I recently was observing in Pisces and recorded some spectra of 74 Psc (also known as Psi1 Psc or STF 88). This is a nearby bright pair (V mag 5.273 and 5.455) widely separated (29.2", position angle 160°).
I posted the gory details here on the Observational Astrophysics forum, but I’d like some opinions from the double star experts here.
Stelle Doppie (WDS) says the primary is B9.5V and the secondary is A0V and that the parallax and common proper motion confirm this pair as physical. But Simbad says that the brighter primary is actually a cooler, dimmer A1V and the secondary is actually a hotter, brighter A0V. Sky Safari is emphatic that the two are an optical pair.
I don’t think everyone can be exactly right here but there should be some reconciliation possible.
Do people often check the WDS vs Simbad for spectral classification? How often is there a discrepancy?
With physical pairs, how often is the brighter primary the cooler star? There are scenarios where this could occur such as unresolved companions and evolved stars. How often are these seen? In closely matched pairs, how common is the subgiant luminosity class IV?
How reliable are parallax and common proper motion to confirming the physical nature? What if the spectroscopy argues against it?
STF 88 is an easily observed pair. Any comments or images are welcome.
Edited by Organic Astrochemist, 26 November 2019 - 10:47 AM.