Globular cluster photometry with the Hubble Space Telescope. III. Blue stragglers and variable stars in the core of M3

Puragra Guhathakurta, Brian Yanny, John N. Bahcall, Donald P. Schneider

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

This paper describes Hubble Space Telescope (HST)/Planetary Camera-I images of the core of the dense globular cluster M3 (NGC 5272). Stellar photometry in the F555W (V) and F785LP (I) bands, with a 1σ photometric accuracy of about 0.1 mag, has been used to construct color-magnitude diagrams of about 4700 stars above the main-sequence turnoff within r≲1′ of the cluster center. We have also analyzed archival HST F336W (U) images of M3 obtained by the Wide Field/Planetary Camera-I Instrument Definition Team. The UVI data are used to identify 28 blue straggler (BS) stars within the central 0.29 arcmin2. The specific frequency of BSs in this region of M3,NBS/NV<V(HB)+2 = 0.094 ± 0.019, is about a factor of 2-3 higher than that found by Bolte et al. in a recent ground-based study of the same region, but comparable to that seen in the sparse outer parts of the same cluster and in HST observations of the core of the higher density cluster 47 Tuc. The BSs in M3 are slightly more centrally concentrated than red giant branch stars while horizontal branch stars are somewhat less concentrated than red giants. The radial distribution of V-selected subgiant and turnoff stars is well fit by a King model with a core radius rcore=28″±2″ (90% confidence limits), which corresponds to 1.4 pc. Red giant and horizontal branch stars selected in the ultraviolet data (U<18) have a somewhat more compact distribution (rcore=22″.5). The HST U data consist of 17 exposures acquired over a span of three days. We have used these data to isolate 40 variable stars for which relative astrometry, brightnesses, colors, and light curves are presented. A Kolmogorov-Smirnov test indicates that, typically, the variability for each star is significant at the 95% level. We identify two variable BS candidates (probably of the SX Phe type), out of a sample of ∼25 BSs in which variability could have been detected. Most of the variables are RR Lyrae stars on the horizontal branch. All of them have periods P≳8 h.

Original languageEnglish (US)
Pages (from-to)1786-1809
Number of pages24
JournalAstronomical Journal
Volume108
Issue number5
StatePublished - Nov 1 1994

Fingerprint

blue stars
variable stars
globular clusters
Hubble Space Telescope
photometry
horizontal branch stars
stars
curves
subgiant stars
cameras
Kolmogorov-Smirnov test
confidence limits
astrometry
color-magnitude diagram
radial distribution
light curve
brightness
diagram
color
radii

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

@article{546e15d95ea94029b01a10837b644bac,
title = "Globular cluster photometry with the Hubble Space Telescope. III. Blue stragglers and variable stars in the core of M3",
abstract = "This paper describes Hubble Space Telescope (HST)/Planetary Camera-I images of the core of the dense globular cluster M3 (NGC 5272). Stellar photometry in the F555W (V) and F785LP (I) bands, with a 1σ photometric accuracy of about 0.1 mag, has been used to construct color-magnitude diagrams of about 4700 stars above the main-sequence turnoff within r≲1′ of the cluster center. We have also analyzed archival HST F336W (U) images of M3 obtained by the Wide Field/Planetary Camera-I Instrument Definition Team. The UVI data are used to identify 28 blue straggler (BS) stars within the central 0.29 arcmin2. The specific frequency of BSs in this region of M3,NBS/NV<V(HB)+2 = 0.094 ± 0.019, is about a factor of 2-3 higher than that found by Bolte et al. in a recent ground-based study of the same region, but comparable to that seen in the sparse outer parts of the same cluster and in HST observations of the core of the higher density cluster 47 Tuc. The BSs in M3 are slightly more centrally concentrated than red giant branch stars while horizontal branch stars are somewhat less concentrated than red giants. The radial distribution of V-selected subgiant and turnoff stars is well fit by a King model with a core radius rcore=28″±2″ (90{\%} confidence limits), which corresponds to 1.4 pc. Red giant and horizontal branch stars selected in the ultraviolet data (U<18) have a somewhat more compact distribution (rcore=22″.5). The HST U data consist of 17 exposures acquired over a span of three days. We have used these data to isolate 40 variable stars for which relative astrometry, brightnesses, colors, and light curves are presented. A Kolmogorov-Smirnov test indicates that, typically, the variability for each star is significant at the 95{\%} level. We identify two variable BS candidates (probably of the SX Phe type), out of a sample of ∼25 BSs in which variability could have been detected. Most of the variables are RR Lyrae stars on the horizontal branch. All of them have periods P≳8 h.",
author = "Puragra Guhathakurta and Brian Yanny and Bahcall, {John N.} and Schneider, {Donald P.}",
year = "1994",
month = "11",
day = "1",
language = "English (US)",
volume = "108",
pages = "1786--1809",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "IOP Publishing Ltd.",
number = "5",

}

Globular cluster photometry with the Hubble Space Telescope. III. Blue stragglers and variable stars in the core of M3. / Guhathakurta, Puragra; Yanny, Brian; Bahcall, John N.; Schneider, Donald P.

In: Astronomical Journal, Vol. 108, No. 5, 01.11.1994, p. 1786-1809.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Globular cluster photometry with the Hubble Space Telescope. III. Blue stragglers and variable stars in the core of M3

AU - Guhathakurta, Puragra

AU - Yanny, Brian

AU - Bahcall, John N.

AU - Schneider, Donald P.

PY - 1994/11/1

Y1 - 1994/11/1

N2 - This paper describes Hubble Space Telescope (HST)/Planetary Camera-I images of the core of the dense globular cluster M3 (NGC 5272). Stellar photometry in the F555W (V) and F785LP (I) bands, with a 1σ photometric accuracy of about 0.1 mag, has been used to construct color-magnitude diagrams of about 4700 stars above the main-sequence turnoff within r≲1′ of the cluster center. We have also analyzed archival HST F336W (U) images of M3 obtained by the Wide Field/Planetary Camera-I Instrument Definition Team. The UVI data are used to identify 28 blue straggler (BS) stars within the central 0.29 arcmin2. The specific frequency of BSs in this region of M3,NBS/NV<V(HB)+2 = 0.094 ± 0.019, is about a factor of 2-3 higher than that found by Bolte et al. in a recent ground-based study of the same region, but comparable to that seen in the sparse outer parts of the same cluster and in HST observations of the core of the higher density cluster 47 Tuc. The BSs in M3 are slightly more centrally concentrated than red giant branch stars while horizontal branch stars are somewhat less concentrated than red giants. The radial distribution of V-selected subgiant and turnoff stars is well fit by a King model with a core radius rcore=28″±2″ (90% confidence limits), which corresponds to 1.4 pc. Red giant and horizontal branch stars selected in the ultraviolet data (U<18) have a somewhat more compact distribution (rcore=22″.5). The HST U data consist of 17 exposures acquired over a span of three days. We have used these data to isolate 40 variable stars for which relative astrometry, brightnesses, colors, and light curves are presented. A Kolmogorov-Smirnov test indicates that, typically, the variability for each star is significant at the 95% level. We identify two variable BS candidates (probably of the SX Phe type), out of a sample of ∼25 BSs in which variability could have been detected. Most of the variables are RR Lyrae stars on the horizontal branch. All of them have periods P≳8 h.

AB - This paper describes Hubble Space Telescope (HST)/Planetary Camera-I images of the core of the dense globular cluster M3 (NGC 5272). Stellar photometry in the F555W (V) and F785LP (I) bands, with a 1σ photometric accuracy of about 0.1 mag, has been used to construct color-magnitude diagrams of about 4700 stars above the main-sequence turnoff within r≲1′ of the cluster center. We have also analyzed archival HST F336W (U) images of M3 obtained by the Wide Field/Planetary Camera-I Instrument Definition Team. The UVI data are used to identify 28 blue straggler (BS) stars within the central 0.29 arcmin2. The specific frequency of BSs in this region of M3,NBS/NV<V(HB)+2 = 0.094 ± 0.019, is about a factor of 2-3 higher than that found by Bolte et al. in a recent ground-based study of the same region, but comparable to that seen in the sparse outer parts of the same cluster and in HST observations of the core of the higher density cluster 47 Tuc. The BSs in M3 are slightly more centrally concentrated than red giant branch stars while horizontal branch stars are somewhat less concentrated than red giants. The radial distribution of V-selected subgiant and turnoff stars is well fit by a King model with a core radius rcore=28″±2″ (90% confidence limits), which corresponds to 1.4 pc. Red giant and horizontal branch stars selected in the ultraviolet data (U<18) have a somewhat more compact distribution (rcore=22″.5). The HST U data consist of 17 exposures acquired over a span of three days. We have used these data to isolate 40 variable stars for which relative astrometry, brightnesses, colors, and light curves are presented. A Kolmogorov-Smirnov test indicates that, typically, the variability for each star is significant at the 95% level. We identify two variable BS candidates (probably of the SX Phe type), out of a sample of ∼25 BSs in which variability could have been detected. Most of the variables are RR Lyrae stars on the horizontal branch. All of them have periods P≳8 h.

UR - http://www.scopus.com/inward/record.url?scp=0041033089&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0041033089&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0041033089

VL - 108

SP - 1786

EP - 1809

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 5

ER -