Strange Quarks

The astronomer’s telegram reported the discovery of a nova, V0419 Mus, in the constellation Musca on May 24 by K. Stanek of the All-Sky Automated Survey for Supernovae (ASAS-SN). Archival data showed the outburst started on May 10. AAVSO sent out an alert notice on May 29.

Last night was the first opportunity I’d had to attempt an observation. Although the sky conditions were far from ideal, between clouds I obtained enough data (19 cloud-free FITS files with Seestar S50) to carry out photometry.

The field containing V0419 Mus (aka Nova Mus 2026) and photometry in progress (nova in cross hairs and reference stars in green at top right) is shown above.

Another faint star in the field led to the need for careful photometry aperture sizing:

The result of photometry is shown in the plot below (under the cross hairs): a visual (Tri-Color Green) magnitude of 7.966 (with error 0.058). The visual (Johnson V) observation about 3.5 hours immediately before of 7.943 (with error 0.024) was submitted several hours after mine by an observer in Queensland, and the visual magnitude 8 (using eyeball + binoculars or telescope) was made about 4 hours later by an observer in Botswana.

There were only around 70 visual band observations as of around midday today, not surprising given the weather and the nova’s very southern declination, along with about the same number of observations in red and blue bands.

Nova light curves often appear quite non-descript and messy early on.

The following 1.2 degree finder chart needs to be rotated about 45 degrees clockwise to match the Seestar images above:

It’s a fairly sparse patch of sky.

The AAVSO Variable Star Index VSX record gives more detail about the nova including visual band magnitude range, currently 19 to 7.7. Novae often have pre-eruption magnitudes of 19 or dimmer.

We’ll see what happens next with V0419 Mus, whether it brightens again or continues to decline.

A couple of months ago I was asked to give an update at the July 2 2025 ASSA general meeting about T CrB, the binary star system that is anticipated to reach magnitude 2 or 3 when it goes into outburst as a recurrent nova (one of only 10 known), which it has done a few times before at roughly 80 year intervals.

In the meantime, we had two bright southern hemisphere novae (around magnitude 5) in June, so my T CrB talk turned into an update about 3 novae: T CrB, V462 Lup, and V572 Vel. The second and third were the subject of my last two posts.

My update was followed by a great talk about variable star photometry with the Seestar S50 by a former colleague, Andrew Murphy. The slides for his talk (and a course project) are here, as of 20 July 2025.

Here’s the PDF for the talk I gave, with thanks to Kym Thalassoudis for allowing me to include his images of V462 Lup and V572 Vel:

Here are the Powerpoint slides as well:

We may still be waiting for T CrB, but within less than a month we’ve seen 2 bright southern hemisphere novae: V462 Lup and now PNV J10251200-5331109 (aka V572 Vel)!

Technically it’s still classed as a possible nova (PNV) before spectroscopic confirmation, although there was a positive Gamma-ray Space Telescope observation overnight while I was sleeping.

Australian John Seach (NSW) discovered this (at magnitude 5.7), and Andrew Pearce (WA) independently found it (magnitude 5.5) on June 25 .

This object has eta Carina at its upper left in this Stellarium screenshot, and below it the “false cross” which consists of stars from Carina and Vela.

This smaller field of view provides more detail with 3 stars at the upper left of the false cross asterism (if the cross was standing upright) at bottom of the picture.

The observing campaign for PNV J10251200-5331109 (aka V0572 Vel) reports the progenitor star as likely being a 22.2 blue star with large amplitude variability.

The sky conditions were not great last night, but I estimated the nova candidate at 4.8 through 15×70 binoculars, through gaps in cloud with DSLR photometry pending.

Rotate this 20 degree FOV AAVSO finder chart 90 degrees right to get the false cross asterism in the same orientation as the screenshots above.

This 8 degree FOV finder chart provides the comparison stars of interest at the moment within a binocular field or two.

As I write this there have been less than 40 observations submitted to the AAVSO International Database.

After being away for a couple of days, I read an email yesterday from Andrew Wendelborn (ASSA) before seeing the official announcements, so thanks for the early heads-up Andrew! The timing worked out well in general.

A nova, now designated V462 Lup, was discovered on June 12 by the ASAS-SN survey at magnitude 8.7 and has since risen to around magnitude 5.5. It has apparently not yet peaked. The progenitor star is thought to have been around magnitude 22, and as with all novae, the rapid brightness increase over a few days is impressive (although not as rapid as some).

Lupus, and the nova, are high in the evening sky as shown in this Stellarium screenshot:

The orientation here is at around midnight on June 21 2025 but Lupus is visible from early evening. This Stellarium screenshot shows the region around the nova corresponding to the image at top.

With the help of this AAVSO finder chart I have made a few visual estimates and there is some DSLR photometry pending. The visual light curve as of the early hours of June 21 is shown below with two of my binocular visual estimates in purple, the last one just a few hours ago:

Meanwhile, T CrB is still quiet.