R Lyrae

[Bill Ward]

Hi,
I’m not a variable star observer but a few nights ago whilst trying to get a spectrum of Vega with one of my meteor cameras that carries a diffracion grating I noticed a star that, to me looked almost as bright as Vega in the frame. I went and got a pair of binoculars and had a look. It think it’s R Lyrae. Having a look online I find out this is a red star. With the IR sensitivity of the camera it would appear much brighter that in the visual.
However, to regular observers, is it doing anything odd…? It could easily make out the colouration in 11×80’s and to me it just looked bright.
Cheers,
Bill.

[Jeremy Shears]

Hello Bill,

I looked at the BAA VSS and AAVSO data and R Lyr appears to be behaving “normally”, though the most recent data are from a week ago.
It is a semi-regular variable (SRB), spectral type M5, hence red as you found. The amplitude is small: 3.81 – 4.44 V.
The V-I is ~2.5 mag (brighter in IR than visual) – this varies a bit, in time with its overall brightness variations.
I can’t see any spectra in the BAA database.

As you say, these meteor cameras can very red sensitive.

Whilst you have your binoculars out (you don’t need such large ones, though these are good to pick up the colour, and you might be able to use naked eye), why not have a go at estimating its brightness to check where its at now? Chart here: https://britastro.org/vss/xchartcat/R%20Lyr%20330%2001.gif

Finally, I note that R Lyr was discovered by the Mancunian, Joseph Baxendell in 1856.

JS

[Bill Ward]

Hi,
Very interesting, It was just startling bright in the unfiltered ccd image.
I’ll keep an eye out for any meteor captures that have it in frame.
Bill.

[Robin Leadbeater]

Here are typical spectra of M5iii in red (R Lyr) and A0v in blue (Vega) with a typical sensor QE curve (black) overlaid, first at equal V magnitude and then with the correct relative magnitudes assuming RR Lyr Vmag =4.0.

R Lyr is ~ as bright as Vega in the I band but should still look significantly fainter integrated over the response of an unfiltered image. (Unless perhaps close to the horizon where atmospheric extinction would reduce the difference)

Cheers
Robin

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   Vega_RLyr_same_Vmag_QE_overlay.png
   

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   vega_RLyr_fluxscaled_QE_overlay.png
   

[Bill Ward]

Hi,
Thanks for the info, also very interesting. I didn’t take any specific measurements as that was not what I was interested in but it was sufficiently bright to catch my attention.
Just a curiosity for me.
Cheers,
Bill.

[Mike Harlow]

This all-sky view does show R Lyr as significantly brighter than the blue stars beta and gamma Lyr which are listed as a magnitude brighter. I guess a meteor camera is even more red sensitive.
Do you have an image you could share?
Mike.

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   cal_20240314-scaled.jpg
   

[Nick James]

Mike,

Here’s an example from one of my meteor cameras with R Lyr marked. This is an average of 256 video frames (at 25 fps) using an IMX291LQR based camera with no IR filter. The Bayer matrix on these cameras is designed so that all the pixels have a passband at IR so the chip is effectively a mono sensor in IR. This is one of the problems of trying to use these meteor cameras to monitor variables.

Nick.

Attachments:

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   FF_UK004H_20240418_033046_785_0711168.fits.jpg
   

[Bill Ward]

Hi,
Thanks for the ongoing feed back. Mike, no I didn’t keep any of the short exposure images that I was taking whilst finding Vega to test my latest system.
As with comments Robin made, Vega was low to my NE at the time but the image you post is pretty much what drew my attention to the star, with extinction it even looked a touch brighter when compared to Vega at that point in time.
I’ll now use it as a guide post when reviewing my meteor images!
Cheers,
Bill.

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