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 reported the Hα emission, derived from a wide-field photometric survey of the Small Magellanic Cloud (Maravelias et al. 2017, IAUS 329, 373; Maravelias et al. 2019, in prep.), of the proposed optical counterpart source [M2002] 20671 to the X-ray transient XTE J0052-723 pulsar (SXP 4.78; Swift J005139.2-721704; ATel #12209). In addition to this clear detection, the work of Bonanos et al. (2010, AJ, 140, 416) showed that the IR colors of this source ([2dFS]0811; J=15.54 mag, J-[3.6]=0.56 mag) are indicative of a “photometric” Be star, defined as sources with an intrinsic color of JIRSF-[3.6]>0.5 mag.

However, to confirm the nature of the counterpart optical spectroscopy is needed. We obtained optical spectra using the LDSS-3 spectrograph on the 6.5m Clay/Magellan telescope (Las Campanas Observatory). The observations were performed on Nov. 20, 2018, acquiring two exposures of 600s each with a 1″ slit using the VPH-All grism (resulting in a 2630 — 10859 Å wavelength range, at a nominal dispersion of 1.9 Å/pix). The spectrum shows a clear single-peaked Hα line in emission, with a corresponding equivalent width of -10.65±0.14 Å. This is the first optical spectroscopic confirmation of the presence of Hα in emission. We note that Hβ appears in emission as well.

The spectral classification was based on the blue part of the spectrum and the classification scheme used in Maravelias et al. (2014, MNRAS, 438, 2005). The presence of the OII+CIII 4640-4650 blend and the strong HeI 4471 line point to an early-type star (spectral type up to B2), which is consistent with the absence of the MgII 4481 line and the weak SiII 4552 triplet line. The HeII 4200 and 4686 lines, which are indicative of B0.5 and earlier-spectral types, are absent, thus pointing to later types.

Combining these criteria we constrain the optical classification to a B1-2e source (with an error of 0.5 subtype). This is consistent with the early-type B star classification proposed in ATel #12229, as well as the previous classification of B0-B3 by Evans et al. (2004, MNRAS, 351, 601; source ID [2dFS]0811).

Thus, we provide the first optical spectrum with Hα emission of the optical counterpart of XTE J0052-723, further confirming its Be/X-ray binary nature.

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), F. Haberl (MPE)

on 17 Nov 2018; 19:01 UT /

ATel #12209 reported the detection of a new X-ray transient in the Small Magellanic Cloud (SMC), Swift J005139.2-721704, exhibiting outbursting activity. The system has been classified as a new SMC high-mass X-ray binary based on its identification with the B-type star [M2002]20671. NICER followed up this source immediately (ATel #12219), reporting an absorption-corrected luminosity of LX ~7×1037erg s-1 (0.5-8 keV; 60 kpc). Temporal analysis of NICER and Fermi/GBM observations (ATel #12222) identified Swift J005139.2-721704 with the known X-ray pulsar XTE J0052-723 (SXP 4.78). Evans et al. (2004, MNRAS, 353, 601) obtained a refined B0-3(III) spectral type for [M2002]20671 (= [2dFS]0811) based on optical spectroscopy, but they do not report Hα emission.

Here, we report the identification of the SMC star [M2002]20671, and thus XTE J0052-723, with an Hα emitting source, which confirms XTE J0052-723 as a Be/X-ray binary (Be-XRB) pulsar in the SMC. This source is identified in Hα and R-band observations covering the SMC almost completely (Maravelias et al. 2017, IAUS 329, 373) using the Wide Field Imager on the 2.2m MPG/ESO telescope at La Silla (16/17 November 2011) and the MOSAIC-II camera on the 4m Blanco telescope at Cerro Tololo (15/16 December 2011).

The Hα emitting source is found at RA=00:51:38.78 and DEC=-72:17:04.7 (better than 0.2″ relative astrometry with respect to the 2MASS catalog). It is located 2.2″ away from the Swift position (ATel #12209), with Hα and R-band magnitudes equal to 15.476±0.006 and 15.613±0.008, respectively. The resulting Hα-R color is -0.137±0.010 mag with an SNR~13 above the continuum and an Hα excess significance of ~6σ above the Hα-R baseline value. The only nearby source with significant Hα-R excess is much fainter (Hα and R ~22 mag), has a lower SNR (~4) and is located at a larger distance from the X-ray source (~6″).

Observations with the IMACS f/2 camera on the 6.5m Magellan Telescope (4 October 2004) give B=15.652±0.009 mag and I=15.524±0.017 mag (Strantzalis et al. 2018, IAUS 344, 453; Strantzalis et al. 2019, in prep.), compatible with an OB star.

All the identifications described above secure the nature of Swift J005139.2-721704 = XTE J0052-723 = SXP 4.78 as Be-XRB pulsar in the SMC.

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 to Astronomy”

G. Maravelias, E. Vourliotis, K. Marouda, I. Belias, E. Kardasis, P. Papadeas, J. D. Strikis, E. Vakalopoulos, O. Voutyras

One of the most regular activities of amateur clubs is scientific outreach, a paramount chan-
nel to disseminate scientific results. It is typically performed through talks given by both ex-
perts (professional astronomers) and non-experts to a diverse audience, including amateur as-
tronomers. However, this is a rather passive, one-way, approach. The advance of technology
has provided all the tools that can help the audience/amateurs to become more active in the
scientific output. What is often missing is the proper guidance. To address that within the
Greek amateur community the Hellenic Amateur Astronomy Association materialized a train-
ing program (free-of-charge and open-accessed) to develop scientific thought and the practical
capabilities for amateurs to produce valuable results. The program ran from November 2014 to
May 2015 focusing each session (month) to: the Sun, variable stars, comets, planets, artificial
satellites, meteors. A professional and/or an experienced amateur astronomer was leading each
session consisting of a theoretical part (highlights of the field, necessary observational tech-
niques) and a hands-on part (observations and data analysis). At least 50 unique participants
gained significant experience by following parts or the complete program.

arXiv: 1810.04562

2. A talk at the meeting of Division G: Stars and Stellar Physics (August 24 and 27, 2018)

“Rings around B[e] Supergiants”

G. Maravelias, M. Kraus, L. Cidale, M. Borges Fernandes, M. L. Arias, A. F. Torres

Massive stars affect strongly the insterstellar medium through their intense stellar winds and their rich chemically processed material as they evolve. In specific short-lived transition phases (e.g. B[e] Supergiants, Luminous Blue Variables, Yellow Hypergiants) the mass-loss becomes more enhanced and usually eruptive. This leads to the formation of a complex circumstellar environment, which is not always well understood. To improve our knowledge on these phases we examined the structures found around the B[e] supergiants for a sample of Galactic and Magellanic Cloud sources. Using high-resolution optical and near-infrared spectra, we examine a set of key emission features ([OI], [CaII], CO bandheads) to trace their physical conditions and kinematics in their formation regions. Assuming Keplerian rotation of the circumstellar material we find that each B[e] Supergiant is surrounded by a unique distribution of single and/or multiple equatorial rings. Moroever, we find that these structures seem to be more stable and long-lived around single stars rather than binaries that show significant spectroscopic and photometric variability.

3. A poster at the IAU Symposium 346 on High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact objects (August 27 – 31, 2018)

Clarifying the population of HMXBs in the Small Magellanic Cloud

G. Maravelias, A. Zezas, V. Antoniou, D. Hatzidimitriou, F. Haberl

Almost all confirmed optical counterparts of HMXBs in the SMC are OB stars with equatorial decretion disks (OBe). These sources emit strongly in Balmer lines and standout when imaged through narrow-band Hα imaging. The lack of secure counterparts for a significant fraction of the HMXBs motivated us to search for more. Using the catalogs for OB/OBe stars (Maravelias et al. 2017) and for HMXBs (Haberl & Sturm 2016) we detect 70 optical counterparts (out of 104 covered by our survey). We provide the first identification of the optical counterpart to the source XTEJ0050-731. We verify that 17 previously uncertain optical counterparts are indeed the proper matches. Regarding 52 confirmed HMXBs (known optical counterparts with Hα emission), we detect 39 as OBe and another 13 as OB stars. This allows a direct estimation of the fraction of active OBe stars in HMXBs that show Hα emission at a given epoch to be at least ∼ 75% of their total HMXB population.

arXiv: 1811.10933

And a short note:
I had opted to present the poster works as e-posters, i.e. displayed as an electronic pdf/presentation on interactive monitors which would be placed at each poster halls. The motivation behind this was the fact that the posters could be uploaded before the official start of each session and be available over the whole (two-week) period. But there were some issues:
1. There were only two monitors at each hall, so if somebody else was talking over their poster you had to wait… and wait… and wait… It happened to me that I wanted to show my poster to a colleague but some other people were in front of the monitor for such a long time that it became obvious that it would be easier finally to show it through my laptop.
2. It was not finally that appealing to use as somebody would have to go and see the list of all posters and select each poster to see in detail. In other words you couldn’t browser the posters like what you do when you walk around in the poster session. It would have been much nicer to have the posters rolling somehow randomly in the monitors and continuously to widen their visibility.
3. Interactive it might have been but it was not easy to navigate (e.g. change the session and see another than the active one at that time), while in many cases there were a few bugs (zooming in that resulted in hiding some presentations, or crashing during the slide change).

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 the second day of the Division Days where I had a talk (in Division G) on the B[e] Supergiants (see for more the post on my contributions to this GA).

Apart from the scientific part there were again a lot of people (with an important percentage being different from the first week) going around the exhibition and the various happenings. One of them was of course the General Assembly itself.

The booth of Officina Stellare.

Display of a telescope system from PlaneWave Instruments.

The booths of ESA, ESO, and of the IAU’s Office of Astronomy for Development (2nd week).

Exhibition “boxes” for the 100 years of the IAU.

Before any official discussion engagement at the General Assembly, there was a musical performance:

One of the key issues to discuss in this assembly was the suggestion to rename the Hubble law to Hubble-Lemaitre law. There was actually a lively discussion with arguments from both sides. An indicative voting was made but the final decision will be based on a more detailed poll sent to all members of the IAU.

Although not formally decided, the revised Hubble-Lemaitre law was presented.

Presenting the resolution for renaming the Hubble law to Hubble-Lemaitre law (during the IAU GA 2018, in Viena)

The, indicative, voting process for the Hubble-Lemaitre law.

Then, the assembly proceed with more bureaucratic issues (among which was also the approval of new members, such myself!). Last but not least, there was the announcement for the organizer of the IAU GA of 2024 (as for 2021 is Korea) which is South Africa (after a strong competition with Mexico). The GA resolved with some folklore dance and music.

Another voting process during the IAU General Assembly of 2018.

At the very end of the GA, kids and adults (mainly from the IAU’s Office of Astronomy for Development) were playing with this giant Earth-like balloon.

The final day ended a bit earlier than others allowing us a bit more more time to relax. After all it was almost two weeks of many conferences and meetings in parallel that had developed considerable tiredness. I was more than happy to return home the next day and rest a bit more over the weekend, and enjoy some of the promotional stuff (see below!).

A small collection of various promotional stuff (pins, stickers, etc) and my badge from the IAU GA 2018 (and I have actually forgotten to put some more…!).

Various stuff from the IAU GA. I actually won this t-shirt at the lottery of the Korean booth (!).

Dinner time during IAU2018

Conferences feed the brain … but the body needs fuel too! Enjoying some local Viennese cuisine and wine.

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 all parties with a strong interest in open processes including other areas beyond just the software, such as hardware, society, economy, etc. Starting in 2008, it has been organized in 6 different cities so far (but not in Heraklion!), gathering a few hundred participants each time.

With such a diverse and different audience we (myself, Antonis Manousakis, and Eva Ntormousi) thought that it would be a great opportunity to present our (relatively biased) collected experience of these processed and applications from the modern research in Astronomy. So the title and the corresponding abstract was:

“Examples of openess in Astronomy”

Grigoris Maravelias, Antonis Manousakis, Eva Ntormousi

Traditionally Astronomy is a collaborative science in the sense that many researchers collaborate to observe a phenomenon, and they share their observations for further analysis and interpretation. Building upon this tradition many observatories today make available their observations so that modern astronomers have access to large datasets. Additionally, the technological advance of the instruments allows the observation of the Universe almost at the entire electromagnetic spectrum, even at the very recently confirmed gravitational waves. Thus, the modern astronomers are not only required to understand the Astrophysics behind these huge datasets but often they are called to develop the own necessary tools to conduct their research. Given the knowledge and the vast volume of data available today the collaborations are, more than ever, vital (especially with the forthcoming large projects that are currently built, e.g. 30m telescopes). In the framework of modern Astronomy we are going to present successful examples of how open approach has been applied.

While presenting openess in Astronomy, during the Free and Open Source Software Community Meeting of 2018 in Heraklion, Greece.

While presenting openess in Astronomy, during the Free and Open Source Software Community Meeting of 2018 in Heraklion, Greece. [Copyright 2018 Pierros Papadeas, CC BY-SA-NC]

Openess in Astronomy v1.0 (FOSSCOMM talk in pdf, in Greek)

This particular talk is released under the CC-BY-SA license, so we are going to provide all necessary material along with the presentation. Although in Greek, most probably an english version will become also available in the future.


UPDATE 2019/06/24:
– After some time  I managed to put all the material of this talk under a github repository: This will the place where I will put everything related with this subject in an effort to promote more Openness in Astronomy. Although this talk is actually in Greek, I will updated with an English version also.

– The video from the talk itself (in Greek though…) is available now here:


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 cm-3 for sources S 18, S 12, S 134, and R 126, respectively. Having calculated a maximum disk radius of 300R*, they calculate a mean density of few 109 cm-3. These values are consistent with both estimates from IR emission and by McGregor et al. (1988), who independently found densities of about 109 cm-3 from the CO first overtone emission in S 12, S 134, and R 66.

Kick-off meeting at a new position!

Posted September 10, 2018 By grigoris

Today it was my first day at the new job! It will be based at the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS) of the National Observatory of Athens (Greece).

I will be working with Alceste Bonanos, along with Ming Yang and Frank Tramper, in a project related to the “Episodic Mass Loss in Massive Stars: Key to Understanding the Explosive Early Universe” (ASSESS).

Although excited I am too tired to write something more now. But more will come in the future!

XXXth General Assembly of IAU – week 1

Posted August 26, 2018 By grigoris

The XXXth General Assembly of the IAU is held in Vienna, Austria, from Aug 20 to 31, 2018. The first week is finished now and tomorrow the second starts.

It is the biggest convention I have been so far with almost 3000 attendees, from all around the world literally. If I was to use only one world to describe it, ti would be “HUGE”! The Vienna International Center is great as it is neally easy to navigate and it can accommodate such an event. It is also very interesting and definitely uncommon to see exhibitors in astronomical conferences. You can find a large variety of booths from publishers, telescope/instrument companies, universities/telescopes/institutions advertising their projects, societies promoting their work, ESO and ESA, and an exhibition dedicated to the 100th anniversary of IAU. To all of these add the promotional stuff and gifts (from stickers to t-shirts and bags) and you get a rather different atmosphere sometimes.

A perspective of the exhibition.

A perspective of the exhibition.

The supernova - part of the 100th anniversary of the IAU.

The supernova – part of the 100th anniversary of the IAU.

LEGO models of some telescope facilities - part of the 100th anniversary of the IAU.

LEGO models of some telescope facilities – part of the 100th anniversary of the IAU.

Of course the main core is the various symposia and meetings. I came in Vienna on Tuesday (Aug 22) so as to take a look at the session on circumstellar environment around AGB stars (IAU Symposium 343: Why Galaxies Care About AGB Stars: A Continuing Challenge through Cosmic Time). Then, in the afternoon I went to the reception of the Focus Meeting 14: IAU’s role on global astronomy outreach, the latest challenges and bridging different communities, which was held at the Natural History Museum of Vienna. That was finally an amazing experience. Apart from getting to know fellow participants we got a free tour around the museum by its director. The museum exhibits an overwhelming collection, which represents only a small fraction of its collection (which is stored under the floors that are open to the public, and is accessible only to its scientists). On the next day (Thursday) the meeting took place, where I had an eposter representing the collective work we have done with the Hellenic Amateur Astronomy Association.

Then on Friday the Division G (Stars and Stellar Physics) Days, started, which I followed as much as possible, although I did tried to listen to other talks (the University of Vienna provided a very useful app to check the program and create your own agenda to easily follow whatever interests you most).

Another interesting week in starting tomorrow. I have a talk at the Division G Days and a poster contribution at the IAU Symposium 346: High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact objects.

A fascinating comparison of what we knew in 1919 and in 2019 - Part of the 100th anniversary of the IAU.

A fascinating comparison of what we knew in 1919 and in 2019. It is amazing how our knowledge has advances. (Part of the 100th anniversary of the IAU.)

For a certain project I had created a number of photometric catalogs, each one corresponding to a specific observing field. I would like to construct the final (merged) one but for this I needed to add a unique source identifier at the beginning of each row. I decided to create a F#-**** tag for each source with “F#” corresponding to the field id and **** to a counter for each source per field. The final command was:

for i in {1,2,4,5,6,7,8,9,10,11,12,13,16};do echo F$;awk -v id="$i" 'FNR>1 {print "F"id"-"1+c++, $0}' F$ >> results.tmp; done

So the command reads all the specific numbers for which a catalog with a filename of F* exists. The number of each field ($i) is parsed as an external variable (id) to awk which places it as the unique identifier “Fid-counter” with the incremental “counter” (1+c++) corresponding actually to the number of row (1+counter to begin from 1 instead of 0 – FNR avoids the first line of each catalog which is a column description). All results are written appended to the output file results.tmp (created automatically when non-existing).

Then, we can use sed to add the header:

sed -i '1i\#SourceID ...' results.tmp

An amazing drawing of Saturn

Posted August 2, 2018 By grigoris

In the era of imaging even from our cell phones making a drawing of a planet seems redundant. However, this is certainly a different perspective of a direct experience at the eyepiece of a telescope. And the final result can be fascinating, such as this drawing from Paul G. Abel, using the Clark telescope (a 24″ refractor) at Lowell observatory.

A drawing of Saturn using the 24" Clark refractor at Lowell observatory (Paul G. Abel).

A drawing of Saturn using the 24″ Clark refractor at Lowell observatory (Paul G. Abel).

Source: ALPO-Japan