Discovery of an extended G giant chromosphere in the 2019 eclipse of γ Per

The November 2019 eclipse of γ Per was a rare opportunity to seek evidence for a chromosphere of the G8 giant, hitherto suspected but not detected. Twenty-nine years after the only other observed eclipse, we aim to find chromospheric absorption in the strong Caa II H&K lines, and to determine its column densities and scale height. Using the Telescopio Internacional de Guanajuato Rob\uf3tico-Espectrosc\uf3pico (TIGRE) in Guanajuato (central Mexico) before, during and after the 8 days of total eclipse, we obtained good S/N spectra of the G8 giant alone and composite spectra of the partial phases, near eclipse and far from eclipse. In the near UV of the Caa II H&K and H\ucfμ lines, the G giant spectrum that was adequately scaled was subtracted from the composite spectra in partial phases, near and far from eclipse, to obtain the A3 companion spectra with and without traces of chromospheric absorption. In addition, we used PHOENIX full non-local thermodynamic equilibrium model atmospheres on the blue A star spectrum, iSpec spectral analysis of the red G giant spectrum, and evolution tracks to study both components of γ Per. For the first time, we present evidence for this rare type of a not very extended G giant chromosphere, reaching out about half of an A-star radius (~1.5 Gm) with a scale height of only 0.17 Gm. By its location in the Hertzsprung-Russell diagram, the γ Per G8 giant is very close to the onset of more extended chromospheres. Furthermore, we show that this giant has a rather inactive chromosphere, and a recent 5 ksec XMM pointing reveals only a very faint, low-energy corona. While the γ Per primary has a mass of ~3.6 M\u27, and its A3 companion has one of ~2.4 M\u27, the latter is too cool (8400 \ub1 300 K), which is too evolved on the main sequence to be the same age as the primary. The high eccentricity of the 5329.08 days long-period orbit may therefore be reminiscent of a rare capture event. Using the eclipse method, we resolve a pivotal case of a G giant chromosphere, which seems to represent a low-gravity analogue of the inactive Sun. A systematic change of giant chromospheric extent by Hertzsprung-Russell diagram position is confirmed. Compared to the solar chromosphere, the density scale height increases with gravity by \uc9\ua1\u271.5

The extended chromosphere of CoRoT-2A: Discovery and analysis of the chromospheric Rossiter-McLaughlin effect

The young G7V dwarf CoRoT-2A is transited by a hot Jupiter and among the most active planet host-stars known to date. We report on the first detection of a chromospheric Rossiter-McLaughlin effect observed in the Ca ii H and K emission-line cores. In Ca ii H and K, the transit lasts 15% longer than that observed in visual photometry, indicating that chromospheric emission extends 100 000 km beyond the photosphere. Our analysis is based on a time series of high-resolution UVES spectra obtained during a planetary transit and simultaneously obtained photometry observed with one of the PROMPT telescopes. The chromospheric Rossiter-McLaughlin effect provides a new tool to spatially resolve the chromospheres of active planet host-stars

The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants

We present X-ray data for all late-type (A, F, G, K, M) giants and supergiants (luminosity classes I to III-IV) listed in the Bright Star Catalogue that have been detected in the ROSAT all-sky survey. Altogether, our catalogue contains 450 entries of X-ray emitting evolved late-type stars, which corresponds to an average detection rate of about 11.7 percent. The selection of the sample stars, the data analysis, the criteria for an accepted match between star and X-ray source, and the determination of X-ray fluxes are described.

The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars

We present X-ray data for all main-sequence and subgiant stars of spectral types A, F, G, and K and luminosity classes IV and V listed in the Bright Star Catalogue that have been detected as X-ray sources in the ROSAT all-sky survey; several stars without luminosity class are also included. The catalogue contains 980 entries yielding an average detection rate of 32 percent. In addition to count rates, source detection parameters, hardness ratios, and X-ray fluxes we also list X-ray luminosities derived from Hipparcos parallaxes

The ROSAT all-sky survey catalogue of optically bright OB-type stars

For the detailed statistical analysis of the X-ray emission of hot stars we selected all stars of spectral type O and B listed in the Yale Bright Star Catalogue and searched for them in the ROSAT All-Sky Survey. In this paper we describe the selection and preparation of the data and present a compilation of the derived X-ray data for a complete sample of bright OB stars

X-ray/optical observations of stars with shallow convection zones

We present Walraven photometry and ROSAT All-Sky Survey data for a sample of 173 bright main-sequence stars with spectral types between A8V and G2V. These observations are part of a study of the onset of magnetic surface activity along the main sequence. Values for the effective temperature, surface gravity and interstellar reddening have been obtained from a comparison of the observed Walraven colours with theoretical values. These parameters have been used to derive accurate surface flux densities

The ROSAT all-sky survey catalogue of the nearby stars

We present X-ray data for all entries of the Third Catalogue of Nearby Stars (Gliese & Jahreiß 1991) that have been detected as X-ray sources in the ROSAT all-sky survey. The catalogue contains 1252 entries yielding an average detection rate of 32.9 percent. In addition to count rates, source detection parameters, hardness ratios, and X-ray fluxes we also list X-ray luminosities derived from Hipparcos parallaxes

New “weak-line"–T Tauri stars in Lupus

We present first results obtained by a survey of the Lupus star forming region in search of new T Tauri stars. This study has been performed on the basis of deep pointed ROSAT observations in the Lupus dark clouds as well as data from the ROSAT All-Sky-Survey in the surrounding, less obscured regions. Our survey covers an area of about 230 square degrees, located between $\rm 15^h\,6^m$ and $\rm 16^h\,24^m$ in right ascension and between $-47^\circ$ and $-32^\circ$ in declination. Identification of ROSAT All-Sky-Survey sources in this area by means of optical spectroscopy revealed 89 T Tauri stars, 86 of them “weak-line" T Tauri stars (WTTS) not known from previous studies of this region. Our pointed ROSAT observations led to the identification of 47 more T Tauri stars, giving a total of 136 new T Tauri stars. The large area of our study, as compared with previous works, allows us to study the spatial distribution of WTTS in this star forming region on a large scale. We find the new WTTS to be distributed over the whole area of our survey, indicating that their spatial distribution might extend well beyond our study area. Contrary to the Lupus T Tauri stars known prior to this study, the WTTS discovered by the ROSAT All-Sky-Survey are not clustered in the regions of highest extinction, i.e. the dark clouds

New weak-line T Tauri stars in Orion from the ROSAT all-sky survey

We present results of the spectroscopic and photometric follow-up observations of the ROSAT all-sky survey in the direction of the Orion cloud complex. The main goal of these observations is the search for X-ray emitting pre-main sequence stars. 820 X-ray sources were detected with high confidence in about 450 square degrees. The mean density of X-ray sources in this region is a factor of about two higher than that of the whole RASS. 5% of the RASS sources in this region are identified with previously known and likely pre-main sequence stars. We have investigated spectroscopically 181 new RASS sources widely distributed over the entire cloud complex. On the basis of the presence of strong Li I λ6707 absorption, spectral type later than F0 and chromospheric emission, 112 new weak-line T Tauri stars could be found. We present coordinates, X-ray count-rates and finding charts of the new PMS. Optical $UBV(RI)$ KC, near-infrared JHKLM and uvby-β photometry for the new WTTS is also provided. In addition 24 dKe-dMe stars were also found on the basis of the RASS data

Erratum:Atmospheric characterization of the ultra-hot Jupiter MASCARA-2b/KELT-20b: Detection of Ca II, Fe II, Na I, and the Balmer series of H (H α, H β, and H γ) with high-dispersion transit spectroscopy (Astronomy and Astrophysics (2019) 628 (A9) DOI: 10.1051/0004-6361/201935623)

The original article has two errors which are corrected below and which do not have any impact on the conclusions. 1. In Fig. 7 of the original article, the labels inside the plot are inverted. The corrected figure is shown in Fig. 1. 2. There was an error in the constant value used for the conversion between the standard deviation (-) and the full width at half maximum (FWHM) when fitting the exoplanet atmospheric absorption with a Gaussian profile. As a result, all of the FWHM values shown in the original article change by a constant value. The affected tables and figures from the main text are those containing FWHM information, that is to say, Tables 4, 5, and Fig. 13. In the appendix, this affects Table B.1 and all corner plots from Appendix D (Figs. D.1 D.7). The corrected tables and figures are presented below in the same order as in the original article. (Table Presented).</p