Sunday, August 28, 2016

The Possible SETI Target HD 164595 - more messing around with Aladin

Last Update:  9 September 2016

There been a lot of kerfuffle lately about a possible SETI detection more than a year ago at the RATAN-600 radio telescope in Russia. Some would say far too much kerfuffle, since it was only seen once and may well admit to alternative explanations. SETI scientists like  Eric Korpela are unimpressed.

Some basic facts about the star:

Effective temperature is 5790 deg Kelvin per Porto del Mello, et. al.(2013)

The SIMBAD Page. The parallax (from Hipparcos) of 35.26 milliarcseconds corresponds to a distance of 92.5 light years. Gaia is unlikely to change this much.

The ALLWISE Page on Vizier. It's J180038.80+293420.6 in ALLWISE.

no surprise, it's in the 2MASS catalog as 18003890+2934188.

Apparently not in the variable star index compiled by AAVSO.

Here's a reference to the warm Neptune orbiting the star. It orbits the star once every 40 days and is about 16 times the mass of Earth. It was found with a radial velocity search.

A companion? Yes!

Unlike Tabby's Star, this star has been studied quite a bit, but I'm a little confused by this star and its environs. Does HD 164595 have a red dwarf companion? In Simbad a "sibling" is listed - HD 164595B, and is listed as "rotationally variable star". Is it a companion, or just a nearby star? It has a closely similar proper motion (it is slowly moving the same way in the sky at about the same speed). HD 164595 is 88194 in the Hipparcos catalog, and is not listed by Lepine and Bongiorno as having a wide companion.  It is however, listed in the Washington Double Star Catalog, maintained by the USNO. For now, I think it's probable it does have the M-dwarf companion. Marshall Eubanks has pointed out that this paper by Gould and Chaname says that they are a binary.

Apparently, HD 164595B is not in the Hipparcos catalog (perhaps a bit too dim for that), but should be in the upcoming Gaia data release. It is, however in the 2MASS catalog as J18004543+2933566.

Here is the color 2MASS image, with the two stars side by side. You can see they are about 1.5 minutes of arc apart, which if they are at the same distance, implies a separation of about 2550 astronomical units, which is a wide companion. Note the little "objects" just to the south and north of HD 164595 - they're not in any catalog I can find, including 2MASS.  I suspect they're not real, but an artifact of how the color image is put together. They don't show up in other images.

HD 164595 A and B

Here's the POSSII image in near infrared. Those stars that appear to be close to HD 164595 are probably much further away.
POSSII image of HD 164595 in near infrared