J/A+A/478/755 Variable stars in Cen A (de Jong+, 2008)
Ground-based variability surveys towards Centaurus A: worthwhile or not?
de Jong J.T.A., Kuijken K.H., Heraudeau P.
<Astron. Astrophys. 478, 755 (2008)>
=2008A&A...478..755D 2008A&A...478..755D
ADC_Keywords: Galaxies, nearby ; Stars, variable
Keywords: galaxies: individual: Centaurus A - galaxies: stellar content -
stars: variables: general - gravitational lensing
Abstract:
Difference imaging has proven to be a powerful technique for detecting
and monitoring the variability of unresolved stellar sources in M 31.
Using this technique in surveys of galaxies outside the Local Group
could have many interesting applications. The goal of this paper is to
test difference imaging photometry on Centaurus A, the nearest giant
elliptical galaxy, at a distance of 4Mpc.
We obtained deep photometric data with the Wide Field Imager at the
ESO/MPG 2.2m at La Silla spread over almost two months. Applying
the difference imaging photometry package DIFIMPHOT, we produced
high-quality difference images and detected variable sources. The
sensitivity of the current observational setup was determined through
artificial residual tests.
In the resulting high-quality difference images, we detect
271 variable stars. We find a difference flux detection limit
corresponding to mR~=24.5. Based on a simple model of the halo of
Centaurus A, we estimate that a ground-based microlensing survey would
detect in the order of 4 microlensing events per year due to lenses in
the halo. Conclusions: Difference imaging photometry works very well
at the distance of Centaurus A and promises to be a useful tool for
detecting and studying variable stars in galaxies outside the local
group. For microlensing surveys, a higher sensitivity is needed than
achieved here, which would be possible with a large ground-based
telescope or space observatory with wide-field imaging capabilities.
Description:
Basic data for 271 variable stars detected in Centaurus A. For all
variables, an identifier, RA and Dec (J2000.0), and a classification
is given. For a subset of 29 variables a period is provided as well;
for the other variables a robust period determination was not possible
due to the intrinsic nature of the object or due to the limited
timespan of the observations.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 35 271 Variable stars in Centaurus A
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [CAVS]
6- 8 I3 --- CAVS CAVS number
10- 17 F8.4 deg RAdeg Right ascension in decimal degrees (J2000)
19- 26 F8.4 deg DEdeg Declination in decimal degrees (J2000)
28- 31 F4.1 d Per ? Period
33- 35 A3 --- VType Type of variation: V* = variable star,
No* = Nova variable
--------------------------------------------------------------------------------
Acknowledgements:
Jelte de Jong, mailjelte(at)gmail.com
(End) Jelte de Jong [MPIA], Patricia Vannier [CDS] 10-Dec-2007