arXiv subjects

N. C. Hastings

Publications and source records attributed to N. C. Hastings.

57 records · Page 4Linked to original sources

arXiv2002

Optical monitoring of the gravitationally lensed quasar Q2237+0305 from APO between June 1995 and January 1998

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 (>~ 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. 2000a).

astro-ph↗

arXiv2000

Uniformity of V minus Near Infrared Color Evolution of Type Ia Supernovae, and Implications for Host Galaxy Extinction Determination

From an analysis of SNe 1972E, 1980N, 1981B, 1981D, 1983R, 1998bu, 1999cl, and 1999cp we find that the intrinsic V-K colors of Type Ia SNe with multi-color light curve shape (MLCS) parameter -0.4 < Delta < +0.2 suggest a uniform color curve. V-K colors become bluer linearly with time from roughly one week before B-band maximum until one week after maximum, after which they redden linearly until four weeks after maximum. V-H colors exhibit very similar color evolution. V-J colors exhibit slightly more complex evolution, with greater scatter. The existence of V minus near infrared color relations allows the construction of near infrared light curve templates that are an improvement on those of Elias et al. (1985). We provide optical BVRI and infrared JHK photometry of the Type Ia supernovae 1999aa, 1999cl, and 1999cp. SN 1999aa is an overluminous "slow decliner" (with Delta = -0.47 mag). SN 1999cp is a moderately bright SN unreddened in its host. SN 1999cl is extremely reddened in its host. The V minus near infrared colors of SN 1999cl yield A_V = 2.01 +/- 0.11 mag. This leads to a distance for its host galaxy (M 88) in agreement with other distance measurements for members of the Virgo cluster.

astro-ph↗

arXiv1998

High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557

We present phase-resolved spectral and multicolor CCD-photometric observations of the eclipsing polar RX J0719.2+6557 obtained with relatively high time (~600 sec/15 sec) and spectral (2.1 A) resolution when the system was in a high accretion state. The trailed spectrograms clearly reveal the presence of three different line components with different width and radial velocity variation. We were able to resolve all three components by line deblending, and by means of Doppler tomography were able to unambiguously identify the emission components with the secondary star, the ballistic part of the accretion stream and the magnetically funnelled part of the stream. The light curves and eclipse profiles provide additional information about the system geometry.

astro-ph↗