Spectrography of variable stars
Below there are some examples of the results of our CCD spectroscopy of variable stars.
Some of these stars were included in our CATS project (for transient sources) described at the following link: http://www.irf.lu.it/ccd-imagery-photometry.htm
Dwarf Nova PNV J03093063+2638031
after the discovery (October 29th 2014) of the optical transient PNV
J03093063+2638031 by the japanese amateur S. Ueda, at OAC we have
included (October 30th 2014) this transient in our above mentioned CATS
project, in order to clarify its nature; infact Ueda's discovery lacked
a spectroscopic confirmation.
ATel 6653 lists the results of our
(Santangelo & Gambogi) CCD spectrography of PNV J03093063+2638031;
you can find ATel 6653 on the Internet at: http://www.astronomerstelegram.org/?read=6653PNV.
With ATel 6653 we were among the first in the world to classify this
transient and to unveil its true nature: namely not a nova but a dwarf
nova. We used IRF's SBIG SGS spectrograph + ST-7 XME CCD camera at the
Cassegrain focus of OAC's 0.60 m f/9.83 reflector, while this source
shined as an 11th magnitude star.
Please, follow the above link to ATel 6653 in order to read the details.
Dwarf novae are a sub-class of cataclysmic variabe stars.
The main astrophysical model for the dwarf novae is the following: the
dwarf novae are made of two extremely close stars (extremely close each
other, of course. Not necessarily close to us); one of these stars
being a normal dwarf and the other one being a white dwarf having an
accretion disk around it. Material sucked from the normal star is
attracted by the white dwarf and hits the accretion disk creating an
hot spot on it.
Sometimes, dynamical instabilities in the accretion disk can give rise
to explosions and to optical outbursts like the one discovered by Ueda.
Italian readers can also follow the following link of the Municipality of Capannori (Italy) where OAC was built: http://www.comune.capannori.lu.it/node/15117
V339 DEL = Nova Delphini 2013
Nova Delphini 2013 = V339 DEL was discovered around mid august 2013 by the japanese amateur Itagaki.
At OAC we decided to include V339 DEL among the targets to be monitored
both photoelectrically and spectroscopically at OAC; in fact this
target was included in our C.A.T.S. project which stands for Capannori
Astronomical Transients Survey. You can find more about C.A.T.S.
project in the following link (CCD Photometry and Imagery).
A couple of days after the discovery, we made our first photoelctric photometry and CCD spectrography of V339 DEL.
In the aftermath we monitored the photometric and spectroscopic
developement of V339 DEL. Some preliminary results of this monitoring
are listed in the following two papers published on line:
Santangelo, M. M. M.,Pasquini M., Gambogi S., Cavalletti G., 2013 ATel.5313
Santangelo, M. M. M.,Pasquini M. 2013 ATel.5295
ATel 5295 we were the first in the world to claim the presence of the
NIR neutral oxygen triplet at 777.4 nm. Moreover we were among the
first to claim the presence of strong P-Cygni profiles of Hydrogen, Fe
II, and various other elements. We were also the first to publish R
band photoelectric photometry of this nova.
Finally in ATel 5313 we were the first in the world to publish an estimate of the distance of V339 DEL.
In the following link you can find a spectrum of V339 DEL from H-alpha to the near infra-red region.
Tracing of a medium dispersion long-slit CCD spectrum of Nova DEL 2013, with the 30 cm Schmidt-Cassegrain