American Association of Variable Star Observers (AAVSO)
Sun, 01/29/2012 - 18:15

CO Ori appears to be having another fade. The AAVSO recent lightcurve (with some very nice multiband observations - thanks to whoever it was!) in fact shows a couple of fades over the period shown. One to keep an eye on.

American Association of Variable Star Observers (AAVSO)
CO Ori

Hi all,

I am monitoring CO Ori with the W28 of AAVSONet since begin Januari in BVIc and R645 and HA (results of R645 and HA will be submitted asap). I'll keep you posted on the results.

About V1000 Sco: according to M. Walter (ApJ, 306:573-586, 1986) it's an PTTS, but V. Shevchenko & W. Herbst (AJ, 116: 1419-1431, 1998) classify the star as an WTTS (the terminology used for PMS stars is not always that clear ...). I hope someone on the list can help me out on this.

Bart Staels (SBL)



American Association of Variable Star Observers (AAVSO)
YSO Terminology

Hi Bart,

These were some new ones I recently learned also.

 WTTS = Weak T Tauri Star.  A T Tauri star that lacks strong emission lines in its optical spectrum (EW(Hα) < 10Å), and lacks both strong stellar winds and a circumstellar accretion disk. Also known as naked T Tauri star. GCVS types INT and IT. 

PTTS = Post T Tauri star.  Post T Tauri stars (PTTS) are late‐type stars in the age range between 10 and 100 Myr filling the gap between T Tauri (TTS) and zero‐age main sequence phases. 


American Association of Variable Star Observers (AAVSO)
YSO terminology

Hi Mike!

yes, I know the basic definitions, but the problem is to find useable parameters to classify a YSO as CTTS, WTTS, NTTS or PTTS.

An article you might find interesting:

An empirical criterion to classify T Tauri stars and substellar analogs using low-resolution optical spectroscopy


I'll check for V1000 Sco if it can be fit in on the basis of the parameters described in the article. I'll keep you posted

clear skies!


  Unfortunately, due to my

  Unfortunately, due to my job schedule, evening observing of Orion has been off limits to me. Sorry I missed out on observing CO Ori and all of the other fascinating YSO's in Orion! The good news is that I often work well past midnight but by the time I drive home all of the YSO's in Lyra, Serpens, Scutum, Cepheus and Cygnus are getting to be springtime pre-dawn objects, so hopefully I can start making early visual estimates of them!