Search

The Normal-incidence Extreme Ultraviolet Photometer (NExtUP) is a smallsat mission concept designed to measure the EUV radiation conditions of exoplanet host stars, and F-M type stars in general. EUV radiation is absorbed at high altitude in a planetary atmosphere, in the exosphere and upper thermosphere, where the gas can be readily heated to escape temperatures. EUV heating and ionization are the dominant atmospheric loss drivers during most of a planet’s life. There are only a handful of accurately measured EUV stellar fluxes, all dating from Extreme Ultraviolet Explorer (EUVE) observations in the ‘90s. Consequently, current models of stellar EUV emission are uncertain by more than an order of magnitude and dominate uncertainties in planetary atmospheric loss models. NExtUP will use periodic and aperiodic multilayers on off-axis parabolic mirrors and a prime focus microchannel plate detector to image stars in 5 bandpasses between 150 and 900°A down to flux limits two orders of magnitude lower than reached by EUVE. NExtUP may also accomplish a compelling array of secondary science goals, including using line-of-sight absorption measurements to understand the structure of the local interstellar medium, and imaging EUV emission from energetic processes on solar system objects at unprecedented spatial resolution. NExtUP is well within smallsat weight limits, requires no special orbital conditions, and would be flown on a spacecraft supplied by MOOG Industries. It draws on decades of mission heritage expertise at SAO and LASP, including similar instruments successfully launched and operated to observe the Sun.

The astrophysical study of mass loss, both steady-state and transient, on the cool half of the HR diagram has implications both for the star itself and the conditions created around the star that can be hospitable or inimical to supporting life. Stellar coronal mass ejections (CMEs) have not been conclusively detected, despite the ubiquity with which their radiative counterparts in an eruptive event (flares) have been. I will review some of the different observational methods which have been used and possibly could be used in the future in the stellar case, emphasizing some of the difficulties inherent in such attempts. I will provide a framework for interpreting potential transient stellar mass loss in light of the properties of flares known to occur on magnetically active stars. This uses a physically motivated way to connect the properties of flares and coronal mass ejections and provides a testable hypothesis for observing or constraining transient stellar mass loss. Finally I will describe recent results using observations at low radio frequencies to detect stellar coronal mass ejections, and give updates on prospects using future facilities to make headway in this important area.

We present an XMM-Newton survey of the part of Orion A cloud south of the Orion Nebula. This survey includes the Lynds 1641 (L1641) dark cloud, a region of the Orion A cloud with very few massive stars and hence a relatively low ambient UV flux, and the region around the O9 III star Iota Orionis. In addition to proprietary data, we used archival XMM data of the Orion Nebula Cluster (ONC) to extend our analysis to a major fraction of the Orion A cloud. We have detected 1060 X-ray sources in L1641 and Iota Ori region. About 94% of the sources have 2MASS & Spitzer counterparts, 204 and 23 being Class II and Class I or protostars objects, respectively. In addition, we have identified 489 X-ray sources as counterparts to Class III candidates, given they are bright in X-rays and appear as normal photospheres at mid-IR wavelengths. The remaining 205 X-ray sources are likely distant AGNs or other galactic sources not related to Orion A. We find that Class III candidates appear more concentrated in two main clusters in L1641. The first cluster of Class III stars is found toward the northern part of L1641, concentrated around Iota Ori. The stars in this cluster are more evolved than those in the Orion Nebula. We estimate a distance of 300-320 pc for this cluster and thus it is closer than the Orion A cloud. Another cluster rich in Class III stars is located in L1641 South and appears to be a slightly older cluster embedded in the Orion A cloud. Furthermore, other evolved Class III stars are found north of the ONC toward NGC 1977., 42 pages, 14 figures, accepted for publication in ApJ

The binary system RW Aur consists of two classical T~Tauri stars (CTTSs). The primary recently underwent its second observed major dimming event ($\Delta V\,\sim2\,$mag). We present new, resolved Chandra X-ray and UKIRT near-IR (NIR) data as well as unresolved optical photometry obtained in the dim state to study the gas and dust content of the absorber causing the dimming. The X-ray data show that the absorbing column density increased from $N_H, Comment: 5 pages, 4 figures, accepted by A&A letters

A type stars are expected to be X-ray dark, yet weak emission has been detected from several objects in this class. We present new Chandra/HRC-I observations of the A5 V star \beta{} Pictoris. It is clearly detected with a flux of 9+-2 10^{-4} counts/s. In comparison with previous data this constrains the emission mechanism and we find that the most likely explanation is an optically thin, collisionally dominated, thermal emission component with a temperature around 1.1 MK. We interpret this component as a very cool and dim corona, with \log L_X/L_{bol}=-8.2 (0.2-2.0 keV). Thus, it seems that \beta{} Pictoris shares more characteristics with cool stars than previously thought., Comment: accepted by ApJ, 5 pages, 2 figures

International audience; M-stars are among the most active and numerous stars in our galaxy. Their activity plays a fundamentally important role in shaping the exoplanetary biosphere since the habitable zones are very close to these stars. Therefore, modeling M-star activity has become a focal point in habitability studies. The fully convective members of the M-star population demand more immediate attention due to the discovery of Earth-like exoplanets around our stellar neighbors Proxima Centauri and TRAPPIST-1 which are both fully convective. The activity of these stars is driven by their convective dynamo, which may be fundamentally different from the solar dynamo due the absence of radiative cores. We model this dynamo mechanism using high-resolution 3D anelastic MHD simulations. To understand the evolution of the dynamo mechanism we simulate two cases, one with a fast enough rotation period to model a star in the `saturated' regime of the rotation-activity realtionship and the other with a slower period to represent cases in the `unsaturated' regime. We find the rotation period fundamentally controls the behavior of the dynamo solution: faster rotation promotes strong magnetic fields (of order kG) on both small and large length scales and the dipolar component of the magnetic field is dominant and stable, however, slower rotation leads to weaker magnetic fields which exhibit cyclic behavior. In this talk, I will present the simulation results and discuss how we can use them to interpret several observed features of the M-star activity.

X-ray observations have been made of a sample of 20 classical Cepheids, including two new observations (Polaris and {\it l} Car) reported here. The occurrence of X-ray flux around the pulsation cycle is discussed. Three Cepheids are detected ($\delta$ Cep, $\beta$ Dor, and Polaris). X-rays have also been detected from the low--mass F, G, and K companions of 4 Cepheids (V473 Lyr, R Cru, V659 Cen, and W Sgr), and one hot companion (S Mus). Upper limits on the X-ray flux of the remaining Cepheids provide an estimate that 28\% have low mass companions. This fraction of low--mass companions in intermediate mass Cepheids is significantly lower than expected from random pairing with the field IMF. Combining the companion fraction from X-rays with that from ultraviolet observations results in a binary/multiple fraction of 57\% $\pm$12\% for Cepheids with the ratios q $>$ 0.1 and separations a $>$ 1 au. This is a lower limit since M stars are not included. X-ray observations detect less massive companions than other existing studies of intermediate mass stars. Our measured occurrence rate of unresolved, low-mass companions to Cepheids suggests that intermediate-period binaries derive from a combination of disk and core fragmentation and accretion. This yields a hybrid mass-ratio distribution that is skewed toward small values compared to a uniform distribution but is still top-heavy compared to random pairings drawn from the IMF., Comment: Accepted by ApJ

The past two decades have seen dramatic progress in our knowledge of the population of young stars of age, 7 pages, 5 figures; to appear in Proceedings of "The 20th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun" (ed. S.J. Wolk)

The rotational evolution of solar-type stars is moderately well-understood up to the age of the Sun. One way to extend the gyrochronology relation to stars of later spectral type is by matching the near solar-type member of each pair of a visual binary star with its later-type companion. The precise parallaxes and proper motions in Gaia Data-Release 2 has made it possible to identify a substantial number of wide binary (common proper motion) stars in the Kepler Mission field of view, many of which already have measured rotation periods. I have identified 313 wide binary pairs in the Kepler catalog. A period-color diagram of 116 of those pairs for which rotations of both components have been measured show that many, but not all of the systems having components of nearly equal color also have roughly equal periods. However, the period-color relation for binary pairs with larger color differences is somewhat more chaotic. In particular, the cooler component of some systems rotates more slowly than the hotter component contrary to the expected trend.

The formation and evolution of young star clusters and OB associations is fundamental to our understanding of the star formation process, the conditions faced by young binary and planetary systems, and the formation of long-lived open and globular clusters. Despite this our understanding of the physical processes that drive this evolution has been limited by the static nature of most observations. This is all changing thanks to a revolution in kinematic data quality from large-scale radial velocity surveys and new astrometric facilities such as {\it Gaia}. Here I summarise recent studies of multiple OB associations from both {\it Gaia} and ground-based astrometric surveys. These observations show that OB associations have considerable kinematic substructure and no evidence for the radial expansion pattern predicted by theories such as residual gas expulsion. This means that, contrary to the standard view of OB associations as expanded star clusters, these systems could never have been dense star clusters in the past and were most likely born as extended and highly substructured groups of stars. This places strong constraints on the primordial clustering of young stars and the conditions faced by young planetary systems., {"references":["Allison, R. J., Goodwin, S. P., Parker, R. J., Portegies Zwart, S. F., de Grijs, R., et al. 2009, MNRAS, 395, 1449.","Ambartsumian, V. A. 1947, Stellar Evolution and Astrophysics (Armenian Acad. of Sci.).","Ambartsumian, V. A. 1949, Dokl. Akad. Nauk SSR, 68.","Armstrong, J. J., Wright, N. J., & Jeffries, R. D. 2018, MNRAS, 480, L121.","Baumgardt, H. & Kroupa, P. 2007, MNRAS, 380, 1589.","Blaauw, A. 1952, BAIN, 11, 414.","Blaauw, A. 1964, ARA&A, 2, 213.","Bonnell, I. A., Bate, M. R., Clarke, C. J., & Pringle, J. E. 2001, MNRAS, 323, 785.","Briceño, C., Preibisch, T., Sherry, W. H., Mamajek, E. A., Mathieu, R. D., et al. 2007, In Protostars and Planets V, edited by B. Reipurth, D. Jewitt, & K. Keil, pp. 345–360.","Brown, A. G. A., Blaauw, A., Hoogerwerf, R., de Bruijne, J. H. J., & de Zeeuw, P. T. 1999, In NATO Advanced Sci- ence Institutes (ASI) Series C, edited by C. J. Lada & N. D. Kylafis, vol. 540, p. 411.","Brown, A. G. A., Dekker, G., & de Zeeuw, P. T. 1997, MNRAS, 285, 479.","Cartwright, A. & Whitworth, A. P. 2004, MNRAS, 348, 589.","Chen, C. H., Mamajek, E. E., Bitner, M. A., Pecaut, M., Su, K. Y. L., et al. 2011, ApJ, 738, 122.","Dahm, S. E., Slesnick, C. L., & White, R. J. 2012, ApJ, 745, 56.","de Zeeuw, P. T., Hoogerwerf, R., de Bruijne, J. H. J., Brown, A. G. A., & Blaauw, A. 1999, AJ, 117, 354.","Dobbs, C. L. & Pringle, J. E. 2013, MNRAS, 432, 653.","Drew, J. E., Greimel, R., Irwin, M. J., & Sale, S. E. 2008, MN- RAS, 386, 1761.","Gaia Collaboration, Brown, A. G. A., Vallenari, A., Prusti, T., de Bruijne, J. H. J., et al. 2016a, A&A, 595, A2.","Gaia Collaboration, Prusti, T., de Bruijne, J. H. J., Brown, A. G. A., Vallenari, A., et al. 2016b, A&A, 595, A1.","Geary, R. C. 1954, The Incorporated Statistician, 5, 115.","Gontcharov, G. A. 2006, Astronomy Letters, 32, 759.","Griffiths, D. W., Goodwin, S. P., & Caballero-Nieves, S. M. 2018, MNRAS, 476, 2493.","Hills, J. G. 1980, ApJ, 235, 986.","Kharchenko, N. V., Scholz, R.-D., Piskunov, A. E., Röser, S., & Schilbach, E. 2007, Astronomische Nachrichten, 328, 889.","Kiminki, D. C., Kobulnicky, H. A., Kinemuchi, K., Irwin, J. S., Fryer, C. L., et al. 2007, ApJ, 664, 1102.","Kruijssen, J. M. D. 2011, In Stellar Clusters and Associations: A RIA Workshop on Gaia, pp. 137–141.","Lada, C. J. & Lada, E. A. 2003, ARA&A, 41, 57.","Lada, C. J., Margulis, M., & Dearborn, D. 1984, ApJ, 285, 141.","Mamajek, E. E. & Bell, C. P. M. 2014, MNRAS, 445, 2169.","Mamajek, E. E., Meyer, M. R., & Liebert, J. 2002, AJ, 124, 1670.","Maschberger, T. & Clarke, C. J. 2011, MNRAS, 416, 541.","Moran, P. A. P. 1950, Biometrika, 37, 17.","Parker, R. J. & Wright, N. J. 2016, MNRAS, 457, 3430.","Parker, R. J., Wright, N. J., Goodwin, S. P., & Meyer, M. R. 2014, MNRAS, 438, 620.","Pecaut, M. J. & Mamajek, E. E. 2016, MNRAS, 461, 794.","Pfalzner, S. 2009, A&A, 498, L37.","Preibisch, T. & Mamajek, E. 2008, The Nearest OB Associa- tion: Scorpius-Centaurus (Sco OB2), p. 235 (Handbook of Star Forming Regions).","Rizzuto, A. C., Ireland, M. J., & Robertson, J. G. 2011, MNRAS, 416, 3108.","Rygl, K. L. J., Brunthaler, A., Sanna, A., Menten, K. M., Reid, M. J., et al. 2012, A&A, 539, A79.","Weidner, C. & Kroupa, P. 2006, MNRAS, 365, 1333.","Wright, N. J., Bouy, H., Drew, J. E., Sarro, L. M., Bertin, E., et al. 2016, MNRAS, 460, 2593.","Wright, N. J. & Drake, J. J. 2009, ApJS, 184, 84.","Wright, N. J., Drake, J. J., Drew, J. E., & Vink, J. S. 2010, ApJ, 713, 871.","Wright, N. J., Drake, J. J., Guarcello, M. G., Aldcroft, T. L., Kashyap, V. 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Recent studies have been detecting many planets around M dwarfs. Determining the detailed chemical compositions of M dwarfs is crucial for revealing the formation processes of the planetary systems and constraining the internal structures of the terrestrial planets around them. However, their intrinsic faintness and dominant molecular absorption hinder the well-established measurements of accurate chemical composition with high-resolution optical spectra. The problems are mitigated in near-infrared wavelength. The high-resolution near-infrared spectroscopy is now promising because of the increasing development of new spectrometers enabling it. IRD is such a new instrument for the Subaru Telescope constructed for a planet search around nearby M dwarfs. IRD is the first instrument for 8m-class telescopes to cover the Y, J, and H bands simultaneously with a maximum spectral resolution of 70,000. The large diameter and broadband coverage have made it possible to observe more atomic lines than ever before in near-IR spectra of faint M dwarfs. We verified that the quality of IRD spectra is comparable to the existing ones such as CRIRES spectra in terms of wavelength assignment and resolution. We report the interpretation of IRD spectra of Barnard’s Star. We identified the absorption lines throughout the Y, J, and H bands. We detected more than 100 FeH lines, which are dominant in Y band, and examined their behavior. We also determined the elemental abundances for Fe, Ti, Cr, Na, Mg, Al, Si, K, Ca, V, and Mn, based on the equivalent width of the corresponding atomic lines. The result, where the metallicity is lower than the Sun and the abundances of alpha elements (Mg, Al, Si, Ti) are higher than that of Fe, is consistent with the prediction from kinematics and rotation period that the Barnard’s Star is an old star belonging to the thick disk in our galaxy. Besides, we observed LHS 1140 with a similar temperature to the Barnard’s Star and found that it is metal-richer and alpha-poorer than Barnard’s Star., {"references":["Gustafsson, B et al. (2008)","Kupka, F e al. (1999)","Önehag, A et al. (2012)"]}

We present the results of our search for wide binaries in the SUPERBLINK high proper motion catalog of 2.8 million stars with proper motions >40 mas/yr, which has been recently enhanced with data from the GAIA mission. In a first step, we conduct a Bayesian analysis taking into account angular separations and proper motion differences provided by the SUPERBLINK catalog, and identify all possible common proper motion (CPM) pairs with separations up to 60 arcminutes. In the second step we expand the analysis using parallaxes from the Gaia DR2 release, and calculate probabilities for each pair to be a gravitationally bound system. The result is a list of ~18,000 pairs with probabilities of being real binaries greater than 99 percent. We show that the distribution of projected physical separations of these wide, field binaries follows a decreasing power law, and shows no evidence of being bimodal, i.e. there is no evidence of a secondary population of pairs with separations $>10^4$ AU. In addition, we find clear evidence that at least 30 percent of these wide binaries are triples/multiples, based on one of the components being over-luminous., {"references":["Duquennoy & Mayor 1991","Raghavan et al. 2010","Gaia Collaboration et al. 2018b","Gaia Collaboration et al. 2016"]}

In G dwarfs, the surface distribution, coverage and lifetimes of starspots deviate from solar-like patterns as the rotation rate increases. We set up a numerical platform which includes the large-scale rotational and surface flow effects, aiming to simulate evolving surface patterns over an activity cycle for up to 8 times the solar rotation and flux emergence rates. At the base of the convection zone, we assume a solar projected butterfly diagram. We then follow the rotationally distorted trajectories of rising thin flux tubes to obtain latitudes and tilt angles. Using them as source distributions, we run a surface flux transport model with solar parameters. Our model predicts surface distributions of the signed radial fields and the starspots that qualitatively agree with observations., Please prefer this version, for which a few improvements on text clarity have been made., {"references":["Castenmiller et al. (1986). Solar Physics 105, 207","Isik et al. (2011) A&A 528, A135","Isik et al. (2018). arXiv:1810.06728","Jiang et al. (2011). A&A 528, A82","Jiang et al. (2011). A&A 528, A83","O'Neal et al. (2004). Astronomical Journal 128, 1802","Pelt et al. (2010). A&A 513, A48"]}

Dark spots crossing the stellar disk lead to periodic modulations in stellar light-curves that encode information on surface rotation and magnetic activity. Here, we analyze Kepler long-cadence data (four different time-series) for ~50,000 solar-type main-sequence and subgiant stars cooler than 5500 K and with surface gravity log g larger than 3.5 dex. Surface rotation period estimates are obtained through the implementation of a method which combines a wavelet analysis with the autocorrelation of the light-curve. We obtain reliable rotation periods for 23,494 stars. Only 16,600 of these are common to McQuillan (2013, 2014), with an agreement of ~99% within 2sigma. We also take special care to identify and remove possible polluters, such as classical pulsators, misclassified Red Giants, photometric pollution and other instrumental issues in light-curves., {"references":["Aigrain, S., Llama, J., Ceillier, T., et al. 2015, MNRAS, 450, 3211","Barnes, S. A. 2007, ApJ, 669, 1167","Berger, T. A., Huber, D., Gaidos, E., & van Saders, J. L. 2018, ApJ, 866, 99","Borucki, W. J., Koch, D., Basri, G., et al. 2010, Science, 327, 977","Brun, A. S. & Browning, M. K. 2017, Living Rev. Solar Phys., 14, 4","Ceillier, T., Tayar, J., Mathur, S., et al. 2017, A&A, 605, A111","Ceillier, T., van Saders, J., García, R. A., et al. 2016, MNRAS, 456, 119","García, R. A., Ceillier, T., Salabert, D., et al. 2014a, A&A, 572, A34","García, R. A., Hekker, S., Stello, D., et al. 2011, MNRAS, 414, L6","García, R. A., Mathur, S., Pires, S., et al. 2014b, A&A, 568, A10","Jenkins, J. M., Caldwell, D. A., Chandrasekaran, H., et al. 2010, ApJL, 713, L87","Mathur, S., García, R. A., Ballot, J., et al. 2014, A&A, 562, A124","Mathur, S., García, R. A., Régulo, C., et al. 2010, A&A, 511, A46","Mathur, S., Huber, D., Batalha, N. M., et al. 2017, ApJS, 229, 30","McQuillan, A., Aigrain, S., & Mazeh, T. 2013a, MNRAS, 432, 1203","McQuillan, A., Mazeh, T., & Aigrain, S. 2013b, ApJ, 775, L11","McQuillan, A., Mazeh, T., & Aigrain, S. 2014, ApJS, 211, 24","Nielsen, M. B., Gizon, L., Schunker, H., & Karoff, C. 2013, A&A, 557, L10","Pires, S., Mathur, S., García, R. A., et al. 2015, A&A, 574, A18","Reinhold, T., Reiners, A., & Basri, G. 2013, A&A, 560, A4","Simonian, G. V. A., Pinsonneault, M. H., & Terndrup, D. M. 2018, arXiv:1809.02141","Skumanich, A. 1972, ApJ, 171, 565","Torrence, C. & Compo, G. P. 1998, Bull. Amer. Meteor. Soc., 79, 61","Wilson, O. C. 1963, ApJ, 138, 832","Wilson, O. C. & Skumanich, A. 1964, ApJ, 140, 1401"]}

We present a study of the kinematics of nearby (d ≲ 1.2 kpc) high-velocity K and M dwarfs and subdwarfs from the SUPERBLINK proper motion catalog (μ > 40 mas/yr), incorporating data from the second Gaia Data Release 2. All K and M stars were selected based on their GBP - GRP colors and absolute G magnitudes, and distances were calculated from Gaia parallaxes. We plot transverse velocities, vT, of stars in six different directions on the sky, to examine the distribution of local K and M stars in the (U, V, W) velocity space system. Our analysis suggests that the velocity space distribution of local thick disk and halo stars, much like the velocity-space distribution of disk stars, is inhomogeneous and shows the signature of at least one global "stream" consisting of stars drifting toward Galactic center., {"references":["Bensby et al., 2014, A&A, 562, 71","Gaia Collaboration, 2016, A&A, 595, 1","Gaia Collaboration, 2018b, arXiv:1804.09365","Gaia Collaboration: A. Helmi, F. van Leeuwen, \nP. McMillan, et al., 2018, arXiv:1804.09381","Helmi et al., 1999, Nature, 402, 53","Lepine, S. & Shara, M. M., 2005, AJ, 129, 1483","Lepine, S., 2005, AJ, 130, 1247","Lepine, S. & Gaidos, E., 2011, AJ, 142, 138"]}

The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes and proper motions for 1.3 billion sources. The resulting Hertzsprung-Russel diagram reveals fine structures throughout the mass range. This paper aims to investigate the content of Gaia DR2 at the low-mass end and to characterize ultra-cool and brown dwarfs. We first retrieved the sample of spectroscopically confirmed ultra-cool stars and brown dwarfs (>M6) in Gaia DR2. We used their locus in the precise Hertzsprung-Russel diagram to select new candidates and to investigate their properties. About 70% of the bright enough objects from the known sample are recovered, filling the gap with Gaia DR1. Furthermore, Gaia DR2 contains ∼100 000 >M6 and ∼1000 L candidates (all are . L5). A tentative classification suggests that a few hundred of them are young or subdwarf candidates. Their distance distribution shows that the solar neighbourhood census is still not complete. Gaia DR2 offers a great wealth of information on low-mass objects. It provides a homogeneous and precise catalogue of candidates that is worthwhile to be further characterized with spectroscopic observations., {"references":["Allard, F., Homeier, D., & Freytag, B. 2013, MmSAI, 84,1053","Artigau, É., Lafrenière, D., Doyon, R., et al. 2009, in Ameri-can Institute of Physics Conference Series, Vol. 1094, 15thCambridge Workshop on Cool Stars, Stellar Systems, andthe Sun, ed. E. Stempels, 493–496","Baraffe, I., Homeier, D., Allard, F., & Chabrier, G. 2015,A&A, 577, A42","Best, W. M. J., Liu, M. C., Magnier, E., & Dupuy, T. 2018a,in American Astronomical Society Meeting Abstracts, Vol.231, American Astronomical Society Meeting Abstracts#231, 349.19","Best, W. M. J., Magnier, E. A., Liu, M. C., et al. 2018b, ApJS,234, 1","Burrows, A., Sudarsky, D., Sharp, C., et al. 1998, in Astro-nomical Society of the Pacific Conference Series, Vol. 134,Brown Dwarfs and Extrasolar Planets, ed. R. Rebolo, E. L.Martin, & M. R. Zapatero Osorio, 354","Capitanio, L., Lallement, R., Vergely, J. L., Elyajouri, M., &Monreal-Ibero, A. 2017, A&A, 606, A65","Cui, X.-Q., Zhao, Y.-H., Chu, Y.-Q., et al. 2012, Research inAstronomy and Astrophysics, 12, 1197","Dalton, G., Trager, S., Abrams, D. C., et al. 2014, in SPIE,Vol. 9147, Ground-based and Airborne Instrumentation forAstronomy V, 91470L","de Jong, R. S., Barden, S. C., Bellido-Tirado, O., et al. 2016,in SPIE, Vol. 9908, Ground-based and Airborne Instrumen-tation for Astronomy VI, 99081O","Eisenstein, D. J., Weinberg, D. H., Agol, E., et al. 2011, AJ,142, 72","Evans, D. W., Riello, M., De Angeli, F., et al. 2018, A&A,616, A4","Faherty, J. K., Gagne, J., Burgasser, A. J., et al. 2018, ArXive-prints","Faherty, J. K., Riedel, A. R., Cruz, K. L., et al. 2016, ApJS,225, 10","Folkes, S. L., Pinfield, D. J., Jones, H. R. A., et al. 2012,MNRAS, 427, 3280","Gaia Collaboration, Babusiaux, C., van Leeuwen, F., et al.2018a, A&A, 616, A10","Gaia Collaboration, Brown, A. G. A., Vallenari, A., et al.2018b, A&A, 616, A1","Gaia Collaboration, Brown, A. G. A., Vallenari, A., et al.2016a, A&A, 595, A2","Gaia Collaboration, Prusti, T., de Bruijne, J. H. J., et al.2016b, A&A, 595, A1","Majewski, S. R., Schiavon, R. P., Frinchaboy, P. M., et al.2017, AJ, 154, 94","Marocco, F., Jones, H. R. A., Day-Jones, A. C., et al. 2015,MNRAS, 449, 3651","Marrese, P. M., Marinoni, S., Fabrizio, M., & Giuffrida, G.2017, A&A, 607, A105","Paletou, F. & Zolotukhin, I. 2014, ArXiv e-prints 1408.7026","Rajpurohit, A. S., Reylé, C., Allard, F., et al. 2014, A&A, 564,A90","Robert, J., Gagné, J., Artigau, É., et al. 2016, ApJ, 830, 144","Schmidt, S. J., Hawley, S. L., West, A. A., et al. 2015, AJ,149, 158","Scholz, R.-D. & Bell, C. P. M. 2018, Research Notes of theAmerican Astronomical Society, 2, 33","Skrutskie, M. F., Cutri, R. M., Stiening, R., et al. 2006, AJ,131, 1163","Skrzypek, N., Warren, S. J., & Faherty, J. K. 2016, A&A, 589,A49","Smart, R. L., Marocco, F., Caballero, J. A., et al. 2017, MN-RAS, 469, 401","Smith, L., Lucas, P. W., Bunce, R., et al. 2014, MNRAS, 443,2327","Smith, L. C., Lucas, P. W., Kurtev, R., et al. 2018, MNRAS,474, 1826","Taylor, M. B. 2005, in Astronomical Society of the PacificConference Series, Vol. 347, Astronomical Data AnalysisSoftware and Systems XIV, ed. P. Shopbell, M. Britton, &R. Ebert, 29","Theissen, C. A., West, A. A., Shippee, G., Burgasser, A. J., &Schmidt, S. J. 2017, AJ, 153, 92","Wenger, M., Ochsenbein, F., Egret, D., et al. 2000, A&AS,143, 9","Zhang, Z. H., Gálvez-Ortiz, M. C., Pinfield, D. J., et al. 2018,MNRAS"]}

There is a discrepancy between the frequency of rocky planets in the inner AU known around Sun-like stars and the frequency of stars observed to be undergoing the collisions that form these planets. The discrepancy may indicate that rocky planets are less common than believed or that they form very differently than we have imagined, producing little or no debris signature. A third, less dramatic possibility is that planet-forming systems retain a tenuous reservoir of gas that whisks away the warm dust (debris) produced by planet-forming collisions. Over the past decade, it has been recognized that fluorescent FUV molecular hydrogen emission is an excellent tracer of gas in the planet forming regions of disks around young stars. We are using HST+COS with the G130M grating to survey the FUV spectrum between 1100 - 1370 Å for molecular hydrogen emission from a sample of 30 stars in the 11 Myr old Upper Scorpious star forming region. These data will test whether small amounts of disk gas remove the debris from planet forming collisions, or whether rocky planet formation possibly proceeds much differently than currently thought. Here we report initial results from this survey. &nbsp

One of the key questions in exoplanetary science is formation conditions and early stages of planet lives. The search for young K and M dwarfs in the Solar neighbourhood below 100 Myr is thus essential to characterize their young planets. Here we present systematic data-driven and model-independent search of young field single stars in large stellar surveys. It is based on direct comparison of spectra with the same atmospheric parameters drawn from large databases of stellar surveys and identifying stars with spectroscopic features of stellar youth. In the GALAH survey, we identify over 3000 stars with detectable Lithium absorption line, and 38,000 candidate active stars with Ca II infrared triplet emission in the RAVE survey., {"references":["Žerjal, M. et al. 2017, ApJ, 835, 61, DOI: 10.3847/1538-4357/835/1/61"]}

The second release of Gaia is revolutionizing the study of star formation and young clusters. In this talk I discussed the potential in detecting multiple populations in young clusters, and the importance of a membership well defined as a starting point. I presented, as an example, the results on the multiple population of one of the closest low-mass star forming region, the Chamaeloen I. Using the Gaia data we found the region to be at slightly higher distance than previously thought. We confirmed the presence of two populations with a peculiar spatial distribution, which might be influenced by the filamentary molecular cloud present in the region. Presenting the method applied to find kinematically the multiple populations, I discussed the effect on the results of taking into account the correlations between parallaxes and proper motions. I finally presented the impact of the refined distance of young stars and clusters using the Gaia data on other fields of star formation, e.g. the study of the evolution of protoplanetary disks and the disk structure., splinter session contributed talk, {"references":["Andrews, S. M., Wilner, D. J., Zhu, Z., Birnstiel, T., Carpenter, J. M., et al. 2016, ApJL, 820, L40","Armstrong, J. J., Wright, N. J., & Jeffries, R. D. 2018, MNRAS, 480, L121","Bailer-Jones, C. A. L. 2015, PASP, 127, 994","Brown, A. G. A., Arenou, F., van Leeuwen, F., Lindegren, L., & Luri, X. 1997, In Hipparcos - Venice '97, edited by R. M. Bonnet, E. Høg, P. L. Bernacca, L. Emiliani, A. Blaauw, C. Turon, J. Kovalevsky, L. Lindegren, H. Hassan, M. Bouffard, B. Strim, D. Heger, M. A. C. Perryman, & L. Woltjer, ESA Special Publication, vol. 402, pp. 63–68","Cantat-Gaudin, T., Mapelli, M., Balaguer-Núñez, L., Jordi, C., Sacco, G., et al. 2018, ArXiv e-prints","Comerón, F., Reipurth, B., Henry, A., & Fernández, M. 2004, A&A, 417, 583","Fedele, D., Carney, M., Hogerheijde, M. R., Walsh, C., Miotello, A., et al. 2017, A&A, 600, A72","Fedele, D., Tazzari, M., Booth, R., Testi, L., Clarke, C. J., et al. 2018, A&A, 610, A24","Feigelson, E. D. & Lawson, W. A. 2004, ApJ, 614, 267","Franciosini, E., Sacco, G. G., Jeffries, R. D., Damiani, F., Roccatagliata, V., et al. 2018, A&A, 616, L12","Gagné, J. & Faherty, J. K. 2018, ApJ, 862, 138","Gagné, J., Faherty, J. K., & Mamajek, E. E. 2018, ApJ, 865, 136","Gaia Collaboration, Brown, A. G. A., Vallenari, A., Prusti, T., de Bruijne, J. H. J., et al. 2018, ArXiv e-prints.","Haikala, L. K., Harju, J., Mattila, K., & Toriseva, M. 2005, A&A, 431, 149","Haisch, K. E., Jr., Lada, E. A., & Lada, C. J. 2001, ApJL, 553, L153","Hénault-Brunet, V., Gieles, M., Evans, C. J., Sana, H., Bastian, N., et al. 2012, A&A, 545, L1","Hernández, J., Hartmann, L., Megeath, T., Gutermuth, R., Muzerolle, J., et al. 2007, ApJ, 662, 1067.","Jeffries, R. D., Jackson, R. J., Cottaar, M., Koposov, S. E., Lanzafame, A. C., et al. 2014, A&A, 563, A94","Lindegren, L., Hernandez, J., Bombrun, A., Klioner, S., Bastian, U., et al. 2018, ArXiv e-prints","Lindegren, L., Madsen, S., & Dravins, D. 2000, A&A, 356, 1119","Luhman, K. L. 2007, ApJS, 173, 104","Luri, X., Brown, A. G. A., Sarro, L. M., Arenou, F., Bailer- Jones, C. A. L., et al. 2018, ArXiv e-prints","Mapelli, M. 2017, MNRAS, 467, 3255","Pérez, L. M., Carpenter, J. M., Andrews, S. M., Ricci, L., Isella, A., et al. 2016, Science, 353, 1519","Perryman, M. A. C., Lindegren, L., Kovalevsky, J., Hoeg, E., Bastian, U., et al. 1997, A&A, 323, L49","Roccatagliata, V., Bouwman, J., Henning, T., Gennaro, M., Feigelson, E., et al. 2011, ApJ, 733, 113","Roccatagliata, V., Sacco, G. G., Franciosini, E., & Randich, S. 2018, A&A, 617, L4","Sacco, G. G., Spina, L., Randich, S., Palla, F., Parker, R. J., et al. 2017, Astronomy & Astrophysics, 601, A97. ISSN 1432- 0746","Sicilia-Aguilar, A., Hartmann, L., Calvet, N., Megeath, S. T., Muzerolle, J., et al. 2006, ApJ, 638, 897","Stelzer, B., Micela, G., & Neuhäuser, R. 2004, A&A, 423, 1029","Tognelli, E., Prada Moroni, P. G., & Degl'Innocenti, S. 2011, A&A, 533, A109","van der Marel, N., van Dishoeck, E. F., Bruderer, S., Birnstiel, T., Pinilla, P., et al. 2013, Science, 340, 1199","Voirin, J., Manara, C. F., & Prusti, T. 2018, A&A, 610, A64","Whittet, D. C. B., Prusti, T., Franco, G. A. P., Gerakines, P. A., Kilkenny, D., et al. 1997, A&A, 327, 1194","Zhang, K., Isella, A., Carpenter, J. M., & Blake, G. A. 2014, ApJ, 791, 42"]}

I summarize results on transitional and degenerate brown dwarfs presented in a series titled Primeval very low-mass stars and brown dwarfs. I introduce an L subdwarf classification scheme, which classified L subdwarfs into three metal subclasses. I would also like to draw your attention to transitional brown dwarfs which have long-lasting unsteady hydrogen fusion in their cores to replenish the dissipation of their initial thermal energy. The mass range of transitional brown dwarfs with solar metallicity is between 0.065 and 0.079 solar mass according to the latest evolutionary models. The temperature distribution of transitional brown dwarfs are stretched to a wide range and formed a substellar transition zone. The substellar transition zone is most significant in the old halo population and ranges from 1000 K to 2200-3000 K depending on metallicity. The transition zone has impacts on our observational properties of field brown dwarf population. Because field L dwarfs are composed of very low-mass stars, transitional brown dwarfs, and relative younger electron-degenerate brown dwarfs., {"references":["Allard, F. 2014, In Exploring the Formation and Evolution of Planetary Systems, edited by M. Booth, B. C. Matthews, & J. R. Graham, IAU Symposium, vol. 299, pp. 271–272.","Allard, F. & Hauschildt, P. H. 1995, ApJ, 445, 433.","Baraffe, I., Chabrier, G., Allard, F., & Hauschildt, P. H. 1997, A&A, 327, 1054.","Baraffe, I., Chabrier, G., Barman, T. S., Allard, F., & Hauschildt, P. H. 2003, A&A, 402, 701.","Baraffe, I., Homeier, D., Allard, F., & Chabrier, G. 2015, A&A, 577, A42.","Burgasser, A. J. 2004, ApJL, 614, L73.","Burgasser, A. J. 2007, ApJ, 659, 655.","Burgasser, A. J., Cruz, K. L., Cushing, M., Gelino, C. R., Looper, D. L., et al. 2010, ApJ, 710, 1142.","Burgasser, A. J., Cruz, K. L., & Kirkpatrick, J. D. 2007, ApJ, 657, 494.","Burrows, A., Hubbard, W. B., Lunine, J. I., & Liebert, J. 2001, Reviews of Modern Physics, 73, 719.","Burrows, A., Marley, M., Hubbard, W. B., Lunine, J. I., Guillot, T., et al. 1997, ApJ, 491, 856.","Burrows, A., Sudarsky, D., Sharp, C., Marley, M. S., Hubbard, W. B., et al. 1998, In Brown Dwarfs and Extrasolar Planets, edited by R. Rebolo, E. L. Martin, & M. R. Zapatero Osorio, Astronomical Society of the Pacific Conference Series, vol. 134, p. 354.","Chabrier, G. & Baraffe, I. 1997, A&A, 327, 1039.","Dupuy, T. J. & Liu, M. C. 2017, ApJS, 231, 15.","Hayashi, C. & Nakano, T. 1963, Progress of Theoretical Physics, 30, 460.","Kirkpatrick, J. D. 2005, ARA&A, 43, 195.","Kirkpatrick, J. D., Looper, D. L., Burgasser, A. J., Schurr, S. D., Cutri, R. M., et al. 2010, ApJS, 190, 100.","Kumar, S. S. 1963, ApJ, 137, 1121.","Lazorenko, P. F. & Sahlmann, J. 2018, ArXiv e-prints.","Nakajima, T., Oppenheimer, B. R., Kulkarni, S. R., Golimowski, D. A., Matthews, K., et al. 1995, Nature, 378, 463.","Rebolo, R., Zapatero Osorio, M. R., & Martín, E. L. 1995, Na- ture, 377, 129.","Zhang, Z. H., Gálvez-Ortiz, M. C., Pinfield, D. J., Burgasser, A. J., Lodieu, N., et al. 2018a, MNRAS.","Zhang, Z. H., Homeier, D., Pinfield, D. J., Lodieu, N., Jones, H. R. A., et al. 2017a, MNRAS, 468, 261.","Zhang, Z. H., Pinfield, D. J., Gálvez-Ortiz, M. C., Burningham, B., Lodieu, N., et al. 2017b, MNRAS, 464, 3040.","Zhang, Z. H., Pinfield, D. J., Gálvez-Ortiz, M. C., Homeier, D., Burgasser, A. J., et al. 2018b, MNRAS, 479, 1383.","Zhang Z. H., Burgasser A. J., Galvez-Ortiz M. C., Lodieu N., Zapatero Osorio M. R., Pinfield D. J., Allard F., 2019b, MNRAS, 486, 1260.","Zhang Z. H., Burgasser A. J., Smith L. C., 2019a, MNRAS, 486,1840."]}

This contributed poster was given in the poster session at the 20th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (Cool Stars 20) in July 2018., Chang et al. in preparation (2018) soon to be submitted to PASA.

Open Clusters (OCs), and in particular the oldest ones, have been widely used to test formation and evolution theories of the galaxy. Also, since their HR diagrams provide an snapshot of stellar evolution, they are very good targets to investigate stellar formation and evolution models, together with dynamical interactions among stars. In particular, the most nearby ones profit from the best accuracies in astrometry, photometry and spectroscopy, and therefore they are commonly used as benchmark targets to assess performances of methods and calibrate results. Our project is devoted to perform an in-depth study of the physical properties of a sample of benchmark evolved clusters inside a radius within 500 pc around the Sun. Our aim is to revisit their properties of shape, radii, extinction, galactic velocity, age and chemical composition, using recent data release from Gaia, complemented with ground-based high resolution spectroscopic data. Here we present the first results of this project after the release of Gaia DR2 concerning the cluster Ruprecht 147, the oldest nearby OC. We do a membership selection taking into account proper motions, parallax and photometry of the stars in a region of 4 deg radius around the center of the cluster. We study the peculiar kinematics of this cluster compared to the field stars in the solar neighbourhood. Finally, we do a spectroscopic analysis of the cluster using HARPS and HARPSN spectra for 5 main sequence stars and 6 red giants. We obtain preliminary chemical abundances for 8 species, pointing that the cluster has in general solar abundances.

We show our very first results regarding the stellar atmospheric parameter determinations (Teff, log g, [M/H]) of M-type stars observed with CARMENES by means of the spectral synthesis method. We have selected spectral ranges around iron and titanium lines and molecular bands in three reference M-type stars: GX And (M1.0 V), Luyten's star (M3.5 V), and Teegarden's star (M7.0 V). We employ PHOENIX stellar model atmospheres, the radiative transfer code Turbospectrum and line data from the VALD3 database to obtain a grid of synthetic spectra, and a Markov Chain Monte Carlo process implemented in SteParSyn code to derive the value of the stellar atmospheric parameters., {"references":["Alvarez & Plez 1998, A&A, 330, 1109","Blanco-Cuaresma et al. 2014, A&A, 569, A111","Husser et al. 2013, A&A, 553, A6","Passegger et al. 2018, A&A, 615, A6","Quirrenbach et al. 2016, in Proc. SPIE, 9908, 990812","Ryabchikova et al. 2015, PhysScr, 90, 5","Tabernero et al. 2018, MNRAS, 476, 3106"]}

The young (7 Myr) 1.5 M⊙ T Tauri star T Cha shows dramatic variability. The optical extinction varies by at least 3 magnitudes on few hour time-scales. The obscuration is produced by material at the inner edge of the circumstellar disk and therefore characterizing the absorbing material can reveal important clues regarding the transport of gas and dust within such disks. The inner disk of T Cha is particularly interesting, because T Cha has a transitional disk with a large gap at 0.2- 15 AU in the dust disk and allows study of the gas and dust structure in the terrestrial planet formation zone during this important rapid phase of protoplanetary disk evolution. For this reason we have conducted a comprehensive, multi-spectral- region, observing campaign to study the UV/X-ray/optical variability of T Cha. During 2018 February/March we monitored the optical photometric and spectral variability using LCOGT and the SMARTS telescopes. These optical data provide a broad context within which to interpret our shorter UV and X-ray observations. We observed T Cha during 3 coordinated observations (each 5 HST orbits + 25 ksec XMM; on 2018 Feb 22, Feb 26, Mar 2) using HST COS/STIS to measure the UV-optical spectra and XMM-Newton to measure the X-ray energy distribution. The observed spectral changes are well correlated and demonstrate the influence of the same absorbing material in the different spectral regions. In this poster we examine which spectral features in the different spectral regions (FUV/NUV/optical/X-ray) change and by how much, and thereby determine the location of different emitting regions within the complex stellar/inner disk system relative to the absorbers along the line-of-sight to the stellar photosphere. Understanding these contributions is vital for estimating the properties of the absorbing gas and dust. (This work is supported by grant HST-GO-15128 and time awarded by HST, XMM-Newton, LCOGT, and SMARTS.), Poster #33

The detection of thousands of extrasolar planets by the transit method naturally raises the question of whether potential extrasolar observers could detect the transits of the Solar system planets, and in particular those of the Earth. In this talk I will present an analysis of the regions in the sky from where transit events of the Solar system planets can be detected - named "transit zones". I will discuss how probable it is to detect one or more Solar system planet, the timescales over which they are valid, plus the current list of known exoplanets in these zones and the prospects of finding temperate extrasolar planets which could observe transits of Earth. I will also report on a habitable zone candidate situated in one of the transit zones - a super-Earth near the inner-edge of the HZ of an early M-dwarf. We hope to find more systems with the ongoing Kepler-K2 mission.

Recent Kepler-space-telescope observations found more than 1000 superflares on 300 solar-type stars (e.g., Maeahra+2012 Nature; Shibayama+2013 ApJS). Many of the superflare stars show quasi-periodic brightness variations with the typical period of 1-30 days and the typical amplitude of 0.1-10 percent. We conducted spectroscopic observations of these superflare stars using Subaru/HDS and APO 3.5m telescope (Notsu+2015a&b, 2018 in prep). The projected rotation velocity (v sin i) values are consistent with brightness variation period, and there is a good correlation between Kepler brightness variation amplitude and the intensity of Ca II lines (Ca II H&K, Ca II 8542Å). These results support that the above brightness variations are caused by stellar rotation with large starspots, and existence of large starspots should be a key to understand superflares. More detailed spectroscopic studies (e.g., activity cycle) of superflare stars are important, but Kepler target stars are faint and not appropriate for such detailed studies. TESS satellite, launched in April 2018, brings us a large sample of brighter (e.g., V < 12 mag) superflare stars. We have started spectroscopic monitoring observations of nearby active solar-type stars (superflare candidate stars) in the TESS field. These results can have good collaborations with multi-wavelength project observations (e.g., X-ray, UV, polarimetry) of young solar-type stars., {"references":["Notsu et al. (2015, PASJ, 67, 32)","Notsu et al. (2015, PASJ, 67, 33)"]}

We present an analysis of high-resolution spectropolarimetric observations of the active M dwarf AD Leo in all four Stokes parameters. We derived the least-squares deconvolved Stokes profiles and detected linear polarisation signatures in spectral lines. This is the first report of a detection of Zeeman linear polarisation in the spectral lines of an M dwarf. Simultaneously, we discovered that the circular polarisation profiles corresponding to our data set are significantly weaker and broader than those present in all archival spectra of AD Leo, which exhibited approximately constant profiles over the period 2006–2012. Magnetic maps obtained using Zeeman Doppler imaging confirm a significant - and apparently rather sudden - change in the surface magnetic field. On the one hand, the topology of the magnetic field is mostly unchanged and remains close to an axisymmetric dipole. On the other hand, the total energy of the large-scale magnetic field has decreased by about 20 percent between 2012 and 2016 and the filling factor of this component has decreased by about a factor of two. These results suggest that the field responsible for the observed circular polarisation signatures corresponds to a stronger field component occupying a smaller fraction of the stellar surface in the more recent map. These results represent the first evidence that an active M dwarf with dipole-dominated axisymmetric field topology can undergo a long-term global magnetic field evolution.

Flares on Proxima Cen are ubiquitous. As on the Sun, they are expected to be distributed as power-laws of the form N(E)∝E−α. We track the variations of α over the stellar cycle, using data from multiple observatories using ASCA, Swift, Chandra, and XMM. After correcting for coronal temperature variations, we find a remarkable consistency in the shape of the flare distributions across the epochs, with α>2. If flare onset is attributable to self-organized critical proccesses, this suggests that the characteristics of the magnetic field structure like the filling factor and the plasma heating mechanism on Proxima Cen remain stable throughout the cycle.

A lot of efforts have been made recently in understanding the rotational evolution of low-mass stars. However, modelling stars of different clusters at different ages suggests at least slightly different chemical composition. These become even bigger if one aims at studying the whole Kepler field. We investigate here the effects of a variation of chemical composition through metallicity (-1.0 < [Fe/H] < +0.3) on the rotation period evolution of low-mass stars (0.2 - 1.5 M⊙ )., {"references":["Allard, F. et al. (2011) in ASPC vol 448 CS16 ed. Johns-Krull, C. Browning, M.K. and West, A.A.","Amard, L. et al. (2016) in A&A, 587, A105","Asplund, M. et al. (2009) in ARA&A, 47, 481","Bovy, J. (2016), in ApJ, 817, 49","Mathis, S. et al. (2018) in arXiv:1808.01814","Matt, S. et al. (2015) in ApJ, 799, L23","Netopil, M. et al. (2016) in A&A, 585, A150","Zahn, J.-P. (1992) in A&A, 265, 115"]}

M-type stars are quickly stepping into the forefront as some of the best candidates in searches for habitable Earth-like exoplanets, and yet many M-dwarfs exhibit extraordinary flaring events which would bombard otherwise habitable planets with ionizing radiation. In recent years, observers have found that the fraction of M-stars demonstrating significant magnetic activity transitions sharply from roughly $10\%$ for main-sequence stars earlier (more massive) than spectral type M3.5 (0.35 M$_\odot$) to nearly $90\%$ for stars later than M3.5. Suggestively, it is also later than M3.5 at which main-sequence stars become fully convective, and may no longer contain a tachocline. Using the spherical 3D MHD simulation code Rayleigh, we compare the peak field strengths, topologies, and time dependencies of convective dynamos generated within a quickly rotating (2 $\Omega_\odot$) M2 (0.4 M$_\odot$) star, with the computational domain either terminating at the base of the convection zone or including the tachocline. We find that while both models generate strong ($\sim$10kG), wreathlike toroidal fields exhibiting polarity reversals, the tachocline model provided a further reservoir for the toroidal field, which slowed the average reversal period from 100 rotations to more than 220 rotations and increased the spectral power of the low-order modes of the near-surface radial field by a factor of 4., Comment: The 20th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun

We present an overview of K2 short cadence observations for 34 M dwarfs observed in Campaigns 1 - 9 which have spectral types between M0 - L1. All of the stars in our sample showed flares with the most energetic reaching $3\times10^{34}$ ergs. As previous studies have found, we find rapidly rotating stars tend to show more flares, with evidence for a decline in activity in stars with rotation periods longer than approximately 10 days. We determined the rotational phase of each flare and performed a simple statistical test on our sample to determine whether the phase distribution of the flares is random or if there is a preference for phase. We find, with the exception of one star which is in a known binary system, that none show a preference for the rotational phase of the flares. This is unexpected and all stars in our sample show flares at all rotational phases, suggesting these flares are not all originating from one dominant starspot on the surface of the stars. We outline three scenarios which could explain the lack of a correlation between the number of flares and the stellar rotation phase. In addition we also highlight preliminary observations of DP Cnc, observed in campaigns 16 and 18, and is one of the stars in our extended sample from K2Campaigns 10 -18 which are still to be examined., {"references":["Bopp, B. W. & Moett, T. 1973, ApJ, 185, 239.","Davenport, J. R., Hawley, S. L., Hebb, L., Wisniewski, J. P., Kowalski, A. F., et al. 2014, ApJ, 797, 122.","Doyle, L., Ramsay, G., Doyle, J. G., Wu, K., & Scullion, E. 2018, Monthly Notices of the Royal Astronomical Society, 480, 2153.","Gaia Collaboration, Brown, A. G. A., Vallenari, A., Prusti, T., de Bruijne, J. H. J., et al. 2018, ArXiv e-prints.","Gershberg, R. 1972, Astrophysics and Space Science, 19, 75.","Gershberg, R. & Shakhovskaya, N. 1983, ApSS, 95, 235.","Gershberg, R. E. 2005, Solar-type activity in main-sequence Stars (Springer Science & Business Media).","Hawley, S. L., Davenport, J. R., Kowalski, A. F., Wisniewski, J. P., Hebb, L., et al. 2014, ApJ, 797, 121.","Huber, D., Bryson, S., Haas, M., Barclay, T., Barentsen, G., et al. 2016, VizieR Online Data Catalog, 222.","Kowalski, A. F., Hawley, S. L., Wisniewski, J. P., Osten, R. A., Hilton, E. J., et al. 2013, The Astrophysical Journal Supple- ment Series, 207, 15.","Luger, R., Agol, E., Kruse, E., Barnes, R., Becker, A., et al. 2016, AJ, 152, 100.","Lurie, J. C., Davenport, J. R., Hawley, S. L., Wilkinson, T. D., Wisniewski, J. P., et al. 2015, The Astrophysical Journal, 800, 95.","Ramsay, G. & Doyle, J. G. 2015, Monthly Notices of the Royal Astronomical Society, 449, 3015.","Ramsay, G., Doyle, J. G., Hakala, P., Garcia-Alvarez, D., Brooks, A., et al. 2013, MNRAS, 434, 2451.","Stelzer, B., Damasso, M., Scholz, A., & Matt, S. P. 2016, MN- RAS, 463, 1844."]}

I will present XMM-Newton-RGS observations of the Seyfert 1 Galaxies Mrk 335 and NGC 4051 that unveiled an emission line-rich spectrum during a low flux state of the AGN continuum.Line ratio diagnostics from H-like and He-like ions indicate that the emission lines arise in X-ray photoionized plasma. The physical properties of the line emitting material were derived using the CLOUDY photoionization code. Although the properties of the plasma cannot be uniquely determined, we found that the density of the X-ray photoionized gas in Mrk 335 is constrained at 99% c.l. to 10^9-10^{11} cm^{-3}, placing the gas within the inner edge of the optical Broad Line Region. For NGC 4051, the density and the location of the plasma are instead consistent with outer region of the AGN. I will briefly present other Seyfert 1 sources where X-ray photoionized emission lines possibly arise in the Broad Line Region and I will review the implication of these findings in a broader context.

In this work we use solar observations with the ALMA radio telescope at the wavelength of 1.21 mm. The aim of the analysis is to improve understanding of the solar chromosphere, a dynamic layer in the solar atmosphere between the photosphere and corona. The study has an observational and a modeling part. In the observational part full-disc solar images are analyzed. Based on a modied FAL atmospheric model, radiation models for various observed solar structures are developed. Finally, the observational and modeling results are compared and discussed.