Archive for the ‘VStar’ Category

« Older Entries

VStar Citations and other References

August 14, 2022

The purpose of this post to maintain a list of publications and other direct references to VStar.

At the time of writing, 23 papers in the following journals cite the use of VStar:

  • The Journal of the American Association of Variable Star Observers
  • Research Notes of the American Astronomical Society
  • Publications of the Astronomical Society of Australia
  • Open European Journal on Variable stars
  • Acta Astronomica
  • arXiv (open-access archive)

The 2012 Algorithms + Observations = VStar” JAAVSO paper is currently the suggested way to cite use of VStar (as per the main AAVSO VStar page), although a CFF citation entry on GitHub or software publication DOI may be recommended as an alternative in future.

In the videos section, John Percy is author of the 2007 text book, Understanding Variable Stars.

Web

Publications

Videos

Posted in VStar | Leave a Comment »

Making sense of variable star observations

February 23, 2022

I recently gave a talk via ASSA@Home about making the connection between variable star observations (from the AAVSO International Database and Kepler mission) with the processes in the star systems themselves.

I gave examples of pulsating variables (Chi Cyg, RS Pup, RR Lyr, T Umi), an Algol type eclipsing binary (ASAS J035812+1629.7), the enigmatic luminous blue variable eta Car, and the recurrent nova RS Oph, showed videos linking light curves with stellar processes, inspected time series observations, created phase plots and carried out analyses such as period search and time-frequency analysis using VStar.

While not as polished and more ad hoc and exploratory than last year’s RS Oph recurrent nova eruption talk for ASSA, it was fun and seemed to be appreciated, despite less than best audio and video at times. It’s also not easy watching yourself give a talk. 🙂

Posted in Astronomy, Variable Stars, VStar | Leave a Comment »

Nova Ret 2020 Update #2

July 24, 2020

As of July 24 2020, there are more than 100 Nova Ret 2020 observations, most visual, with a handful of CCD submissions. Mine (visual) are shown in purple.

Most observers are from Brazil (10), then Bolivia and Australia (5 each), with one from Italy and South Africa.

The southerly declination of the target and comparison stars in Reticulum (almost -55o degrees) makes northern hemisphere observations difficult.

A linear fit shows an overall decline of around 0.17 magnitudes per day, but there’s a lot of spread in the data and novae are unpredictable.

Posted in Astronomy, Variable Stars, VStar | Leave a Comment »

AAVSO Merit Award

November 9, 2019

I was humbled recently to be a recipient of the 2019 Merit Award from the American Association of Variable Star Observers (AAVSO), having previously received The Director’s Award in 2011 and the Bill Bradfield Award from ASSA in 2012.

IMG_4406

fdf8d7ca-b612-4850-964d-671d55a5cc4f

Receiving the Merit Award at Melbourne University from AAVSO Director, Stella Kafka, Dec 10 2019

Patrick Wills also received the AAVSO Merit Award this year for his work on the AAVSO Variable Star Index, a database that VStar also uses, including the web services Patrick has created.

Posted in Astronomy, Variable Stars, VStar | Leave a Comment »

500 visual variable star observations

June 11, 2019

Last night’s binocular observation of eta Carinae was my 500th visual observation submission to the AAVSO International Database (AID).

eta Car BDJB 2019

An extremely modest number really, compared with other observers over a similar timeframe.

But still, somehow a nice milestone.

500th

I’ve also submitted more than 100 DSLR photometry observations to AID. Again, not many in comparative terms.

eta Car LC BV

The light curve shows the last ten years of visual and B band data along with the 169 (in purple) visual and DSLR eta Carinae observations I’ve made during that time. The red trend line shows the steady rise in eta Carinae’s brightness that has been going on for decades now.

Between VStar, work, and life in general, I don’t get a lot of time to observe these days, but I try to make each observation count.

For anyone following Strange Quarks, you will have noticed my preoccupation with other things in recent months.

Indeed, my last variable star blog post was regarding a southern nova  in March 2018.

This pre-occupation is taking its toll in various ways on me and those around me.

Posted in Astronomy, Life Musings, Science, Variable Stars, VStar | 2 Comments »

Nova Carina 2018 update #2

March 27, 2018

Shortly after my last post I observed the nova again. Within 24 hours it has dropped by a full magnitude after peaking at 5.7, a little higher than my binocular estimate of 5.8 from last night.

My two observations are in purple, as usual, with the observation an hour ago under the cross-hairs.

ASASSN-18fv-2018-03-27

 

Posted in Astronomy, Science, Variable Stars, VStar | 2 Comments »

Nova Carina 2018 update

March 27, 2018

A “happy snap” (with iPhone) of the sky over my backyard rooftop, with Luna peeping through cloud. The nova’s location is behind me from this vantage point.

After being away for a week and a cloudy sky on Sunday, I caught my first glimpse of Nova Carinae 2018 (ASASSN-18fv) in 7×50 binoculars minutes before the sky started clouding out.

I estimated it to be 5.8 (purple, at top right) at just after 11pm Adelaide time.

Note also the upward trend-line.

I had hoped to subsequently image the nova to carry out DSLR photometry for better accuracy but that didn’t pan out due to cloud.

At the time of submission to AAVSO the last observation before mine was 6.5, several hours earlier. Since then, others have submitted observations up to 5.9. So, I appear to have caught Nova Car 2018 on the rise and at its peak so far.

Posted in Astronomy, Science, Variable Stars, VStar | Leave a Comment »

Nova Cir 2018

January 28, 2018

In my last post on January 20 about Nova Mus 2018, I said that another southern nova had been discovered, this one by John Seach in the early hours of January 19 in the constellation of Circinus, near alpha and beta Centauri. That post also showed a Stellarium context screenshot and pointed to an AAVSO finder chart.

This nova has slowly been on the rise for the last several days from around magnitude 8.5 to 6.3 by January 27.

The following 15 second DSLR images I took on Jan 22, 23, 26 and 27 show the nova brightening over time:

NovaCir2018Panels

If the images seem out of focus, that’s because they are. They were used for photometry rather than with the intention of being pretty; use of defocus is part of the procedure. See this talk I gave about DSLR photometry in 2015 for more detail. There’s some positional differences between frames, reflecting the difference in observation time from night to night.

The light curve below shows visual, Johnson V, and Tri-Color Green (DSLR) observations from January 19 to 28; mine are in purple. I’ve also submitted observations in blue and red bands.

NovaCir2018LCJan28

This light curve doesn’t appear to show a simple linear increase, so it will be interesting to see where the rise stops.

Rob Kaufman (discoverer of Nova Mus 2018) said that a low resolution spectrum he took on January 26 was essentially featureless.

The sky is largely clouded out tonight here in Adelaide at the end of a hot day (42° C), but I just caught a quick glimpse of the nova in 7×50 binoculars, but wasn’t able to check against comparison stars. It’s around the same magnitude as last night though. I’ll carry out more DSLR photometry as soon as I can.

In the meantime I have two more nights of Nova Mus 2018 (currently on the decline) DSLR images to process. I’ll write an update post for that nova too.

 

Posted in Astronomy, Science, Variable Stars, VStar | 1 Comment »

Nova near Southern Cross

January 15, 2018

Rob Kaufman in Victoria discovered a possible nova (PNV J11261220-6531086) near the Southern Cross (Crux) in the constellation of Musca on January 14 2018. All novae start out having the designation PNV or possible nova.

Rob’s discovery visual estimate was magnitude 7. I estimated it tonight with 7×50 binoculars at magnitude 6.7 relative to magnitude 6.4 and 7.1 comparison stars.

This context screenshot from Stellarium shows the nova’s location (cross-hairs at upper middle of image) relative to familiar stellar sign posts, including Crux and Alpha Muscae at 10pm Adelaide time (AEDT).
PNV J11261220-6531086 wide

The next shows a narrower field of view with the nova at right of the helpful triangular, A-shaped asterism.

PNV J11261220-6531086 narrow

Here’s a 10º finder chart from AAVSO
X22594EOand an 8º finder chart with the orientation closer to that of the sky around tonight’s observation time. The two comparison stars I used are circled in red.

X22594EI

After submitting my observation tonight to AAVSO I noticed that since Rob’s discovery observation, only two have been submitted other than mine:

  • another visual estimate by Sebastian Otero in Argentina (6.85);
  • and a tri-colour green DSLR observation (6.72) by David Blane in South Africa.

What I love about such transients, is their spectacular brightness rise and unpredictability.

Initial spectroscopy by Rob indicates a classical nova. I’d expect to see more amateur spectroscopy of this object in the near future.

Will it become visible to the naked eye like the similarly southern and close-to-Crux V1369 Cen did in 2013 (peaking at around magnitude 3.4)? One never knows with these things but it’s worth noting, as per the CBAT transient report page, ASAS-SN observations suggest the nova may actually have started in the first few days of January. If so, perhaps we’re a little too far down the track to expect naked eye visibility. All we can do is to observe it and see!

Being such a southerly object, it will not be as well observed as novae in the northern hemisphere, but it’s in a great location, so have a go if you can! I’ll be out every clear night observing it when I can in the days to come, visually and possibly via DSLR.

Posted in Astronomy, Science, Uncategorized, Variable Stars, VStar | Leave a Comment »

ASASSN-16ma declining?

November 11, 2016

Poor weather prevented any observations last night but tonight the sky cleared after a late afternoon storm and I estimated the nova at magnitude 6.3.

asassn-16manov11

So, it’s been gradually declining for 3 days, but whether that continues remains to be seen.

Posted in Astronomy, Science, Variable Stars, VStar | Leave a Comment »

« Older Entries