Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements

N. Kains, A. Calamida, K. C. Sahu, S. Casertano, J. Anderson, A. Udalski, M. Zoccali, H. Bond, M. Albrow, I. Bond, T. Brown, M. Dominik, C. Fryer, M. Livio, S. Mao, M. Rejkuba

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We report on the first results from a large-scale observing campaign aiming to use astrometric microlensing to detect and place limits on the mass of single objects, including stellar remnants. We used the Hubble Space Telescope to monitor stars near the Galactic Center for three years, and we measured the brightness and positions of ∼2 million stars at each observing epoch. In addition to this, we monitored the same pointings using the VIMOS imager on the Very Large Telescope. The stars we monitored include several bright microlensing events observed from the ground by the OGLE collaboration. In this paper, we present the analysis of our photometric and astrometric measurements for six of these events, and derive mass constraints for the lens in each of them. Although these constraints are limited by the photometric precision of ground-based data, and our ability to determine the lens distance, we were able to constrain the size of the Einstein ring radius thanks to our precise astrometric measurements - the first routine measurements of this type from a large-scale observing program. This demonstrates the power of astrometric microlensing as a tool to constrain the masses of stars, stellar remnants, and, in the future, extrasolar planets, using precise ground- and space-based observations.

Original languageEnglish (US)
Article number145
JournalAstrophysical Journal
Volume843
Issue number2
DOIs
StatePublished - Jul 10 2017

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stars
lenses
extrasolar planets
planet
Hubble Space Telescope
brightness
time measurement
telescopes
radii
rings
programme
analysis

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kains, N., Calamida, A., Sahu, K. C., Casertano, S., Anderson, J., Udalski, A., ... Rejkuba, M. (2017). Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements. Astrophysical Journal, 843(2), [145]. https://doi.org/10.3847/1538-4357/aa78eb
Kains, N. ; Calamida, A. ; Sahu, K. C. ; Casertano, S. ; Anderson, J. ; Udalski, A. ; Zoccali, M. ; Bond, H. ; Albrow, M. ; Bond, I. ; Brown, T. ; Dominik, M. ; Fryer, C. ; Livio, M. ; Mao, S. ; Rejkuba, M. / Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements. In: Astrophysical Journal. 2017 ; Vol. 843, No. 2.
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Kains, N, Calamida, A, Sahu, KC, Casertano, S, Anderson, J, Udalski, A, Zoccali, M, Bond, H, Albrow, M, Bond, I, Brown, T, Dominik, M, Fryer, C, Livio, M, Mao, S & Rejkuba, M 2017, 'Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements', Astrophysical Journal, vol. 843, no. 2, 145. https://doi.org/10.3847/1538-4357/aa78eb

Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements. / Kains, N.; Calamida, A.; Sahu, K. C.; Casertano, S.; Anderson, J.; Udalski, A.; Zoccali, M.; Bond, H.; Albrow, M.; Bond, I.; Brown, T.; Dominik, M.; Fryer, C.; Livio, M.; Mao, S.; Rejkuba, M.

In: Astrophysical Journal, Vol. 843, No. 2, 145, 10.07.2017.

Research output: Contribution to journalArticle

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AU - Bond, H.

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AU - Bond, I.

AU - Brown, T.

AU - Dominik, M.

AU - Fryer, C.

AU - Livio, M.

AU - Mao, S.

AU - Rejkuba, M.

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N2 - We report on the first results from a large-scale observing campaign aiming to use astrometric microlensing to detect and place limits on the mass of single objects, including stellar remnants. We used the Hubble Space Telescope to monitor stars near the Galactic Center for three years, and we measured the brightness and positions of ∼2 million stars at each observing epoch. In addition to this, we monitored the same pointings using the VIMOS imager on the Very Large Telescope. The stars we monitored include several bright microlensing events observed from the ground by the OGLE collaboration. In this paper, we present the analysis of our photometric and astrometric measurements for six of these events, and derive mass constraints for the lens in each of them. Although these constraints are limited by the photometric precision of ground-based data, and our ability to determine the lens distance, we were able to constrain the size of the Einstein ring radius thanks to our precise astrometric measurements - the first routine measurements of this type from a large-scale observing program. This demonstrates the power of astrometric microlensing as a tool to constrain the masses of stars, stellar remnants, and, in the future, extrasolar planets, using precise ground- and space-based observations.

AB - We report on the first results from a large-scale observing campaign aiming to use astrometric microlensing to detect and place limits on the mass of single objects, including stellar remnants. We used the Hubble Space Telescope to monitor stars near the Galactic Center for three years, and we measured the brightness and positions of ∼2 million stars at each observing epoch. In addition to this, we monitored the same pointings using the VIMOS imager on the Very Large Telescope. The stars we monitored include several bright microlensing events observed from the ground by the OGLE collaboration. In this paper, we present the analysis of our photometric and astrometric measurements for six of these events, and derive mass constraints for the lens in each of them. Although these constraints are limited by the photometric precision of ground-based data, and our ability to determine the lens distance, we were able to constrain the size of the Einstein ring radius thanks to our precise astrometric measurements - the first routine measurements of this type from a large-scale observing program. This demonstrates the power of astrometric microlensing as a tool to constrain the masses of stars, stellar remnants, and, in the future, extrasolar planets, using precise ground- and space-based observations.

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Kains N, Calamida A, Sahu KC, Casertano S, Anderson J, Udalski A et al. Microlensing Constraints on the Mass of Single Stars from HST Astrometric Measurements. Astrophysical Journal. 2017 Jul 10;843(2). 145. https://doi.org/10.3847/1538-4357/aa78eb