SDSS J214807.80+293848.0 - AGN or CV?

Affiliation

None

Sat, 10/01/2016 - 20:23

Hi all,

I noticed this object that seemed to be of high amplitude variable nature, being relatively faint in SDSS9 (around mag +20.5 visually). However, in POSS-II Blue the object is of mag +16.4 (USNO-B1.0) and the GSC2.3 has it listed at +17.0 (Blue). The POSS-I O blue plates show it at mag +20.1 (USNO-B1.0). The object is also visible in GALEX.

Coordinates (J2000.00): 21 48 7.80 +29 38 48.72

It is also listed as USNO-B1.0 1196-0562514 and

The object was listed as a possible Quasar candidate acc. to Vizier (SDSS DR10 catalogue of candidate quasars, Brescia et al., 2015), which makes it seem like the brightening is due to an AGN. It does look identical to the other objects listed in that catalogue.

However, the object looks oddly like many confimed and candidate CVs, acc. to their colorimetry in SDSS and appearance in GALEX (see attachement). Many CV candidates from the CSS also appeared alot brighter in DSS Red or Blue images, with a similar magnitude range as SDSS J214807.80+293848.0 as seen in DSS2-Blue and SDSS. It also looked alot like a confirmed CV candidate found by ASAS too.

I was going to add this object to the VSX before I saw it was listed as a possible Quasar candidate.

I'm really not sure what this object is, but it did seem rather interesting to bring up.

Thank you for your help in clearing things!

Best regards,

Trygve Prestgard

File Upload

SDSS star.png61.47 KB

Possible CV candidate SDSS and GALEX.png677.2 KB

Sebastian Otero

Affiliation

American Association of Variable Star Observers (AAVSO)

Sun, 10/02/2016 - 00:06

Likely a CV

Hi Trygve,

Do not worry about that quasar candidate catalogue, almost every new CV being found nowadays is listed as a quasar candidate there... :(
The SDSS DR9 catalogue lists it as a star and it is not in WISE or AllWISE, I would expect a quasar to be in those catalogues.
The magnitude range also supports the CV classification.
Use the 16.4 blue magnitude from USNO-B1.0 for the maximum. The fatintest magnitude available is from SDSS and in order to list the magnitude more similar to B, use the g mag. in SDSS which is 21.0.

So submit it to VSX :)

Cheers,
Sebastian