Paul S. Smith

Optical Follow-Up of GRB 970508

We report on the results of optical follow-up observations of the counterpart of the gamma-ray burst GRB 970508, starting 7 hr after the event. Multicolor U-, B-, V-, Rc-, and Ic-band observations were obtained during the first three consecutive nights. The counterpart was monitored regularly in Rc until ~4 months after the burst. The light curve after the maximum follows a decline that can be fitted with a power law with exponent α = -1.141 ± 0.014. Deviations from a smooth power-law decay are moderate (rms = 0.15 mag). We find no flattening of the light curve at late times. The optical afterglow fluence is a significant fraction, ~5%, of the GRB fluence. The optical energy distribution can be well represented by a power law, the slope of which changed at the time of the maximum (the spectrum became redder).

Photometric Calibration of Stars in the Fields of Selected BL Lacertae Objects and Quasars

We present the results of UBVRI photometry of stars in the fields of 13 BL Lacertae objects and quasars. The calibrated stars are intended to facilitate photoelectric and CCD differential photometry of these highly variable active galactic nuclei (AGNs). The magnitudes of most of the stars were measured on more than two occasions, and we provide two to five stars per field. Several stars are common to those calibrated by previous observers, although the earlier efforts do not cover all five bandpasses. Our results for these stars are typically in close agreement with previous measurements obtained using common filters. In addition, we present UBVRI magnitudes for stars in the fields of four AGNs (CTA 26, 0716+332, OV–236, and PKS 2345–167) with no previously published comparison stars.

Long-Term Spectroscopic Monitoring of Low-Redshift Quasars. I. 5 Year Report

We present the first results of a long-term optical spectroscopic monitoring program of a sample of 14 luminous (LBol ~ 1045-1046 ergs s-1) low-redshift (z = 0.14-0.59) quasars. Our spectra have been taken annually over a period of 5 yr and for four objects have been supplemented by digital spectra obtained approximately 20 years earlier. For these four objects, we find relatively little change in both the shapes and fluxes of the broad lines from the first observations to the present. However, in one quasar, B2 1721+34, the emission in the core of the Hα profile has decreased while that in the profile wings has increased, suggesting that material has moved from the outer intermediate-line region to the inner very broad line region (VBLR). Our 5 year monitoring campaign reveals variability in the core, but not the wings, of the Hβ profile of several objects in response to variations in the continuum. In a few objects, notably PKS 1451-37, we observe year-to-year variability in the strength of the He II λ4686 line that also appears to be a response to variability in the ionizing continuum. The lack of significant long-term variability in the wings of the Balmer lines supports models in which the VBLR takes the form of a relativistic accretion disk, as opposed to an episodic flow to or from the central engine. In the latter case, current constraints on the gas crossing time of the VBLR indicate that variability would occur on a timescale of months, which we do not observe. The lack of response of the wings of Hβ to continuum variability provides additional evidence that the VBLR is fully ionized in hydrogen.

NOAO queue-observing experiment on the WIYN Telescope

For the last 3 years, most of NOAOs 40 percent observing share on the WIYN 3.5 m telescope has been used for queued observing, with the goal of facilitating highly ranked science proposals that require rare observing conditions and/or synoptic or target of opportunity observations. The ease of switching between imaging on one Nasmyth focus and multi- object fiber fed bench spectroscopy on the other Nasmyth port offers the choice of making the best use of the extant observing conditions. We assess the results of this experiment and highlight some of the forefront observing programs that have been executed. We discuss algorithms that facilitate making decisions on both long and short time scales so that we can provide the best match of program requirements and observing conditions. We suggest a way of quantifying the prioritization of programs beyond simple ranking that will greatly aid decision making, and evolve the procedures to where queued observations better serve the emphases placed by the time allocation process, without compromising the intent of the scientific investigators.

Optical gamma-ray burst followup at Kitt Peak National Observatory

The discovery of probable X-ray, optical, and radio counterparts to gamma-ray bursts (GRBs) may allow significant advances in GRB research. More data are sorely needed, however. We have a target of opportunity program this semester at the 0.9 meter telescope to search for optical counterparts to GRBs. Images from the search will be made publicly available at our web site (http://www.noao.edu/noao/grb/) as quickly as we can reduce them.

Flexible observing modes employed at the WIYN Observatory

The WIYN 3.5 meter telescope on Kitt Peak, Arizona is operated by a consortium involving three universities and the National Optical Astronomical Observatories (NOAO) each with their own set of scientific requirements and research objectives. To meet this diversity a variety of operational modes are being used. It is the purpose of this paper to describe the experience acquired so far with queue scheduling, remote observing, consortium-wide coordinated programs, and student involvement. Observing time is block scheduled in such a way that each WIYN member receives their equitable distribution with respect to season and lunation. NOAO provides operations support and receives 40 percent of the observing time which is made available to the general astronomical community through the same mechanism as for other NOAO facilities. The largest fraction of this time, however, is devoted to queue scheduling. The remaining 60 percent of the observing time is divided among the three universities in proportion to their contribution to the capital costs of the observatory. Each university has its own approach to assigning observing time and utilizing their blocks. Among the modes employed are traditional on-site, service, and remote observing. The WIYN telescope supports rapid changing of instrumentation and it is common to do multiple-instrument observing during the course of a night. This also expedites the sharing of nights by more than one observer. The flexibility also provides the means to respond to targets of opportunity. In this paper we shall try to evaluate the ways in which this flexibility has been able to enhance scientific return.