•We performed spectroscopic observations of four extragalactic novae in M31 and M33.•Nova M31 2009-10b is one of the most luminous novae ever observed in M31.•Nova M33 2010-07a is the first recorded ...nova in M33 that underwent a second mass ejection.
We report the spectroscopic observations of four extragalactic novae in M31 and in M33, secured at Loiano Observatory, Italy. Nova M31 2009-10b is a luminous nova that needed some days to achieve the peak brightness. We confirm that it is a Fe II nova and we show that it is one of the most luminous novae ever observed in M31, showing an evolution close to that of the bright extragalactic novae M31 2007-11d, LMC 1991 and SN 2010U. The novae M31 2010-07a and M31 2011-07b are standard Fe II novae. Nova M33 2010-07a is a Fe II nova that showed a peculiar rebrightening, during which we observed emission lines with P Cyg profiles: we suggest that it is the first observed nova in M33 that underwent a second mass ejection.
The recurrent nova (RN) V3890 Sgr was observed during the seventh day after the onset of its most recent outburst, with the Chandra ACIS-S camera and High Energy Transmission Gratings. A rich ...emission line spectrum was detected, due to transitions of Fe-L and K-shell ions ranging from neon to iron. The measured absorbed flux is 10−10 erg cm−2 s−1 in the 1.4-15 range (0.77-8.86 keV). The line profiles are asymmetric, blueshifted, and skewed toward the blue side, as if the ejecta moving toward us are less absorbed than the receding ejecta. The full width at half-maximum of most emission lines is 1000-1200 km s−1, with some extended blue wings. The spectrum is thermal and consistent with a plasma in collisional ionization equilibrium with column density 1.3 × 1022 cm−2 and at least two components at temperatures of about 1 and 4 keV, possibly a forward and a reverse shock, or regions with differently mixed ejecta and a red giant wind. The spectrum is remarkably similar to the symbiotic RNe V745 Sco and RS Oph, but we cannot distinguish whether the shocks occurred at a distance of a few au from the red giant, or near the giant's photosphere, in a high-density medium containing only a low mass. The ratios of the flux in lines of aluminum, magnesium, and neon relative to the flux in lines of silicon and iron probably indicate a carbon-oxygen white dwarf.
We report the spectroscopic follow-up of the nova V5558 Sgr carried out in 2008 and 2009 at the Loiano Observatory, Italy, during the decline stage, as a part of an ongoing monitoring campaign. The ...spectra suggest that V5558 Sgr has entered the nebular stage, as shown by the presence of high ionization lines, and confirm that it is very similar to the slow nova V723 Cas, as previously suggested. We have estimated the decline time by three magnitudes, 170
±
2
days, typical of slow novae. We have revised the estimation of the absolute magnitude at maximum (−6.3 to −5.9) and the distance (1.3–1.6
kpc) of V5558 Sgr, in agreement with previous results. The revised white dwarf mass (0.58–0.63
M
⊙) confirms that V5558 Sgr is a critical system whose mass is close to the lower limit to trigger the nova outburst.
We have secured optical spectroscopy of the nova V5584 Sgr at the Loiano Observatory, Italy, during the post outburst decline. V5584 Sgr showed the presence of nebular lines. We have estimated the ...decline time by two magnitudes, 27 days, the absolute magnitude at maximum, −7.2 to −7.7, the white dwarf mass, 0.8 to 0.9
M
⊙
, the distance, 5.8 to 7.1 kpc.
We report the spectroscopic follow-up of the nova V459 Vul carried out at the Loiano Observatory, Italy, at three epochs after the outburst. The spectroscopy showed high ionization lines of iron. The ...photometry has been used to estimate the absolute magnitude at maximum and the distance of the nova. V459 Vul is a fast nova, with decline times by two and three magnitudes of 18 and 30 days respectively. The nova achieved an absolute magnitude at maximum of −8.7…−7.7. The distance of V459 Vul is in the range 2.3–5.0 kpc.
The spectral evolution of the slow nova V5558 Sgr has been monitored at the Loiano Observatory, Italy, during the pre-maximum stage and the early decline. The nova exhibited a long pre-maximum stage ...and several secondary outbursts after the initial maximum. The spectra during the pre-maximum stage showed emission lines of H I and Fe II. The spectra after the first maximum showed intense emission lines of H I, Fe II and emerging He I lines. During a secondary brightening absorption components appeared on H I, He II and Fe II lines. The spectroscopic evolution is similar to the evolution of the slow nova V723 Cas. The estimated distance of V5558 Sgr is 1.3
±
0.3
kpc.
The nova V5584 Sgr was discovered during 2009 October. It has been monitored in different domains of the electromagnetic spectrum: optical, infrared and X-rays. The optical and infrared observations ...suggest that V5584 Sgr is a Fe II nova that formed dust. No X-ray emission was observed around the time of maximum.
We present the optical spectral evolution of the nova V2362 Cyg during the first 15 months after the outburst, from 2006 April to 2007 July. The spectroscopy, performed at the Loiano telescope, ...Italy, covers the evolution from the early decline to the nebular stage. V2362 Cyg exhibited an unusual secondary outburst during the decline. We have used the optical spectroscopy and photometry to investigate the physical properties of the ejecta and to constrain the nova distance. V2362 Cyg is a fast nova, with decline rates by two or three magnitudes of 4.3 and 15.8 days, respectively. The derived magnitude at maximum is
M
V
=
-
9.0
. The distance is in the range 7.2–15.8
kpc. Our observations during the first decline showed strong emission lines, typical of a Fe II nova; during the secondary outburst the spectrum reverted to features typical of early decline. After the secondary outburst V2362 Cyg entered the nebular phase. The spectroscopic evolution resembles the history of nova V1493 Aql.
The early spectral evolution of the nova V458 Vul has been monitored at the Loiano Observatory, Italy. The nova exhibited a couple of oscillations during the decline from initial maximum. We have ...performed spectroscopic observations to study the physical properties of the ejected material. The photometric light curve has been used to derive the nova distance and its absolute magnitude at maximum. V458 Vul is a fast nova, with decline rates by two or three magnitudes of 7 and 15 days respectively. The magnitude at maximum is
M
V
=−8.8. The nova distance is in the range 6.7–10.3 kpc. The spectra secured a few days after initial maximum showed emission lines of H I and Fe II, making V458 Vul a Fe II nova at this stage. After the oscillations V458 Vul came back to a standard decline curve, but evolved towards the He/N class. Thus V458 Vul is a hybrid nova.
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