LOTIS Upper Limits and the Prompt OT from GRB 990123

GRB 990123 established the existence of prompt optical emission from gamma-ray bursts (GRBs). The Livermore Optical Transient Imaging System (LOTIS) has been conducting a fully automated search for this kind of simultaneous low energy emission from GRBs since October 1996. Although LOTIS has obtained simultaneous, or near simultaneous, coverage of the error boxes obtained with BATSE, IPN, XTE, and BeppoSAX for several GRBs, image analysis resulted in only upper limits. The unique gamma-ray properties of GRB 990123, such as very large fluence (top 0.4%) and hard spectrum, complicate comparisons with more typical bursts. We scale and compare gamma-ray properties, and in some cases afterglow properties, from the best LOTIS events to those of GRB 990123 in an attempt to determine whether the prompt optical emission of this event is representative of all GRBs. Furthermore, using LOTIS upper limits in conjunction with the relativistic blast wave model, we weakly constrain the GRB and afterglow parameters such as density of the circumburster medium and bulk Lorentz factor of the ejecta.Comment: 5 pages, 2 figures, To appear in Proceedings of the 5th Huntsville Gamma-Ray Burst Symposiu

CO-bandhead spectroscopy of IC 342: mass and age of the nuclear star cluster

We have used the NASA Infra-Red Telescope Facility (IRTF) to observe the nuclear stellar cluster in the nearby, face-on, giant Scd spiral IC 342. From high resolution (R = 21500) spectra at the 12CO (2-0) bandhead at 2.3 micron we derive a line-of-sight stellar velocity dispersion sigma = (33 +- 3) km/s. To interpret this observation we construct dynamical models based on the Jeans equation for a spherical system. The light distribution of the cluster is modeled using an isophotal analysis of an HST V-band image from the HST Data Archive, combined with new ground-based K-band imaging. Under the assumption of an isotropic velocity distribution, the observed kinematics imply a K-band mass-to-light ratio M/L_K = 0.05, and a cluster mass M ~ 6 times 10^6 Msun. We model the mass-to-light ratio with the `starburst99' stellar population synthesis models of Leitherer and collaborators, and infer a best-fitting cluster age in the range 63-630 Myears. Although this result depends somewhat on a number of uncertainties in the modeling (e.g., the assumed extinction along the line-of-sight towards the nucleus, the IMF of the stellar population model, and the velocity dispersion anisotropy of the cluster), none of these can be plausibly modified to yield a significantly larger age. We discuss the implications of this result on possible scenarios for the frequency of nuclear starbursts and their impact on secular evolution of spiral galaxy nuclei. As a byproduct of our analysis, we infer that IC 342 cannot have any central black hole more massive than 0.5 million solar masses. This is ~ 6 times less massive than the black hole inferred to exist in our Galaxy, consistent with the accumulating evidence that galaxies with less massive bulges harbor less massive black holes.Comment: 27 pages, incl. 9 figures, submitted to The Astronomical Journa

LOTIS Search for Early Time Optical Afterglows: GRB 971227

We report on the very early time search for an optical afterglow from GRB 971227 with the Livermore Optical Transient Imaging System (LOTIS). LOTIS began imaging the `Original' BATSE error box of GRB 971227 approximately 14 s after the onset of gamma-ray emission. Continuous monitoring of the position throughout the evening yielded a total of 499 images (10 s integration). Analysis of these images revealed no steady optical afterglow brighter than R=12.3 +- 0.2 in any single image. Coaddition of different combinations of the LOTIS images also failed to uncover transient optical emission. In particular, assuming a constant early time flux, no optical afterglow brighter than R=14.2 +- 0.2 was present within the first 1200 s and no optical afterglow brighter than R=15.0 +- 0.2 was present in the first 6.0 h. Follow up observations by other groups revealed a likely X-ray afterglow and a possible optical afterglow. Although subsequent deeper observations could not confirm a fading source, we show that these transients are not inconsistent with our present knowledge of the characteristics of GRB afterglows. We also demonstrate that with the upgraded thermoelectrically cooled CCDs, LOTIS is capable of either detecting very early time optical afterglow or placing stringent constraints on the relationship between the gamma-ray emission and the longer wavelength afterglow in relativistic blast wave models.Comment: 17 pages, 3 eps figures, revisions based on reviewers comment

New Constraints on Simultaneous Optical Emission from Gamma-Ray Bursts Measured by the Livermore Optical Transient Imaging System Experiment

LOTIS is a gamma-ray burst optical counterpart search experiment located near Lawrence Livermore National Laboratory in California. Since operations began in 1996 October, LOTIS has responded to five triggers as of 1997 July 30, which occurred during good weather conditions. GRB 970223 (BATSE trigger 6100) was an exceptionally strong burst, lasting »30 s with a peak at »8 s. LOTIS began imaging the error box »11 s after the burst began and achieved simultaneous optical coverage of 100% of the region enclosed by the BATSE 3 j error circle and the interplanetary network annulus. No optical transients were observed brighter than the m » 11 completeness limit of the resulting images, providing a new V upper limit on the ratio of simultaneous optical to gamma-ray fluence of R \u3c 1024 and on the ratio of L simultaneous optical (at 700 nm) to gamma-ray (at 100 keV) flux density of R ! 305 for a B-type spectrum and R \u3c 475 for an M-type spectrum

Future Precision Neutrino Oscillation Experiments and Theoretical Implications

Future neutrino oscillation experiments will lead to precision measurements of neutrino mass splittings and mixings. The flavour structure of the lepton sector will therefore at some point become better known than that of the quark sector. This article discusses the potential of future oscillation experiments on the basis of detailed simulations with an emphasis on experiments which can be done in about ten years. In addition, some theoretical implications for neutrino mass models will be briefly discussed.Comment: Talk given at Nobel Symposium 2004: Neutrino Physics, Haga Slott, Enkoping, Sweden, 19-24 Aug 200

Instrumentation of LOTIS: Livermore Optical Transient Imaging System; a fully automated wide field of view telescope system searching for simultaneous optical counterparts of gamma ray bursts

LOTIS is a rapidly slewing wide-field-of-view telescope which was designed and constructed to search for simultaneous gamma-ray burst (GRB) optical counterparts. This experiment requires a rapidly slewing ({lt} 10 sec), wide-field-of-view ({gt} 15{degrees}), automatic and dedicated telescope. LOTIS utilizes commercial tele-photo lenses and custom 2048 x 2048 CCD cameras to view a 17.6 x 17.6{degrees} field of view. It can point to any part of the sky within 5 sec and is fully automated. It is connected via Internet socket to the GRB coordinate distribution network which analyzes telemetry from the satellite and delivers GRB coordinate information in real-time. LOTIS started routine operation in Oct. 1996. In the idle time between GRB triggers, LOTIS systematically surveys the entire available sky every night for new optical transients. This paper will describe the system design and performance