My recent publications in reverse chronological order

full texts are gzip-ped PostScript or pdf, abstracts are HTML

Measuring the Atmospheric Attenuation at 47 (and 24) GHz

DUBUS x/xxxx, xx (20xx)
Summary: For frequencies above about 20 GHz the attenuation of signals by the Earth atmosphere becomes important. ITU’s Recommendation P.676 predicts for any radio frequency the average attenuation at the zenith based on local weather data. The actual attenuation we can determine by measuring the noise from the empty sky at various elevations. We did this on 47 and 24 GHz for various sky situations. If the sky is clear or blue with only a few white clouds, the measured values agree indeed within ± 0.1 dB with the results from the ITU formula. Clouds may increase the attenuation appreciably, and if the sky is covered with grey clouds, the actual attenuation will be substantially greater, by as much as a few dB. In order to measure the attenuation of the solar noise at various elevations, we tracked the Sun on its daily path across the sky. This more direct method shows that at lower elevations the Sun noise decreases but the sky noise increases in the expected way, and in agreement with the sky noise profile. Thus, we can reliably measure the current attenuation by taking a ‘sky profile’ of the empty sky noise.

Know your Parabolic Antenna better from Measurements of Sun, Moon, and Ground Noise

DUBUS 1/2024, 14 (2024)
Summary: With measurements of the noise from the Sun, Moon, and ground, along with the sky noise at the elevations of the Sun and Moon, we can obtain three estimates for the noise figure or system temperature of a receiving station which tells about the efficiency of a (parabolic) antenna. Ideally, all three values should be the same or very close to each other. Should the values differ in a significant way, a measured value could be in error, or the measuring setup or procedures might need improvement. Three agreeing values will reveal the overall noise figure of the station. Because the side and rear lobes of the antenna will pick up noise from the surroundings, this value will be somewhat larger than the noise figure of the receiver on its own. This gives an idea of the efficiency of the antenna, which can be used to help to optimize the antenna and the station's overall performance.

Get Atmospheric Attenuation and Noise Figure from a Skyprofile

DUBUS 4/2023, 7 (2023)
Summary: Above about 20 GHz, the attenuation by the Earth atmosphere becomes an important parameter in the EME link budget. It is possible to take the attenuation predicted for the average atmosphere, but this remains an estimation, and may appreciably differ from the actual atmospheric conditions above the station. Measuring the noise level of the empty sky at several elevations allows us to determine not only the actual attenuation but also the noise figure (or system temperature) of the receiving system. A JavaScript tool to analyse the data is available on the internet at:

How to Measure the Width of a Narrow Beam Antenna

DUBUS 3/2023, 5 (2023)
Summary: The width of the main lobe of a paraboloidal antenna provides a direct measure of the antenna gain. While it is easy to measure it easily by the width of a drift scan across the Sun or the Moon, this method no longer works with the narrow beams of large dishes and higher frequencies, because one would only measure the angular diameter of the celestial body. Fortunately, the discs of both Sun and Moon have sharp outer edges, which the antenna beam smoothes out into wider rim profiles. This article describes how we can use the width of the observed rim to determine the antenna beam width.

EME with Narrow Beam Antennas

J.Köppen, G.Ihninger
DUBUS 2/2023, 32 (2023)
Summary: EME with large parabolic antennas benefits from the higher gain, but is faced with the problem that the antenna beam widths become comparable or even narrower than the disc of the Moon. In consequence, the power of the reflected signal is lower than predicted from the radar range equation. We compute numerically a correcting factor, the Beam Width Factor. Narrow beams also make it possible that the beams of the participating stations may not or cannot be pointed accurately to the same position on the Moon's face, resulting in a further loss in signal power. This article explains how these correction factors to the radar range equation are computed for any arrangement of the beams. A JavaScript tool to perform the calculations and display the results is available at

Aim a Narrow Beam at the Moon

DUBUS 1/2023, 72 (2023)
Summary: EME communications above about 30 GHz need high gain antennas to provide adequate transmission power as well as strong signals on reception. The associated antenna beams can be as narrow as to cover only a part of the lunar disc. This places higher demands on the pointing and tracking of the Moon. At these higher frequencies, the Moon no longer represents a disc of uniform radio brightness. During its monthly apparent journey around the Earth the Moon is illuminated by the Sun, causing the variation of the thermal radio emission which is greater at higher frequencies. This also increases the variation of the noise over the lunar face, which also varies with time. Thus, pointing the antenna at the maximum lunar noise does not lead to hitting the middle of the disc. Radio images of the Moon can be computed for any frequency and lunar phase, and the position of the brightest spot can be determined. On 47 GHz and for antenna beam widths wider than about 0.2° the brightest spot remains always within about 0.05° of the disc centre, and the search for maximum noise would always lead close to the centre. Only larger antennas – e.g. HPBW 0.1° – require a greater effort for a more accurate positioning and tracking of the Moon's middle. With the predicted radio images of the Moon one may determine offsets from the brightest spot to centre. The interactive JavaScript tool at allows to predict the orientation of the radio Moon for any given location, time and frequency.

The Arecibo Galaxy Environment Survey XII : Optically dark HI clouds in the Leo I Group

R.Taylor, J.Köppen, P.Jáchym, R.Minchin, J.Palouš, J.L.Rosenberg, S.Schneider, R.Wünsch, B.Deshev
Astron.J. 164, 233 (2022)
Summary: Using data from the Arecibo Galaxy Environment Survey, we report the discovery of five HI clouds in the Leo I group without detected optical counterparts. Three of the clouds are found midway between M96 and M95, one is only 100 arcmin from the south-east side of the well-known Leo Ring, and the fifth is relatively isolated. HI masses range from 2.6 E6 - 9.0 E6 Msun and velocity widths (W50) from 16-42 km/s. Although a tidal origin is the most obvious explanation, this formation mechanism faces several challenges. For the most isolated cloud, the diffculties are its distance from neighbouring galaxies and the lack of any signs of disturbance in the HI discs of those systems. The clouds also follow the baryonic Tully-Fisher relation between mass and velocity width for normal, stable galaxies which is not expected if they are tidal in origin. By contrast, the three clouds between M96 and M95 have no optical counterparts even though they have very similar properties and location to the optically detected galaxy LeG 13. While overall we favour a tidal debris scenario to explain the clouds, we cannot rule out a primordial origin. If the clouds were produced in the same event that gave rise to the Leo Ring, they may provide important constraints on any model attempting to explain that structure.

Lunar Noise at 80 GHz

D.Fedorov, J.Köppen
DUBUS 4/2022, 22 (2022)
Summary: The expected EME activity in the amateur 4mm (76-80 GHz) band motivates to pay attention to the Moon’s radiation itself, because the lunar noise is an important natural factor limiting the receiver system temperature and therefore the real sensitivity of EME receiving systems. We measured the lunar radio noise at various times during the Moon's apparent orbit around the Earth with a 0.9 m offset dish at 80 GHz. Measurements at 80 GHz are faced with several problems: attenuation by the Earth atmosphere cannot be neglected, the beam of a 1 m diameter antenna is narrower than the lunar angular size, and the brightness of the lunar surface changes not only during one lunation but also varies across the lunar face, similar to the different faces of the Moon at visual wavelengths. These issues can be solved and are discussed. The results agree very well with previous radioastronomical measurements. Thus, one can predict with confidence the noise floor of an EME receiving system.

How to Measure Spillover of a Parabolic Antenna

DUBUS 1/2022, 63 (2022)
Summary: If the radiation pattern of the feed is wider than the parabolic dish which it illuminates, the antenna picks up ground noise from outside the rim of the dish. This causes the sky noise in the zenith to be higher than at lower elevations. This article explains how this noise contribution can be computed. From measurements of the sky noise at different elevation angles we can work out the spill-over contribution in a quantitative way. This is done by modelling the data with the aid of the online interactive JavaScript tool at

A Closer Look at Filling Factors

DUBUS 4/2021, 15 (2021)
Summary: A parabolic dish antenna is sensitive only in a narrow beam whose width corresponds to its size. The efficiency of EME operations depends on how much of the transmitting antenna's radiated power is concentrated on the Moon, but also how much of the lunar thermal emission is picked up by the receiving antenna. Likewise, for a sensible interpretation of measurements in radio astronomy we need to know how much of a source's emssion reaches the radio telescope. The beam width of a 40 cm dish at 100 GHz is already as narrow as the Sun's angular diameter. This renders the interpretation of measured solar noise by simple formulae useless. For this purpose one defines and computes the filling factor as the fraction of the antenna beam which is filled by the source. In this article we compare simple as well as realistic filling factor formulations, which can be inspected with the JavaScript tool at

Noise from the Moon

DUBUS 3/2021, 100 (2021)
Summary: At radio frequencies the Moon emits thermal radiation from its surface which is heated by the Sun. With a model for the heat transport in the lunar soil it is possible to predict the monthly variation of the lunar brightness temperature at any frequency. A comparison with radio measurements of the lunar emission from the professional literature shows that already a rather simple model is capable of matching the observations quite well. Thus one may use the Moon as a natural noise generator with predictable output to measure the sensitivity of a receiving system or to act as a calibrating source for radioastronomical observations. This article describes an on-line JavaScript tool that displays the model predictions and compares them with existing observations.

A Tool to Look at the Feeding of Parabolic Dish Antennas

DUBUS 1/2021, 8 (2021)
Summary: If one ever wanted to operate a parabolic dish with 100% efficiency, the feed antenna in its focus would need to illuminate the mirror dish evenly, but it also must put all the power onto the dish without losing any part by spilling over the rim of the dish. Real and realistic feeds cannot match these conflicting requirements. Thus, a compromise must be accepted by the highest efficiency that a given feed is able to furnish. If the radiation pattern of the feed is known, one can compute the dish illumination, the efficiency, and the radiation pattern of the entire assembly. As an extension of the program Feedpatt by W1GHZ, I wrote for my use an interactive JavaScript tool. The results are presented graphically and numerically, so that the user can easily evaluate the properties of the antenna. This online tool is available

Radio Observations of the Annular Solar Eclipse of 2012

K.Seki, M.Hidehiko, with J.Köppen
DUBUS 4/2020, 26 (2020)
Summary: A test observation by JJ1NNJ on 2.3 GHz of the annular solar eclipse of 21 may 2012 in Japan gave an interesting but puzzling curve, with two dips near maximum obscuration which made it look like the letter W. The independent observation on 1.4 GHz by JH3NYP showed the same features, proving their reality. In the challenging and exciting process of trying to understand the data, it was realized that the 'W' had a simple origin in the limb brightening of the Sun at radio wavelengths: When the Moon covers the Sun centrally, this bright ring is fully seen, but just before and just after maximum obscuration, the Moon also covers parts of the ring, thus resulting in the reduced signal making the two dips. A couple of radio-bright active regions associated with the visible sunspots are responsible for making the data curve unsymmetric and uneven. With the knowledge of these features of the radio Sun, the recorded data could be very nicely modelled. We can only strongly encourage anyone who encounters a solar eclipse to record careful and calibrated measurements. The interpretation is a lot of work … but a lot of fun!

The 2015 Lunar Eclipse Observed at Radio Frequencies

DUBUS 2/2020, 74 (2020)
Summary: Radio noise from the Moon is thermal emission of its surface, heated by solar radiation. The signals measured by DL0SHF during the 2015 total lunar eclipse on 1.3, 8.4, 10, and 24 GHz did not show any drop of the noise level during the obscuration of sunlight. Since the lunar soil is not solid rock but dust, sand, and small pieces of rock, it has a rather low thermal conductivity. Hence the heat deposited at the surface layer is shared only slowly with the deeper layers which are responsible for the radio noise in the UHF and SHF ranges. The rather short interruption of solar irradiation during the eclipse causes a signal drop too small to be detectable with amateur equipment.

Faint and fading tails: the fate of stripped HI gas in Virgo cluster galaxies

R.Taylor, J.Köppen, P.Jáchym, R.Minchin, J.Palouš, R.Wünsch
Astron.J.159, 218 (2020)
Abstract: Although many galaxies in the Virgo cluster are known to have lost significant amounts of HI gas, only about a dozen features are known where the HI extends significantly outside its parent galaxy. Previous numerical simulations have predicted that HI removed by ram pressure stripping should have column densities far in excess of the sensitivity limits of observational surveys. We construct a simple model to try and quantify how many streams we might expect to detect. This accounts for the expected random orientation of the streams in position and velocity space as well as the expected stream length and mass of stripped HI. Using archival data from the Arecibo Galaxy Environment Survey, we search for any streams which might previously have been missed in earlier analyses. We report the confident detection of ten streams as well as sixteen other less sure detections. We show that these well-match our analytic predictions for which galaxies should be actively losing gas, however the mass of the streams is typically far below the amount of missing HI in their parent galaxies, implying that a phase change and/or dispersal renders the gas undetectable. By estimating the orbital timescales we estimate that dissolution rates of 1-10 Msun/yr are able to explain both the presence of a few long, massive streams and the greater number of shorter, less massive features.

The Widefield Arecibo Virgo Extragalactic Survey I: New structures in the Kent cloud complex and an extended tail on NGC 4522

R.F.Minchin, R.Taylor, J.Köppen, J.I.Davies, W.van Driel, O.Keenan
Astron.J.158, 121 (2019)
Abstract: We are carrying out a sensitive blind survey for neutral hydrogen (HI) in the Virgo cluster and report here on the first 5° x 1° area covered, which includes two optically-dark gas features: a fivecloud HI complex (Kent et al. 2007, 2009) and the stripped tail of NGC 4522 (Kenney et al. 2004). We discover a sixth cloud and low velocity gas that extends the velocity range of the Kent complex to over 450 km/s, find that around half of the total HI ux comes from extended emission rather than compact clouds, and see around 150 percent more gas, raising the total HI mass from 5.1E8 Msun to 1.3E9 Msun. This makes the identification of NGC 4445 and NGC 4424 by Kent et al. (2009) as possible progenitors of the complex less likely, as it would require an unusually high fraction of the gas removed to have been preserved in the complex. We also identify a new component to the gas tail of NGC 4522 extending to ~200 km/s below the velocity range of the gas in the galaxy, pointing towards the eastern end of the complex. We consider the possibility that NGC 4522 may be the parent galaxy of the Kent complex, but the large velocity separation (~1800 km/s) leads us to rule this out. We conclude that, in the absence of any better candidate, NGC 4445 remains the most likely parent galaxy, although this requires it to have been particularly gas-rich prior to the event that removed its gas into the complex.

The 2-D Radiation Pattern of Parabolic Dish Antennas

DUBUS 1/2019, 28 (2019)
DUBUS Technik XVII, 19 (2018)
Summary: By measuring the power received at several offset positions from the Sun one can probe the radiation pattern of an antenna, but this gives only a rough view. A complete 2-dimensional map of the pattern can easily be obtained by letting the Sun cross the field of view of the antenna held fixed for a few weeks in spring or autumn. This makes use of the apparent motion of the Sun via its daily travel over the sky but also during its slow seasonal rise in spring or fall in autumn. Such a map shows all the details, such as the shape of the main lobe, the levels of the side lobes, and any asymmetries and irregularities.

Radio Observations of the Total Solar Eclipse on 20 March 2015

J.Köppen, with J.J.Maintoux
DUBUS 3/2018, 24 (2018)
Summary: The total eclipse on March 20th, 2015 is observed on 1.3, 2.3, 8.4, and 10 GHz at DL0SHF and on 1.42 GHz at F6KSX. The signal on 8.4 and 10 GHz drops in a way very similar to that expected for visible light, because radio emission near 10 GHz comes from the chromosphere, a thin and warm layer just on top of the photosphere which is responsible for the visible light. On 1.3 and 2.3 GHz the eclipse begins earlier and lasts longer than the optical eclipse and is less deep, because the radio emission is produced by the hot corona which extends well above the chromosphere. The curve of signal level versus time shows a couple of features, which can well be explained by the presence of several active regions that provide radio-bright spots on the Sun.

Radiation Pattern of a Parabolic Antenna Blocked by its Feed

DUBUS 1/2018, 15 (2018)
DUBUS Technik XVII, 10 (2018)
Summary: The radiation pattern of a parabolic dish antenna whose central parts are blocked by the feed assembly differs from the pattern expected for the full dish in these aspects: The number of side lobes is reduced by suppression of even numbered side lobes and enhancement of the odd numbered lobes. Depending on the size of the blocking feed, it can result in the presence of a deep minimum. The width of the main lobe is slightly reduced. This provides a good explanation of the features seen in the patterns measured with the antennas at DL0SHF.

Ram Pressure Stripping Made Easy: An Analytical Approach

J.Köppen, P.Jáchym, R.Taylor, J.Palouš
MNRAS 479, 4367 (2018)
Abstract: The removal of gas by ram pressure stripping of galaxies is treated by a purely kinematic description. The solution has two asymptotic limits: if the duration of the ram pressure pulse exceeds the period of vertical oscillations perpendicular to the galactic plane, the commonly used quasi-static criterion of Gunn & Gott is obtained which uses the maximum ram pressure that the galaxy has experienced along its orbit. For shorter pulses the outcome depends on the time-integrated ram pressure. This parameter pair fully describes the gas mass fraction that is stripped from a given galaxy. This approach closely reproduces results from SPH simulations. We show that typical galaxies follow a very tight relation in this parameter space corresponding to a pressure pulse length of about 300 Myr. Thus, the Gunn & Gott criterion provides a good description for galaxies in larger clusters. Applying the analytic description to a sample of 232 Virgo galaxies from the GoldMine database, we show that the ICM provides indeed the ram pressures needed to explain the deficiencies. We also can distinguish current and past strippers, including objects whose stripping state was unknown.

Several interactive JavaScript tools which evaluate the analytical considerations of this paper are available at this URL

Evaluating Parabolic Antennas

DUBUS 4/2017, 27 (2017)
DUBUS Technik XVI, 68 (2017)
Radio Astronomy (SARA) March-April 2018, 35 (2018)
Summary: The radiation pattern of a parabolic dish antenna, in particular the width of its main lobe and the spacing and the level of the side lobes, gives essential information of its performance, and from which the antenna parameters can be determined, such as gain, effective area, and efficiency. Measurements of the sky noise and the ground noise allow the determination of the system temperature which describes the overall internal noise level. With these parameters one can predict the signal-to-noise ratio from a radio source.

How to Measure the Atmospheric Absorption at Radio Wavelengths

DUBUS 1/2016, 70 (2016)
Summary: Since the Earth atmosphere modifies the strength of radio signals from celestial sources and space probes by absorption and noise emission, an accurate interpretation of the signal level requires appropriate correction. Hence one needs to know the atmospheric parameters, the most important of which is the antenna temperature measured at the zenith. This can be determined by measuring the sky noise at several elevations. Likewise, measurements of the Sun or the Moon at several elevations allow to determine the sky absorption. Both methods require some time and care, but their use at DL0SHF at frequencies between 1.3 and 24 GHz has proven that they give reliable results, well worth the extra effort. This article explains the procedures of the measurements and interpretation, and presents some results from DL0SHF.

Pointing Corrections for Large Radio Antennas

DUBUS 4/2015, 74 (2015)
Summary: The inevitable small errors in the pointing of a large antenna, such as tilts of the axes or collimation errors, can easily be corrected by software which applies compensations to the desired values for azimuth and elevation. These position-dependent corrections are computed by a set of rather simple formulae which are described by a small number of parameters. The parameters are derived from the differences of measured and predicted positions of known celestial sources (Sun, Moon, CasA, etc) and by finding the set of model parameters whose predicted errors match best the measured differences. This technique is used at DL0SHF to allow accurate pointing at celestial sources and to ensure accurate tracking of e.g. the Moon for EME communications. The essential details of such software are described, along with our experiences and some examples.

Efficiently Measuring Sky Positions for Pointing Corrections of Radio Telescopes

DUBUS 3/2015, 17 (2015)
Summary: For optimum EME operations and for radio astronomy a large antenna needs to be pointed accurately. The basis for a reliable pointing correction scheme are accurate measurements of the pointing errors, which can be obtained by observing the Sun, Moon, and other celestial radio sources whose positions can precisely be predicted. The results of the simple method of searching for the maximum signal can greatly be improved, if one also uses the information of how the signal decreases as one goes away from the source. Bracketing the source in horizontal and vertical position by seeking the same signal level below the maximum is an efficient and accurate approach, as applications at DL0SHF have shown.

SALT reveals the barium central star of the planetary nebula Hen 2-39

B.Miszalski, H.M.Boffin, D.Jones, A.I.Karakas, J.Köppen, A.A.Tyndall, S.S.Mohamed, P.Rodrigues-Gil, M.Santander-García
MNRAS 436, 3068 (2013)

IC 4663: The first unambiguous [WN] Wolf-Rayet central star of a planetary nebula

B.Miszalski, P.A.Crowther, O.DeMarco, J.Köppen, A.F.J.Moffat, A.Acker, T.C.Hillwig
ASPC 459, 281 (2013)

BD-22°3467, a DAO-type star exciting the nebula Abell 35

M.Ziegler, T.Rauch, K.Werner, J.Köppen, J.W.Kruk
Astron.Astrophys. 548, 109 (2012)

A barium central star binary in the Type-I diamond ring planetary nebula Abell 70

B.Miszalski, H.M.J.Boffin, D.J.Frew, A.Acker, J.Köppen, A.F.J.Moffat, Q.A.Parker
MNRAS 419, 39 (2012)

PHR1315-6555: a bipolar planetary nebula in the compact Hyades-age open cluster ESO 96-SC04

Q.A.Parker,D.J.Frew, B.Miszalski, A.V.Kovacevic, P.M.Frinchaboy, P.D.Dobbie, J.Köppen
MNRAS 413, 1835 (2011)

The influence of binarity on dusty obscuration events in the planetary nebula M 2-29 and its analogues

B.Miszalski, J.Mikolajewska, J.Köppen, T.Rauch, A.Acker, M.Cohen, D.J.Frew, A.F.J.Moffat, Q.A.Parker, A.F.Jones, A.Udalski
Astron.Astrophys. 528, A39 (2011)

Mit Spritzgebäck und Silberscheibe zum eigenen Spektroskop

Sterne und Weltraum 04/2010

Starbursts in isolated galaxies: I. The influence of stellar birth function and the IMF

Ch.Theis, J.Köppen
Astron.Astrophys. 502, 486 (2009)

Ram pressure stripping of tilted galaxies

P.Jáchym, J.Köppen, J.Palouš, F.Combes
Astron.Astrophys. 500, 693 (2009)

Mit "ESA-Dresden" ins Radiouniversum

Sterne und Weltraum 03/2009

Gas stripping in galaxy clusters: a new SPH simulation approach

P.Jáchym, J.Palouš, J.Köppen, F.Combes
Astron.Astrophys. 472, 5 (2007)
Full paper in gzipped pdf-file (4.4 MB)

A possible origin of the mass-metallicity relation of galaxies

J.Köppen, C.Weidner, P.Kroupa
MNRAS 375, 120 (2007)
Full paper in pdf-file (467 kB)

Chemical compositions and plasma parameters of planetary nebulae with Wolf-Rayet type central stars

P.Girard, J.Köppen, A.Acker
Astron.Astrophys. 463, 265 (2006)
Full paper in pdf-file (412 kB)
ASCII file of fluxes and intensities (54 kB)

The Macquarie/AAO/Strasbourg H$\alpha$ Planetary Nebula Catalogue: MASH

Q.A.Parker, A.Acker, D.J.Frew, M.Hartley, A.E.J.Peyaud, S.Phillipps, D.Russeil, S.F.Beaulieu, M.Cohen, J.Köppen, J.Marcout, B.Miszalski, D.H.Morgan, R.A.H.Morris, F.Ochsenbein, M.J.Pierce, A.E.Vaughan
MNRAS 373, 79 (2006)
Full paper in pdf-file (1.8 MB)

Effects of episodic gas infall on the chemical abundances in galaxies

J.Köppen, G.Hensler
Astron.Astrophys. 434, 531 (2005)
Full paper in pdf-file (750 kB)

PFP 1: A Large Planetary Nebula Caught in the First Stages of ISM Interaction

M.J.Pierce, D.J.Frew, Q.A.Parker, J.Köppen
Pub.Astron.Soc.Australia 21, 334 (2004)
Full paper (950 kB)

What PNe could tell about extinction inside external galaxies

Planetary Nebulae beyond the Milky Way, Proc. ESO Workshop, Garching 19-21 May 2004, eds. J.R. Walsh, L. Stanghellini, N.G. Douglas, "ESO Astrophysics Symposia", Springer, (2006), p.217
Full paper (1 kB)

Das CDROM Spectroskop

Sterne und Weltraum 11/2003

Discussion: Between simple and chemodynamical models

Galaxy Evolution - III. From simple approaches to self-consistent models, Proc. EuroConference Kiel July 16-20, 2002, eds. G.Hensler, G.Stasińska, S.Harfst, P.Kroupa, Chr.Theis, Astrophys. Space Sciences, 284, 881, Kluwer, (2003)
This is the summary of one of the discussions sections of the conference. Full paper (100 kB)

A comparison of chemical and chemodynamical models

Galaxy Evolution - III. From simple approaches to self-consistent models, Proc. EuroConference Kiel July 16-20, 2002, eds. G.Hensler, G.Stasińska, S.Harfst, P.Kroupa, Chr.Theis, Astrophys. Space Sciences, 284, 837, Kluwer, (2003)
Full paper (85 kB)

Evolution Chimique des Galaxies

Formation et évolution des galaxies, Ecole CNRS de Goutelas XXV, eds. A.Lançon, D.Egret, J.-L.Halbwachs, Obs.Strasbourg et SFAA, p. 129 (2003)
This is the text (in French) of lectures held in a summer school.
Full paper in ps-file (440 kB)

An inverse method to interpret colour-magnitude diagrams

J.-L.Vergely, J.Köppen, D.Egret, O.Bienaymé
Astron.Astrophys. 390, 917 (2002)
Full paper in pdf-file (3.7 MB)

PN G291.4-00.3: A new Type I planetary nebula

D.Nürnberger, S.Durand, J.Köppen, Th.Stanke, M.Sterzik, S.Els
Astron.Astrophys. 377, 241 (2001)
Full paper (800 kB)

On The Cosmic Origins Of Carbon And Nitrogen

R.B.C.Henry, M.G.Edmunds, J.Köppen
Astrophys.J. 541, 660 (2000)
Full paper (pdf) (200 kB)

Planetary Nebulae in Clusters

J.Köppen, A.Acker
Massive Stellar Clusters, Proceedings of the international workshop held in Strasbourg, France, November 8-11, 1999. Eds. A.Lançon and C.Boily.
Astronomical Society of the Pacific Conference Series., p.151 (2000)
Full paper (33 kB)

Observations of planetary nebulae in the Galactic bulge

F.Cuisinier, W.J.Maciel, A.Acker, J.Köppen, B.Stenholm
Astron.Astrophys. 353, 543 (2000)
Full paper (98 kB)

The hidden past of Sakurai's object: Stellar properties before the final helium flash

F.Kerber, J.Köppen, M.Roth, S.C.Trager
Astron.Astrophys. 344, L79 (1999)
Full paper (144 kB)

HaTr 10, a planetary nebula with extremely strong nitrogen lines

A. Tajitsu, S.Tamura, Y.Yadoumaru, R.Weinberger, J.Köppen
PASP 111, 1157 (1999)
Text of paper (30 kB)
Fig.1 (207 kB)
Fig.2 (5 kB)
Fig.3 (7 kB)
Fig.4 (4 kB)

Classification and spectral analysis of faint central stars of highly excited planetary nebulae

T.Rauch, J.Köppen, R.Napiwotzki, K.Werner
Astron.Astrophys. 347, 169 (1999)

Gas Flows and the Chemical Evolution of Galaxies: III. Graphical Analysis and Secondary Elements

J.Köppen, M.G.Edmunds
MNRAS 306, 317 (1999)
Full paper (492 kB)
There is an interactive JAVA Applet available which demonstrates the results of the paper with chemical evolution models with an arbitrary history of star formation and accretion specified by the user.

The Law of Starformation in Disk Galaxies

in The Magellanic Clouds and other dwarf galaxies, Workshop Bonn/Bochum, eds. T.Richtler, J.M.Braun, Shaker Verlag, in press (1998)
Full paper (78 kB)

The Interstellar Extinction in the Solar Neighbourhood

J.-L.Vergely, R.Freire Ferrero, D.Egret, J.Köppen
Astron.Astrophys. 340, 543 (1998)

The Opacity of the Galactic Disk derived with Planetary Nebulae

J.Köppen, J.-L.Vergely
MNRAS 299, 567 (1998)
Full paper (125 kB)

Condensation and evaporation of interstellar clouds in chemodynamical models of galaxies

J.Köppen, Ch.Theis, G.Hensler
Astron.Astrophys. 331, 524 (1998)
Full paper (232 kB)
If you like to have a more detailed description of how the system of equations was analyzed and what came out, you can get a rough manuscript here (255 kB)

The star formation law in disk galaxies - a Bayesian view

J.Köppen, H.-E.Fröhlich
Astron.Astrophys. 325, 961 (1997)
Full paper (111 kB)

The variation of abundances in planetary nebulae with height above the Galactic plane

J.Köppen, F.Cuisinier
Astron.Astrophys. 318, 98 (1996)
Full paper (132 kB)

Spectral analysis of the planetary nebula LoTr 4 and its very hot hydrogen-deficient central star

T.Rauch, J.Köppen, K.Werner
Astron.Astrophys. 310, 613 (1996)

Spectrophotometric observations of planetary nebulae high above the Galactic plane

F.Cuisinier, A.Acker, J.Köppen
Astron.Astrophys. 307, 217 (1995)

Quasar absorption lines: The chemical compositions of the absorbing clouds

O.J.Dittmann, J.Köppen
Astron.Astrophys. 297, 671 (1995)

The self-regulated star formation in chemodynamical models of galaxies

J.Köppen, C.Theis, G.Hensler
Astron.Astrophys. 296, 99 (1995)
Full paper (146 kB)

Chemical evolution in an inhomogeneous interstellar medium

M.Wilmes, J.Köppen
Astron.Astrophys. 294, 47 (1994)

Analysis of BD+33 2642 - a newly detected planetary nebula in the galactic halo and its central star

R.Napiwotzki, U.Heber, J.Köppen
Astron.Astrophys. 292, 239 (1994)

Spectral analysis of the planetary nebula K 1-27 and its very hot hydrogen-deficient central star

T.Rauch, J.Köppen, K.Werner
Astron.Astrophys. 286, 543 (1994)

Abundance gradients from disk planetary nebulae: O, Ne, S, and Ar

W.J.Maciel, J.Köppen
Astron.Astrophys. 282, 436 (1994)

The evolution of abundance gradients in spiral galaxies

Astron.Astrophys. 281, 26 (1994)

Spectrophotometric survey of southern planetary nebulae: III. Automatic model analysis

M.Samland, J.Köppen, A.Acker, B.Stenholm
Astron.Astrophys. 264, 184 (1991)

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last update: May 2024 J.Köppen