TY  - JOUR
A1  - Schmidt, Robert W.
A1  - Kundic, T.
A1  - Pen, U.-L.
A1  - Wambsganß, Joachim
A1  - Bergeron, L. E.
A1  - Colley, W.
A1  - Corson, C.
A1  - Hastings, N. G.
A1  - Hoyes, T.
A1  - Long, D. C.
A1  - Loomis, K. A.
A1  - Malhotra, S.
A1  - Rhoads, J. E.
A1  - Stanek, K. Z.
T1  - Optical monitoring of the gravitationally lensed quasar Q2237+0305 from APO between June 1995 and January 1998
N2  - We present a data set of images of the gravitationally lensed quasar Q2237+0305, that was obtained at the Apache Point Observatory (APO) between June 1995 and January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help of exact quasar image positions from HST observations. We obtain a light curve with 73 data points for each of the images A and B. There is evidence for a long (ga 100 day) brightness peak in image A in 1996 with an amplitude of about 0.4 to 0.5 mag (relative to 1995), which indicates that microlensing has been taking place in the lensing galaxy. Image B does not vary much over the course of the observation period. The long, smooth variation of the light curve is similar to the results from the OGLE monitoring of the system (Wozniak et al. cite{Wozniak00}). Based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Wambsganß, Joachim
A1  - Schmidt, Robert W.
A1  - Colley, W.
A1  - Kundic, T.
A1  - Turner, E. L.
T1  - Microlensing results from APO monitoring of the double quasar Q0957+561A,B between 1995 and 1998
N2  - If the halo of the lensing galaxy 0957+561 is made of massive compact objects (MACHOs), they must affect the lightcurves of the quasar images Q0957+561 A and B differently. We search for this microlensing effect in the double quasar by comparing monitoring data for the two images A and B - obtained with the 3.5m Apache Point Observatory from 1995 to 1998 - with intensive numerical simulations. This way we test whether the halo of the lensing galaxy can be made of MACHOs of various masses. We can exclude a halo entirely made out of MACHOs with masses between 10-6 Msun and 10-2 Msun for quasar sizes of less than 3x 1014 h60-1/2 cm, hereby extending previous limits upwards by one order of magnitude.
Y1  - 2000
ER  -