According to Gray and Corbally (P192-199) As well as generally being of low metallicity, among other characteristics, Lamda Boo stars are best characterised by their low Mg II 4481/Fe 4383 line ratio which is significantly lower than in normal A type stars
Yes, a lot of people told me that. I don't know a lot about spectroscopy, but i have a collaborator who can interpret the data for me if it's owner can't do it.
The star I'm talking about is Galati V22 in the VSX. It's an A4Vp spectral type (p stands for peculiarity). I didn't find any available spectra on the internet, that's why I'm asking for data
A quick look in VizieR and SIMBAD suggests that the most recent spectral classification remains that of Helmet Abt and Nidia Morrell (1995ApJS...99..135A), who call it A5Vp, noting weak MgII 4481A. The MgII weakness is a necessary but not sufficient condition for being a lambda Boo star. But it is a candidate, as you suggest.
A good summary of what's required for lambda Boo-ness is Simon Murphy et al.'s very nice summary, accessible here:
They obtained new spectra with resolution of roughly 2A per pixel-pair and high S/N to classify the stars. (HD 46089 is not included.) So that is what will be required for someone to do this in a dispositive way.
Sounds great. If you can get the imporant region between 3900A and 4500A (between H&K and the MgII line at 4481A), that will probably do the trick. I suppose Simon Murphy (or Richard Gray or Father Corbally) would like to see the spectrum, too, in case it is interesting to them!
Of course. Timing is very weather dependent, particularly at this time of year (This year has been very poor in this already cloudy corner of England) It is well placed for the next few months though.
I had a brief window of clear sky last night so took a look at this star. The spectrum covers 4200-4550A at ~3A rescolution. A second spectrum covers the Ca K line at much lower (~10A) resolution due to the spectrograph achromatic optics. The spectra are compared with bet Leo taken the same night, A3v, the same reference as Gray and Corbally p 195 fig 5.20. ( I planned to attach figures showing a comparison of the rectified spectra but I can no longer see the facility to add attachments. Has it been removed ? If so I will try to find somewhere to upload them and add a link)
The spectrum of HD46089 is almost identical to that of bet Leo with only marginally weak Mg 4481 and no obvious reduced metallicity. Although noisy and low resolution, the spectra also look similar around the Ca K line (Though there does appear to be a curious additional feature on the blue edge of the Ca K line in the HD46089 spectrum which might warrant investigation at higher resolution.)
The spectrum (1D fits) is available for download from the BAA database.
I also see that the Fe II 4383 is weak. Indeed the spectra looks interesting. Do you want to do more research on it? Who do you think can get a better resolution? By analysing some Gaia EDR3 data, an exoplanet posibility looks very real, so we may have an orbiting exoplanet around it.
>....I also see that the Fe II 4383 is weak. Indeed the spectra looks interesting....
This is not my interpretation. (The rectification is not perfect at the 4383 line. The line strength is the same in both target and reference) Perhaps Brian can comment but I do not see anything unusual in this spectrum. It shows that, except for perhaps a very marginally weak Mg 4481 line, the spectrum is that of a normal main sequence mid A star, almost identical to beta Leo which is an A3v MK standard (Gray and Corbally page 561 table A6). Based on the spectral characteristics of Lam Boo stars in Gray and Corbally I would have expected it to show much weaker metal lines and a bigger difference in Mg4481 than here if it was a Lam Boo star.
I have posted a low-res (R~700) spectrum of Galati V22, taken in the evening of 18 Dec (California time), to the AVSpec database. Ca II (3969), Fe I (4299, 4303), and Mg II (4481) lines are quite visible. This doesn't seem to match the low metallicity expected of a lamda Bootis star.
Where is the star, and what lines are you interested in?
It depends on the the spectral type but the Fe lines are usually used to measure metallicity as they are strong and plentiful
According to Gray and Corbally (P192-199) As well as generally being of low metallicity, among other characteristics, Lamda Boo stars are best characterised by their low Mg II 4481/Fe 4383 line ratio which is significantly lower than in normal A type stars
Here is the archetype Lamda Boo at an SNR of 420 in the ELODIE archive.
http://atlas.obs-hp.fr/elodie/fE.cgi?n=e500&c=i&z=s1d|vs&o=elodie:19950220/0012
I suspect a very high SNR may be needed to measure the metal lines which are already weak in A stars anyway
Yes, a lot of people told me that. I don't know a lot about spectroscopy, but i have a collaborator who can interpret the data for me if it's owner can't do it.
For such a bright target there is a possibility that a high quality spectrum already exists. Have you chcked the ELODIE archive for example ?
http://atlas.obs-hp.fr/elodie/
Cheers
Robin
Hello
The star I'm talking about is Galati V22 in the VSX. It's an A4Vp spectral type (p stands for peculiarity). I didn't find any available spectra on the internet, that's why I'm asking for data
Gabriel
A quick look in VizieR and SIMBAD suggests that the most recent spectral classification remains that of Helmet Abt and Nidia Morrell (1995ApJS...99..135A), who call it A5Vp, noting weak MgII 4481A. The MgII weakness is a necessary but not sufficient condition for being a lambda Boo star. But it is a candidate, as you suggest.
A good summary of what's required for lambda Boo-ness is Simon Murphy et al.'s very nice summary, accessible here:
https://ui.adsabs.harvard.edu/abs/2015PASA...32...36M/abstract
They obtained new spectra with resolution of roughly 2A per pixel-pair and high S/N to classify the stars. (HD 46089 is not included.) So that is what will be required for someone to do this in a dispositive way.
\Brian
It should be possible to meet these requirements (Using a LHIRES and 600l/mm grating) I will add it to my observing list
Cheers
Robin
Sounds great. If you can get the imporant region between 3900A and 4500A (between H&K and the MgII line at 4481A), that will probably do the trick. I suppose Simon Murphy (or Richard Gray or Father Corbally) would like to see the spectrum, too, in case it is interesting to them!
\Brian
Who are they? Do they research Lambda Bootis stars? If yes, it could really be interesting
https://ui.adsabs.harvard.edu/abs/2009ssc..book.....G/abstract
Pretty much the modern "bible" on spectral classifcation
Thank you. Please notify me when you finish the observations. When do you think you can do that?
Of course. Timing is very weather dependent, particularly at this time of year (This year has been very poor in this already cloudy corner of England) It is well placed for the next few months though.
Cheers
Robin
I had a brief window of clear sky last night so took a look at this star. The spectrum covers 4200-4550A at ~3A rescolution. A second spectrum covers the Ca K line at much lower (~10A) resolution due to the spectrograph achromatic optics. The spectra are compared with bet Leo taken the same night, A3v, the same reference as Gray and Corbally p 195 fig 5.20. ( I planned to attach figures showing a comparison of the rectified spectra but I can no longer see the facility to add attachments. Has it been removed ? If so I will try to find somewhere to upload them and add a link)
The spectrum of HD46089 is almost identical to that of bet Leo with only marginally weak Mg 4481 and no obvious reduced metallicity. Although noisy and low resolution, the spectra also look similar around the Ca K line (Though there does appear to be a curious additional feature on the blue edge of the Ca K line in the HD46089 spectrum which might warrant investigation at higher resolution.)
The spectrum (1D fits) is available for download from the BAA database.
https://britastro.org/specdb/data.php
Please note the conditions of use
Cheers
Robin
http://www.threehillsobservatory.co.uk/astro/temp/hd46089_20201221_125_…
http://www.threehillsobservatory.co.uk/astro/temp/hd46089_20201221_125_…
Cheers
Robin
Hi
I also see that the Fe II 4383 is weak. Indeed the spectra looks interesting. Do you want to do more research on it? Who do you think can get a better resolution? By analysing some Gaia EDR3 data, an exoplanet posibility looks very real, so we may have an orbiting exoplanet around it.
Regards.
Gabriel
>....I also see that the Fe II 4383 is weak. Indeed the spectra looks interesting....
This is not my interpretation. (The rectification is not perfect at the 4383 line. The line strength is the same in both target and reference) Perhaps Brian can comment but I do not see anything unusual in this spectrum. It shows that, except for perhaps a very marginally weak Mg 4481 line, the spectrum is that of a normal main sequence mid A star, almost identical to beta Leo which is an A3v MK standard (Gray and Corbally page 561 table A6). Based on the spectral characteristics of Lam Boo stars in Gray and Corbally I would have expected it to show much weaker metal lines and a bigger difference in Mg4481 than here if it was a Lam Boo star.
Cheers
Robin
I have posted a low-res (R~700) spectrum of Galati V22, taken in the evening of 18 Dec (California time), to the AVSpec database. Ca II (3969), Fe I (4299, 4303), and Mg II (4481) lines are quite visible. This doesn't seem to match the low metallicity expected of a lamda Bootis star.