2 Selection criteria

The PNe and PPNe form a broad but limited group in the IRAS colour-colour diagram (Pottasch et al. 1988; van der Veen & Habing 1988). They are reasonably well separated from most of the other objects. Based on the IRAS colour-colour diagram one can conclude that there is a good chance that an object is a PNe or PPNe if its IRAS colours F(12 $\mu$m)/F(25 $\mu$m) < 0.35 and F(25 $\mu$m)/F(60 $\mu$m) > 0.3. An occasional HII region, Seyfert galaxy, or T-Tau star is not excluded from this range. With the above mentioned criteria, the IRAS point source catalogue was searched to select the post-AGB candidates. We have considered only the sources which have good quality fluxes at 100 microns (a flux quality flag of 2 or 3 in the IRAS point source catalog) and which have optical counterparts brighter than 14th magnitude. From this we made a short list of southern objects (which can be observed from CTIO) which are associated with early type (OB) stars in the HD or SAO catalogues, or with early type emission line stars (Henize 1976; Wackerling 1970). Some of these stars were listed in two earlier papers (Parthasarathy & Pottasch 1989; Parthasarathy 1993a). We also found that some of the LS, LSS and LSE stars (Hardrop et al. 1959; Stephenson & Sanduleak 1971; Drilling & Bergeron 1995 and references therein) are IRAS sources with far-IR colours similar to PPNe and PNe (Parthasarathy 1993a,b and 1994; Conlon et al. 1993).

 

Table 1: Spectral types of optical counterparts of IRAS sources

IRAS	b	Name	Old Sp. Type	New Sp. Type	mag	comment
07377-2523	-1.61			B8III-Ve	12.5
09470-4617	+5.59	LSS 1351	OB+r	B1Iae	12.4	post-AGB
10178-5958	-2.72	Hen 401	Be	PN	12.5	bipolar PPN
11065-6026	-0.31	Hen 591	Be	LBV?	11.8	post-AGB?
12175-5338	+8.67	-53 5072	A9Iab	A7I	9.4	post-AGB
13266-5551	+6.36	-55 5588	Be	B1Ibe	10.7	post-AGB
14072-5446	+6.12	-54 5573		A3I	10.9	post-AGB
14331-6435	-4.20	Hen 1013	Be	B3Ie	10.9	post-AGB
15141-6238	-4.58	LSS 3332	OB+	O8III	11.3
16024-1813	+24.60			G8V	13.5	$\beta$ Pic
16206-5956	-7.49	SAO 243756	B8Ia	A3Ie	9.7	post-AGB
16336-5536	-5.77	HD 149427		PN	11.8
16590-5351	-7.46	-53 8315		PN	10.5
17041-2709	+8.00	Hen 1336	Be	K7V	12.2	T-Tau
17074-1845	+12.28	Hen 1347	Be	B3IIIe	9.5	post-AGB
17086-2403	+8.99			G5IV-V	11.9	$\beta$ Pic
17203-1534	+11.49			B1IIIpe	12.5	post-AGB
17311-4924	-9.04	Hen 1428	Be	B1IIe	10.7	post-AGB
17381-1616	+7.50	LSS 4331	OB+	B1Ibe	12.2	post-AGB
17395-0841	+11.10			PN	13.2
17412-0614	+11.95	SAO 141834	Ape	Ape	8.9
17423-1755	+5.78	Hen 1475	Be	PN	11.0	bipolar PPN
17460-3114	-1.88	SAO 209306	B0.5II	O8III	7.9	post-AGB
18023-3409	-6.31	LSS 4634	OB+	B2IIIe	11.6	post-AGB?
18040-1457	+2.78			B0V	12.5
18062+2410	+19.79	SAO 85766		B1IIIpe	11.5	post-AGB
18070-2346	-2.16	SAO 186389	B2V	B2Vn	8.0
18227-1243	-0.13	RY Scuti		B1IIIpe	9.1	binary
18237-0715	+2.23	MWC 930	Be	Be	11.0
18313-1738	-4.27	MWC 939	Be	B5?	12.4
18367-1233	-3.09	LSIV -12 97	OB	B3V	10.4
18371-3159	-11.82	LSE 63	OB+	B1Iabe	11.9	post-AGB
18379-1707	-5.42	LSS 5112	OB+h	B1IIIpe	11.8	post-AGB
18435-0052	+0.81			B2II	12.5	post-AGB?
18442-1144	-4.34	BD -11 4747		A3V	9.3	see notes
18489-3703	-16.09			K7V	11.9	T-Tau
19157-0247	-7.22	LSIV -2 29	B9Ib	B1III	11.5	post-AGB
19336-0400	-11.75			B1Iape	12.5	post-AGB
19399+2312	+0.08	LSII +23 17	OB(ce)h,r	B1III	10.4	post-AGB?
19590-1249	-21.26	LSIV -12 111	OB+h	B1Ibe	11.3	post-AGB