4 research outputs found
Feasibility of an Infrared Parallax Program Using the Fan Mountain Tinsley Reflector
Despite the continuing importance of ground-based parallax measurements, few
active programs remain. Because new members of the solar neighborhood tend
towards later spectral types, infrared parallax programs are particularly
desirable. Consequently, the astrometric quality of the new infrared camera,
FanCam, developed by the Virginia Astronomical Instrumentation Laboratory
(VAIL) for the 31-in (0.8-m) Tinsley reflector at Fan Mountain Observatory was
assessed using 68 J-band exposures of an open cluster, NGC 2420, over a range
of hour angles during 2005. Positions of 16 astrometric evaluation stars were
measured and the repeatability of those positions was evaluated using the mean
error in a single observation of unit weight. Overall, a precision of 1.3 +/-
0.7 microns in x (RA) and 1.3 +/- 0.8 microns in y (Dec) was attained, which
corresponds to 0.04" +/- 0.02" in each axis. Although greater precision is
expected from CCDs in the visual and near-infrared, this instrument can achieve
precision similar to that of the ESO NTT infrared parallax program. Therefore,
measuring parallaxes in the infrared would be feasible using this equipment. If
initiated, such a program could provide essential distances for brown dwarfs
and very low mass stars that would contribute significantly to the solar
neighborhood census.Comment: accepted by New Astronomy, minor revisions per refere
Near-Infrared Photometry of the Type IIn SN 2005ip: The Case for Dust Condensation
Near-infrared photometric observations of the Type IIn SN 2005ip in NGC 2906
reveal large fluxes (>1.3 mJy) in the K_s-band over more than 900 days. While
warm dust can explain the late-time K_s-band emission of SN 2005ip, the nature
of the dust heating source is ambiguous. Shock heating of pre-existing dust by
post-shocked gas is unlikely because the forward shock is moving too slowly to
have traversed the expected dust-free cavity by the time observations first
reveal the K_s emission. While an infrared light echo model correctly predicts
a near-infrared luminosity plateau, heating dust to the observed temperatures
of ~1400-1600 K at a relatively large distance from the supernova (> 10^{18}
cm) requires an extraordinarily high early supernova luminosity (~1 X 10^{11}
L_solar). The evidence instead favors condensing dust in the cool, dense shell
between the forward and reverse shocks. Both the initial dust temperature and
the evolutionary trend towards lower temperatures are consistent with this
scenario. We infer that radiation from the circumstellar interaction heats the
dust. While this paper includes no spectroscopic confirmation, the photometry
is comparable to other SNe that do show spectroscopic evidence for dust
formation. Observations of dust formation in SNe are sparse, so these results
provide a rare opportunity to consider SNe Type IIn as dust sources.Comment: 11 pages, 6 figures, 3 tables, Accepted for Publication to ApJ:
January 20, 200