Discovery of two new Galactic candidate luminous blue variables with Wide-field Infrared Survey Explorer

Authors

  • V. V. Gvaramadze,

    Corresponding author
    1. Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992, Russia
    2. Isaac Newton Institute of Chile, Moscow Branch, Universitetskij Pr. 13, Moscow 119992, Russia
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  • A. Y. Kniazev,

    1. Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992, Russia
    2. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    3. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • A. S. Miroshnichenko,

    1. Department of Physics and Astronomy, University of North Carolina at Greensboro, Greensboro, NC 27402-6170, USA
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  • L. N. Berdnikov,

    1. Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992, Russia
    2. Isaac Newton Institute of Chile, Moscow Branch, Universitetskij Pr. 13, Moscow 119992, Russia
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  • N. Langer,

    1. Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
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  •  G. S. Stringfellow,

    1. CASA, University of Colorado, UCB 389, Boulder, CO 80309, USA
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  • H. Todt,

    1. Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
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  • W.-R. Hamann,

    1. Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
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  • E. K. Grebel,

    1. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
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  • D. Buckley,

    1. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • L. Crause,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • S. Crawford,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • A. Gulbis,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • C. Hettlage,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • E. Hooper,

    1. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
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  • T.-O. Husser,

    1. Institut für Astrophysik Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Gottingen, Germany
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  • P. Kotze,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • N. Loaring,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • K. H. Nordsieck,

    1. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
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  • D. O’Donoghue,

    1. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • T. Pickering,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • S. Potter,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • E. Romero Colmenero,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • P. Vaisanen,

    1. South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
    2. Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
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  • T. Williams,

    1. Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854, USA
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  • M. Wolf,

    1. Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA
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  • D. E. Reichart,

    1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
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  • K. M. Ivarsen,

    1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
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  • J. B. Haislip,

    1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
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  • M. C. Nysewander,

    1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
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  • A. P. LaCluyze

    1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USA
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Based on observations obtained with the South African Large Telescope (SALT), commissioning programmes 2010-1-RSA_OTH-001 and 2010-1-RSA_OTH-013.

E-mail: vgvaram@mx.iki.rssi.ru

ABSTRACT

We report the discovery of two new Galactic candidate luminous blue variable (LBV) stars via detection of circular shells (typical of confirmed and candidate LBVs) and follow-up spectroscopy of their central stars. The shells were detected at 22 μm in the archival data of the Mid-Infrared All Sky Survey carried out with the Wide-field Infrared Survey Explorer (WISE). Follow-up optical spectroscopy of the central stars of the shells conducted with the renewed Southern African Large Telescope (SALT) showed that their spectra are very similar to those of the well-known LBVs P Cygni and AG Car, and the recently discovered candidate LBV MN112, which implies the LBV classification for these stars as well. The LBV classification of both stars is supported by detection of their significant photometric variability: one of them brightened in the R and I bands by 0.68 ± 0.10 and 0.61 ± 0.04 mag, respectively, during the last 13–18 years, while the second one (known as Hen 3-1383) varies its BVRI and Ks brightnesses by ≃0.5–0.9 mag on time-scales from 10 d to decades. We also found significant changes in the spectrum of Hen 3-1383 on a time-scale of ≃3 months, which provides additional support for the LBV classification of this star. Further spectrophotometric monitoring of both stars is required to firmly prove their LBV status. We discuss a connection between the location of massive stars in the field and their fast rotation, and suggest that the LBV activity of the newly discovered candidate LBVs might be directly related to their possible runaway status.

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