AAVSO Alert Notice 490
Optical monitoring of T Ori requested
August 30, 2013
Dr. William Herbst (Wesleyan University) and Rachel Pedersen (Bates
College) have requested AAVSO assistance in monitoring the Orion
variable T Ori in support of spectroscopy they will be obtaining
during September 2013. AAVSO nightly coverage (visual or
electronic, not time series) of this star is crucial throughout the
month of September.
Dr. Herbst writes: "T Ori is one of the first variable stars
discovered, varies by up to several magnitudes, and remains a
mysterious object. The cause of its variability is not fully known
more than a century after its discovery!
"To help address this issue, my student Rachel Pedersen and I will
be obtaining high resolution spectra with the SMARTS 1.5m telescope
at the Cerro Tololo Interamerican Observatory in Chile during the
month of September, 2013. We hope to observe spectral changes
accompanying the brightness variations that will shed light on
their cause. It is critical that we be able to assign a magnitude
to each spectrum. Amateur astronomers could make a terrific
contribution to this project by more intensively monitoring the
star during September.
"For visual observers: Estimates of the brightness using the AAVSO
charts will be helpful. Since the star changes brightness by up to
several magnitudes, an accuracy of 0.1 or even 0.2 mag as can be
achieved by (careful!) visual observers will be sufficient.
Observations made with care by experienced observers will be most
helpful to us.
"For CCD observers: V magnitude or even unfiltered observations
will be most useful. If colors can be obtained (e.g. UBVRI) they
could be helpful, but we primarily need a magnitude estimate.
"Of course, during this time period T Ori is an early morning -
pre-dawn - object. There is no need for time series during the
short window that the star is high enough in the sky for accurate
measurement. We really need just one observation per night - it
generally does not change significantly on the time scale of
minutes or even an hour.
"...We look forward to unveiling some of the mysteries of this
star -- or at least trying!"
When the variable is relatively bright, as in the case of T Ori,
a filtered observation is always preferred to an unfiltered one
as it is much easier to integrate with data from other observers.
Observations in the AAVSO International Database show T Ori with a
visual range of magnitude 9.3-~12.6; recent visual and V magnitudes
show it between ~9.7 and 11.9. Because of the nebulosity associated
with the area around T Ori, observations need to be made very
carefully and consistently.
Coordinates: 05 35 50.44 -05 28 34.9 (2000.0)
Finder charts for T Ori may be created using the AAVSO International
Variable Star Plotter (VSP, http://www.aavso.org/vsp).
Please report observations to the AAVSO International Database
using the name T ORI.
This campaign is being followed on the AAVSO Observing Campaigns
page (www.aavso.org/observing-campaigns).
Many thanks for your help with this campaign. You are key to its
success!
This AAVSO Alert Notice was prepared by Elizabeth O. Waagen.
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發表於 2013-8-31 10:19:59