The Nova V 5584 Sgr : A Short Review

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.


Introduction
Nova Sagittarii No. 4 was discovered by Nishiyama and Kabashima (2009) on 2009 October 26 and later designated V5584 Sgr (Samus, 2009).V5584 Sgr is a classical example of multi-wavelength astrophysics, since it has been observed in different parts of the electromagnetic spectrum: optical, infrared and X-rays.The very early optical spectroscopic observations secured by Kinugasa et al. (2009), Maehara et al. (2009), Fujii (Maehara et al., 2009), Munari et al. (2009) in the optical and by Raj et al. (2009) in the infrared showed that V5584 Sg is a Fe II nova, in the context of the classification by Williams et al. (1991), Williams (1992).Spectra secured by Russell et al. (2010) during 2010 February showed that dust formation had occurred.Poggiani (2011) has monitored V5584 Sgr during the late decline.V5584 has been investigated in the optical domain by the Stony Brook/SMARTS Consortium (Walters et al., 2012).The present paper reviews the history of V5584 Sgr observations.

Light Curve
The photometric evolution and the main parameters of V5584 Sgr has been reported by Poggiani (2011) and will be briefly summarized below for completeness.The V band light curve is reported in Fig. 1.The epoch of maximum is MJD=55134.208(2009 October 29), while the decline time by two magnitudes is 27±2 days, making V5584 Sgr a moderately fast nova, according to the classification by Payne-Gaposchkin (1957).The reddening of V5584 Sgr is 0.82±0.12.The estimated distance of V5584 Sgr is in the interval 5.8-7.1 kpc.The absolute magnitude at maximum is in the range -7.2....-7.7, while the white dwarf mass is in the range 0.8-0.9M .All parameters extracted by the analysis of the light curve suggest that V5584 Sgr is a Fe II nova, according to the classification by Della Valle & Livio (1998).The spectroscopic observations described below will provide further evidence for the classification.The importance of monitoring of novae over long time intervals has been addressed by several contributors at this conference (Pagnotta, 2013), (Ederoclite, 2013), (Tappert, 2013).At the moment of writing V5584 Sgr is very far from quiescence.At the moment of discovery, Corelli (2009) showed that nothing was visible at the nova position on a Palomar plate with limiting magnitude 21.

Infrared Observations
The relevance of observations of novae in the infrared has been discussed by Banerjee and Ashok (2012) and by Chesneau and Banerjee (2012).Banerjee and Ashok (2012) suggest that the Fe II and He/N classes share a set of common spectral lines in the near infrared, namely hydrogen, helium, nitrogen and oxygen.On the other hand, there is a clear signature belonging only to novae of Fe II class, the presence of strong carbon lines: thus the near infrared observations can provide an additional suggestion of the spectroscopic class of a nova.Several novae, mostly novae belonging to Fe II class, produce dust during the decline.The dust presence is marked by a rise of infrared emission and can become apparent also as a dip in the optical light curve.The last signature is not necessarily observed, since dust can be arranged as an optically thin shell.2010) observed V5584 Sgr in the region 3-14 µm with AEOS telescope, discovering that the nova had formed dust since the previous observations.The infrared continuum was dominated by the thermal emission of the dust at a temperature of 880±50 K; no details of the dust composition or the derivation of the temperature are reported.The above infrared observatons provide a clue that was not available due to the lack of observations during the seasonal gap.

X-Ray Observations
The importance of X-ray observations of novae has been addressed by several authors, also at this conference (Ness, 2013), (Orio, 2013).V5584 Sgr has been observed with the Monitor of All-Sky X-ray Image (MAXI) (Shimanoe et al., 2010).The system is on board of ISS and uses two high sensitivity X-ray detectors, the Gas Slit Camera (32 CCD chips) and the Solid State Slit Camera (a Xenon filled proportional conunter).MAXI scans all sky every 92 minutes.Shimanoe et al. (2010) have searched the prompt X-ray emission at the ignition of the thermonuclear runaway.The authors suggested that classical novae could emit X-rays at the outburst in analogy to the type I X-ray bursts of X-ray binaries.The observations included several peculiar novae: V1723 Aql, V407 Cyg, V2673 and V2674 Oph, V1722 Aql, KT Eri, V496 Sct.The authors have focused on the archive data in the energy band 1.5-4 keV, the lowest energy available, assuming that nova outbursts preferentially emit soft X-rays.They also investigated the 4-10 keV and 10-20 keV bands.No prompt emission was detected in the three bands for any nova.There are no reported X-ray observations of V5584 Sgr at later stages, when supersoft emission could have occurred.

Conclusions
V5584 Sgr is a standard Fe II nova.The sinergy of observations in different domains allowed a classification of the spectral class and the discovery of dust production during the seasonal gap.

Figure 3 :
Figure 3: Line profiles of Hα during the nebular stage(Poggiani, 2011) Infrared observations of V5584 Sgr have been secured by Raj et al. (2009) on October 29 at Mt. Abu telescope showed Paschen, Brackett, O I, C I, N I lines with P Cyg profiles, whose components wew separated by about 550-650 km/s.The emission components strengthened, while the absorption components faded by November 3. The transitions observed in spectra are typical of the Fe II class novae, providing an independent confirmation of the classification of V5584 Sgr.The following observations in the infrared were secured after the seasonal gap.On 2010 February 10 Russell et al. (