BRIGHT NOVA RETICULI 2020

Following the posting on the CBET 4811 & 4812 about the NOVA RETICULI 2020 we performed some follow-up of this object through a TEL 0.1-m f/3.6 astrograph + CCD located in the Heaven's Mirror Observatory, Australia (MPC code Q56) and operated by Telescope Live network.

On images taken on July 16.82, 2020 we can confirm the presence of an optical counterpart (with R-filtered magnitude about +4.5; B-filtered magn. +5.6; V-filtered magn. +5.6) at coordinates:

R.A. = 03 58 29.61, Decl.= -54 46 39.8

(equinox 2000.0; Gaia DR2 catalogue reference stars for the astrometry).

This transient was discovered by Robert H. McNaught (Coonabarabran, NSW, Australia) as an apparent 5th-magnitude nova on CCD images obtained on July 15.590 UT with a Canon 6D camera and an 8-mm-f.l. f/2.8 lens (at ISO 800). The position is very close to an object listed as "MGAB-V207" in the AAVSO's VSX online database (which gives position R.A. = 3h58m29s.55, Decl. = -54d46'41".2, equinox J2000.0, which calls it a novalike "VY Scl"-type variable with V magnitude range 15.8-18.0).

Spectroscopy by E. Aydi et al. (ATel #13867) using the High Resolution Spectrograph (HRS) mounted on the 11m Southern African Large Telescope as part of the SALT Large Science Program on Transients shows a spectrum that resembles that of a classical nova, likely after optical peak. Also, R. Kaufman (Bright, VIC, Australia) reports a low-resolution spectrum obtained by him on 2020 Jul. 16.62 UT (with a Canon 800D camera + 200-mm-f.l. f/3.5 lens) indicates the object to be a "Fe II-type" classical nova.

According to ATel #13868 "the positional coincidence of the optical/gamma-ray transient with the previously known VY Scl-type cataclysmic variable (d = 2.7 kpc from Gaia DR2; Bailer-Jones et al. 2018) suggests that the transient is a Galactic nova, which was confirmed with SALT spectroscopy (ATel #13867). It is only the third time that a classical nova eruption is observed in a previously known white dwarf hosting binary after V407 Cyg (ATel #2487) and V392 Per (ATel #11590), which were also detected by Fermi-LAT."

According to Cbet 4812 "the following pre-discovery V magnitudes from all-sky video images taken by M. A. Phillips at the Edward Pigot Seismic Observatory, Coonabarabran, using a ZWO ASI178MC-COOL color CMOS camera and a 1.4-mm-f.l. f/1.8 fish-eye lens: July 6.81, [6.0; 7.79, [5.5; 8.78, 5.4; 11.76, 3.7; 12.8, 3.8; 13.83, 4.0; 14.8, 4.4; 15.8, 4.7.  No variability was seen on single nights.  Further CCD magnitudes reported by McNaught from his images:  June 30.727, [9.8; July 1.763, [9.9; 2.826, [8.8; 15.747, 5.1; 15.785, 5.1; 15.804, 5.1. 

P. Schmeer, Bischmisheim, Germany, reports the following g magnitudes for the nova from the ASAS-SN Sky Patrol:  July 2.183, 16.6; 2.186, 16.3; 4.189, 15.5; 8.173, 6.8.  Schmeer adds that no previous outbursts or eruptions were recorded in ASAS-SN patrol images since 2014 June 18."

Below our confirmation image. Click on the image for a bigger version: 

An animation showing a comparison between my image and the archive POSS2/UKSTU Red plate (1993-12-17). 

by  Ernesto Guido, Marco Rocchetto & Adriano Valvasori

V659 SCUTI = NOVA SCUTI 2019

Following the posting on the Central Bureau's Transient Object Confirmation Page about a possible Nova in Scutum (TOCP Designation: PNV J18395972-1025415) I performed some follow-up of this object through a TEL 0.6-m f/6.5 astrograph + CCD located in the El Sauce Observatory in Chile and operated by Telescope Live network.  

On images taken on October 31.01, 2019 I can confirm the presence of an optical counterpart with R-filtered CCD magnitude about +8.4 (saturated in a 10-second exposure) at coordinates:

R.A. = 18 39 59.71, Decl.= -10 25 41.9

(equinox 2000.0; Gaia DR2 catalogue reference stars for the astrometry).

This transient was discovered (discovered magnitude 11.5 g-Sloan Filter) by the All-Sky Automated Survey for Supernovae (ASAS-SN) on 2019 Oct. 29 at 01:12UT and reported to Transient Name Server (TNS) on Oct. 29 at 02:07:49 UTC as ASASSN-19aad = AT 2019tpb. According to CBET 4690, several independents discoveries have been reported to the Central Bureau of a nova in Scutum: Koichi Nishiyama (unfiltered magnitude 9.4 on Oct. 29.397), Hideo Nishimura (unfiltered magnitude 9.8 on Oct. 29.421), Shizuo Kaneko (unfiltered magnitude 9.8 on Oct. 29.462) (on AAVSO VSX is reported also Fujio Kabashima as independent discoverer). 

Spectroscopy by S. C. Williams et al. (see ATel #13241) & by  M. Pavana et al. (see ATel #13245) show that AT 2019tpb/ASASSN-19aad is a Galactic nova in the early stages of eruption.

N. Samus writes that the permanent GCVS designation V659 Sct has been assigned to this nova.

Below my confirmation image (sum of two unfiltered 30-sec exposure through a 0.6-m f/6.5 astrograph + CCD; El Sauce Observatory, Chile). Click on the image for a bigger version: 

An animation showing a comparison between my image and the archive POSS1 Blue plate (1951-07-30).

Below the same animation with a larger field of view. At the bottom left of V659 Sct you will notice a star occupying a different position in the new image with respect to the 1951 archive image. This star (Gaia designation DR2 4155146598548456064) is a high proper  motion star. Most stars are so distant that their apparent motion even over hundreds of years is all but negligible to naked eye observers. Some stars have very significant movements compared to the background stars (Click on it for a bigger version:

Below an image that is the difference between the new image and the archive image useful to highlight the "new" objects. There you can easily see the new galactic nova V659 Sct and the  high proper motion star.

by Ernesto Guido

Bright Transient in Carina

Following the posting on the ATel #11454 about the discovery by All Sky Automated Survey for SuperNovae survey (ASAS-SN) of a new transient source, possibly a classical nova, near the Galactic plane in Carina (ASAS-SN Designation: ASASSN-18fv) I performed some follow-up of this object through a 0.43-m f/6.8 astrograph + CCD from MPC Code Q62 (iTelescope Observatory, Siding Spring).

On images taken on March 23.4, 2018 I can confirm the presence of an optical counterpart with R-filtered CCD magnitude +5.7 at coordinates:

R.A. = 10 36 15.42, Decl.= -59 35 53.7

(equinox 2000.0; UCAC-4 catalogue reference stars).

Below you can see my confirmation image (single 20-sec exposure through a 0.43-m f/6.8 astrograph + CCD), click on it for a bigger version:

While below you can see a wide-field color image (90 second exposures) I obtained on March 23.4, 2018 through a Takahashi SKY90 Apochromatic Refractor f5/6 + Color CCD. In the image ASASSN-18fv is visible at the centre of the field together with part of the Carina Nebula (click on it for a bigger version):

This transient was discovered using data from the quadruple 14-cm "Cassius" telescope in CTIO, Chile of ASAS-SN survey on images obtained on UT 2018-03-20.32 at V<10 2018-03-16.32="" also="" asas-sn="" asassn-18fv="" at="" detected="" detection="" no="" on="" possibly="" saturated="" starting="" ut="" v="">17.0) of this object in subtracted images taken on UT 2018-03-15.34 and before by the same survey. No previous outbursts or variability are detected at the position of ASASSN-18fv since ASAS-SN started observing this location in February 2016. 

According to Atel #11467 pre-discovery images have been identified on images obtained by Evryscope-South, an array of 6-cm telescopes continuously monitoring 8000 square degrees of sky at 2-minute cadence from CTIO, Chile. The transient is not detected at UT 2018-03-16.0316 with an upper-limit of 11.9 +/- 0.1 mag (g'). Beginning at UT 2018-03-16.227, they detected a new source at 10.21 +/- 0.05 mag (g'). (click on the images below for a bigger version).

Credit: Evryscope

Credit: Evryscope

An animation showing a comparison between my confirmation image and the archive POSS2/UKSTU Red plate (1991-02-10). Click on it for a bigger version:

Spectroscopy by  P. Luckas (see ATel #11460) seems to indicate that ASASSN-18fv is a classical nova brightening and in the optically thick (Fe curtain) phase. 

But according to L. Izzo et al. (ATel #11468): "The lack of a strong blue continuum, that is however typical of classical nova outburst, and the low expansion velocities suggest a possible different nature for this object. The presence of many narrow absorptions also suggests a similarity with other peculiar explosions, like the luminous red variable V4332 Sgr (Martini et al. 1999), the possible luminous red novae V838 Mon and V1309 Sco (Tylenda et al. 2011, Mason et al. 2010) or the 'helium-flash' explosion observed in the Sakurai object (Duerbeck and Benetti 1996)". Doubts about the nova nature of this object were expressed also by J. Strader et al. (ATel #11456)

So further spectroscopic observations are important to clarify the nature of this very interesting transient.

by Ernesto Guido