Double Stars Discovered by IOTA and Reported to JDSO

(Journal of Double Star Observations) (or in process to be reported)

Tony George

Presented at IOTA 2012 Conference North Las Vegas, NV

JDSO Reports Submitted January 2010 – July 2011Summary Table

JDSO Publish Date

Event Date Asteroid (No) Name

Target Star Separation (mas)

PA

Vol. 8 No.4 Oct1, 2012

2009April 6

(336) Lacadiera

3UC197-115376 7.5 ± 0.9 124.9 ± 6.3

2009 April 16 (336) Lacadiera occults 3UC197-115375

Carl Bracken, Bob Cadmus , Al Carcich , John Centala , Robert Modic, Doug Slauson

The Lacadiera event found a fourth component of a previously known triple star system, making it a quadruple star system. This is an example of an ABAB event with very unequal star magnitudes. This was also the fist time that we used the UCAC3 catalog to report a double star. We used UCAC3 because it contained the other three components of the quadruple star system

Lacadiera Continued

Quaternary Star in

previously known triple star system

Reports Currently in ProgressJDSO Publish Date

Event Date Asteroid (No) Name

Target Star Separation (mas)

PA

Report Discontinued

2010August 31

(695)Bella

TYC 2322-01054-1 ?.? ?.?

Submitted Not Yet Published

2012March 11

(57) Mnemosyne

BN OrionisTYC 126-0781-1SAO 112952HD 245465

3.8 ± 0.8 63.6 ± 15.2

In Process Not Yet Submitted

2012August 12

(52) Europa TYC 6223-00442-1 37.8 ± ?.? ?.?

2010 August 31 (695) Bella occults TYC 2332-01054-1

T Beard, David Dunham, Paul Maley, Walt Morgan, R Stanton

The Bella event was originally thought to have found a component so close to the primary star that the secondary occultation was barely detectable. Unfortunately, this event was only observed with mini telescopes using PC164CEX2 cameras. The PC164CEX2 camera uses on-chip integration methods that smears star images across multiple pixels when the target star is drifting across the field of view. The variation in brightness due to the PC164CEX2 on-chip integration is approximately 20%. If this variation occurs during an occultation step transition, it can ‘mimic’ a brief step event. Since all the data was obtained with PC164CEX2 cameras, no clear unambiguous step event could be evaluated. Therefore, no report has been submitted.

Two chords showed a clear ‘step’ event in the data, while a third chord showed a partial occultation of only one of the two components – essentially a graze event with only one component occulted. This may be a first for IOTA observers.

BN Orionis (TYC 126-0781-1) Duplicity Discovery from an asteroidal occultation by (57) Mnemosyne

John Brooks, Steve Conard, Joan Bixby Dunham, David W. Dunham, Robert Jones,

Thomas R. Lipka, Wayne Thomas, Wayne H. Warren Jr., Rick Wasson, Jan Wisniewski,

Unknown to the observers at the time of the occultation:

TYC 126-0781-1 is also listed in the General Catalogue of Variable Stars as BN Ori, an INSB eruptive variable. An A7 (Pre Main Sequence) star, 2-5 solar masses, with some surrounding gas and dust (faint emission nebula) and possessing an accretion disk, at a distance of some 400 pc but is rotating at speeds upward of 220 km/sec.

Source: “The FUOR characteristics of the PMS star BN Orionis inferred from new spectroscopic and photometric observations”; Shevchenko, V. S.; Ezhkova, O.; Tjin A Djie, H. R. E.; van den Ancker, M. E.; Blondel, P. F. C.; de Winter, D. Astronomy & Astrophysics Supplement series, Vol. 124, July 1997, 33-54.

The authors of the above referenced paper were contacted about the observation and were very excited to learn that BN Orionis was indeed a double star. This star will likely be the source of much study in the future.

BN Orionis (TYC 126-0781-1) by (57) Mnemosyne(continued)

TYC 6223-00442-1 duplicity discovery from occultation by (52) Europa

A singe chord observation by Brazilian IOTA observer Breno Loureiro Giacchini

Because there is only one observing chord, there are at least two potential solutions for any ellipsoid major or minor

axis assumption – four total combinations!

Conclusions1. Occultations continue to be an excellent method of finding or

verifying double stars. Any time a light curve is obtained from a video record, it should be carefully examined for the presence of step events that could be due to duplicity of the target star.

2. The PC164CEX2 camera may produce results that can mimic very short step events in normal instantaneous occultations. As a result, double star claims from very short step events using these cameras must be verified by other non-integrating cameras.

3. Single-chord observations can discover double stars, however there is a great deal of uncertainty in the PA and Separation.