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Published July 2002 | Published
Journal Article Open

The Y Band at 1.035 Microns: Photometric Calibration and the Dwarf Stellar/Substellar Color Sequence


We define and characterize a photometric bandpass (called "Y") that is centered near 1.035 μm, in between the traditionally classified "optical" and "infrared" spectral regimes. We present Y magnitudes and Y−H and Y−K colors for a sample consisting mostly of photometric and spectral standards, spanning the spectral type range sdO to T5 V. Deep molecular absorption features in the near‐infrared spectra of extremely cool objects are such that the Y−H and Y−K colors grow rapidly with advancing spectral type especially from late M through mid‐L, substantially more rapidly than J−H or H−K, which span a smaller total dynamic range. Consistent with other near‐infrared colors, however, Y−H and Y−K colors turn blueward in the L6–L8 temperature range, with later T‐type objects having colors similar to those of warmer M and L stars. Y−J colors remain constant at 1.0 ± 0.15 mag from early‐L through late‐T dwarfs. The slope of the interstellar reddening vector within this filter is A_Y = 0.38A_V. Reddening moves stars nearly along the YHK dwarf color sequence, making it more difficult to distinguish unambiguously very low mass candidate brown dwarf objects from higher mass stars seen, e.g., through the Galactic plane or toward star‐forming regions. Other diagrams involving the Y band may be somewhat more discriminating.

Additional Information

© 2002 Astronomical Society of the Pacific. Received 2002 March 19. Accepted 2002 April 10. Published 2002 June 4. We acknowledge with appreciation Adam Burgasser for obtaining P60/IRC ("X") Y‐band data for us of several T dwarfs. L. A. H. thanks John Carpenter for allowing her to talk him into observing with the Keck/NIRC ("Z") Y‐band filter during data acquisition for our H/K study of Orion Nebula Cluster faint stars and brown dwarfs. This publication makes use of data products from the Two Micron All Sky Survey (2MASS) and has benefited from information provided by the SIMBAD database.

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Published - Hillenbrand_2002_PASP_114_708.pdf


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