Spectroscopy requested for VV Cephei - Periodic precession of B star's rotational axis after periastron 2025
Abstract:
Manfred Schwarz (Wiener Neustadt, Austria), a colleague of Dr. Ernst Pollmann, wries: Thanks to the previous campaigns and the great efforts of amateur astronomers, VV Cephei is one of the best observed stars in the northern hemisphere. The large amount of data allows new insights into the system that are not covered by professional astronomers previously. Another high-cadence spectroscopic observation would now be necessary as the B component approaches the periastron. Ernst Pollmann predicts a disturbance of the disc precession 43-day-period by mass exchange from the M supergiant to the B component during the coming orbital phase started in 2025. It would be interesting to see whether this long-term process will change the 43-day precession period of the B star's rotational axis. All of this can only be determined through long-term spectroscopic observation of this system. Thank you for your support.
Justification:
"VV Cephei is a binary star consisting of an M-type supergiant star and a B-type companion on an orbit of 20.36 years. A lot of amateur and professional astronomers as well did contribute particularly during the eclipse 2017-2019 with high professional spectra of the Hα region. Ernst Pollmann collected all the spectra and performed a new wavelength calibration with typical metal lines of the M-star (according to K. O. Wright) to archive a correct and common base for evaluation of the Hα profile. That procedure leads to discover a new unknown periodic behaviour of R/V and EW(R), EW(V) of 43 days. Together with Philip Bennett (University of Halifax), they found a plausible explanation for that periodicity. The 43 day-period is produced by the precession of the rotational axis of the B star. This variability was also measured during the eclipses, where the disk was completely behind the M-star. Therefore, Philip Bennett proposed a model of two Hα emission lobes developing primary in the accretion disk." For more information on this campaign, please see the campaign paper here: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://forum.astronomie.de/attachments/vv-cep-2025-pdf.432428/&ved=2ahUKEwib-rP9rdCMAxVawvACHWgoC-YQFnoECCAQAQ&usg=AOvVaw303lytPf4Q49Id1K_ZYKWP
Requested Data Types:
Spectroscopy
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| VV Cep | 4.88 | EA/GS+SRC | Not Requested |
Cadence: Custom Resolution: 10000 Desired SNR: 100 |
Spectroscopy Lines:
H-alpha (6563.0 Å)
Photometry Filters:
No photometry filters provided
Comparison Stars:
Finder charts may be created using the AAVSO Variable Star Plotter (VSP; https://apps.aavso.org/vsp/).
Co-Authorship
Observers are eligible for co-authorship.
Additional Observer Input:
Spectroscopic resolution: R >= 9000; Minimum wavelength range: 6540 – 6580; Heliocentric Correction: not necessary; Cadence of observation: each single spectra is valuable, one or more spectra per week would be great (one spectrum per night would be ideal). We need reduced 1D spectra, wavelength calibrated and instrument response corrected. It should not be telluric-corrected.
Additional Submission Location:
Observers are requested to send their spectra to Manfred Schwarz <ms@astrophoto.at>. Please contact him to request access to a Dropbox folder. Observers should also submit their spectra to the AAVSO Spectroscopic Database (AVSpec, https://apps.aavso.org/avspec/submit).
Notes:
Spectroscopic resolution: R >= 9000 Minimum wavelength range: 6540 – 6580 Heliocentric Correction: not necessary Cadence of observation: each single spectra is valuably, one or more spectra per week would be great