62,877 research outputs found
Long-Term V-Band Monitoring of the Bright Stars of M33 at the Wise Observatory
We have conducted a long-term V-band photometric monitoring of M33 on 95
nights during four observing seasons (2000 - 2003). A total number of 6418
lightcurves of bright objects in the range of 14 - 21 mag have been obtained.
All measurements are publicly available. A total of 127 new variables were
detected, of which 28 are periodic. Ten previously known non-periodic variables
were identified as periodic, 3 of which are Cepheids, and another previously
known periodic variable was identified as an eclipsing binary. Our derived
periods range from 2.11 to almost 300 days. For 50 variables we have combined
our observations with those of the DIRECT project, obtaining lightcurves of up
to 500 measurements, with a time-span of ~7 years. We have detected a few
interesting variables, including a 99.3 day periodic variable with a 0.04 mag
amplitude, at the position of SNR 19.Comment: 29 pages, accepted for publication in MNRAS. Additional material is
available at http://wise-obs.tau.ac.il/~shporer/m33
The Long Term Optical Variability of the BL Lac object S5 0716+714: Evidence for a Precessing Jet
We present the historic light curve of the BL Lac object S5 0716+714,
spanning the time interval from 1953 to 2003, built using Asiago archive plates
and our recent CCD observations, together with literature data. The source
shows an evident long term variability, over which well known short term
variations are superposed. In particular, in the period from 1961 to 1983 the
mean brightness of S5 0716+714 remained significantly fainter than that
observed after 1994. Assuming a constant variation rate of the mean magnitude
we can estimate a value of about 0.11 magnitude/year. The simultaneous
occurrence of decreasing ejection velocities of superluminal moving components
in the jet reported by Bach et al. (2005) suggests that both phenomena are
related to the change of the direction of the jet to the line of sight from
about 5 to 0.7 degrees for an approximately constant bulk Lorentz factor of
about 12. A simple explanation is that of a precessing relativistic jet, which
should presently be close to the smallest orientation angle. One can therefore
expect in the next ten years a decrease of the mean brightness of about 1
magnitude.Comment: to appear on The Astronomical Journal, 17 pages, 7 figures. Fig.2 is
given as a separated jpg fil
Constraints on inelastic dark matter from XENON10
It has been suggested that dark matter particles which scatter inelastically
from detector target nuclei could explain the apparent incompatibility of the
DAMA modulation signal (interpreted as evidence for particle dark matter) with
the null results from CDMS-II and XENON10. Among the predictions of
inelastically interacting dark matter are a suppression of low-energy events,
and a population of nuclear recoil events at higher nuclear recoil equivalent
energies. This is in stark contrast to the well-known expectation of a falling
exponential spectrum for the case of elastic interactions. We present a new
analysis of XENON10 dark matter search data extending to E keV
nuclear recoil equivalent energy. Our results exclude a significant region of
previously allowed parameter space in the model of inelastically interacting
dark matter. In particular, it is found that dark matter particle masses
GeV are disfavored.Comment: 8 pages, 4 figure
Exploring the SDSS Dataset with Linked Scatter Plots: I. EMP, CEMP, and CV Stars
We present the results of a search for extremely metal-poor (EMP),
carbon-enhanced metal-poor (CEMP), and cataclysmic variable (CV) stars using a
new exploration tool based on linked scatter plots (LSPs). Our approach is
especially designed to work with very large spectrum data sets such as the
SDSS, LAMOST, RAVE, and Gaia data sets, and it can be applied to stellar,
galaxy, and quasar spectra. As a demonstration, we conduct our search using the
SDSS DR10 data set. We first created a 3326-dimensional phase space containing
nearly 2 billion measures of the strengths of over 1600 spectral features in
569,738 SDSS stars. These measures capture essentially all the stellar atomic
and molecular species visible at the resolution of SDSS spectra. We show how
LSPs can be used to quickly isolate and examine interesting portions of this
phase space. To illustrate, we use LSPs coupled with cuts in selected portions
of phase space to extract EMP stars, CEMP stars, and CV stars. We present
identifications for 59 previously unrecognized candidate EMP stars and 11
previously unrecognized candidate CEMP stars. We also call attention to 2
candidate He~II emission CV stars found by the LSP approach that have not yet
been discussed in the literature.Comment: Accepted by the Astrophysical Journal Supplement (February 2017
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