frank and Hall, Oliver J. and Hekker, Saskia and Ireland, Michael J. and Latouf, Natasha and LeBrun, Danny and Levine, Alan M. and Matzko, William and Natinsky, Eva and Page, Emma and Plavchan, Peter and Mansouri-Samani, Masoud and McCauliff, Sean and Mullally, Susan E. and Orenstein, Brendan and Soto, Aylin Garcia and Paegert, Martin and van Saders, Jennifer L. and Schnaible, Chloe and Soderblom, David R. and Szabó, Róbert and Tanner, Angelle and Tinney, C. G. and Teske, Johanna and Thomas, Alexandra and Trampedach, Regner and Wright, Duncan and Yuan, Thomas T. and Zohrabi, Farzaneh}, issn = {0004-6256}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {6}, publisher = {IOP Publishing}, title = {{A hot Saturn orbiting an oscillating late subgiant discovered by TESS}}, doi = {10.3847/1538-3881/ab1488}, volume = {157}, year = {2019}, } @article{11613, abstract = {Over 2,000 stars were observed for 1 month with a high enough cadence in order to look for acoustic modes during the survey phase of the Kepler mission. Solar-like oscillations have been detected in about 540 stars. The question of why no oscillations were detected in the remaining stars is still open. Previous works explained the non-detection of modes with the high level of magnetic activity of the stars. However, the sample of stars studied contained some classical pulsators and red giants that could have biased the results. In this work, we revisit this analysis on a cleaner sample of main-sequence solar-like stars that consists of 1,014 stars. First we compute the predicted amplitude of the modes of that sample and for the stars with detected oscillation and compare it to the noise at high frequency in the power spectrum. We find that the stars with detected modes have an amplitude to noise ratio larger than 0.94. We measure reliable rotation periods and the associated photometric magnetic index for 684 stars out of the full sample and in particular for 323 stars where the amplitude of the modes is predicted to be high enough to be detected. We find that among these 323 stars 32% of them have a level of magnetic activity larger than the Sun during its maximum activity, explaining the non-detection of acoustic modes. Interestingly, magnetic activity cannot be the primary reason responsible for the absence of detectable modes in the remaining 68% of the stars without acoustic modes detected and with reliable rotation periods. Thus, we investigate metallicity, inclination angle of the rotation axis, and binarity as possible causes of low mode amplitudes. Using spectroscopic observations for a subsample, we find that a low metallicity could be the reason for suppressed modes. No clear correlation with binarity nor inclination is found. We also derive the lower limit for our photometric activity index (of 20–30 ppm) below which rotation and magnetic activity are not detected. Finally, with our analysis we conclude that stars with a photometric activity index larger than 2,000 ppm have 98.3% probability of not having oscillations detected.}, author = {Mathur, Savita and García, Rafael A. and Bugnet, Lisa Annabelle and Santos, Ângela R.G. and Santiago, Netsha and Beck, Paul G.}, issn = {2296-987X}, journal = {Frontiers in Astronomy and Space Sciences}, keywords = {Astronomy and Astrophysics}, publisher = {Frontiers Media}, title = {{Revisiting the impact of stellar magnetic activity on the detectability of solar-like oscillations by Kepler}}, doi = {10.3389/fspas.2019.00046}, volume = {6}, year = {2019}, } @article{11615, abstract = {The recently published Kepler mission Data Release 25 (DR25) reported on ∼197 000 targets observed during the mission. Despite this, no wide search for red giants showing solar-like oscillations have been made across all stars observed in Kepler’s long-cadence mode. In this work, we perform this task using custom apertures on the Kepler pixel files and detect oscillations in 21 914 stars, representing the largest sample of solar-like oscillating stars to date. We measure their frequency at maximum power, νmax, down to νmax≃4μHz and obtain log (g) estimates with a typical uncertainty below 0.05 dex, which is superior to typical measurements from spectroscopy. Additionally, the νmax distribution of our detections show good agreement with results from a simulated model of the Milky Way, with a ratio of observed to predicted stars of 0.992 for stars with 10<νmax<270μHz. Among our red giant detections, we find 909 to be dwarf/subgiant stars whose flux signal is polluted by a neighbouring giant as a result of using larger photometric apertures than those used by the NASA Kepler science processing pipeline. We further find that only 293 of the polluting giants are known Kepler targets. The remainder comprises over 600 newly identified oscillating red giants, with many expected to belong to the Galactic halo, serendipitously falling within the Kepler pixel files of targeted stars.}, author = {Hon, Marc and Stello, Dennis and García, Rafael A and Mathur, Savita and Sharma, Sanjib and Colman, Isabel L and Bugnet, Lisa Annabelle}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, asteroseismology, methods: data analysis, techniques: image processing, stars: oscillations, stars: statistics}, number = {4}, pages = {5616--5630}, publisher = {Oxford University Press}, title = {{A search for red giant solar-like oscillations in all Kepler data}}, doi = {10.1093/mnras/stz622}, volume = {485}, year = {2019}, } @article{11614, abstract = {The NASA Transiting Exoplanet Survey Satellite (TESS) is about to provide full-frame images of almost the entire sky. The amount of stellar data to be analysed represents hundreds of millions stars, which is several orders of magnitude more than the number of stars observed by the Convection, Rotation and planetary Transits satellite (CoRoT), and NASA Kepler and K2 missions. We aim at automatically classifying the newly observed stars with near real-time algorithms to better guide the subsequent detailed studies. In this paper, we present a classification algorithm built to recognise solar-like pulsators among classical pulsators. This algorithm relies on the global amount of power contained in the power spectral density (PSD), also known as the flicker in spectral power density (FliPer). Because each type of pulsating star has a characteristic background or pulsation pattern, the shape of the PSD at different frequencies can be used to characterise the type of pulsating star. The FliPer classifier (FliPerClass) uses different FliPer parameters along with the effective temperature as input parameters to feed a ML algorithm in order to automatically classify the pulsating stars observed by TESS. Using noisy TESS-simulated data from the TESS Asteroseismic Science Consortium (TASC), we classify pulsators with a 98% accuracy. Among them, solar-like pulsating stars are recognised with a 99% accuracy, which is of great interest for a further seismic analysis of these stars, which are like our Sun. Similar results are obtained when we trained our classifier and applied it to 27-day subsets of real Kepler data. FliPerClass is part of the large TASC classification pipeline developed by the TESS Data for Asteroseismology (T’DA) classification working group.}, author = {Bugnet, Lisa Annabelle and García, R. A. and Mathur, S. and Davies, G. R. and Hall, O. J. and Lund, M. N. and Rendle, B. M.}, issn = {1432-0746}, journal = {Astronomy & Astrophysics}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, publisher = {EDP Science}, title = {{FliPerClass: In search of solar-like pulsators among TESS targets}}, doi = {10.1051/0004-6361/201834780}, volume = {624}, year = {2019}, }