We present GALEX near ultraviolet (NUV:1750 - 2750A) and far ultraviolet (FUV: 1350 - 1750A) imaging observations of two 1.2 degree diameter fields in the Hyades and Pleiades open clusters in order to detect possible UV variability of the member star
s. We have performed a detailed software search for short-term UV flux variability during these observations of the approx 400 sources detected in each of the Hyades and Pleiades fields to identify flare-like (dMe) stellar objects. This search resulted in the detection of 16 UV variable sources, of which 13 can be directly associated with probable M-type stars. The other UV sources are G-type stars and one newly discovered RR Lyrae star, USNOB1.0 1069-0046050, of period 0.624 day and distance 4.5-7.0 kpc. Light curves of photon flux versus time are shown for 7 flare events recorded on six probable dMe stars. UV energies for these flares span the range 2E27 to 5E29 erg, with a corresponding NUV variability change of 1.82 mag. Only one of these flare events (on the star Cl* Melotte 25 LH129) can definitely be associated with an origin on a member the Hyades cluster itself. Finally, many of our M-type candidates show long periods of enhanced UV activity but without the associated rapid increase in flux that is normally associated with a flare event. However, the total UV energy output during such periods of increased activity is greater than that of many short-term UV flares. These intervals of enhanced low-level UV activity concur with the idea that, even in quiescence, the UV emission from dMe stars may be related to a superposition of many small flare events possessing a wide range of energies.
We present high resolution (R = 60,000) measurements of the NaI D1 and D2 (5890 A) and CaII K (3933 A) interstellar absorption line profiles recorded towards several post-AGB stars located within the M13 and M15 globular clusters, supplemented with a
lower resolution spectrum of the CaII K-line observed in absorption towards an Ofpe/WN9 star in the central region of the M33 galaxy. The normalized interstellar absorption profiles have been fit with cloud component velocities, doppler widths and column densities in order to investigate the kinematics and physical conditions of the neutral and partially ionized gas observed along each sight-line. Our CaII observations towards M13 have revealed 4 absorption components that can be identified with galactic Intermediate Velocity Clouds (IVCs) spanning the -50 > Vlsr > -80 km/s range. The NaI/CaII ratio for these IVCs is<0.3, which characterizes the gas as being warm (T=1000 K) and partially ionized. Similar observations towards two stars within M15 have revealed absorption due to a galactic IVC at Vlsr=+65 km/s. This IVC is revealed to have considerable velocity structure, requiring at least 3 cloud components to fit the observed NaI and CaII profiles. CaII K-line observations of a sight-line towards the center of the M33 galaxy have revealed at least 10 cloud components. A cloud at Vlsr=-130 km/s is either an IVC associated with the M33 galaxy occurring at +45 km/s with respect to the M33 local standard of rest, or it is a newly discovered HVC associated with our own Galaxy. In addition, 4 clouds have been discovered in the -165 > Vlsr > -205 km/s range. Three of these clouds are identified with the disk gas of M33, whereas a component at - 203 km/s could be IVC gas in the surrounding halo of M33.
