arXiv subjects

R. Street

Publications and source records attributed to R. Street.

40 records · Page 3Linked to original sources

arXiv2009

Interpretation of Strong Short-Term Central Perturbations in the Light Curves of Moderate-Magnification Microlensing Events

To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short time-scale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.

astro-ph.EP↗

arXiv2008

RoboNet-II: Follow-up observations of microlensing events with a robotic network of telescopes

RoboNet-II uses a global network of robotic telescopes to perform follow-up observations of microlensing events in the Galactic Bulge. The current network consists of three 2m telescopes located in Hawaii and Australia (owned by Las Cumbres Observatory) and the Canary Islands (owned by Liverpool John Moores University). In future years the network will be expanded by deploying clusters of 1m telescopes in other suitable locations. A principal scientific aim of the RoboNet-II project is the detection of cool extra-solar planets by the method of gravitational microlensing. These detections will provide crucial constraints to models of planetary formation and orbital migration. RoboNet-II acts in coordination with the PLANET microlensing follow-up network and uses an optimization algorithm ("web-PLOP") to select the targets and a distributed scheduling paradigm (eSTAR) to execute the observations. Continuous automated assessment of the observations and anomaly detection is provided by the ARTEMiS system.

astro-ph↗

arXiv2004

Photometric Observations of the Type Ia SN 2002er in UGC 10743

Extensive light and colour curves for the Type Ia supernova SN 2002er are presented as part of the European Supernova Collaboration. We have collected UBVRI photometry from ten different telescopes covering the phases from 7 days before until 619 days after maximum light. Corrections for the different instrumental systems and the non-thermal spectrum of the supernova (S-corrections) have been applied. With the densely sampled light curves we can make detailed comparisons to other well-observed objects. SN 2002er most closely resembles SN 1996X after maximum, but clearly shows a different colour evolution before peak light and a stronger shoulder in V and R bands compared to other well-observed SNe Ia. In particular, the rise time appears to be longer than what is expected from rise-time vs.decline-rate relation. We use several methods to determine the reddening towards SN 2002er based on the colour evolution at near peak and at late phases. The uvoir (bolometric) light curve shows great similarity with SN 1996X, but also indications of a higher luminosity, longer rise time and a more pronounced shoulder 25 days past maximum. The interpretation of the light curves was done with two independent light curve codes. Both find that given the luminosity of SN 2002er the 56Ni mass exceeds 0.6 Msun with prefered values near 0.7 Msun. Uncertainties in the exact distance to SN 2002er are the most serious limitation of this measurement. The light curve modelling also indicates a high level of mixing of the nickel in the explosion of SN 2002er.

astro-ph↗

arXiv2001

Can Jupiters be found by monitoring Galactic Bulge microlensing events from northern sites?

In 1998 the EXPORT team monitored microlensing event lightcurves using a CCD camera on the IAC 0.8m telescope on Tenerife to evaluate the prospect of using northern telescopes to find microlens anomalies that reveal planets orbiting the lens stars. The high airmass and more limited time available for observations of Galactic Bulge sources makes a northern site less favourable for microlensing planet searches. However, there are potentially a large number of northern 1m class telescopes that could devote a few hours per night to monitor ongoing microlensing events. Our IAC observations indicate that accuracies sufficient to detect planets can be achieved despite the higher airmass.

astro-ph↗