J/MNRAS/482/1080 UVIT-HST-GAIA view of NGC 288 hot stars (Sahu+, 2019)
UVIT-HST-GAIA view of NGC 288: a census of the hot stellar population and its
properties from UV.
Sahu S., Subramaniam A., Cote P., Rao N.K., Stetson P.B.
<Mon. Not. R. Astron. Soc., 482, 1080-1095 (2019)>
=2019MNRAS.482.1080S 2019MNRAS.482.1080S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, horizontal branch ; HR diagrams ; Clusters, globular ;
Photometry, ultraviolet
Keywords: stars: blue stragglers - stars: horizontal branch -
stars: Hertzsprung-Russell and colour-magnitude diagrams -
globular clusters: individual: NGC 288 - ultraviolet: stars -
stars: imaging - catalogues
Abstract:
A complete census of the blue horizontal branch (BHB) and blue
straggler star (BSS) population within a 10' radius from the centre of
the globular cluster NGC 288 is presented, based on images from the
Ultraviolet Imaging Telescope (UVIT). The UV and UV-optical
colour-magnitude diagrams (CMDs) are constructed by combining the
UVIT, HST-ACS and ground data and are compared with the Bag of Stellar
Tracks and Isochrones (BaSTI) isochrones generated for UVIT filters.
We used stellar proper motion data from GAIA DR2 to select the cluster
members. Our estimations of the temperature distribution of 110 BHB
stars reveal two peaks, with the main peak at Teff∼10300K, and with
the distribution extending up to Teff∼18000K. We identify the
well-known photometric gaps, including the Grundahl jump (G-jump) in
the BHB distribution, which are located between the peaks. We detect a
plateau in the far-ultraviolet (FUV) magnitude for stars hotter than
Teff∼11500K (G-jump), which could be caused by atomic diffusion. We
detect two extreme horizontal branch (EHB) candidates, with
temperatures ranging from 29000 to 32000K. The radial distribution of
68 BSSs suggests that the bright BSSs are more centrally concentrated
than the faint BSSs and the BHB stars. We find that the BSSs have a
mass range of 0.86-1.25M☉ and an age range of 2-10Gyr, with
peaks at 1M☉ and 4Gyr respectively. This study showcases the
importance of combining UVIT with HST, ground and GAIA data in
deriving HB and BSS properties.
Description:
The data presented in this paper were obtained from the UVIT
instrument on-board the Indian space observatory, AstroSat. It
collects data in three channels simultaneously, namely in the FUV, NUV
and visible bands, corresponding to λ=1300-1800, 2000-3000 and
3200-5500 Å, respectively. The cluster was observed during 2016
August 20-21 as part of the Guaranteed Time (GT) proposal (G05_009).
The images were acquired in three filters of UVIT: F148W and F169M
(FUV channel) and N279N (NUV channel). A customized software package,
CCDLAB (Postma & Leahy 2017PASP..129k5002P 2017PASP..129k5002P), was used to correct for
the spacecraft drift, geometric distortion and flat-field correction
in the images.
The catalogue of UVIT detected members along with the proper
motions from GAIA DR2 is given in Table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 129 189 List of UVIT detected possible cluster members
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Type Star type (1)
10- 15 A6 --- ID Star ID
17- 18 I2 h RAh Right ascension (J2000)
20- 21 I2 min RAm Right ascension (J2000)
23- 27 F5.2 s RAs Right ascension (J2000)
29 A1 --- DE- Declination sign (J2000)
30- 31 I2 deg DEd Declination (J2000)
33- 34 I2 arcmin DEm Declination (J2000)
36- 39 F4.1 arcsec DEs Declination (J2000)
41- 46 F6.3 mag F148Wmag ? F148W UVIT filter magnitude
48- 52 F5.3 mag e_F148Wmag ? Error on F148Wmag
54- 59 F6.3 mag F169Mmag ? F169M UVIT filter magnitude
61- 65 F5.3 mag e_F169Mmag ? Error on F169Mmag
67- 72 F6.3 mag N279Nmag N279N UVIT filter magnitude
74- 78 F5.3 mag e_N279Nmag Error on N279Nmag
80- 85 F6.3 mag Vmag Optical V magnitude
87- 92 F6.3 mag V-I Optical V-I magnitude
94- 99 A6 --- r_Vmag Reference for Vmag and V-I (2)
101-104 F4.2 arcmin r Radial distance from the cluster centre
106-110 F5.3 mas/yr pmRA ? Proper motion in right ascension from Gaia
DR2 (Gaia Collaboration et al.
2018A&A...616A..12G 2018A&A...616A..12G, Cat. I/345)
112-116 F5.3 mas/yr e_pmRA ? Error on pmRA
118-123 F6.3 mas/yr pmDE ? Proper motion in declination from Gaia DR2
(Gaia Collaboration et al.
2018A&A...616A..12G 2018A&A...616A..12G, Cat. I/345)
125-129 F5.3 mas/yr e_pmDE ? Error on pmDE
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Note (1): Type as follows:
BHB = Blue Horizontal Branch Stars
RR Lyrae = RR Lyrae variables (the Star IDs are taken from
Arelleno Ferro et al. 2013AcA....63..429A 2013AcA....63..429A, Cat. J/AcA/63/429)
Gap Obj = Bright gap object
EHB = Extreme Horizontal Branch Stars
BSS = Blue Straggler Star candidates
SX Phe = SX Phe Variables (the Star IDs are taken from
Arelleno Ferro et al. 2013AcA....63..429A 2013AcA....63..429A, Cat. J/AcA/63/429 and
Martinazzi et al. 2015MNRAS.447.2235M 2015MNRAS.447.2235M)
EBSS = Evolved Blue Straggler Star (Bellazzini et al. 2002AJ....123.1509B 2002AJ....123.1509B)
Note (2): References as follows:
HST = Magnitudes taken from the HST-ACS (Sarejedini et al.
2007AJ....133.1658S 2007AJ....133.1658S, Cat. J/AJ/133/1658)
Ground = Magnitudes taken from ground (Peter Stetson)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 24-Jun-2022