J/A+A/436/853 IR photometry of Alpha Per low-mass members (Lodieu+, 2005)
A near-infrared survey for new low-mass members in Alpha Per.
Lodieu N., McCaughrean M.J., Barrado y Navascues D., Bouvier J.,
Stauffer J.R.
<Astron. Astrophys. 436, 853 (2005)>
=2005A&A...436..853L 2005A&A...436..853L
ADC_Keywords: Clusters, open ; Photometry, CCD ; Photometry, infrared
Keywords: stars: low-mass, brown dwarfs - techniques: photometry -
techniques: spectroscopy - infrared: stars -
stars: Hertzsprung-Russell (HR) and C-M diagrams -
open clusters and associations: individual : alpha Persei
Abstract:
We present a near-infrared (K'-band) survey of 0.7 square degree area
in the α Persei open cluster (age=90Myr, distance=182pc)
carried out with the Omega-Prime camera on the Calar Alto 3.5-m
telescope. Combining optical data (Rc and Ic) obtained with the
KPNO/MOSA detector and presented in Stauffer et al.
(1999ApJ...527..219S 1999ApJ...527..219S; S99) with the K' observations, a sample of new
candidate members has been extracted from the optical-infrared
colour-magnitude diagram. The location of these candidates in the
colour-colour diagram suggests that two-thirds of them are actually
reddened background giants. About 20 new candidate members with masses
between 0.3 and 0.04M☉ are added to the ∼400 known Alpha Per
cluster members. If they are indeed Alpha Per members, four of the new
candidates would be brown dwarfs. We discuss the advantages and
drawbacks of the near-infrared survey as compared to the optical
selection method. We also describe the outcome of optical spectroscopy
obtained with the Twin spectrograph on the Calar Alto 3.5-m telescope
for about 30 candidates, including selected members from the optical
sample presented in Barrado y Navascues et al. (2002, Cat.
J/A+A/395/813) and from our joint optical/infrared catalogue. These
results argue in favour of the optical selection method for this
particular cluster.
Description:
Optical detections in five different fields of view (A, C, E, K, and
L) are matched with the near-infrared detections described in this
paper. The central coordinates of the five optical fields-of-view are
as follows: (see Stauffer et al. 1999ApJ...527..219S 1999ApJ...527..219S for more
details):
A : RA = 03:27:10.0 DE = +49:24:00.0
C : RA = 03:24:50.0 DE = +48:42:00.0
E : RA = 03:19:35.0 DE = +49:27:00.0
K : RA = 03:27:00.0 DE = +50:13:00.0
L : RA = 03:23:10.0 DE = +48:11:00.0
The objects matched between the optical and the near-infrared
catalogues are gathered in table2.dat. Optical and near-infrared
coordinates (J2000.0) are provided as well as magnitudes and their
associated errors. The last column give the name of the object
according to the IAU convention.
File Summary:
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FileName Lrecl Records Explanations
-------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 116 22129 Matched objects between the optical (Stauffer et al.
(1999ApJ...527..219S 1999ApJ...527..219S, S99) and the near-infrared
catalogue
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See also:
J/A+A/395/813 : Alpha Per faint stars photometry (Barrado y Navascues+, 2002)
J/A+A/416/125 : RI photometry in alpha Per and Pleiades (Deacon+, 2004)
J/AN/319/201 : Alpha Per cluster low-mass members. I. (Prosser+, 1998)
J/AN/319/215 : Alpha Per cluster low-mass members. II. (Prosser+, 1998)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq Identification number
7- 8 I2 h RAh Optical Right ascension (J2000.0)
10- 11 I2 min RAm Optical Right ascension (J2000.0)
13- 17 F5.2 s RAs Optical Right ascension (J2000.0)
19 A1 --- DE- Optical Declination sign (J2000.0)
20- 21 I2 deg DEd Optical Declination (J2000.0)
23- 24 I2 arcmin DEm Optical Declination (J2000.0)
26- 29 F4.1 arcsec DEs Optical Declination (J2000.0)
31- 32 I2 h RAIh Near-infrared Right ascension (J2000.0)
34- 35 I2 min RAIm Near-infrared Right ascension (J2000.0)
37- 41 F5.2 s RAIs Near-infrared Right ascension (J2000.0)
43 A1 --- DEI- Near-infrared Declination sign (J2000.0)
44- 45 I2 deg DEId Near-infrared Declination (J2000.0)
47- 48 I2 arcmin DEIm Near-infrared Declination (J2000.0)
50- 53 F4.1 arcsec DEIs Near-infrared Declination (J2000.0)
55- 60 F6.3 mag K'mag K' magnitude
62- 66 F5.3 mag e_K'mag Error on the K' magnitude
68- 73 F6.3 mag Rcmag R_c magnitude from KPNO/MOSA (S99)
75- 79 F5.3 mag e_Rcmag Error on the R_c magnitude (S99)
81- 86 F6.3 mag Icmag I_c magnitude from KPNO/MOSA (S99)
88- 92 F5.3 mag e_Icmag Error on the I_c magnitude (S99)
94- 95 A2 --- --- [AP] (1)
97-115 A19 --- APname Object name (1)
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Note (1): The numbering of the object conforms to the IAU convention.
The prefix used is AP J for Alpha Per at the J2000 equinox:
AP JHHMMSS.ss+DDMMSS.s
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Acknowledgements: Nicolas Lodieu, nl41(at)star.le.ac.uk
(End) Nicolas Lodieu [Leicester Univ., UK], Patricia Vannier [CDS] 15-Mar-2005