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Title: OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE

Abstract

We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT, and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color–magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf (WD) cooling sequences, consistent with the cooling tracks of He WDs with masses between 0.15 M{sub ⊙} and 0.20 M{sub ⊙}. For each identified companion, mass, cooling age, temperature, and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded at a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non-degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2σ astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs.

Authors:
; ; ; ;  [1];  [2];  [3]
  1. Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy)
  2. Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)
  3. Max-Planck-Institute für Radioastronomie, D-53121 Bonn (Germany)
Publication Date:
OSTI Identifier:
22525262
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 812; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; CARBON MONOXIDE; COLOR; COOLING; DIAGRAMS; INCLINATION; MASS; PULSARS; SPACE; TELESCOPES; WHITE DWARF STARS

Citation Formats

Cadelano, M., Pallanca, C., Ferraro, F. R., Dalessandro, E., Lanzoni, B., Salaris, M., and Freire, P. C. C. OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE. United States: N. p., 2015. Web. doi:10.1088/0004-637X/812/1/63.
Cadelano, M., Pallanca, C., Ferraro, F. R., Dalessandro, E., Lanzoni, B., Salaris, M., & Freire, P. C. C. OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE. United States. https://doi.org/10.1088/0004-637X/812/1/63
Cadelano, M., Pallanca, C., Ferraro, F. R., Dalessandro, E., Lanzoni, B., Salaris, M., and Freire, P. C. C. Sat . "OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE". United States. https://doi.org/10.1088/0004-637X/812/1/63.
@article{osti_22525262,
title = {OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE},
author = {Cadelano, M. and Pallanca, C. and Ferraro, F. R. and Dalessandro, E. and Lanzoni, B. and Salaris, M. and Freire, P. C. C.},
abstractNote = {We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT, and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color–magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf (WD) cooling sequences, consistent with the cooling tracks of He WDs with masses between 0.15 M{sub ⊙} and 0.20 M{sub ⊙}. For each identified companion, mass, cooling age, temperature, and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded at a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non-degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2σ astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs.},
doi = {10.1088/0004-637X/812/1/63},
url = {https://www.osti.gov/biblio/22525262}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 812,
place = {United States},
year = {2015},
month = {10}
}