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J/other/NewA/58.1      Hogg 16 peculiar stars                   (Cariddi+, 2018)

A search for peculiar stars in the open cluster Hogg 16. Cariddi S., Azatyan N.M., Kurfurst P., Stofanova L., Netopil M., Paunzen E., Pintado O.I., Aidelman Y.J. <New Astron., 58, 1-9 (2018)> =2018NewA...58....1C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, CCD ; Stars, peculiar Keywords: open clusters and associations: individual (Hogg 16) - stars: chemically peculiar - stars: emission-line, Be - techniques: photometric Abstract: The study of chemically peculiar (CP) stars in open clusters provides valuable information about their evolutionary status. Their detection can be performed using the Delta-a photometric system, which maps a characteristic flux depression at lambda 5200Å. This paper aims at studying the occurrence of CP stars in the earliest stages of evolution of a stellar population by applying this technique to Hogg 16, a very young Galactic open cluster (about 25Myr). We identified several peculiar candidates: two B-type stars with a negative Delta-a index (CD-60 4701, CPD-60 4706) are likely emission-line (Be) stars, even though spectral measurements are necessary for a proper classification of the second one; a third object (CD-60 4703), identified as a Be candidate in literature, appears to be a background B-type supergiant with no significant Delta-a index, which does not rule out the possibility that it is indeed peculiar as the normality line of Delta-a for supergiants has not been studied in detail yet. A fourth object (CD-60 4699) appears to be a magnetic CP star of 8 Msun, but obtained spectral data seem to rule out this hypothesis. Three more magnetic CP star candidates are found in the domain of early F-type stars. One is a probable nonmember and close to the border of significance, but the other two are probably pre-main sequence cluster objects. This is very promising, as it can lead to very strong constraints to the diffusion theory. Finally, we derived the fundamental parameters of Hogg 16 and provide for the first time an estimate of its metal content. Description: The photometric observations of Hogg 16 were performed on 2004 June 15, with the EFOSC2 instrument, installed on the 3.6m telescope at ESO - La Silla within the program 073.C-0144(A), and the target field was centred on the main concentration of stars in the cluster area (J2000 RA=13:29:18, DE=-61:12:00). The field-of-view is about 5.2'x5.2', and the 2x2 binning mode results in a resolution of 0.31"/pixel. Thus, we cover almost the complete cluster area if adopting a diameter of 6' as listed in the updated open cluster catalogue by Dias et al. (2002, version 3.5, Cat. B/ocl). We used a Δa filter set with the following characteristics: g1 (λc=5007Å, FWHM=126Å, TP=78%), g2 (5199, 95, 68), and y (5466, 108, 70). We have investigated 150 stars in the area of the young open cluster Hogg 16 using the Delta-a photometric system. We have performed a membership analysis and identified several chemically peculiar cluster stars. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file hogg16.dat 71 150 Observed program stars of Hogg 16 (table 4)
Byte-by-byte Description of file: hogg16.dat
Bytes Format Units Label Explanations
1- 3 I3 --- ID Sequential number 5- 15 F11.7 deg RAdeg Right ascension, ICRS, epoch=J2000 17- 27 F11.7 deg DEdeg Declination, ICRS, epoch=J2000 29- 34 F6.3 mag (g1-y) Mean colour index (g1-y) 36- 40 F5.3 mag e_(g1-y) rms uncertainty on (g1-y) 42- 47 F6.3 mag amag Mean a index 49- 53 F5.3 mag e_amag rms uncertainty on a 55- 57 I3 mmag Deltaa ? Peculiarity index Δa in mmag (1) 59- 62 F4.2 mag (b-y) Colour index (b-y) (2) 64- 68 F5.2 mag Vmag V magnitude (2) 70- 71 A2 --- Member [m nm] Membership flag (m: member, nm: nonmember)
Note (1): The Δa index is only given for cluster member stars. Note (2): Calibrated using data by McSwain and Gies (2005ApJS..161..118M)
Acknowledgements: Martin Netopil, martin.netopil(at)univie.ac.at
(End) Patricia Vannier [CDS] 25-Jul-2017
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