H.-J. Hagen

Spectral analysis of sdB stars from the Hamburg Quasar Survey

We present the results of a spectral analysis of a large sample of subdwarf B stars selected from follow-up obser- vations of candidates from the Hamburg Quasar Survey. Fundamental parameters (eective temperature, gravity, and helium abundance) were determined by matching synthetic line profiles calculated from model atmospheres to all hydrogen and helium absorption lines present in the observed optical spectra. The derived helium abundances are compared with the atmospheric parameters to search for possible trends. We discovered a correlation between the helium abundance and the eective temper- ature: the larger the temperature, the larger the photospheric helium content of sdB stars. Additionally, a separation into two sequences of sdB stars in the eective temperature - helium abundance plane is detected. We compared our analysis results with data from the literature. The stars from our sample are found to be somewhat more luminous. This can only partly be explained by NLTE eects. Three apparently normal B stars were discovered, which could be massive stars far away from the galactic plane (7-19 kpc). Radial velocities were measured for 23 stars from which we discovered a new radial velocity variable sdB star.

The Hamburg/RASS Catalogue of optical identifications Northern high-galactic latitude ROSAT Bright Source Catalogue X-ray sources

We present the Hamburg/RASS Catalogue (HRC) of optical identifications of X-ray sources at high-galactic latitude. The HRC includes all X-ray sources from the ROSAT Bright Source Catalogue (RASS-BSC) with galactic latitudejbj30 and declination 0. In this part of the sky covering10 000 deg 2 the RASS-BSC contains 5341 X-ray sources. For the optical identification we used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC an identification could be given. For the rest either no counterpart was visible in the error circle or a plausible identification was not possible. With 42% AGN represent the largest group of X-ray emitters,31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only4% and5%, respectively. In3% of the RASS-BSC sources no object was visible on our blue direct plates within 40 00 around the X-ray source position. The catalogue is used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters.

Sbs 0909+532: a new double gravitational lens or binary quasar?

The z = 1.377, B = 17.0 mag quasar SBS 0909+532 A, B is a double with two images separated by Δθ = 1107 ± 0006. Because the faint image has an emission line at the same wavelength as the Mg II 2798 A emission line of the quasar, and it lacks the broad Mg Ib absorption feature expected for a star with the same colors (a K star), we conclude that image B is a quasar with similar redshift to image A. The relative probabilities that the double is the smallest separation (4.7 h-1 kpc for Ω0 = 1) correlated quasar pair or a gravitational lens are ~1:106. If the object is a lens, the mean lens redshift is zl = 0.5 with 90% confidence bounds of 0.18 < zl < 0.83 for Ω0 = 1. If the lens is an elliptical galaxy, we expect it to be brighter than I < 19.5 mag. The broadband flux ratio varies with wavelength, with ΔI = 0.31, ΔR = 0.58, and ΔB = 1.29 magnitudes, which is difficult to reconcile with the lensing hypothesis.

The Hamburg/SAO Survey for low metallicity blue compact H II galaxies (HSS–LM) - I. The first list of 46 strong-lined galaxies

We present the description and the first resultsof a new project devoted to the search for extremely metal- deficient blue compact/H uf769uf769-galaxies (BCGs) and to the creation of a well selected large BCG sample with strong emission lines. Such galaxies should be suitable for reliable determination of their oxygen abundance through the measurement of the faint (O uf769uf769uf769) λ4363 A line. The goals of the project are two-fold: a) to discover a significant number of new extremely metal- poor galaxies (Z 1/20 Z� ), and b) to study the metallicity distribution of local BCGs. Selection of candidates for follow-up slit spectroscopy is performed on the database of objective prism spectra of the Hamburg Quasar Survey. The sky region is limited by δ ≥ 0 ◦ and b II ≤− 30 ◦ . In this paper we present the results of the follow-up spectroscopy conducted with the Russian 6m telescope. The list of observed candidates contained 52 objects, of which 46 were confirmed as strong-lined BCGs (EW((O uf769uf769uf769) λ5007) ≥ 100 A). The remaining five lower excitation ELGs include three BCGs, and two galaxies classified as SBN (Starburst Nucleus) and DANS (Dwarf Amorphous Nucleus Starburst). One object is identified as a quasar with a strong Lyα emission line near λ5000 A (z ∼ 3). We provide a list with coordinates, measured radial velocities, B-magnitudes, equiv- alent widths EW((O uf769uf769uf769) λ5007) and EW(Hβ) and for the 46 strong-lined BCGs the derived oxygen abundances 12+log(O/H). The abundances range between 7.42 and 8.4 (corresponding to metallicities between 1/30 and 1/3 Z� ). The sample contains four galaxies with Z 1/20 Z� , of which three are new discoveries. This demonstrates the high efficiency of the new project to find extremely metal-deficient galaxies. The radial velocities of the strong-lined ELGs range between 500 and 19000 kms −1 with a median value of ∼6400 kms −1 . The typical B-magnitudes of the galaxies presented are 17. m 0−18. m 0.

The Hamburg/SAO survey for emission-line galaxies

We present the second part of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO – Special Astrophysical Observatory, Russia) which is based on the digitized objective-prism photoplates database of the Hamburg Quasar Survey (HQS). The main goal of the project is the search for emission-line galaxies (ELG) in order to create a new deep sample of blue compact/Hii galaxies (BCG) in a large sky area. Another important goal of this work is to search for new extremely low-metallicity galaxies. In this paper we present new results of spectroscopy obtained with the 6 m Russian telescope. The main ELG candidate selection criteria applied are blue or flat enough continuum (near λ4000 A) and the presence of strong or moderate [Oiii]λλ4959, 5007 A emission lines recognized on digitized prism spectra of galaxies with the survey estimated B-magnitudes in the range 16 − 19. 5. No other criteria were applied. The spectroscopy resulted in detection and quantitative spectral classification of 134 emission-line objects. For 121 of them the redshifts are determined for the first time. For 13 ELGs known before emission line ratios are presented at first time. 108 of 134 emission-line objects are classified as BCG/Hii galaxies and probable BCGs, 6 – as QSOs, 1 – as Seyfert galaxy, 1 – as super-association in a dwarf spiral galaxy, 2 – as probable LINERs, 14 are low excitation objects – either of starburst nuclei (SBN), or dwarf amorphous nuclei Send offprint requests to: sap@sao.ru ? Deceased September 22, 1996. 1 Tables 2 to 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html. Figures A1 to A13 will be made available only in the electronic version of the journal. Appendix A is only available at http://www.edpsciences.com starburst galaxy (DANS) type, and 2 – nonclassified. 23 galaxies did not show significant emission lines. The five most metal-deficient BCGs discovered have oxygen abundances log(O/H)+12 in the range 7.4 to 7.7, similar to the most metal-deficient BCGs known before.We present the fourth list with results of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS hereafter, SAO - Special Astrophysical Observatory, Russia). The list is a result of the follow-up spectroscopy conducted with the 6m SAO RAS telescope in 1998, 1999 and 2000. The data of this snap-shot spectroscopy survey confirmed 127 emission-line objects out of 176 observed candidates and allowed their quantitative spectral classification. We could classify 76 emission-line objects as BCG/HII galaxies or probable BCGs, 8 - as QSOs, 2 - as Seyfert galaxies, 2 - as super-associations in a subluminous spiral and an irregular galaxy, and 37 as low-excitation objects - either starburst nuclei (SBN), or dwarf amorphous nuclei starburst galaxies (DANS). We could not classify 2 ELGs. Furthermore, for 5 galaxies we did not detect any significant emission lines. For 91 emission-line galaxies, the redshifts and/or line intensities are determined for the first time. Of the remaining 28 previously known ELGs we give either improved data on the line intensities or some independent measurements. The candidates were taken from three different samples selected by different criteria. Among our first priority candidates we achieved a detection rate of emission-line objects (ELGs + QSOs) of 68%, among which 51% are BCGs. Observations of a random selected sample among our second priority candidates showed that only ~10% are BCGs. We found that the confirmed BCGs have usually a blue colour ((B-R)<1.0) and a non-stellar appearance in the APM database. Our third sample is comprised of second priority candidates fulfilling these criteria derived from the APM. Follow-up spectroscopy of a small subsample indicates that the expected detection rate for BCGs is ~40%.

Spectrum radial velocity analyser (SERVAL): High-precision radial velocities and two alternative spectral indicators

Context: The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. nAims: We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity Analyser (SERVAL), a publicly available python code. nMethods: We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star.We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. nResults: Using HARPS data, our SERVAL code achieves a RV precision at the level of 1m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. nConclusions: We find that at the red optical wavelengths (700--900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.

The Hamburg/SAO survey for emission-line galaxies - VI. The sixth list of 126 galaxies

We present the sixth list with results of the Hamburg/SAO Survey for Emission-Line Galaxies. The final list resulted from follow-up spectroscopy conducted with the 4.5 m MMT telescope in 1996, and with 2.2 m CAHA and 6 m SAO telescopes in 2000 to 2003. The data of this snap-shot spectroscopy survey confirmed 134 emission-line objects out of 182 observed candidates and allowed their quantitative spectral classification and redshift determination. We classify 73 emission-line objects as definite or probable blue compact or Huf769uf769 galaxies (BCG), 8 as QSOs, 4 as Seyfert 1 and 2 galaxies. 30 low-excitation objects were classified as definite or probable starburst nuclei (SBN), 3 as dwarf amorphous nuclei starburst galaxies (DANS) and 2 as LINERs. Due to the low signal-to-noise ratio we could not classify 14 ELGs (NON). For another 9 galaxies we did not detect any significant emission lines. For 98 emission-line galaxies, the redshifts and/or line intensities are determined for the first time. For the remaining 28 previously-known ELGs we give either improved data the line intensities or some independent measurements. The detection rate of ELGs is ∼70%. This paper completes the classification of strong-lined ELGs found in the zone of the Hamburg/SAO survey. Together with previously known BCG/H uf769uf769 galaxies in this zone, this sample of ∼500 objects is the largest to date in a well bound region.

The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18

CARMENES is an instrument for the Centro Astronomico Hispano-Aleman de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de lEspai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia, and Centro Astronomico Hispano-Aleman), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation (DFG), the states of Baden-Wurttemberg and Niedersachsen, and the Junta de Andalucia. P.S. would like to thank Christoph Mordasini for his helpful comments on an early draft and Sudeshna Boro-Saikia for her help on calculating the calcium indices of the HARPS data set. I.R. and J.C.M. acknowledge support by the Spanish Ministry of Economy and Competitiveness (MINECO) and the Fondo Europeo de Desarrollo Regional (FEDER) through grant ESP2016-80435-C2-1-R, as well as the support of the Generalitat de Catalunya/CERCA program. A.P.H. acknowledges the support of the Deutsche Forschungsgemeinschaft (DFG) grant HA 3279/11-1. J.A.C., P.J.A. and D.M. acknowledge support by the Spanish Ministry of Economy and Competitiveness (MINECO) from projects AYA2016-79425-C3-1, 2, 3-P. V.J.S.B. is supported by program AYA2015-69350-C3-2-P from Spanish Ministry of Economy and Competitiveness (MINECO). We thank the anonymous referee for useful comments that improved the paper.

CARMENES. IV: instrument control software

The overall purpose of the CARMENES instrument is to perform high-precision measurements of radial velocities of late-type stars with long-term stability. CARMENES will be installed in 2014 at the 3.5 m telescope in the German- Spanish Astronomical Center at Calar Alto observatory (CAHA, Spain) and will be equipped with two spectrographs in the near-infrared and visible windows. The technology involved in such instrument represents a challenge at all levels. The instrument coordination and management is handled by the Instrument Control System (ICS), which is responsible of carrying out the operations of the different subsystems and providing a tool to operate the instrument from low to high user interaction level. The main goal of the ICS and the CARMENES control layer architecture is to maximize the instrument efficiency by reducing time overheads and by operating it in an integrated manner. The ICS implements the CARMENES operational design. A description of the ICS architecture and the application programming interfaces for low- and high-level communication is given. Internet Communications Engine is the technology selected to implement most of the interface protocols.

CARMENES: data flow

CARMENES, the new Calar Alto spectrograph especially built for radial-velocity surveys of exoearths around M dwarfs, is a very complicated system. For reaching the goal of 1 m/s radial-velocity accuracy, it is appropriate not only to monitor stars with the best observing procedure, but to monitor also the parameters of the CARMENES subsystems and safely store all the engineer and science data. Here we describe the CARMENES data flow from the different subsystems, through the instrument control system and pipeline, to the virtual-observatory data server and astronomers.