High resolution spectroscopy of the young eruptive star V2492 Cyg currently peaking at record brightness
ATel #10183; U. Munari (INAF Padova), G. Traven (Univ. Ljubljana), S. Dallaporta (ANS Collaboration), D. Lorenzetti, T. Giannini, S. Antoniucci (INAF Roma)
on 18 Mar 2017; 18:45 UT
Credential Certification: U. Munari (firstname.lastname@example.org)
Subjects: Optical, Variables, Young Stellar Object, Pre-Main-Sequence Star
Referred to by ATel #: 10259
Recently, Ibryamov and Semkov (ATel #10170) have reported on a new record
brightness attended by the young eruptive star V2492 Cyg along the complex
outburst it started in 2010 (Itagaki CBET #2426, Munari et al. CBET #2428).
They monitored the star to rise from V=14.63 on Nov 5, 2016 to V=13.52 on
Mar 5, 2017.
We have obtained BVRI photometry of V2492 Cyg with ANS Collaboration
telescope 31 on Mar 17.141 UT and found B=15.681 (+/-0.019), V=13.930
(+/-0.009), Rc=12.884 (+/-0.005), and Ic=11.840 (+/-0.004). While our
colors are only mildly redder than those measured by Ibryamov and Semkov at
peak brightness, the fainter magnitude we obtain signals the object is now
past the recent maximum.
Simultaneous with the photometry, on March 17.135 UT we exposed also a
deep and high-resolution spectrum of V2492 Cyg with the Echelle spectrograph
mounted on the Asiago 1.82m telescope (range 3600-7300 Ang, resolving power
18,000). The spectrum is characterized by a great deal of emission lines
from low ionization metals, with the FWHM ranging from 45 to 85 km/s
depending on ion and multiplet. Deep P-Cyg profiles characterize the Balmer
lines, with the absorption component being distinctively boxy in shape due
to the essentially null transmission at the center. The flat bottom runs
from -90 to -220 km/sec for Halpha, and from -55 to -200 for NaI doublet
(seen split from the corresponding interstellar components). FeII
multiplets 42 and 49 and MgI multiplet 2 are seen in absorptions at -120
km/s heliocentric RV, with a nearly Gaussian profile of FWHM=150 km/s. The
emission profile of Balmer lines has at least two components: one weak and
very broad (FWZI of 1300 km/s) on top of which sits the main one, with +80
km/s heliocentric RV and FWHM=255 km/s. While the emission line spectrum
bears resemblace to that for 2010 Sept 5 presented by Colin (2011, AJ 141,
196), the absorptions are now far stronger. An emission line is seen at
6707.7 Ang, its identification with null-velocity LiI as proposed by
Hillenbrand et al. (2013 AJ 145, 59) needs however careful scrutiny given
the great number of other similarly weak emission lines present all around.
Various diffuse interstellar bands are present (in particular DIBs 5778,
5780, 5797 and 6614 Ang).