COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 2917

                                                      Konkoly Observatory
                                                      Budapest
                                                      17 July 1986

                                                      HU ISSN 0374 - 0676

          INFRARED PHOTOMETRY OF THE DWARF NOVA AH Her

The variability of the dwarf nova AH Her (type Z Cam) was first
reported by Jacchia (1941). Its magnitude shows a range of variation
between 10.2 and 14.7 in visible (Kukarkin 1969), and a mean outburst
period of 19.6 day (Beyer 1967).
   We present infrared measurements during the rise to the outburst
that took place in the third week of April 1986.
   The observations were made with the 1.5 m Infrared Flux Collector
at the Observatorio de Izana (Tenerife) during a period of 5 nights
from 20 to 25 April 1986, using the infrared single-channel photometer
with an InSb detector cooled with liquid-Nitrogen and the broad-band
filters J, H, K.
   This photometer has a double beam, chopped at 10 Hz to monitor
the sky. The star was exposed for 10 sec. in alternate beams until
a good signal/noise was achieved. The uncertainty in each infrared
measurement is about 0.07 magnitudes. The observed magnitudes were
corrected for extinction by observation of standard stars and placed
on Johnson's system.

   Table I shows the initial and final Julian Date for each night
of observation, the magnitude J, and the J-H, J-K colours.


                 Table 1

JD_init    JD_fin      J     J-H    J-K  
     2446000+

541.639    541.683   12.39   0.33   0.49
542.660    542.718   12.02   0.34   0.50
543.726    543.741   11.64    --    0.28
544.716    544.743   11.61   0.29   0.34
545.630    545.666   11.49   0.24   0.34


                          [FIGURE 1]
                   

   In the figure the values of J, H, K magnitudes are plotted vs.
the Julian Date along with the V magnitudes for the whole April
given by 'The Astronomer' magazine.
   It is important to point out that there are significant changes
of colour during the rise to maximum and it is noted that the maximum
in the IR could be delayed compared to the visible.


                 C. LAZARO and M.J. AREVALO
             Instituto de Astrofisica de Canarias.
               38071 La Laguna, Tenerife, Spain


References:

Jacchia, L: 1941, Harv. Bull. 915, Cambridge Observatory, 17 [BIBCODE 1941BHarO.915...17J ]
Kukarkin, B.V.: 1969, General Catalogue of Variable Stars, Moscow [BIBCODE 1969okpz.book.....K ]
Beyer, M.: 1967, Astron. Nachr. 290, 29 [BIBCODE 1967AN....290...29B ]