OGLE-2015-BLG-1395Lb: A Cold Sub-Saturn Mass Planet Orbiting an M Dwarf

@misc{cole2026ogle2015blg1395lb,
  title = {{OGLE-2015-BLG-1395Lb: A Cold Sub-Saturn Mass Planet Orbiting an M Dwarf}},
  author = {Andrew A. Cole and Joshua W. Blackman and Jean-Philippe Beaulieu and Etienne Bachelet and Jean-Baptiste Marquette and Natalia Rektsini and Erica Thygesen and A. Udalski and R. Poleski and P. Mróz and K. A. Rybicki and M. K. Szymański and I. Soszyński and P. Pietrukowicz and S. Kozłowski and J. Skowron and K. Ulaczyk and R. A. Street and Y. Tsapras and M. Dominik and A. Cassan and R. Figuera-Jaimes and K. Horne and R. Schmidt and C. Snodgrass and J. Wambsganss and I. A. Steele and J. Menzies and F. Abe and R. K. Barry and D. P. Bennett and A. Bhattacharya and I. A. Bond and A. Fukui and R. Hamada and Y. Hirao and A. Idei and S. Ishitani Silva and S. Miyazaki and Y. Muraki and T. Nagai and K. Nunota and G. Olmschenk and C. Ranc and N. J. Rattenbury and Y. K. Satoh and T. Sumi and D. Suzuki and T. Tamaoki and S. K. Terry and P. J. Tristram and A. Vandorou and H. Yama and M. P. G. Hundertmark and U. G. Jorgensen and P. Longa-Pena and N. Peixinho and J. Skottfelt and J. Southworth and M. I. Andersen},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.32020},
  eprint = {2610.32020},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.32020},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - OGLE-2015-BLG-1395Lb: A Cold Sub-Saturn Mass Planet Orbiting an M Dwarf
AU  - Andrew A. Cole
AU  - Joshua W. Blackman
AU  - Jean-Philippe Beaulieu
AU  - Etienne Bachelet
AU  - Jean-Baptiste Marquette
AU  - Natalia Rektsini
AU  - Erica Thygesen
AU  - A. Udalski
AU  - R. Poleski
AU  - P. Mróz
AU  - K. A. Rybicki
AU  - M. K. Szymański
AU  - I. Soszyński
AU  - P. Pietrukowicz
AU  - S. Kozłowski
AU  - J. Skowron
AU  - K. Ulaczyk
AU  - R. A. Street
AU  - Y. Tsapras
AU  - M. Dominik
AU  - A. Cassan
AU  - R. Figuera-Jaimes
AU  - K. Horne
AU  - R. Schmidt
AU  - C. Snodgrass
AU  - J. Wambsganss
AU  - I. A. Steele
AU  - J. Menzies
AU  - F. Abe
AU  - R. K. Barry
AU  - D. P. Bennett
AU  - A. Bhattacharya
AU  - I. A. Bond
AU  - A. Fukui
AU  - R. Hamada
AU  - Y. Hirao
AU  - A. Idei
AU  - S. Ishitani Silva
AU  - S. Miyazaki
AU  - Y. Muraki
AU  - T. Nagai
AU  - K. Nunota
AU  - G. Olmschenk
AU  - C. Ranc
AU  - N. J. Rattenbury
AU  - Y. K. Satoh
AU  - T. Sumi
AU  - D. Suzuki
AU  - T. Tamaoki
AU  - S. K. Terry
AU  - P. J. Tristram
AU  - A. Vandorou
AU  - H. Yama
AU  - M. P. G. Hundertmark
AU  - U. G. Jorgensen
AU  - P. Longa-Pena
AU  - N. Peixinho
AU  - J. Skottfelt
AU  - J. Southworth
AU  - M. I. Andersen
PY  - 2026
DA  - 2026/10/23
PB  - arXiv
DO  - 10.48550/arxiv.2610.32020
UR  - https://arxiv.org/abs/2610.32020
AB  - We present an analysis of the high-magnification microlensing event OGLE-2015-BLG-1395 and report the discovery of a sub-Saturn mass companion to the lens. Photometric coverage of the planetary anomaly in the light curve was obtained from the University of Tasmania's Harlingten 1.27m telescope. Additional data were obtained following the peak from several other observatories, allowing photometric calibration and color measurement of the source. Fits to the light curve reveal a companion with mass ratio of q = 0.00062 +/- 0.00007 and two degenerate solutions for the projected separation, s = 1.7 +/-0.1 or 0.59 +/-0.04 Einstein ring radii. Source and lens parameters are further constrained by Subaru and Keck adaptive optics (AO) imaging in 2016. Finite source effects and AO flux constraints allow us to determine the planet and host star parameters to better than a factor of 2. The system is an ~0.2 Jupiter-mass planet orbiting an ~0.25 solar mass (early-mid M-dwarf) main-sequence star in the Galactic disk, at a distance of ~2 kpc. The two degenerate solutions from the light curve both place the planet beyond the snow line. As a cold sub-Saturn around an M dwarf, OGLE-2015-BLG-1395Lb is in possible conflict with core accretion theory. Spitzer photometry from the time of the event is consistent with this conclusion, although highly uncertain due to faintness and crowding. The inferred relative proper motion of 9.4 mas/yr is consistent with a source star in the bulge and a lens in the disk, and predicts that the source and lens could be resolved a decade after the event.
ER  -