MAGELLAN ADAPTIVE OPTICS FIRST-LIGHT OBSERVATIONS OF THE EXOPLANET β PIC b. I. DIRECT IMAGING IN THE FAR-RED OPTICAL WITH MagAO+VisAO AND IN THE NEAR-IR WITH NICI

• Published in: The Astrophysical journal 2014-05, Vol.786 (1), p.32
• Main Authors: Males, Jared R., Close, Laird M., Morzinski, Katie M., Wahhaj, Zahed, Liu, Michael C., Skemer, Andrew J., Kopon, Derek, Follette, Katherine B., Puglisi, Alfio, Esposito, Simone, Riccardi, Armando, Pinna, Enrico, Xompero, Marco, Briguglio, Runa, Biller, Beth A., Nielsen, Eric L., Hinz, Philip M., Rodigas, Timothy J., Hayward, Thomas L., Chun, Mark, Ftaclas, Christ, Toomey, Douglas W., Wu, Ya-Lin
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHARGE-COUPLED DEVICES; COLOR; COMPARATIVE EVALUATIONS; DETECTION; DEUTERIUM; GRAVITATION; HEAT EXCHANGERS; MASS; NEAR INFRARED RADIATION; OPTICS; PHOTOMETRY; PLANETS; PROBABILITY; SATELLITES; SIGNAL-TO-NOISE RATIO; STARS; TELESCOPES; VISIBLE RADIATION
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/786/1/32

We present the first ground-based CCD (λ < 1 μm) image of an extrasolar planet. Using the Magellan Adaptive Optics system's VisAO camera, we detected the extrasolar giant planet β Pictoris b in Y-short (Y{sub S} , 0.985 μm), at a separation of 0.470 ± 0.''010 and a contrast of (1.63 ± 0.49) × 10{sup –5}. This detection has a signal-to-noise ratio of 4.1 with an empirically estimated upper limit on false alarm probability of 1.0%. We also present new photometry from the Gemini Near-Infrared Coronagraphic Imager instrument on the Gemini South telescope, in CH {sub 4S,1%} (1.58 μm), K{sub S} (2.18 μm), and K {sub cont} (2.27 μm). A thorough analysis of our photometry combined with previous measurements yields an estimated near-IR spectral type of L2.5 ± 1.5, consistent with previous estimates. We estimate log (L {sub bol}/L {sub ☉}) = –3.86 ± 0.04, which is consistent with prior estimates for β Pic b and with field early-L brown dwarfs (BDs). This yields a hot-start mass estimate of 11.9 ± 0.7 M {sub Jup} for an age of 21 ± 4 Myr, with an upper limit below the deuterium burning mass. Our L {sub bol}-based hot-start estimate for temperature is T {sub eff} = 1643 ± 32 K (not including model-dependent uncertainty). Due to the large corresponding model-derived radius of R = 1.43 ± 0.02 R {sub Jup}, this T {sub eff} is ∼250 K cooler than would be expected for a field L2.5 BD. Other young, low-gravity (large-radius), ultracool dwarfs and directly imaged EGPs also have lower effective temperatures than are implied by their spectral types. However, such objects tend to be anomalously red in the near-IR compared to field BDs. In contrast, β Pic b has near-IR colors more typical of an early-L dwarf despite its lower inferred temperature.