Water vapour masers in long-period variable stars. I. RX Boo and SV Peg (2008)
Winnberg, A., Engels, D., Brand, J., Baldacci, L., Walmsley, C. M.
We wish to understand the reasons for the strong variability of H2O masers in circumstellar shells of late-type stars. We monitored RX Boo and SV Peg in the 22-GHz maser line of water vapour with...
Lifetime of OH masers at the tip of the asymptotic giant branch (2007)
Engels, D., Jimenez-Esteban, F.
Context: A large fraction of otherwise similar asymptotic giant branch stars (AGB) do not show OH maser emission. As shown recently, a restricted lifetime may give a natural explanation as to why...
HS1857+5144: A hot and young pre-cataclysmic variable (2007)
Aungwerojwit, A., Gaensicke, B. T., Rodriguez-Gil, P., Giannakis, O., Papadimitriou, C., ...
We report the discovery of a new white dwarf/M dwarf binary, HS1857+5144, identified in the Hamburg Quasar Survey (HQS). Time-resolved optical spectroscopy and photometry were carried out to...
SW Sextantis stars: the dominant population of CVs with orbital periods between 3-4 hours (2007)
Rodriguez-Gil, P., Gaensicke, B. T., Araujo-Betancor, S., Aungwerojwit, A., Prieto, C. Allende, ...
[Abridged] We present time-series optical photometry of five new CVs identified by the Hamburg Quasar Survey. The eclipses observed in HS 0129+2933, HS 0220+0603, and HS 0455+8315 provided very...
RFID tag vulnerabilities in RFID systems (2007)
Jamali, B., Cole, Peter Harold, Engels, D.
The original publication is available at www.springerlink.com
RFID tag vulnerabilities in RFID systems (2007)
Jamali, B., Cole, Peter Harold, Engels, D.
The original publication is available at www.springerlink.com
Near-IR variability properties of a selected sample of AGB stars (2006)
Jiménez-Esteban, F. M., García-Lario, P., Engels, D., Manchado, A.
We present the results of a near-infrared monitoring programme of a selected sample of stars, initially suspected to be Mira variables and OH/IR stars, covering more than a decade of observations....
Dwarf novae in the Hamburg Quasar Survey: Rarer than expected (2006)
Aungwerojwit, A., Gaensicke, B. T., Rodriguez-Gil, P., Araujo-Betancor, S., Baernbantner, O., ...
We report the discovery of five new dwarf novae from the Hamburg Quasar Survey (HQS), and discuss the properties of the sample of dwarf novae in the HQS. The orbital periods of the new dwarf novae...
Optical identification of ROSAT-FSC sources (2006)
Mickaelian, A. M., Hovhannisyan, L. R., Engels, D., Voges, W.
On the evolutionary connection between AGB stars and PNe (2005)
Jiménez-Esteban, F. M., García-Lario, P., Engels, D.
The `O-rich AGB sequence' is a sequence of colours describing the location of O-rich AGB stars in the IRAS two-colour diagram [12]--[25] vs [25]--[60]. We propose an evolutionary scenario for this...
Stellar evolution and the 'O-rich AGB sequence' (2005)
Jimenez-Esteban, F. M., Engels, D., Garcia-Lario, P.
The `O-rich AGB sequence' is a well defined area occupied by oxygen-rich AGB stars (OH/IR) in the IRAS two-colour diagram [12]-[25] vs [25]-[60]. This sequence is interpreted in terms of evolutionary...
HS 2134+0400 - new very metal-poor galaxy, a representative of void population? (2005)
Pustilnik, S. A., Engels, D., Kniazev, A. Y., Pramskij, A. G., Ugryumov, A. V.
We present the SAO 6m telescope spectroscopy of a blue compact galaxy (BCG) HS 2134+0400 discovered in frame of the dedicated Hamburg/SAO survey for Low Metallicity BCGs (HSS-LM). Its very low...
An infrared study of galactic OH/IR stars. II. The `GLMP sample' of red oxygen-rich AGB stars (2005)
Jiménez-Esteban, F. M., García-Lario, P., Engels, D., Calderón, J. V. Perea
We present optical and near-infrared finding charts taken from the DSS and 2MASS surveys of 94 IRAS sources selected from the GLMP catalogue (Garc\'{\i}a-Lario 1992), and accurate astrometry (~0.2")...
Aungwerojwit, A., Gaensicke, B. T., Rodriguez-Gil, P., Harlaftis, E. T., Papadimitriou, C., ...
We present time-resolved optical spectroscopy and photometry of four relatively bright (V~14.0-15.5) long-period cataclysmic variables (CVs) discovered in the Hamburg Quasar Survey: HS0139+0559,...
The Hamburg/SAO survey for emission-line galaxies. VI. The sixth list of 126 galaxies (2005)
Pustilnik, S. A., Engels, D., Lipovetsky, V. A., Kniazev, A. Y., Pramskij, A. G., Ugryumov, A. V., ...
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 4.5m MMT telescope in 1996, and...
HS 0943+1404, a true intermediate polar (2005)
Rodriguez-Gil, P., Gaensicke, B. T., Nogami, D., Torres, M. A. P., Lehto, H., ...
We have identified a new intermediate polar, HS 0943+1404, as part of our ongoing search for cataclysmic variables in the Hamburg Quasar Survey. The orbital and white dwarf spin periods determined...
An infrared study of galactic OH/IR stars. I. An optical/near-IR atlas of the Arecibo sample (2004)
Jiménez-Esteban, F. M., Agudo-Mérida, L., Engels, D., García-Lario, P.
In this paper we present optical and near-infrared finding charts, accurate astrometry (~1") and single-epoch near-infrared photometry for 371 IRAS sources, 96% of those included in the so-called...
HS2331+3905: The cataclysmic variable that has it all (2004)
Araujo-Betancor, S., Gaensicke, B. T., Marsh, T. R., Harlaftis, E. T., Thorstensen, J., ...
We report detailed follow-up observations of the cataclysmic variable HS2331+3905, identified as an emission-line object in the Hamburg Quasar Survey. An orbital period of 81.08min is unambiguously...
Detection of the white dwarf and the secondary star in the new SU UMa dwarf nova HS 2219+1824 (2004)
Rodriguez-Gil, P., Gaensicke, B. T., Marsh, T. R., Harlaftis, E. T., Kitsionas, S., ...
We report the discovery of a new, non-eclipsing SU UMa-type dwarf nova, HS 2219+1824. Photometry obtained in quiescence (V ~ 17.5) reveals a double-humped light curve from which we derive an orbital...
An Early Investigation of The Striated Tail of Comet Hale-Bopp (C/1995) (2004)
Sekanina, Z., Pittichova, J., Boehnhardt, H., Birkle, K., Engels, D., Keller, P.
Sekanina, Z., Ryan, O., Birkle, K., Boehnhardt, H., Engels, D., Keller, P., ...
We report extensive observations of striation patterns in the dust tail of comet Hale-Bopp (C/1995 O1) over a period of more than 10 weeks, from mid-february until early May 1997.
Progress in a Study of Striations in the Dust Tail of Comet Hale-Bopp (C/1995 01) (2004)
Sekanina, Z., Ryan, O., Boehnhardt, H., Birkle, K., Engels, D., Jager, M., ...
Rodriguez-Gil, P., Gaensicke, B. T., Barwig, H., Engels, D.
We present time-resolved optical spectroscopy and photometry, and far-ultraviolet spectroscopy of HS 0728+6738, a cataclysmic variable discovered in the Hamburg Quasar Survey. We show that the system...
The mysterious nature of HS2331+3905 (2004)
Araujo-Betancor, S., Gaensicke, B. T., Marsh, T., Thorstensen, J., Harlaftis, E., ...
We report the discovery of one unique cataclysmic variable drawn from the Hamburg Quasar Survey, HS2331+3905. Follow-up observations obtained over three years unveiled a very unusual picture. The...
HS2237+8154: On the onset of mass transfer or entering the period gap? (2004)
Gaensicke, B. T., Araujo-Betancor, S., Harlaftis, E., Kitsionas, S., Dreizler, S., ...
We report follow-up observations of a new white dwarf/red dwarf binary HS2237+8154, identified as a blue variable star from the Hamburg Quasar Survey. Ellipsoidal modulation observed in the R band as...
Optically bright active galactic nuclei in the ROSAT-Faint source catalogue (2004)
Balayan, S. K., Mickaelian, A. M., Mujica, R., Chavushyan, V., Hakopian, S. A., ...
The mysterious nature of hs 2331+3905 (2004)
Araujo Betancor, S., Engels , D., Fried , R. E., Gansicke , B.T., Hagen , H. J., Harlaftis , E. T., ...
Informamos sobre el descubrimiento de la única variable cataclísmica enana procedente del Hamburg Quasar Survey, HS 2331+3905. Las observaciones obtenidas durante tres años nos revelan un esquema...
Optically bright Active Galactic Nuclei in the ROSAT-Faint Source Catalogue (2003)
Balayan, S. K., Mickaelian, A. M., Mujica, R., Chavushyan, V., Hakopian, S. A., ...
To build a large, optically bright, X-ray selected AGN sample we have correlated the ROSAT-FSC catalogue of X-ray sources with the USNO catalogue limited to objects brighter than O=16.5 and then with...
Engels, D., Reimers, D., Voges, W.
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)...
1RXSJ062518.2+733433: A new intermediate polar (2003)
Araujo-Betancor, S., Gaensicke, B. T., Rodriguez-Gil, P., Engels, D.
We report the identification of the cataclysmic variable 1RXSJ062518.2+733433 as an intermediate polar. The orbital period of the system is determined to be 283.0+-2 min from the radial velocity...
Spectral analysis of sdB Stars from the Hamburg Quasar Survey (2003)
Edelmann, H., Heber, U., Hagen, H.J., Dreizler, S., Napiwotzki, R., Engels, D., ...
The HRX-BL Lac sample - evolution of BL Lac objects (2003)
Beckmann, V., Engels, D., Bade, N., Wucknitz, O.
The unification of X-ray and radio selected BL Lacs has been an outstanding problem in the blazar research in the past years. Recent investigations have shown that the gap between the two classes can...
Spectral analysis of sdB stars from the Hamburg Quasar Survey (2003)
Edelmann, H., Heber, U., Lemke, M., Dreizler, S., Napiwotzki, R., ...
We present the results of a spectral analysis of a large sample of subdwarf B stars selected from follow-up observations of candidates from the Hamburg Quasar Survey. Fundamental parameters...
Ugryumov, A. V., Engels, D., Pustilnik, S. A., Kniazev, A. Y., Pramskij, A. G.
We present the description and the first results og a new project devoted to the search for extremely metal-deficient blue compact/H Ii-galaxies (BCGs) and to the creation of a well selected large...
Ugryumov, A. V., Engels, D., Pustilnik, S. A., Kniazev, A. Y., Pramskij, A. G., Hagen, H. J.
We present the description and the first results of a new project devoted to the search for extremely metal-deficient blue compact/HII-galaxies (BCGs) and to the creation of a well selected large BCG...
Single-dish monitoring of circumstellar water masers (2002)
Brand, J., Baldacci, L., Engels, D.
We present an overview of the long-term water maser monitoring program of a sample of late-type stars, carried out with the Medicina 32-m and Effelsberg 100-m telescopes, and describe the results in...
Properties of a spectroscopically selected CV sample (2001)
Gaensicke, Boris T., Engels, D.
We have initiated a dedicated search for new CVs, selecting candidates on the base of their spectroscopic properties in the Hamburg Quasar Survey (HQS), which lead up to now to the identification of...
The Hamburg/SAO Survey for Emission--Line Galaxies. V. The Fifth List of 161 Galaxies (2001)
Ugryumov, A. V., Engels, D., Kniazev, A. Y., Green, R. F., Izotov, Y. I., Hopp, U., ...
We present the fifth list with results of the Hamburg/SAO Survey for Emission-Line Galaxies (HSS therein, SAO -- Special Astrophysical Observatory, Russia). The list is a result of follow-up...
A study of the H2O maser emission from R Cas (2001)
Brand, J., Baldacci, L., Engels, D.
We describe the monitoring program we have been carrying out during the past 10 years on a sample of late-type stars, with the Medicina 32-m and Effelsberg 100-m antennas. We discuss the observations...
The Hamburg/SAO Survey for Emission--Line Galaxies. IV. The Fourth List of 119 Galaxies (2000)
Kniazev, A. Y., Engels, D., Pustilnik, S. A., Ugryumov, A. V., Kniazeva, T. F., Pramsky, A. G., ...
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...
The Hamburg/RASS optical identification project (2000)
We use digitized Schmidt direct and prism plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) to obtain optical identifications for all high galactic latitude X-ray sources in the...
A Newly Discovered SU UMa-Type Dwarf Nova, HS 1449+6415 (2000)
Nogami, D., Engels, D., Gaensicke, B. T., Pavlenko, E. P., Novak, R., Reinsch, K.
We report time-resolved photometric observations of the Hamburg Quasar Survey-selected dwarf nova HS 1449+6415 (= RX J1450.5+6403) during the interval from JD 2451672 to 2451724. During a long...
HS 0822+3542 - a new nearby extremely metal-poor galaxy (2000)
Kniazev, A. Y., Pustilnik, S. A., Masegosa, J., Marquez, I., Ugryumov, A. V., ...
We present the results of spectrophotometry and BVR CCD photometry, as well as integrated HI radio measurements of a new blue compact galaxy (BCG) HS 0822+3542 with extremely low oxygen abundance:...
HS0907+1902: a new 4.2hr eclipsing dwarf nova (2000)
Gaensicke, B. T., Fried, R. E., Beuermann, K., Engels, D., Hessman, F. V., ...
We report on follow-up spectroscopy and photometry of the cataclysmic variable candidate HS0907+1902 selected from the Hamburg Quasar Survey. B, V, and R photometry obtained during the first observed...
Detection of the first X-ray selected large AGN group (2000)
We have examined the spatial distribution of 856 AGN detected by the ROSAT All-Sky Survey (RASS) using a direct search for structures with the minimal spanning tree. The AGNs were compiled from an...
ROSAC: Studying the clustering properties of X-ray selected AGNs (2000)
Tesch, F., Carrera, F. J., Engels, D., Hu, J., Ledoux, C., Ugryumov, A., ...
We present the first ROSAC results of an AGN clustering analysis. This study comprises a sample of 200 AGNs, 75% of which being at low redshifts z
The Hamburg/SAO Survey for Emission-Line Galaxies. III. The Third List of 81 Galaxies (2000)
Hopp, U., Engels, D., Green, R. F., Ugryumov, A. V., Izotov, Y. I., ...
We present the third list with results {Tables 2 to 6 are available only in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via...
HS 1603+3820: a bright z(em)=2.51 quasar with a very rich heavy element absorption spectrum (1999)
During the course of Hamburg/CfA Bright Quasar Survey we discovered a bright (B=15.9), high redshift (z=2.51) quasar HS 1603+3820. The quasar has a rich complex of CIV absorbers, containing at least...
Spectral analysis of hot subluminous stars. (1999)
Heber, U., Edelmann, H., Lemke, M., Napiwotzki, R., Engels, D.
Large-scale structures in the distribution of X-ray selected AGN (1998)
Engels, D., Tesch, F., Ledoux, C., Wei, J., Ugryumov, A., Valls-Gabaud, D., ...
We are searching for large-scale structures in the distribution of AGN discovered by the ROSAT All-Sky Survey. The RASS detected > 60000 X-ray objects, of which approximately 35% are AGN at z < 0.5....
On the evolutionary behaviour of BL Lac objects (1998)
Engels, D., Barthel, P. D., Douglas, N. G., Beckmann, V., Bade, N., ...
Submitted to: Astron. Astrophys. Abstract: We present a new well defined sample of BL Lac objects selected from the ROSAT All-Sky Survey (RASS). The sample consists of 39 objects with 35 forming a...
On the evolutionary behaviour of BL Lac objects (1998)
Bade, N., Beckmann, V., Douglas, N. G., Barthel, P. D., Engels, D., Cordis, L., ...
We present a new well defined sample of BL Lac objects selected from the ROSAT All-Sky Survey (RASS). The sample consists of 39 objects with 35 forming a flux limited sample down to f_X = 8 x...
Dobrzycka, D., Dobrzycki, A., Engels, D.
We present the analysis of the spectroscopic observations of a newly discovered cataclysmic variable HS0551+7241. In 1995 the star's brightness dropped by Delta(B)~2.5 mag and HS0551+7241 entered a...