- Internal structure and evolution of the Very Small Asteroids
- Global Astrophysical Telescope System
- Photometry and spectroscopy of cepheids and eclipsing binary stars
Selected past projects:
This is currently my main project, whose aim is to observe asteroids smaller than about 150 m (they are called Very Small Asteroids, VSAs for short). The goal is to determine their rotation periods, diameters, and surface properties. With these data it should be possible to search for period changes due to the YORP effect and study critical periods, below which the asteroids may undergo rotational fission. These periods should tell us something about the internal strengths of VSAs.
During the first part of the project I was the Principal Investigator of the observations of VSAs at the 10 m Southern African Large Telescope (SALT). From January 2007 till March 2008 we observed 79 VSAs and for 27 were able to determine their rotation periods.
From October 2008 till April 2009, together with Carl Hergenrother (LPL), we managed to observe 46 asteroids with SALT. The data are still being analyzed.
I am advising in a project led by Krzysztof Kamiński. Its goal is to build a robotic, spectroscopic telescope (PST2), which could observe in pair with the already existing PST1. PST1 is situated near Poznań, Poland and we plan to locate PST2 in the Southern USA. The difference of longitude should allow us to observe stellar radial velocities for the extended period of time, up to 21 hours. PST2 is described at the GATS web page.
In 2002 I started photometric observations of bright eclipsing binaries with our small, 0.4m telescope near Poznan. We wanted to collect data for objects that could be later observed with the spectroscopic telescope (PST1). Combining photometry and spectroscopy for eclipsing binaries makes it possible to obtain their basic physical parameters, which can then be used to test stellar models. Before PST1 became operational I collected some spectroscopy at the 2m DDO telescope. In 2007 PST1 joined in and we managed to get a model of FM Leo. Another star in our queue is V2080 Cyg.
When high accuracy of the PST1 radial velocities became obvious, we also started to observe selected cepheids. We proved that one of them, V440 Per, is the longest-period overtone Cepheid.
I worked together with A. Schwarzenberg Czerny and R. Baranowski (both from our Observatory), with help from many others, to construct a mid-resolution, fiber-fed echelle spectrograph and a small telescope for radial velocity measurements.
The idea was born during a conversation between A. Schwarzenberg-Czerny and Bohdan Paczynski (Princeton) about a spectroscopic follow-up of bright eclipsing variable stars, hundreds of which are being discovered by the ASAS project. To measure radial velocities for 8-10 mag stars with an accuracy of 0.1 km/s one does not need a large instrument. A key to this project was a fiber-fed link between a spectrograph and a telescope, which allowed the spectrograph to be placed in a stabilized environment. Another important factors were a low-noise CCD camera and a perfect match of the F-ratio between the telescope, the fiber and the spectrograph.
After completing the spectrograph (whose specification was based on the French MUSICOS instrument, designed by Jacques Baudrand), we tested it on the existing 0.4m Poznan Imaging Telescope (PIT). We learned a lot during these preliminary observations and this helped us when constructing a new, dedicated telescope for the spectrograph. It was very similar to PIT. To increase its aperture I decided to put two identical 0.4m Optical Tubes on a single fork mount, and connect each of them with a separate fiber feed to the spectrograph. As a result we were able to obtain simultaneously two interleaved spectra and combine them during the reduction.
In 2008 the mirrors were replaced by the larger, 0.5m ones, which combined aperture was similar to that of a single 0.7m mirror. They were cheaper and lighter than the 0.7m mirror and did not required changes in our acquisition box. Since then the Poznań Spectroscopic Telescope (PST1) is observing every clear night, measuring radial velocities of binary and pulsating stars with the accuracy of 0.1 km/s. During a 1 hour exposure it can reach 11 mag objects (with lower accuracy). PST1 is now managed by Wojciech Dimitrow and his team of observers.
In 2001 I was at Pic du Midi Observatory. Together with my colleague Francois Colas, we were observing near-Earth Asteroids. During that time it was announced that the asteroid 1998 SF36 would be observed with radar and supporting photometric observations would be very helpful. Good weather allowed us to obtain the first estimation of the synodical period for this asteroid, which was later named (25143) Itokawa.
Things were not as easy as it now sounds. When I got the data reduced and obtained a 12 hr period, an electrostatic storm was announced at the Observatory and all electronic equipment had to be switched off. With no Internet access to report the results, I phoned my colleague at Poznan Observatory (Francois let me use the land line phone, maybe because it was much cheaper than computer :-) and asked him to let others know about this quite long rotation period.
Later I coordinated an International Campaign to secure more photometric data on Itokawa, so that its spin and shape could be derived. An advanced software of Mikko Kaasalainen allowed us to obtain a detailed 3D shape of this asteroid, which was later visited by the Japanese Hayabusa spacecraft. The samples of Itokawa returned to the Earth in the Summer of 2010 and are now being analyzed.