Addresses:

1. sdB stars (and other horizontal branch stars) and the structure of our galaxy
   (PHD THESIS)
   

   What are Horizontal Branch (HB) Stars?

   Horizontal Branch stars are evolved medium to low mass stellar objects in their core Helium burning phase. Stars, which have used up all their Hydrogen, and subsequently became Red Giants (RGB), which burn Hydrogen in their shell. Meanwhile the inert core grows in mass so that temperature and pressure of the core rise continuously. At one stage a point is reached when the core ignites and the stars starts its HB-phase. In the meantime the star has lost a large part of its outer shell due to strong stellar winds during the RGB phase. The resulting HB star now contains the 0.5 solar masses He-core and between 0.5 solar masses and very little (<0.01 solar masses) Hydrogen making up its envelope. Depending on this shell the star appears either red or blue with surface temperatures ranging from approximately 3500 K to 40000 K. At intermediate temperatures (6000-7500 K) the HB intersects the instability strip. That is where the RR Lyrae variable HB stars lie. The stars blueward of the instability strip are called blue HB stars (BHB) and subdivided into HBA (7500-10000 K) and HBB stars (10000-20000 K). The part which is even hotter than this is called the Extreme or Extended HB. The EHB stars are called sdB (cooler part, no or very little He in their spectra) or sdOB (hotter part, significant He in their spectra). The even hotter sdO stars are either evolved sdB stars or stars settling to become white dwarfs after their second Red Giant phase (AGB).
   

   HB stars and the structure of the Galaxy

   These stars are an useful tool for research trying to determine the structure of the older stellar component of our galaxy. In my PhD thesis I determine the physical, spatial and kinematical (i.e. effective temperature, surface gravity, distance, radial velocity and proper motion) of samples of sdB stars in two fields of high galactic latitude. Knowing the spatial distribution of a statistically complete sample of stars, one can determine the scale height of their distribution perpendicular to the galactic plane. This gives information about the population membership (halo or disk) of these stars. Examining the kinematics of stars shows us whether they have disk-like orbits (high orbital velocity, low eccentricities, small maximum z-heights) or have highly inclined, high eccentricity orbits featuring a low orbital velocity, which would characterise them as halo objects.
   
   
   

   Typical orbits of the different varieties of Horizontal Branch stars. Shown are the meridional plots of RR Lyraes (magenta), HBAs (red), HBBs (green) and sdB stars (blue). The difference in the kinematical behaviour of the HB stars can be clearly seen.

   Want to see how sdB stars move trough our Galaxy?
   Then download this MPEG-File (3.9 MB) showing the trajectories of 110 sdB stars (red) and the Sun (blue) as well as their current positions (green):
   sdB orbits - The Movie!
   Note: the stars move backwards in time over 1 Gyr
   More to come, so stay tuned!!!!!
   Collaborators: Klaas S. de Boer (Bonn), Heinz Edelmann (Bamberg), O.-M. Cordes (Bonn), Torsten Kaempf (Bonn), Philip Willemse (Bonn), Marcio Catelan (Univ. Catolica, Stgo.), Rene Mendez (Univ. de Chile, Stgo.)
2. Establishing a catalogue of spectrophotometric standards in the frame of the DIVA satellite mission (In Collaboration with Uli Heber, Zorica Pavcovic (Bamberg) and Klaas S. de Boer (Bonn).
3. Proper motions of Dwarf Spheroidal Galaxies (In collaboration with Rene Mendez (UdC), Edgaro Da Costa (UdC), Mario Pedreros (Universidad de Tarapaca, Arica, Chile).
4. Wide Field MUSYC and CYDER Surveys. While these are like most surveys of this kind primarily designed to deal with extragalactic topics these two have a strong galactic section and even include the derivation of proper motions. I am looking for White Dwarfs (incl. cool White Dwarfs), substellar Brown Dwarfs and other stellar objects of interrest.
   
   A part of the CYDER C2 field (BVI)
   Full frame (JPEG 5 MB)
   
5. General observing at Hoher-List Observatory

Publication list

Timetable

Programs and utilities

SuperMongo Macros

• clean.m:
  a very simple macro resetting values for all to their defaults (ctype, angle, ltype, box, etc.) and erasing the display. Their are no input parameters.
  
  
• vectorplot.m:
  a macro to produce a vectorplot.
  syntax: vectorplot x y length angle angletype scaling
  
  x and y are the coordinates to which the vector plot is connected, length is the scalar size of the vectorial quantity to be plotted and angle is the position angle, counting from the 3 o'clock position counterclockwise (if your position angle goes otherwise, adapt it accordingly), angletype is a switch, supplying the macro with the information whether the angles are in radian (0) or degrees (1) [Any other value will return an errormessage and a prompt to put in an accepted value, i.e. 0 or 1]. Finally the last parameter, scaling scales the length of the vector, in order to make the plot more appealing and less crowded. x, y, length, angle are vectorial quantities and have to be of the same dimension, angletype and scaling are variables.
  
  
• colours.m:
  This macro (without any input parameters) extends the palette of available colours far beyond the original rgbmycbw palette of SM. I added all xfig colours and many others, more can be added anytime. (Current version: 12th May 2003)

Martins Gallery

Copyright notice: Since there are quite a few enquiries about publication of images from the Gallery Page, I have reviewed and updated the copyright notice, hoping to make things a little clearer.

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Observatories

     

La Silla: 3.6 m and NTT telescopes                                NGC 2997: picture taken with the 1.54 m Danish Telescope
                                                                                       and DFOSC


NGC 5128: The brightest elliptical galaxy in the sky has
obviously interacted with a dusty object, such as a galactic disk.
Image taken in BVR passbands with the 1.54 m Danish Tele-
scope and DFOSC on 03.05.2002 (The absorption due to
cloud cover was at the time approximately 6 mag).

It never snows in a desert, like the Atacama desert, least of all, when it's almost summer! Well, see for yourself (Link refers to a series of pictures taken on the 31.10.1999)

A page with informations (and links) about the various observatories I have visited and the telescopes I have observed with is planned.

Meanwhile for people who cannot wait to see how the weather is like at typical observatories:

CLICK HERE

OR HERE

Links to official sites and other sites concerning some of the observatories, I've been to:

• German Spanish Observatory Calar Alto, Gergal, Co. Almeria (Spain):
  
  1. Max Planck Institut für Astronomie
     (The institution running Calar Alto Observatory)
  2. CA-Homepage at site of MPIA
  3. CA-Homepage in Spain
• ESO Observatories La Silla and Paranal
  
  1. The ESO homepage
  2. La Silla Homepage
  3. Paranal Homepage
• NAO Rozhen (Bulgaria)
  (My page, no official homepage available)
• Observatory Hoher List.

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