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From John Greaves: === Taichi Kato lightheartedly advised : > # Please don't attempt to write a flash news entitled: You've got to agree with this, coz there's a lot of it about. Hence the two alternative subject headings to this mail. The first, the right way, the second the wrong way... I've been looking at some of these Integral xray objects towards the Galactic Centre over the past couple of months, as they crop up at atel.caltech.edu. It seems there's no dedicated optical or similar follow up to this Russian satellite's work, as would be the case with NASA and/or ESA for example, with their access to Chile based observatories. Here's one where it was suggested at the time that I forward it as telegram or iauc or similar, which I didn't. I think it needs near infrared spectroscopy follow up by somebody like the people at ESO, but wouldn't no how to tell them. I'll not give the exact figures to keep it short, but the object is so blatantly obviously there once you look that you can't miss it, so anyone can find it. Anyway, I wouldn't mind any unbiased assessments of all the information already available. Even if not associated with the xray source, it is a weird object. ATEL 178 mentions INTEGRAL observations of the xray pulsar EXO 1722-363 and gives a new positional error box. ATEL 179 mentions a 9.7 day modulation per RXTE and Ginga evidence, suggestive of an orbital period, and refers to earlier works on such matters. So you go to the field, and things get instantly obvious. There's a big IRAS source here. There's also a 'hole' in space. Nothing there. It's a small dark cloud or something, barely an arcmin across. A round emptiness on all POSS images, whether B, R or I, and pretty empty on 2MASS images. The general field shows evidence of extinction, with few fainter stars, but this thing is empty, and also seems to structured to be an artificial pattern, of the sort the eye loves to make, abhorring randomness as it does. The area around it is quite busy with stars. A catalogue based on DENIS and visual data lists Av in this area as being ~ 29 magnitudes!!! This 'cloud' appears to be an IRAS source too, numbers in which can give a clue to its nature. But this wasn't what I first noticed, what I first noticed was the two 2MASS sources embedded within this emptiness, at it's Western edge, sources totally absent in POSS images down to their limits. Trouble is the 2MASS data is a bit confused, there appear to be two objects. A DENIS source coincides with the Southern one and agrees with 2MASS as to the object's J-Ks value, but it is really _essential_ to view the 2MASS quick look images to see what is happening here, and to see that the Southern object is indeed stellar. Because the first thing I noticed when I checked 2MASS J-Ks for this object, and double checked that against DENIS J-Ks, is that it has a J-Ks of ~+4.5!!! This object, not visible in visual bands, not visible in I band POSS plates (or barely visible in them, can't remember now), detected by DENIS easily in J and Ks, but not in gunn i (limit magnitude 17), and around magnitude 10.5 to 11 in the J band, would be just about a naked eye object if our eyeballs worked in the Ks passband! [There's a half mag difference between DENIS and 2MASS J and Ks magnitudes respectively, but as the source is confused, and overexposed to some extent in Ks, this may not indicate anything more than measurement problems, as opposed to variability at different observational epochs]. There's an MSX5C source here too, with bandpass profiles that look thermal more than anything, as is similar to the case with the IRAS source, so it is not certain whether it is more related to the cloud as a whole, or to the source. I think there were one or two other things I found out also, but I forget them now. Applying pulsar formation evolutionary considerations as well as the ATEL 179 evidence, an assumption could be made that this is a hot supergiant embedded in such a small dense cloud of material that it is practically invisible save as a secondary signature in the near infrared due to the warming of the immediate circumstellar material. A fair candidate for an xray pulsar to orbit. The object really needs assessing as to its nature. Unfortunately it's only visible in the infrared, so spectral type, and importantly class, will only be able to be assessed via spectroscopy in the near infrared. I think they do that at ESO, I'm not sure, certainly it needs a Southern Hemisphere site. Whether it is "newsflash" stuff, I couldn't decide. The Integral people thought it was, but didn't want to follow it up themselves. It was suggested I should, something I'd not even considered. The original point of 'circulars' and 'telegrams' was to let people know there was something worth pointing their equipment at. The need for being 'mentioned in despatches' as a sort of 'peer review' for professionals and their surveys, and the ability to be famous for 15 seconds for both them and the rest of us, has sometimes neutered the newsflash medium. And of course, it is actually a heck of a lot easier than getting something formally published, if only in terms of input effort. It is a bit of a problem. Anyway, anyone any thoughts on this object? It's certainly different, whether hot supergiant primary to an xray pulsar or not. I especially do not remember Bok Globules or similar being usually associated with anything other than low or intermediate mass stars. The apparent luminosity of this object suggests it is a high mass supergiant and it's lack of visual evidence a well hidden one, probably by a dense cloud that is capable of being heated by it, but too dense to have been ionised to its surface. (Unless it's a well buried nearby T Tau object lying so incredibly coincident in the line of sight ;^) ) That J-Ks value though, that's impressive. Cheers John John Greaves
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