ELFT HÍRADÓ

[ilka AT konkoly.hu (Kalman Belane)]

                              Meghivó

      az MTA Konkoly Thege Miklós Csillagászati Kutatóintézete
                          
                            szemináriumára


Elõadó: Prof. Dr. A. Hatzes (Tautenburg Obs)

Cím:"Radial Velocity Studies of Rapidly Oscillating Ap Stars"

Abstract:

The rapidly oscillating  Ap (roAp) stars are a pulsating subclass
of the chemically  peculiar Ap stars that exhibit p-mode oscillations with
periods of 5 to 15 minutes. We have been using precise stellar radial
velocity measurements made with an iodine absorption cell to study the
pulsations in roAp stars. These have shown a rather complex behaviour with
different spectral lines showing pulsational amplitudes that differ by
factors of 10-100. I will present results from several roAp stars,
including 33 Lib and HR 1217. 33 Lib shows evidence for amplitude and
phase variations in the pulsations. In particular, it exhibits evidence
for a radial node in the atmosphere. Nd lines formed on opposite sides of
the node pulsate 180 deg out of phase with each other. Stars like 33 Lib
will enable us to study the vertical structure to the pulsations in roAp
stars. In HR 1217 photometric studies have found 7 pulsation modes.
Our spectral observations have uncovered an additional 2-3 pulsation
modes in this star. Finally, I will present evidence for a new ultra-low
amplitude roAp star, Beta CrB, which shows an amplitude of only 3 m/s and
a period of 16.1 minutes. RoAp stars like Beta CrB may help answer what
makes an Ap star pulsate.

A szeminárium idõpontja: 2005. március 17, csütörtök 14 óra. 
      
Helyszine: MTA Konkoly Thege Miklós Csillagászati Kutatóintézete
                  1121 Budapest Konkoly Thege M. út 13-17.

                                      Patkós László s.k.