RW Aur monitoring requested

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RW Aur monitoring requested

文章 PTS » 週三 25 3月, 2015 08:58

AAVSO Alert Notice 514
March 24, 2015

RW Aur monitoring requested

Dr. Hans Moritz Guenther (Massachusetts Institute of Technology)
has requested AAVSO observers' assistance with the classical
T Tauri star RW Aur (component A). He writes:

"RW Aur A is a classical T Tauri surrounded by an accretion disk.
It's a visual binary; the B component is fainter and shows no sign
of a disk. The separation is 1.4 arcsec, but the B component is
so much fainter (V = 13.6) that it's not a problem if the binary
is not resolved.

"In fall 2014 (we don't know the exact date) RW Aur A become
dimmer by about 3 mag in V band. This can be seen e.g. in the
AAVSO database [use www.aavso.org/lcg or see below]. The current
best idea of what causes this dimming is that the secondary
component RW Aur B has passed by the disk of RW Aur A and pulled
mass out of the disk into a stream or cloud that now covers up
part of the light from RW Aur A. The orbit of the binary is > 100
years, so we don't expect this to happen again any time soon!

"We want to use this opportunity to measure what this stream is
composed of. What is the ratio of gas and dust? What is the size
of the dust grains?

"The way we attempt to do this is to observe RW Aur A in as many
different bands as possible...The Chandra X-ray satellite will
observe RW Aur A for 11 hours. The satellite operations team is
currently working on the schedule, so we don't know exactly when
these observations are going to happen, but we expect that they
will likely take place sometime during April 6-12, although
possibly sooner. X-rays are absorbed by all material between the
star and us - the gas and the dust.

"In contrast, optical reddening is only due to the dust around
the star. If we compare the two, we can calculate how much of
the mass in the tidal stream is gas and how much is dust.

"Thus, we ask [AAVSO observers] to observe RW Aur in the next few
weeks (as long as it is still visible) in as many bands as
possible...It would be great to have a dense lightcurve (at least
one point per night in as many bands as possible (incl. JHK if
possible)) for the next few weeks. We expect it to be stable, but
if anything funny (flares, further dimming) happens then we need
to know about it, so we can see how that would affect the X-ray
observations."

RW Aur normally varies between about 10.3 and 11.0 visually,
although it can be as bright as 9.8 and faint as 11.7. Recently,
it declined to 12.6 by 2014 October 28, and it was visual
magnitude 12.4 as of 2015 March 23.

In August 2010, RW Aur declined to visual magnitude 12.6, returning
to mag 10.5 in April 2011.

A light curve of RW Aur observations in the AAVSO International
Database may be plotted using the AAVSO Light Curve Generator
(www.aavso.org/lcg). A recent AAVSO light curve of RW Aur may be
seen on the webpage for this Alert Notice at
http://www.aavso.org/aavso-alert-notice-514 .

Please observe RW Aur nightly in as many bands as possible through
the end of the current observing season. Visual observations are
welcome.

Coordinates: R.A. 05 07 49.57 Dec. +30 24 05.2 (2000.0)

Charts for RW Aur may be plotted using the AAVSO Variable Star
Plotter (VSP, http://www.aavso.org/vsp).

Please use WebObs to report your observations to the AAVSO
International Database using the name RW AUR.

Thank you for your observing efforts and valuable observations!

This AAVSO Alert Notice was prepared by Elizabeth O. Waagen.

----------------------------------
SUBMIT OBSERVATIONS TO THE AAVSO

Information on submitting observations to the AAVSO may be found at:
http://www.aavso.org/webobs

ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION

An Alert Notice archive is available at the following URL:
http://www.aavso.org/alert-notice-archive

Subscribing and Unsubscribing may be done at the following URL:
http://www.aavso.org/observation-notifi ... ertnotices

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