Dear bloggers,

Celia wrote a very nice article in Spanish about the 511 keV emission in the very famous daily

newspaper “El Pais”; you can find it here:

http://www.elpais.com/articulo/sociedad/misterio/positrones/galacticos/elpepusoc/

then, click on Nov. the 16, using this tag: 20091116elpepusoc_9/Tes

If you prefer English, there are also very nice related Press Releases in English there: 

http://www.sciops.esa.int/index.php?project=INTEGRAL&page=Press_Releases

Enjoy!

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By Marion Cadolle Bel

Being an INTEGRAL scientist does not only consist of dealing with the planning, the proposals, the long term plan, the sources and analysing the data (as if this was not enough!): we also have to organize in a coherent and consistent way the huge amount of data from the INTEGRAL instruments we receive almost in real-time and every day, thanks to several big antennae on ground…

Two archives co-exist, one in Geneva (http://isdcul3.unige.ch/?Data+browse) that directly receives the data from the sky and distributes them to the PI (=the lucky guy who submitted a proposal, got it accepted and has his favorite target observed) and the other one here at ESAC (http://integral.esac.esa.int/isda/), officially keeping track of everything, the whole set of data (from the launch!) necessary to re-do any analysis, providing useful data products, like the possibility to search any of the sources published in the last IBIS/ISGRI survey catalog (Bird et al. 2007, ApJS, 170, 175-186) by flux, hardness ratios, etc. and the retrieval of the corresponding light curves.

The gradual evolution of the Archive here at ESAC can be summarized as follows. The INTEGRAL Operations Centre (ISOC) first opened the ISOC Science Data Archive (ISDA) to external users as long ago as July 2005. Since then, the archive has been evolving continuously, with the aim of becoming “science orientated” as opposed to “data orientated”. Version 3 have been released this Summer. The ISDA was developed using the same browser technology as that developed by ESA for the XMM-Newton Science Archive (XSA) and the ISO Data Archive (IDA). Astronomers, who have accessed data via either of these archives, will find the ISDA familiar and easy to use. It offers an alternative and complementary method of accessing INTEGRAL data to the INTEGRAL Science Data Centre (ISDC) archive. In order to support multi-wavelength research, the ISDA now incorporates the capacity to search many other archives to identify data from counterparts for INTEGRAL sources. 

As well as the original browser interface, the current version of the ISDA has a scriptable interface (known as GAIO) on top of which ISDA VO interfaces are built, which allows the easy retrival of raw data and images. Data can be selected using simple search criteria such as source name and position. Data from entire observations of subsets of observations can be retrieved. The GAIO has been extensively used by ISOC for internal processing of INTEGRAL data using the ESAC grid. A valuable part of the ISDA is the INtegral VIsualization Tool and Explorer (INVITE), which has been available as part of the ISOC Science Data Archive (ISDA) since December 2006. It provides an easy and convenient method of manipulating light-curves from INTEGRAL and many other instruments. INVITE is a compact (1.5 Mbytes) programme written entirely in Java. The current version has been considerably enhanced compared to the first version. In particular, it now allows the generation of broad band spectra from lightcurves and for the retrieval of data from either the ISDA or the OMC archive maintained by LAEFF at ESAC.

Future enhancements of the ISDA are already underway. Version 4 is expected to contains a searchable bibliography, which will relate INTEGRAL related publications to sources and observations (which is, believe me, non trivial at all for a mission with so large instruments’ field of view). It will also uses the mass processing capacity provided by the GAIO and ESAC grid to allow on-the-fly processing of INTEGRAL images for and selected period of data.

By Marion Cadolle Bel

In between the usual duties already explained in a previous Post on this blog, I managed, last week, to work a few hours on one of my favourite sources: GRS 1915+105.

The characteristics…

This microquasar hosts a black hole around 14 solar masses, and, because of strong accretion from a huge disk of matter coming from the companion star, it is one of the brightest X-ray sources in the sky. It is also a source of superluminal ejections, and it has a true bulk velocity around 90% of the light speed! From these superluminal motions, an upper limit on the distance to GRS 1915+105 of 11.2 kpc (1parsec=3.08568025×10¹⁶ meters) could be derived, although a distance as low as 6 kpc cannot be excluded.

A small history… 

It is hard to tell you how many people have worked on this source, without  being able to understand the 10% of what this crazy microquasar is doing! GRS 1915+105 has been extensively observed with the Rossi X-ray Timing Explorer (RXTE) since 1996, and now with INTEGRAL through a regular monitoring campaign every 6 days. A rich pattern of variability has emerged from these data, with timescales from years down to 15 milliseconds, and the source been classified into ~12 separate classes based on the count rates (fluxes) and hardness characteristics (as in the famous HR diagram to classify the usual stars).

Multiwavelength observations, involving radio, IR, and X-ray telescopes, have shown a clear but complex association between soft X-rays and radio emission, including radio quasi-periodic oscillations in the range of 20-40 minutes that were associated with X-ray variations on the same timescale. These oscillations were ascribed to small ejections of material from the system and were found to correlate with the disk instability, as observed in the X-ray band. This was the first time the disk-jet relation could be studied in detail. This kind of cycle could also reflect some magnetic flood scenario in which reconnection events would allow the ejection of blobs of material, as one can see from the eruptions of our Sun. Recently, a possible correlation between the amplitude of the radio flare and the duration of the “non-activity” in X-rays (or dips) has been found. The X-ray dips prior to ejections could thus represent the time during which the source accumulates energy and material that is ejected later. These results do not rely on any spectral modelling, thus enhances their robustness. The ejected medium is then the coronal material responsible for the hard X-ray emission. There are also observations indicating that we might see direct emission from the jet at hard X-ray energies. 

The following figure shows the light curves of the source in distinct energy bands of the INTEGRAL instruments JEM-X and IBIS/ISGRI.

1915_7961

For more details, we refer to Jerome Rodriguez et al. 2008a, b available on ADS and ArXiv: 

http://adsabs.harvard.edu/abs/2008ApJ…675.1436R

http://adsabs.harvard.edu/abs/2008ApJ…675.1449R

and to all the references therein. I warmly thank Jerome for the figure of this blog, where GRS 1915+105 was observed to transit between 2 classes within hours, thanks to the fantastic data from the INTEGRAL instruments taken 1 week ago only!

My recent activities… 

This source is really crazy! In less than a day, an hour or even within seconds, the light curve can change from being as flat as The Netherlands to the chaotic and frenetic behaviour you can see on the Figure, with “spikes” and “dips”. The light curves can also be quite regular, with several peaks regularly separated, or with repeated dips with some spikes inside the dips, with always the same interval of separation… 

What I’m trying to do recently, not alone of course, but with many collaborators in Paris at APC, CEA-Saclay, and in Boston at MIT, is to try to find a cyclic behaviour of the source over 11 years of data! You can imagine how many data and observations with many instruments that imply we are all looking at (I will soon need glasses I’m afraid; who might have guessed that being an astronomer can be dangerous for your health?). But it is really worth doing it, as we have already found some interesting patterns that the source seems to repeat in a specific order over the years. This might imply that a more general phenomena is regulating its activity, for example linked to the magnetic flux trapped between the inner disc of accreted matter and the black hole, and the one coming from the continuous accreted matter from the companion star. However, this work is still in progress, so I will let you know when we will have an answer or, at least, an idea, of what could explain such a crazy behaviour… See you!

 …

by Marion Cadolle Bel

Our team is composed of very nice people: I hope this article will convince you that research in Astronomy is cool, and that you will visit us some day (in fact, if you read this article until the end, you will see a possibility of doing so)!

Let me present you the four of us: first, Erik Kuulkers, master of the Galactic Bulge region and fond of neutron stars. He is also doing the Long Term Plan of INTEGRAL that helps a lot our team to optimize the INTEGRAL observations of the sky. Many constraints need to be taken into account, among them: the visibility of the sources one wants to observe, the type of the accepted programs, some of which often need to be repeated on a specific region at a specific time in the year, every two orbits for example; other ones need to be done simultaneously with ground-based facilities and/or space missions. Erik also needs to include “free-time” in this plan to allow the observation of a new source suddenly flaring, that needs to be observed as soon as possible (this happens once in a month or so). Indeed, when I started working here, I remember coming early several Saturday AND Sunday mornings in a row (after nice parties or between two flamenco shows!) to re-plan the satellite observation sequence unlucky-because-working-on-week-end” operators at MOC in Germany (who are actually sending the final “orders” to the wheels of the satellite). But, dude, that is exciting, right? Our Universe is changing in front of our own eyes! 

Then, we have among us the very sportive Guillaume Belanger (with whom I like to train a lot during lunch time!), specialist of Sgr A* and the associated molecular clouds around the “supermassive” black hole of our Galaxy. He is also keen on doing super-cool java programs that allow us to process huge amounts of data on Grid systems, using many machines and resources at the same time. Thanks to him, we will soon have all the INTEGRAL data analysed in several energy bands for all the sky, from… 2003! Finally, we are with two women working here, in this -already quite- nice environment: Celia Sanchez-Fernandez and myself. Celia has many qualities, from the number of different languages she knows to her personal activities to help children born in under-developed countries. But most of all, she is crazy about soft X-ray transients and bursters (you know from her previous blog where she is right now for a week, at the very best place in the world to discuss these topics, and… pyramids: Egypt)! She is also a real expert to do ANY KIND of intelligent queries on our databases in less than two minutes! I will now come to the last person: me! Besides my interests in dancing and discovering the qualities of Spain, I am almost in love with Microquasars. Such systems harbour a black hole next to a normal star (like our Sun), and the powerful jets often emitted by such systems are crazy: tremendous quantities of very energetic photons, from X-rays to soft gamma-rays, can be released when the matter from the star is accreted onto the black hole. Studying them at different wavelengths give us access to distinct emissive zones of these systems, from the cooler outer parts to the inner hot regions (where intense friction takes place), before the matter finally disappears on the black hole… I am also responsible for the very big INTEGRAL Archive here in Madrid at ESAC (6 Terabytes of only “raw” data from the launch up to now have been taken, and much more will come!), where we provide nice and recent products like images, light-curves or spectra of all the gamma-ray sources (421) seen so far by INTEGRAL.

You might wonder: what do we do on a normal working day? 20% of our time is devoted to pure research. What does it mean? We use all the data we have or can find in the Archive from distinct observatories on our favourite stars, but it is true that we are using mainly the INTEGRAL and XMM-Newton data. We analyse these data with dedicated software, try to see what is our source doing, to understand its behaviour, for example through the variations in the number and energy of the photons received by the detectors. Then, we use models to constrain the accretion and ejection physics that occur in such systems. We can deduce, for example, the possible temperatures around a neutron star or a black hole, or coming from the accreted matter; we can calculate a radius or a mass for the compact object, or the associated matter/star which is orbiting around; we can even deduce a distance sometimes… But this needs time, patience, as processing can be quite long and can crash many times :-), and sometimes imagination: to find something, you sometimes need to dig where you think it could be visible!

Therefore, while this is processing, we are in fact mainly doing VERY important duties to make the satellite operate: from the TAC preparation for each AO (see previous blogs), calling for proposals, to the planning of the satellite movements, as well as taking care of the scientific community asking technical questions via our Helpdesk. We are also studying some statistics and simulations, like how the data are used, when a specific program will be finished, etc. We are updating the Archive contents, the documentation of the different instruments: indeed, they need regular calibrations, and this is done by several other teams in the world. In fact, our previous blog messages give nice examples of a day-to-day life in the INTEGRAL team, and I think that, in any scientific laboratory, it looks the same.

Now, I will come to my conclusions and tell you how you can become… an astro-star! We have just started a competition which may relieve Erik from part of the work he does on his project: you can be an INTEGRAL astronomer and analyse INTEGRAL data from the Galactic Bulge monitoring program, which reveals a variable gamma-ray sky, with many sources popping on and of like a Christmas tree, on time-scales ranging from milliseconds to seconds, and days to months, even years. There are some great prizes to be won, including a trip to visit us here at ESAC. The details will be soon available on the ESA International Year of Astronomy web site, astronomy2009.esa.int.

If you want to know more about us and our detailed research, you can consult our specific webpages here:

http://www.rssd.esa.int/index.php?project=ESACFACULTY&page=faculty_members

(then you can click on our names to see our research activities, I’m here for example!

http://www.rssd.esa.int/index.php?project=ESACFACULTY&page=personal_cadolle)

I hope to see you soon on this blog, or even for real in Madrid!

…

by Celia Sanchez Fernandez

Hi there,

Greetings from Egypt, where I travelled two days ago to attend the conference “Frontiers of Space Astrophysics: Neutron Stars & Gamma ray bursts 2009″. Astronomers from all over the world have joined here to present the most important results of their research in these types of objects. Not only that, but these scientific meetings allow people working on the same field to know each other and sent the basis for future collaborations. The meeting started yesterday, Monday 30^th March, and will last till Saturday, April 4^th. Very interesting results will be presented these days.

We are now having a break, and I will invest these minutes to talk to you about the meeting of the Time Allocation Committee (TAC) at ESAC, last week.

 As Erik explained some weeks ago, INTEGRAL is an observatory type mission. To observe with it, astronomers put forward their proposals, which are grouped by scientific categories, and evaluated by 3 panels of experts based on their scientific merit. The panels of experts are composed by people not working for ESA, to ensure that the process is as objective as possible. But we, the four ISOC scientists, take part in the panels as secretaries. We take notes of everything discussed during the meetings (it is all confidential!!!), record  the rate and grade given to each proposal (also if it is accepted or not), and advise the panel members when there is a doubt on the feasibility of a given proposal. The TAC meetings are usually very intense and exciting. There are so many interesting proposals, on so many interesting targets and fields of research requested by the astronomers, that it is difficult to decide which one will or will not be granted INTEGRAL observing time. So, the different panels spend hours trying to decide which ones are the best proposals: those that will provide the most interesting and sometimes unexpected, scientific results.

Following a full day of discussion between panel chairs, the final observing program to be recommended to ESA was agreed upon last week on Wednesday afternoon. It is still confidential, and it will not become public until it is approved by ESA’s General Director. Once this happens, all PIs who submitted proposals in response to this 7^th INTEGRAL Announcement of Opportunity will be contacted by the ISOC team, to inform them of whether their proposals were accepted or not. But this will happen in a couple of weeks, so in the meantime, I will enjoy the conference, where some interesting results based on INTEGRAL observations in previous AOs are also being presented.

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by Guillaume Belanger

Hi,

I was duty scientist this week again. And again, it is the end of the week, but this time it’s just because it was a 3-day work week for me. Anyway, I just wanted to share a mosaic I made this week of the Galactic Centre region, based on 2 years of data (AO-4 and AO-5) from the Key Programme (KP) on the Central Molecular Zone, and of which I am the principal investigator or PI for short.

It is a interesting way to present these data, where the images have been constructed in 3 energy bands: 20-35, 35-60, and 60-100 keV, which are then presented as 3 different colours: red, green, and blue. The intensity of each of the layers is scaled appropriately and superimposed. The sources that appear as almost pure red are present only in the lowest energy band: 20-35 keV; those that appear as yellowish-green have a comparable contribution both in the lowest and the middle energy band: 35-60 keV; and finally, the sources that appears as blueish-white, are bright up to the highest energies in the third band: 60-100 keV. The scaling is such that a source with a spectrum that follows a power-law of index -2, like the Crab, the standard candle in astronomy, will look white. Harder sources will look bluer, slightly softer sources will look yellowish-green, going towards the red as they get softer.

Typically, the red sources are much more likely to be neutron star bursters, and the very few blueish-white sources are black hole candidates, like the now-famous micro-quasars: 1E 1740-2942, very close to the Galactic nucleus Sgr A*, right in the centre of the mosaic; and GRS 1758-258, about 10 degrees to the right of the centre, and slightly below the Galactic plane.

Enjoy.

by Erik Kuulkers

Since INTEGRAL is an observatory type of mission, astronomers from all over the world can ask for their favorite stars or regions to be observed. Since the observing time asked is more than is available, this has to be done in a coordinated and well-regulated way. Basically every year, we announce the opportunity to send in observing proposals. The astronomers have to put forward their favorite stars (such as black holes, neutron stars, or active galatic nuclei - AGN) or regions (such as the Galactic Center region), and say why they want to observe them, how long, why they need INTEGRAL, and show that indeed INTEGRAL is best observatory to do it with.

This year the deadline for sending in proposals was February 20. The total number of proposals received was 76. The total observing time requested is about 1238.4 days (most space observatories do not work with observing time in days, but in seconds; 1238.4 days thus is about 107 megasec or Msec for short). Given that up to about 336 days of observing time are available for the observing programme (note that this does not correspond to the duration of the observation time period which wil last 14.5 months starting on 16 October 2009; this is because we can not observe the sky 24 hours a day), this corresponds to an oversubscription by a factor of about 3.7. This is a high value, showing the continued high interest of the astronomical community in INTEGRAL.

Within a couple of weeks a committee of wise man and women, called the Time Allocation Committee, or TAC for short, will evaluate the proposals on their scientific merit, grade them on how important the proposed science is, and how well it is written, and accept or reject them. Of the accepted ones, those with the highest grades have the highest chance of performed in the coming observing period. (Each observing period has a number; we are currently in the 6th observing period, also called AO-6; the current call for proposals is for the AO-7 cycle).

In the interim period, however, i.e., after the deadline for sending in proposals and before the TAC meeting, we at ISOC have to judge whether the proposals can indeed be performed by INTEGRAL. We do not judge the scientific merit, but we evaluate whether it makes sense to point INTEGRAL to the proposed target. We check whether the source can indeed be seen within the observing time asked for; we check if the instrument settings are ok, we check if the way they want the observing time to be used is efficient enough. This is a tedious task, but fortunately we divide the work among the four of us. Each of us have a special topic to cover. Guillaume evaluates the proposals which are geared towards extra-galactic objects such as galaxies or AGN, Marion and me, the so-called compact objects (those stars containing black holes and neutron stars), while Celia covers the proposals that relate to studies in nucleosynthesis, (mostly regions which emit gamma-ray lines), as well as all other targets that do not fall into these four categories. Every now and then, we come across proposals which may not be suitable for INTEGRAL (e.g., the time asked for is too much or the observing strategy does not match of what INTEGRAL is capable of), but most of the time the proposals are technically feasible, and scientifically well laid-out. Of course, a great advantage of doing these technical evaluations is that we learn to discern what constitutes a better proposal, and thus learn how to write them well.

We have almost completed our task. Today we have to be ready, and the results will be sent to the TAC on monday. Work isn’t fully over then, however, because we have to also prepare for the TAC meeting itself. All four of us have to follow the TAC deliberations as panel secretaries, and record everything that comes out of the discussions. We also have to help the TAC members on all (technical) matters concerning INTEGRAL. In a few weeks we will let you know how this meeting went.

Time flies, and it is now the end of the week, Friday afternoon. Time to enjoy the beautiful spring weather outside, time to start the weekend, and enjoy life outside work. This weekend, however, work comes with me in my pocket, because I am duty scientist for the week. This means that I have to carry the ISOC phone with me, and if anything unexpected happens, some kind of astrophysics emergency, so to speak, I can be called or reached by SMS. If that’s the case I have to stop whatever I’m doing and check out why outer space is disturbing my relaxing weekend…

by Guillaume Belanger

It is now Friday afternoon, and this week has flown by like every other week.

This week was slightly unusual in one respect, for there were 3 long meetings, which seem to have taken up the better part of 2 days, and this is rather rare. One of these was the General Assemble of the Staff Association Committee, which takes place once a year. Another one was a meeting of our team with Martin Kessler, our new head of department, and was the first one of its type, but will also likely take place once a year in the future. Finally, the third one was a general information session on security measures at ESA, and the repercussions on their implementation at ESAC.

It was also unusual in another respect, since for the hours that I spent at my desk, navigating the keyboard as we all do (some better than other, of course), most of my time was spent investigating: investigating like a detective or a spy, the possible cause of a different behaviour on a certain machine named isdabulk, between two users aliased as gbelange and rwilliam. And man oh man, I have looked down so many avenues that I have lost count. Not only that, but I was aided in this by a very competent system administrator who goes by the alias of dtapiador, and we still have not discovered what could cause the problem we have. Here is what I am trying to do and how the problem prensents itself:

The Integral archive that we copy from the ISDC (Integral Science Data Centre), but to which we provide access through an independent archive, contains the raw as well as processed observation data, providing IBIS/ISGRI images per pointing (that we call science window or scw), and light curves and spectra per source. However, there are no mosaics of the different sets of pointings that make up an observation of a given source, which is by far more interesting in order to get a quick look at what Integral actually sees in a region of the sky. Therefore, I set out to develop a systematic way of constructing mosaics for all of the observations for which we have archival data, the intention being to make these available directly through the archive, of course.

Given that this is a rather important computing job, implying making several hundred mosaics from groups of scw of varying sizes, with the help of my colleague dtapiador, we have set up the necessary scripts and programmes to do this on the external ESAC computer grid. After sorting out through all the little problems of syntax errors in the scripts, correct paths to executables and data, proper environment variables, and all the rest of it, we encountered an error that was apparently related to the science analysis software, an area which is indeed under my jurisdiction :)  So, it was up to me to investigate.

After a couple of days of changing little things here and there, and still not overcoming the crash at the very start of ii_skyimage when it is setting up to begin mosaicking, I discovered that if I ran the same sequence of commands under a different user, rwilliam, instead of running it under gbelange, than the mosaic ran all the way through to the end without a problem!

I looked at the groups of recognised computer users that these belong to, and found that both belong to the same groups. I looke at the file permissions everywhere, and apparently all files required to run the analysis are accessible and readable by both in the same manner. After that, I contacted my system administrator friends (2 of them), in order to seek help, asking them to look at how the usernames are mapped to userIDs, and check the coherence of the whole thing in all the groups. This did not bring out the answer.

Then I tried to run everything as gbelange, but defining an indentical environment as rwilliam: identical in the sense that all the environment variables in the shell are the same. This would exclude the possibility that the problem is related to some different paths or variables. Once again, the crash occured in exactly the same way. From this, the conclusion that the problem is related to deeply hidden file permissions is inescapable.

And finally, as I am writing this, I am running another test, where we have actually changed the permissions to all the auxiliary files so that everyone can read, write and execute; we’ll see if this solves it. And …. no. It’s not that.

So, it is now almost 19h00, and it is time to go home for the weekend. I hope to reveal the end of this story to you next time I am around on this blog.

Ciao

this is the first post we publish at this ISOC blog. ISOC is the acronym for ESA’s INTEGRAL Science Operations Center. At ISOC we plan where in the sky this satellite is looking at, at a certain time. In the coming posts, the four of us will try to explain you a bit of INTEGRAL, of our life at ISOC, and of any exciting operational issue that might happen.

Every week, from now on, you will hear from us!

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