BV Sequence for V1159 Ori

(vsnet 665)

VSNet readers, I recently prepared a chart with V sequence for V1159 Ori. The primary reference for star positions and magnitudes was the by A.D. Andrews (1981). This extensive dataset (positions, identifications, UBV and I data for 16000 stars) made it fairly easy to construct a V sequence down to 16 mag. The purpose of this note is to show how Andrews' data (based on specially taken UK Schmidt plates) compares with other V sequences, such as that of the AAVSO, and to draw attention to one or two discordant stars.

I have obtained a copy of the AAVSO "e" chart (12/94, revised 2/96), and also ftp'd the VSNET chart for V1159 Ori. The footnote on the AAVSO chart states that their mags are CCD(V) by T. Kato of Ouda Station, but I am not able to say that the AAVSO mags reproduce exactly all mags measured by Kato. (My ftp'd chart has insufficient width of field).

Table: Comparison of AAVSO mags with V (ptg) by Andrews.
========================================================
Magnitudes
AAVSO  VSNET    ANDREWS       R.A.        DEC.    ANDREWS'
ccd-V  ccd-v    V    B-V    B1950      B1950      ID. #
----------------------------------------------------------
124           12.41 0.69  5h26m16.48s -3d37'46.7" 13308
120   12.06   12.04 0.65  5 26 24.20  -3 38 49.2  13305
136   13.72   13.71 0.55  5 26 34.47  -3 39 46.2  13304
150   15.15   14.82 1.94  5 26 34.66  -3 35 55.9  13311  Note 1.
122           12.32 0.66  5 26 43.07  -3 40 55.7  13302
145           14.67 0.76  5 26 45.93  -3 37 55.8  13306  Note 2.
146           14.70 1.28  5 26 53.55  -3 37 13.2  12629
118           11.89 1.35  5 27  1.14  -3 40 39.7  12622
....                      5 26 29.86  -3 36 11.2  13310  Note 3.

Note 1. Apreciable variation between sources. This star is the reddest in this field. Lies about 1 arcmin East of V1159 Ori. Not in the IRAS PSC.
Note 2. Slightly discordant. I make the point that the AAVSO chart indicates a difference of 0.5 mag between 145 and 150, but Andrews finds a difference of only 0.15mag!
Note 3. V1159 Ori.

General: This field is somewhat reddened. My full list of Andrews' data shows that stars with B-V of less than 0.50 are almost completely absent. For most stars on the AAVSO chart, there is good agreement, but the AAVSO mags tend to be slightly brighter, of the order of 0.1mag. Andrews 13311 needs closer scrutiny, and preferably repeated measurement. It may be variable.

I would like to correlate more of Andrews' data with that from other sources, but the fact that the vast majority of Andrews' stars are rather faint, running down to 16mag, makes it unlikely that many have been measured by other observers. I did find one star (not in the above list): Andr. 12647, at 5h27m22.57s -3d28'34.9". Andrews gives V=12.05, B-V 1.51. This turns out to be Wolf 1450 =G99-14, an M5 V red dwarf. Another source (O.J. Eggen, I think) gives V =12.02, which is reassuring.

I thank Tom Cragg of Coonabarabran, NSW for kindly furnishing a copy of the AAVSO 'e' chart for V1159 Ori.

Reference: Andrews, A.D.: A Photometric Atlas of the Orion Nebula, 1981, Armagh Observatory.

Regards,
Mati Morel

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