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Determination of Cepheid parameters by light-curve template fitting
Berdnikov, L. N.; Tanvir, N. R.; Ngeow, C. C. +3 more
We describe techniques to characterize the light curves of regular variable stars by applying principal component analysis (PCA) to a training set of high-quality data, and to fit the resulting light-curve templates to sparse and noisy photometry to obtain parameters such as periods, mean magnitudes etc. The PCA approach allows us to efficiently r…
CORONAS-F/SPIRIT EUV observations of October-November 2003 solar eruptive events in combination with SOHO/EIT data
Grechnev, V. V.; Chertok, I. M.; Kuzin, S. V. +6 more
The extraordinary solar activity of October-November 2003 manifested itself in many powerful eruptive events, including large coronal mass ejections (CMEs) and extremely powerful flares. A number of major events were accompanied by practically all known phenomena of the solar activity, both local and large-scale, and caused severe space weather di…
Exploring the structure of galaxy clusters: XMM-Newton observations of the REFLEX-DXL clusters at z ∼ 0.3
Zhang, Y. -Y.; Finoguenov, A.; Böhringer, H. +5 more
The precise determination of global properties of galaxy clusters, and their scaling relations, is a task of prime importance for the use of clusters as cosmological probes. We performed a detailed XMM-Newton study of 14 X-ray luminous REFLEX Survey clusters at z ∼ 0.3. We found that the properties of the galaxy clusters show a self-similar behavi…
A HST Study of the Stellar Populations in the Cometary Dwarf Irregular Galaxy NGC 2366
Thuan, Trinh X.; Izotov, Yuri I.
We present V and I photometry of the resolved stars in the cometary dwarf irregular galaxy NGC 2366, using Wide Field Planetary Camera 2 images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram reaches down to I~26.0 mag. It reveals not only a young population of blue main-sequence stars (age <~30 Myr) but also an …
UVCS Observation of Sungrazer C/2001 C2: Possible Comet Fragmentation and Plasma-Dust Interactions
Lamy, P.; Raymond, J. C.; Biesecker, D. A. +5 more
In this paper we analyze SOHO Ultraviolet Coronagraph Spectrometer (UVCS) observations of the sungrazing comet C/2001 C2, a member of the Kreutz family, observed on 2001 February 7 at heliocentric distances of 4.98 and 3.60 Rsolar. This comet apparently went through sequential fragmentation events along its path: further indication of f…
The calm after the storm: XMM-Newton observation of SGR 1806-20 two months after the Giant Flare of 2004 December 27
Tiengo, A.; Mereghetti, S.; Stella, L. +5 more
XMM-Newton observed the soft gamma repeater SGR 1806-20 about two months after its 2004 December 27 giant flare. A comparison with the previous observations taken with the same instrument in 2003-2004 shows that the pulsed fraction and the spin-down rate have significantly decreased and that the spectrum slightly softened. These changes may indica…
How Long Is the Day on Saturn?
Sánchez-Lavega, Agustín
Determining a planet's rotation period can be difficult if the planet lacks a solid surface. However, for planets with an internal magnetic field, emissions at radio wavelengths are modulated by the planet's rotation rate. The latest results from the Cassini spacecraft seem to indicate that Saturn's rotation rate has slowed down by 6 minutes since…
Generation of microwave bursts with zebra pattern by nonlinear interaction of Bernstein modes
Kuznetsov, A. A.
The processes of generation and nonlinear interaction of Bernstein modes are investigated. The physical conditions considered correspond here to the sources of microwave bursts with a zebra pattern. It is shown that the simultaneous generation of plasma waves corresponding to several cyclotron harmonics is possible under these conditions. Nonlinea…
BIMA Millimeter-Wave Observations of the Core-Jet and Molecular Gas in the FR I Radio Galaxy NGC 3801
Baum, Stefi A.; O'Dea, Christopher P.; Vogel, Stuart N. +2 more
We present BIMA 3 mm observations of the radio continuum source and the molecular gas disk in the radio-loud Fanaroff and Riley type I (FR I) galaxy NGC 3801. We have detected a continuum source in the nucleus and determined that it has a flat millimeter-wave spectrum, suggesting that the emission is nonthermal and due to an AGN; the radio core is…
High-resolution observations of SN 2001gd in NGC 5033
Lundqvist, P.; Ros, E.; Guerrero, M. A. +8 more
We report on 8.4-GHz very-long-baseline interferometry (VLBI) observations of SN 2001gd in the spiral galaxy NGC 5033 made on 2002 June 26 (2002.48) and 2003 April 8 (2003.27). We used the interferometric visibility data to estimate angular diameter sizes for the supernova by model fitting. Our data nominally suggest a relatively strong decelerati…