Electronic Telegram No. 3881
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET 209P/LINEAR
     [Editor's note:  this text replaces that on CBET 3880 (heliocentric
distance correction).]
     D. Schleicher, Lowell Observatory, obtained three sets of narrowband
photometry of comet 209P on May 19 (when the comet was at r = 0.99 AU and
Delta = 0.11 AU) using the Hall 1.1-m telescope at Lowell Observatory,
resulting in the following production rates:  Q(OH; Haser) = 1.8 x 10^25
molecules/s, yielding Q(H_2O; vectorial) = 2.5 x 10^25 molecules/s at this r;
Q(CN) = 5.8 x 10^22 molecules/s; Q(C_2) = 6.5 x 10^22 molecules/s; Af(rho) at
524 nm = 0.7 cm.  These values are extremely low, helping explain why this
periodic comet was only discovered ten years ago; the water production implies
an effective active area of only about 0.01 km^2.  Schleicher classifies
209P's compositional class as "typical".  Note that the dust measurements and
the resulting Af(rho) value may be significantly contaminated by light
reflected from the nucleus.

     Quanzhi Ye, University of Western Ontario, reports observations of comet
209P (the parent body of the potential forthcoming May 24 Camelopardalid
meteor outburst; cf. CBET 3869) with the 8-m Gemini North telescope on Apr.
9.25 UT (27 days pre-perihelion, at r = 1.04 AU).  Spectra in the 350-600 nm
range do not reveal any CN, C_2, or C_3 emission features, which puts an upper
limit of around 10**25 molecules/s for CN, around 3 x 10**24 molecules/s for
C_2, and around 10**25 molecules/s for C_3, for the production rates of the
comet.  Syndyne-synchrone modeling computed by Man-To Hui (UCLA) shows that
the optical cometary tail is dominated by particles at the level of beta =
0.0005 (where beta is the ratio of radiation pressure to gravitational
pressure; Finson and Probstein 1968, Ap.J. 154, 327).  The brightest cone of
the tail has tau = 25-50 days (where tau is the lead time that the particles
are released from the parent), which corresponds to material released at r =
1.26-1.41 AU.  Images can be found at website URL http://tinyurl.com/ktzs3ck.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2014 CBAT
2014 May 23                      (CBET 3881)              Daniel W. E. Green