Archive for September, 2017

Extrapolating for the new post-doc position

Posted September 29, 2017 By grigoris

The idea of this post came to me on my second or third day in Chile when I noticed its flag on some boats. As today is my last day at work, perhaps it is the best (and last) opportunity to make a post about it. (So, practically it is either now or never.)

My previous post-doc position was at Ondrejov village, very close to Prague, Czech Republic. My current position is at Valparaiso of Chile. Now let us place their flags next to each other :

Czech Republic Chile

Taking into account the places also we (at least I) notice some similarities:
I. Both countries start with “C”: Czech Republic and Chile.
II. Each flag is split in three regions with the same colors, i.e. blue on the left, white on top and red at the bottom. [The small white star in Chile’s flag is not statistically important compared to the whole flag pattern.]
III. Both places are close to an UNESCO monument city, i.e. Prague and Valparaiso.
IV. There should be an appropriate workplace in Astronomy (e.g. the Astronomical Institute of the Czech Academy of Sciences, the Universidad de Valparaiso).

So, given that I have been to post-doc positions in places with those characteristics, then it is reasonable (what??!!??!) to extrapolate my future track. Let’s see where can I be next.

First, countries starting with “C”:
1. There is Cuba with a slightly different like flag, with alternate blue and white stripes. Havana is an UNESCO heritage city. But there are no job offers in Astronomy. So it is 2.712/4.000 criteria satisfied.

2. Next, there is Croatia, with a different style of flag, with stripes (from top to bottom: red, white, blue) and a big coat of arms. As far as UNESCO cities there is the famous city of Dubrovnik and Trogir, but again no Astronomical institute nearby (by the way I found this historic overview by Garaj 1999, ARSE Conf, 44). In this case we are at 2.187/4.000 criteria satisfied.

With these two countries we actually run out of “C” countries. Then we are left to explore similar flags among other countries.
3. Philippines has almost the same flag to Czech Republic but with only a slight color rearrangement between the triangle (white) and the top stripe (blue). [There is a small symbol within the white triangle but we consider that its significance is rather low compared to the importance of style and colors – similar to what we assumed for Chile’s flag.] There is the historic town of Vigan, but again no astronomical opportunities around this area. So approximately at 2.123/4.000 criteria satisfied.

And then we have practically run out of options, since all other flags have either similar styles but different colors (e.g. Jordan,Sudan), or they have the same colors but with total different styles, such as vertical (e.g. France, Thailand), horizontal stripes (e.g. Russia, Paraguay), and totally different patterns (e.g. USA, UK). So, even though we can find UNESCO cities and astronomical facilities in those countries, these score at most 2.111/4.000.

Thus, we (i.e. I) conclude that there is not an appropriate place (with a score more than 3.455/4.000) that I could continue as a post-doc based on my track so far. In lack of such an option I will have to move to Heraklion (Crete, Greece) up to further changes in the countries that will allow me to reconsider my options!

Proper acknowledgments

Posted September 22, 2017 By grigoris

From a friend with a similar interest in martial arts. He noticed the following acknowledgment (by Zeng & Sasselov 2013, PASP, 125, 227):

We acknowledge partial support for this work by NASA cooperative agreement NNX09AJ50A (Kepler Mission science team).
We would like to thank Michail Petaev and Stein Jacobsen for their valuable comments and suggestions. This research is supported by the National Nuclear Security Administration under the High Energy Density Laboratory Plasmas through DOE grant # DE-FG52-09NA29549 to S. B. Jacobsen (PI) with Harvard University. This research is the authors’ views and not those of the DOE.
Li Zeng would like to thank Professor Pingyuan Li, Li Zeng’s grandfather, in the Department of Mathematics at Chongqing University, for giving Li Zeng important spiritual support and guidance on research. The guidance includes research strategy and approach, methods of solving differential equations and other numeric methods, etc.
Li Zeng would also like to give special thanks to Master Anlin Wang. Master Wang is a Traditional Chinese Kung Fu Master and World Champion. He is also a practitioner and realizer of Traditional Chinese Philosophy of Tao Te Ching, which is the ancient oriental wisdom to study the relation between the universe, nature and humanity. Valuable inspirations were obtained through discussion of Tao Te Ching with Master Wang as well as Qigong cultivation with him.

Personally I find it amazing because it shows the human side of the researchers. Our work does not depend only on the funding scheme! We should be/feel free to credit appropriately what we think.
Plus, I personally sympathize the sentences of the last paragraph …

New paper on the circumstellar environment of MWC 137

Posted September 20, 2017 By grigoris

Resolving the circumstellar environment of the Galactic B[e] supergiant star MWC 137 from large to small scales

Michaela Kraus, Tiina Liimets, Cristina E. Cappa, Lydia S. Cidale, Dieter H. Nickeler, Nicolas U. Duronea, Maria L. Arias, Diah S. Gunawan, Mary E. Oksala, Marcelo Borges Fernandes, Grigoris Maravelias, Michel Cure, Miguel Santander-Garcia

The Galactic object MWC 137 was suggested to belong to the group of B[e] supergiants. However, with its large-scale optical bipolar ring nebula and the high velocity jet and knots, it is a rather atypical representative of this class. We performed multi-wavelength observations spreading from the optical to the radio regime. Based on optical imaging and long-slit spectroscopic data we found that the northern parts of the large-scale nebula are predominantly blue-shifted, while the southern regions appear mostly red-shifted. We developed a geometrical model consisting of two double-cones. While various observational features can be approximated with such a scenario, the observed velocity pattern is more complex. Using near-infrared integral-field unit spectroscopy we studied the hot molecular gas in the close vicinity of the star. The emission from the hot CO gas arises in a small-scale disk revolving around the star on Keplerian orbits. While the disk itself cannot be spatially resolved, its emission is reflected by dust arranged in arc-like structures and clumps surrounding MWC 137 on small scales. In the radio regime we mapped the cold molecular gas in the outskirts of the optical nebula. We found that large amounts of cool molecular gas and warm dust embrace the optical nebula in the east, south and west. No cold gas or dust were detected in the north and north-western regions. Despite the new insights on the nebula kinematics gained from our studies, the real formation scenario of the large-scale nebula remains an open issue.

2017, AJ, 154, 186 / NASA/ADS / 1709.06439

Tough days the last days

Posted September 18, 2017 By grigoris

A couple of hectic weeks finished on last Friday. After two trips to La Serena to observe from the magnificent facilities at CTIO and LCO (posts still pending since there is an overwhelming amount of photos and videos!), I had an intense week to finalize the paper I am preparing (for some looong time now).

At the same time and during the last week I had to prepare an invited review talk on “The circumstellar structures around B[e] supergiants” at the meeting “Massive Stars in Transition Phases” (Tôravere, Estonia, 11-15 Sep, 2017). I participated remotely that made me to get up at 4am each day, due to the time difference between Estonia and Chile (6 hours).

That alone wouldn’t have been so much of a problem if it wasn’t for a Marie Curie fellowship proposal, with a deadline on the same dates! Thankfully, I had most of all these ready to some extend, but still some fine (or more) tuning was needed.

Preparing for the remote talk: Three monitors, a laptop, and a desktop. Overkill? Possbile, but I split the different functions and it worked great.

After a few days of rest I am back to work, as I have only two and half weeks left before I leave Chile. And there are quite a few things to do …

Linking classical to dwarf novae

Posted September 1, 2017 By grigoris

In a recent Nature (Shara et al. 2017, Nature, 548, 558) letter, the authors found that a current dwarf nova is actually the Nova Scorpii AD 1437, recorded by Korean astronomers at that time.

What is interesting is that they managed to trace both the dwarf nova’s position and the center of the observed gas shell back to their positions in 1437. Adding the information derived from the Korean records (and that is interesting to read) they show that the Nova Scorpii 1437 is the source of the current shell and that the dwarf nova in the region was the Nova. This shows that a classical nova, whose eruptions are due to the fusion and explosion of hydrogen accreted around its surface, can display dwarf nova behavior, i.e. eruptions due to instabilities in the accretion disk, providing a link between the two types of novae.

An IFA-UV seminar talk

Posted September 1, 2017 By grigoris

Yesterday, I had finally the opportunity to give a seminar talk at the Instituto de Física y Astronomía de la Universidad de Valparaíso, where I am currently based (and only for about a month more …)

“What have we learned from observations of B[e] Supergiants ?”

B[e] Supergiants are a rare phase among the massive stars, displaying a complex circumstellar environment. However, they may provide an important link to other phases (e.g. the Yellow Hypergiants, the Luminous Blue Variables). Given the importance of massive stars for Stellar Astrophysics and their influence on their host galaxies it is critical to understand their evolution. Starting from an observational point of view, I will provide an overview of the B[e] Supergiants and discuss the latest results.