J/A+A/581/A138 Photometric variability in magnetic CP stars (Bernhard+, 2015)
A search for photometric variability in magnetic chemically peculiar stars
using ASAS-3 data.
Bernhard K., Huemmerich S., Otero S., Paunzen E.
<Astron. Astrophys., 581, A138-138 (2015)>
=2015A&A...581A.138B 2015A&A...581A.138B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Stars, peculiar
Keywords: stars: chemically peculiar - stars: variables: general -
techniques: photometric
Abstract:
The (magnetic) chemically peculiar (CP) stars of the upper main
sequence are well-suited laboratories for investigating the influence
of magnetic fields on the stellar surface because they produce
abundance inhomogeneities (spots), which results in photometric
variability that is explained in terms of the oblique rotator model.
CP stars exhibiting this phenomenon are normally classified as
α2 Canum Venaticorum (ACV) variables. It is important to
increase the sample of known rotational periods among CP stars by
discovering new ACV variables. An increased sample size will
contribute to the understanding of the CP stars' evolution in time. We
aim at discovering new ACV variables in the public data of the third
phase of the All Sky Automated Survey (ASAS-3). Furthermore, by
analysis of the available photometric data, we intend to derive
rotational periods of the stars. The ASAS-3 data were cross-correlated
with the Catalogue of Ap, HgMn, and Am stars in order to analyse the
light curves of bona fide CP and related stars. The light curves were
downloaded and cleaned of outliers and data points with a flag
indicating bad quality. Promising candidates showing a larger scatter
than observed for constant stars in the corresponding magnitude range
were searched for periodic signals using a standard Fourier technique.
Objects exhibiting periodic signals well above the noise level were
considered and visually inspected, whereas borderline cases were
rejected. In total, we found 323 variables, from which 246 are
reported here for the first time, and 77 were probably wrongly
classified before. The observed variability pattern of most stars is
in accordance with an ACV classification. For some cases, it is
difficult to distinguish between the light curves of double-waved ACVs
and the variability induced by orbital motion (ellipsoidal
variables/eclipsing variables), especially for objects exhibiting very
small amplitudes and/or significant scatter in their light curves.
Thus, some eclipsing or rotating ellipsoidal variables might be
present. However, we are confident that the given periods are the
correct ones. There seems to be a possible weak correlation between
the rotational period and colour, in the sense that cooler magnetic CP
stars rotate more slowly. However, this correlation seems to disappear
when correcting for the interstellar reddening. The next steps have to
include a compilation of all available rotational periods from the
literature and a detailed investigation of the astrophysical
parameters of these stars. This includes a determination of the
individual masses, luminosities, ages, and inclination angles.
However, this information cannot be straightforwardly determined from
photometric data alone.
Description:
The targets for the present investigation were primarily chosen among
the Ap stars listed in the most recent version of the Catalogue of Ap,
HgMn, and Am stars (Renson & Manfroid, 2009A&A...498..961R 2009A&A...498..961R, Cat.
III/260, RM09 hereafter).
The light curves of all target stars were downloaded from the ASAS-3
website (http://www.astrouw.edu.pl/asas/). No data from our targets
exist in the ASAS-2 I-band catalogue.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 131 316 Essential data for the 316 stars identified as
photometrically variable chemically peculiar
stars or star candidates in the present paper
tableb1.dat 350 96 Available information on single objects from the
literature and miscellaneous remarks
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See also:
III/260 : General Catalogue of Ap and Am stars (Renson+ 2009)
http://www.astrouw.edu.pl/asas : ASAS-3 Home page
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Star Star name
17- 21 I5 --- Renson ? ID number of Renson & Manfroid
(2009A&A...498..961R 2009A&A...498..961R, Cat. III/260)
23- 24 I2 h RAh Right ascension (J2000)
26- 27 I2 min RAm Right ascension (J2000)
29- 34 F6.3 s RAs Right ascension (J2000)
36 A1 --- DE- Declination sign (J2000)
37- 38 I2 deg DEd Declination (J2000)
40- 41 I2 arcmin DEm Declination (J2000)
43- 47 F5.2 arcsec DEs Declination (J2000)
49- 52 A4 --- Type Type (ACV for alpha2 Canum Venaticorum)
55- 59 F5.2 mag Vmagl Lower value of V magnitude range
60 A1 --- --- [-]
61- 65 F5.2 mag Vmagu Upper value of V magnitude range
67- 76 F10.6 d Per Period
78- 84 F7.6 d e_Per rms uncertainty on Per
86- 96 F11.3 d Epoch Epoch (HJD)
98-102 F5.3 d e_Epoch rms uncertainty on Epoch
104-118 A15 --- Sp MK Spectral type
119-124 F6.3 mag B-V B-V colour index
126-131 F6.3 mag J-Ks J-Ks colour index
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- Star Star name
17- 39 A23 --- LName Variable designation in the literature
41- 69 A29 --- VType Variable type in the literature
71- 81 F11.6 d Per1 ? Period in the literature
82 A1 --- u_Per1 [?] Uncertainty flag on Per1
83-101 A19 --- n_Per Note on Per1
103-106 A4 --- r_Per1 Refernece for Per1 (1)
108-117 F10.7 d Per2 ? Period in the literature
118-119 A2 --- u_Per2 [:? ] Uncertainty flag on Per2
121-131 A11 --- n_Per2 Note on Per2
133-136 A4 --- r_Per2 Reference for Per2 (1)
138-148 F11.7 d Per ? Period (this paper)
150-157 F8.7 d e_Per ? rms uncertainty on Per
159-161 A3 --- r_Per Reference for Per (1)
163 A1 --- Flag [*] Flag (2)
165-350 A186 --- Com Remarks/comments
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Note (1): References as follows:
C08 = Christiansen et al. (2008, Cat. J/MNRAS/385/1749)
C62 = Cousins et al. (1962RGOB...49....3C 1962RGOB...49....3C, Cat. II/222)
E12 = Elkin et al. (2012MNRAS.420.2727E 2012MNRAS.420.2727E)
E83 = Eggen (1983MNRAS.204..377E 1983MNRAS.204..377E)
GCVS = Samus et al. (General Catalogue of Variable Stars, Cat. B/gcvs)
K02 = Koen & Eyer (2002, Cat. J/MNRAS/331/45)
L83 = Lloyd Evans et al. (1983SAAOC...7...82L 1983SAAOC...7...82L)
L89 = Loden & Sundman (1989JApA...10..183L 1989JApA...10..183L)
M81 = Maitzen & Hensberge (1981A&A....96..151M 1981A&A....96..151M)
M90 = Menzies et al. (1990SAAOC..14...33M 1990SAAOC..14...33M)
N10 = Nichols et al. (2010, Cat. J/ApJS/188/473)
O83 = Olsen (1983A&AS...54...55O 1983A&AS...54...55O)
P00 = Pojmaski (2000, Cat. J/AcA/50/177)
P02 = Pojmaski (2002AcA....52..397P 2002AcA....52..397P, Cat. II/264)
R12 = Renson Manfroid (2009A&A...498..961R 2009A&A...498..961R, Cat. III/260)
RM09 = Renson & Manfroid (2009A&A...498..961R 2009A&A...498..961R, Cat. III/260)
v97 = van Leeuwen et al. (1997A&A...323L..61V 1997A&A...323L..61V)
V79 = Vogt & Faundez (1979A&AS...36..477V 1979A&AS...36..477V)
VSX = Watson et al. (AAVSO International Variable Star Index VSX,
Cat. B/vsx)
Note (2): * denotes stars, which status as chemically peculiar objects is
doubtful according to RM09 (Renson & Manfroid, 2009, Cat. III/260).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Nov-2015