1. Home
  2. Forums
  3. About the AAVSO
  4. VSX

Doubts with variable stars type: EA vs EB and R

Tue, 01/16/2018 - 20:56

Hello everyone,

My name is Mariusz and I'm amateur astronomer. I like observe variable stars and finding new.

Yesterday I observed new variable star and I'm not sure of variability type. Main minimu is strong (EA), but moments of begin and end of eclipe are not clear (EB). Calculated period is 0.83 d. This star have indexes: J-K = 0.20 and B-V = 0.43. Phase plot in attachment, file "Phase plot.png".

I also problem with second star. I don't know which type is true. My friend suggest that is variable star with type R. This star also is regular, period is about 1.9 d, J-K = 0.02 and B-V = 0.17. Phase plot in attachment, file "Phase plot period 1.9 d.png".

I'm sorry, my english isn't very good.

Thanks for help,

Mariusz

File Upload
Phase plot.png154.66 KB
Phase plot period 1.9 d.png127.56 KB
FRF
Affiliation
Magyar Csillagaszati Egyesulet, Valtozocsillag Szakcsoport (Hungary) (MCSE)
Thu, 01/18/2018 - 22:27
Well, I think the first is an

Well, I think the first is an EB variable.

In the case of the second, the flat minimum can also be caused by the blending with a close companion, contamination by a fainter star?  Dunno :O

 

FRF
Affiliation
Magyar Csillagaszati Egyesulet, Valtozocsillag Szakcsoport (Hungary) (MCSE)
Thu, 01/18/2018 - 22:37
VSX says:"R:

VSX says:
"R:
Close binary systems characterized by the presence of strong reflection (re-radiation) of the light of the hot star illuminating the surface of the cooler companion. Light curves are sinusoidal..."

This like curve doesn't look like a sinusoidal... :O

Fri, 01/19/2018 - 17:01
My second star

Data is from ASAS-SN, measurements were in V filter from over last 1000 days. According the VSX we know 49 stars with type R, but only Gabriel Murawski submitted star R type with phase plot in good quality. This star has very regular period, I don't know if it can have emission in UV. It can be companion, according Panstarrs catalog is record (sep = 1.3", V mag uncertainty, g_mag = 14.02, r_mag = 12.09, i_mag = 12.64). Other catalog in Vizier database: no bright stars, nearest is in sep = 18" and V = 17 mag.

wlp
Affiliation
Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)
Fri, 01/19/2018 - 21:10
Reflection type variables and period

The shape of the light curve is not the only indication for the type.  E.g. the value of the period itself is important as well. All but 5 of the 49 R variables in VSX have a shorter period than your object with a period of 1.9 days, and most much shorter.  But there are also all the hot subdwarf + red dwarf eclipsing binaries, and many eclipsing binaries with a white dwarf, which also show a reflection effect (as a rule the R type is not added for EA type variables).  Most of these also have a much shorter period.  A longer period means that similar stars are farther apart, so that the hot star needs to be a lot hotter to generate a similar reflection effect, or that the cool companion must be much larger for the surface to be closer to the hot star to be heated similarly.  In general also, the reflection effect is larger when the stars eclipse, because we can then see straight at the heated surface of the cool companion and it disappears completely from view half an orbit later.  I am not saying this is not a reflection type variable, I wouldn't have any doubt if it would have a period of 0.19 days, but at 1.9 days it's not so straightforward.  As suggested before, the GALEX FUV-NUV colour could be an important indication.  Another possibility is an ACV type variable for which 1.9 days is a much more common period. 

Patrick

Fri, 01/19/2018 - 22:29
ACV type

Thanks Patrick,

I have one star with type ACV: https://www.aavso.org/vsx/index.php?view=detail.top&oid=555597. This type has uncertainty, because we don't have spectral analyse for them. I had problem with indentification of type varibility. Administrator of VSX corrected my type. My setup for spectral analysis not yet finish for fainter stars. I don't know which is value of GALEX FUV-NUV colour.

What do you think about my first star, it will EB type? I have some problems with classification for stars, which curves the calls are in between the two types of variability.

Clear skies,

Mariusz

wlp
Affiliation
Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (Belgium) (VVS)
Fri, 01/19/2018 - 23:22
EB or EW

The first star is an eclipsing contact binary.  The difference between EB and EW is just a semantic discussion.  It depends on whether you think the distinction between giants (like beta Lyr with longer periods) and dwarfs (like W UMa with shorter periods) is more important than the difference between the stars in the binary (and therefore more important than the difference in the depth of the eclipses).  In the first case this star would be EW, in the second case EB.  In VSX the "general" lower limit for periods of EB stars has been changed to 0.5 days from the limit of 1 day in the GCVS, to accomodate more overlap between the two classes.  Personally, I would no longer make the distinction.

Patrick