Astronomy Archive

Fixing GPG error “NO_PUBKEY”

Posted March 28, 2019 By grigoris

In Debian, Ubuntu and similar distros that use the APT (Advanced Package Tool – which is a set of tools for managing Debian packages / applications), to update the system you need to run: sudo apt update This will read all repositories (as they are listed in /etc/apt/sources.list and under /etc/apt/sources.list.d/) and checks if everything […]

Working with both Python 2 and 3 in jupyter

Posted January 16, 2019 By grigoris

I have followed the pip install approach to add everything that I wanted for Python. Even though I did the same for jupyter when I was starting it (“jupyter notebook”) it would only start the Python 2 kernel, although Python 3 “was there” but not active actually. After some digging I found that a similar […]

Installing Debian on Lenovo Thinkpad Carbon X-1 (Gen 6)

Posted December 17, 2018 By grigoris

It is exciting to have a new machine, such the Lenovo Thinkpad X-1, but the process for setting it up can be a bit tedious. So this is a small guide what worked or didn’t through my small experience in installing Debian linux. [Just for the fun of it I proceeded with the installation of […]

New paper on rho Cas and its recent outburst in 2013

Posted December 11, 2018 By grigoris

A new outburst of the yellow hypergiant star Rho Cas Michaela Kraus, Indrek Kolka, Anna Aret, Dieter H. Nickeler, Grigoris Maravelias, Tõnis Eenmäe, Alex Lobel, Valentina G. Klochkova Yellow hypergiants are evolved massive stars that were suggested to be in post-red supergiant stage. Post-red supergiants that evolve back to the blue, hot side of the […]

Building upon our previous ATel #12224 we managed to obtain an optical spectrum of the counterpart. The full text follows: ATel #12237; G. Maravelias (NOA), V. Antoniou (TTU/SAO), K. Boutsia (LCO), A. Zezas (UoC/SAO), A. Z. Bonanos (NOA), F. Haberl (MPE), D. Hatzidimitriou (UoA/NOA) on 21 Nov 2018; 23:36 UT / In ATel #12224 we […]

The ATel #12224 was released on 17 Nov 2018 (19:01 UT) regarding the identification of the proposed optical counterpart to the source XTE J0052-723 (SXP 4.78; Swift J005139.2-721704) as an Hα emitting OB star. The full text follows. ATel #12224; G. Maravelias (NOA), V. Antoniou (TTU/SAO), A. Zezas (UoC/SAO), A. Strantzalis (UoA), D. Hatzidimitriou (UoA), […]

Contributions to the XXXth General Assembly of IAU

Posted November 19, 2018 By grigoris

During the XXXth General Assembly of the International Astronomical Union (in Vienna, Austria) I participated in a number of different meetings. In particular: 1. A poster at the IAU Focus Meeting FM14 on IAU’s role on global astronomy outreach, the latest challenges and bridging different communities (August 23, 2018): “A paradigm to develop new contributors […]

XXXth General Assembly of IAU – week 2

Posted October 31, 2018 By grigoris

The second week of the XXXth GA started very early actually as they were actually 3 plenary talks of the IAU 346 Symposium on “High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact objects” (which actually deserves a post of its own, if I ever manage to make…). After that, we had […]

A FOSSCOMM talk on Openess in Astronomy

Posted October 22, 2018 By grigoris

On the previous weekend (October 13-14, 2018) the 11th Free and Open Source Software Communities Meeting was held in Heraklion of Crete (Greece). This is the Greek conference of the communities that develop free and open source software (such as Mozilla, Fegora, etc.). Although the meeting focuses on programmers and students it is open to […]

In Zickgraf et al. 1989 (A&A, 220, 206) there is a comment on the density of the disk around the supergiant LHA 115-S 18. In Table 1 they provide (following Waters 1986) the mean particle density at r=R* for a number of sources: 3.2 x 1012, 2.6 x 1012, 4.6 x 1012, 1.7 x 1012 […]