Spectroscopic and Photometric Monitoring of a Poorly Known Highly Luminous OH/IR Star: IRAS 18278+0931
Abstract
We present the time-dependent properties of a poorly known OH/IR star, IRAS 18278+0931 (hereafter IRAS 18+09), toward the Ophiuchus constellation. We have carried out long-term optical/near-infrared photometric and spectroscopic observations to study the object. From optical R- and I-band light curves, the period of IRAS 18+09 is estimated to be 575 ± 30 days and the variability amplitudes range from ΔR ∼ 4.0 mag to ΔI ∼ 3.5 mag. From the standard period-luminosity relations, the distance (D) to the object, 4.0 ± 1.3 kpc, is estimated. Applying this distance in the radiative transfer model, the spectral energy distribution is constructed from multiwavelength photometric and IRAS-LRS spectral data, which provide the luminosity, optical depth, and gas mass-loss rate of the object to be 9600 ± 500 L⊙, 9.1 ± 0.6 at 0.55 μm, and 1.0 × 10-6 M⊙ yr-1, respectively. The current mass of the object is inferred to be in the range 1.0-1.5 M⊙ assuming solar metallicity. Notably, the temporal variation of atomic and molecular features (e.g., TiO, Na I, Ca I, CO, H2O) over the pulsation cycle of the OH/IR star illustrates the sensitivity of the spectral features to the dynamical atmosphere as observed in pulsating AGB stars.
- Publication:
-
The Astronomical Journal
- Pub Date:
- April 2021
- DOI:
- 10.3847/1538-3881/abe544
- arXiv:
- arXiv:2102.04739
- Bibcode:
- 2021AJ....161..198G
- Keywords:
-
- OH/IR stars;
- Long period variable stars;
- Spectroscopy;
- Asymptotic giant branch stars;
- Late-type stars;
- Observational astronomy;
- Evolved stars;
- Period determination;
- Near infrared astronomy;
- Stellar astronomy;
- 1156;
- 935;
- 1558;
- 2100;
- 909;
- 1145;
- 481;
- 1211;
- 1093;
- 1583;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 14 pages, 7 figures, 5 tables. Accepted for publication in AJ