V445 Pup : The first helium nova ?

Kazuyoshi Kanatsu (Matsue, Shimane, Japan) reported the discovery of a new variable star, which is likely a nova based on the absence of apparent counterparts on his previous image, DSS and 2MASS. His discovery magnitude is mag 8.7p on December 22. K. Takamizawa reported prediscovery observations (November 28, 8.6p mag) on his patrol films. Takamizawa reported that the object was not recorded on 22 films (limiting magnitude 14) between 1994 March 14 and 1999 December 3. He also reported the presence of a close companion of 14.5 mag USNO star (vsnet-campaign-nova 94). This USNO star is recorded by 2MASS survey, which gives J=12.50, H=11.75, Ks=11.51, not particularly red among neibouring stars (vsnet-campaign-nova 101). If the object is a nova, the color suggests either a) usual cataclysmic variable with moderate reddening or b) cataclysmic-type binary with a relatively evolved secondary (vsnet-campaign-nova 104).

CCD image taken by G. Masi

M. Fujii performed spectroscopy on December 31 using a 28-cm reflector which yielded spectrum with rich metal emission lines. He identified prominent emission lines of Fe II (multiplets 19F, 34F, 42, 74) and He I 587.6 nm, while H-beta emission is weak or absent. Fujii suggested that the object is a somewhat peculiar nova (vsnet-campaign-nova 133). Y. Nakamura reported prediscovery observations on his patrol films. They indicates that the major rise of the object took between 2000 September 26 and November 23 in conjunction with K. Haseda's observation (vsnet-campaign-nova 140). Observations on January 3 by some observers indicated there may be a short-lived flare (vsnet-campaign-nova 136), vsnet-campaign-nova 142). G. Masi reported there was no evidence of fluctuations in his two hours run on January 7 (vsnet-campaign 662). S. Otero reported a fading to 9.7mag on January 9 after several days at 9.1mag (vsnet-campaign-nova 148). The object somewhat recovered on January 9 and 10 (vsnet-campaign-nova 152). S. Otero reported it was oscillating stronger as seen in his January 11 observations (vsnet-campaign-nova 154). A short-term fading was detected on January 13 (vsnet-campaign-nova 160). On January 15, a fading to 9.7mag was observed (vsnet-campaign-nova 162). W. Liller reported no short-term variations are seen in 6.5 hours light curve taken on January 14, and following to T. Kato's remark about CK Vul, commented that V445 Pup is perhaps similar to the hydrogen deficient cataclysmic variables CR Boo, CP Eri and V803 Cen, the main difference being temperature (vsnet-campaign-nova 163).

The object has been suggested to be a helium nova (vsnet-campaign-nova 188, vsnet-campaign-nova 189).

The fading trend continued until January 17 at about 9.5-9.6mag (vsnet-campaign-nova 170), however, observations on January 17 also showed it was temporary very faint 9.8-9.9mag (vsnet-campaign-nova 177). The object again entered gradual fading phase (vsnet-campaign-nova 182). B. Monard and J. Bedient reported a brightening to 9.3mag on January 20 and 19, respectively (vsnet-campaign-nova 183). It then became relatively calm (vsnet-campaign-nova 195).

The object kept the relatively quiet state at about 9.5mag until January 30 when S. Otero reported that the ALDA team observed a temporary fading to 10.4mag (vsnet-campaign-nova 196). The object was then recovered, and then, continues fading (vsnet-campaign-nova 205). On February 11, the Kyoto team obtained quasi-continuous 4.5-hour high-speed photometry which yields short-term variations, but the amplitudes were an order of 0.1 mag or less (vsnet-campaign-nova 209). Slightly fainter magnitudes (10.0 - 10.2) were reported on February 12 and 13, and then, the brightness recovered on February 14 (vsnet-campaign-nova 212). The time-series photometry on February 14 showed short-term variation with an amplitude no greater than 0.1mag (vsnet-campaign-nova 213). The Kyoto team performed multi-color photometry on February 15, and reported B-V=0.63, V-R=0.54, R-I=0.69 (vsnet-campaign-nova 214). The VSNET collaboration team received data sets obtained by A. Retter, G. Handler, and M. Martigoni. Combined light curve during February 10 - 19 showed short-term modulations with a time-scale from ten minutes to an hour, and longer scale (a few days) variations. Amplitudes of the short-term modulations were variable, but typically 0.03mag in V-band (vsnet-campaign-nova 219).

A brightening was reported on February 28 - March 2 (~9.8mag; vsnet-campaign-nova 253). The object again fading to 10.1mag on March 3 (vsnet-campaign-nova 258). It again brightened to about 9.5mag on March 12 and 13 (vsnet-campaign-nova 270). The object was bright until March 15 and again back to 10mag (vsnet-campaign-nova 273). The object slightly brightened (~10.0mag) around March 26 (vsnet-campaign-nova 275), and then again gradually faded (vsnet-campaign-nova 277). B. Monard reported that V445 Pup has undergone further fading: The object was observed at mag 11.0 on Apr. 24. This is the faintest magnitude ever reported since the eruption (vsnet-campaign-nova 286). The object was slowly brightening until around May 12 when it again started fading (vsnet-campaign-nova 298). Another brightening to 10.3mag was reported on May 23 (vsnet-campaign-nova 323). It remained at this level for about one week (vsnet-campaign-nova 332). The bright state finished on July 1 as reported to be 11.2mag by B. Monard (vsnet-campaign-nova 375). After gradual fading (vsnet-campaign-nova 392), B. Monard reported a dramatically fading of V445 Pup: It seems to be fainter than 12.9mag on August 1 (vsnet-campaign-nova 424). B. Monard reported the object was fainter than 14.6mag on August 18. The object was fainter than the prenova magnitude at this time (vsnet-campaign-nova 435).

M. Rupen reported that radio observations with VLA detected radio emission from the peculiar variable V445 Pup. The observations showed a new, ~10 mJy radio source coincident with the optical source (vsnet-campaign-nova 550).

Other related articles: vsnet-campaign-nova 106, 108, 109, 110, 113, 118, 119, 124, 133, 139, 145, 146, 147, 150, 151, 154, 155, 156, 157, 159, 163, 164, 166, 167, 168, 169, 171, 172, 173, 174, 175, 176, 179, 180, 184, 185, 186, 187, 190, 191, 192, 193, 194, 197, 198, 199, 200, 201, 202, 203, 204, 206, 207, 208, 210, 211, 215, 216, 217, 218, 221, 222, 224, 225, 242, 249, 267, 268, 273, 274, 279, 282, 283, 284, 287, 288, 289, 292, 293, 294, 295, 297, 300, 317, 331, 341, 342, 375, 492, 507, 578, 623, vsnet-campaign 668, 725, 1164

Field photometry by A. Henden: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/npup00.dat
Spectrum taken by M. Fujii: http://www1.harenet.ne.jp/~aikow/p_n_p.gif
Color image provided by B. Hassforther: http://members.aol.com/bela1996/nova-pup-2000.jpg
A good comparison set of images by A. Henden: http://vela.as.arizona.edu/~rmw/v445pup.html
A bright BVRI field photometry file by A. Henden: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/v445pup.dat
A visual sequence by A. Henden: ftp://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sumner/v445pup.seq

General Information on This Object