Post AiKLRUC5aVp5bKYyBM by vicgrinberg@mastodon.social
(DIR) More posts by vicgrinberg@mastodon.social
(DIR) Post #AiKLR3Fhkxfk2j2yZN by vicgrinberg@mastodon.social
2023-08-26T14:41:47Z
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Want to know what my research is about? Follow this thread 🧵 based on a 10min talk I've drawn for a meeting.The talk was aimed at non-specialist space science colleagues (not the general public!). The slides were built up step by step, but I'm omitting this here & showing only the final graphs, less this becomes a 34-part thread. 11 is plenty enough!So: "Understanding Winds of Massive Stars Using High Mass X-ray Binaries"#astrodon #XraysAreTheBestRays #SciArt #scicomm #VicisAstro1/11
(DIR) Post #AiKLR5eEqiU9TOXb5U by vicgrinberg@mastodon.social
2023-08-26T14:45:11Z
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O/B supergiants are the "superstars" of the Universe: they have much higher temperature & luminosity than our sun (& higher mass). They live short & bright lives during which they can loose up to one hundred-thousandth of mass per year through winds. That's a VERY high mass loss and strongly influences how these stars develop and interact with their environment. Yet, we struggle understanding these winds because their clumpy structure is hard to study in single stars.#VicisAstro2/11
(DIR) Post #AiKLR85xkbqn3xWlZw by vicgrinberg@mastodon.social
2023-08-26T14:47:39Z
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Luckily, nature gave us High Mass X-ray Binaries (HMXB), where a black hole or neutron star (short: compact object) is close to an O/B star & accretes matter from its wind. The accretion process leads to production of high energy radiation.These X-rays then pass through the remaining wind and can be used as a "backlight" to probe individual wind clumps & overall wind structure. To do so, we need to observe the X-rays with space-based X-ray telescopes, such as XMM-Newton.#VicisAstro3/11
(DIR) Post #AiKLRB5ibyRCM4R77A by vicgrinberg@mastodon.social
2023-08-26T14:51:07Z
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There are two main ways how we can observe the effects of the wind on the X-rays. 1. looking at broadband energy spectra (say in the 1-100 keV range), we see increased overall absorption, seen as additional decline in soft X-rays in HMXBs vs. source where we can more directly look onto the compact object, without the intervening wind material.This gives us information about the total amount of wind material along the line of sight.Example study: https://ui.adsabs.harvard.edu/abs/2015A%26A...576A.117G/abstract#VicisAstro4/11
(DIR) Post #AiKLRDooTHhIoVY9gG by vicgrinberg@mastodon.social
2023-08-26T14:53:00Z
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2. Looking at high resolution spectra at low X-ray energies where there are many line transitions from different ions, we can see narrow features (lines, RRC) imprinted in absorption or emission onto the continuum.This gives us information about properties of the wind material such as ionization level and sometimes process, temperature, composition etc.Example studies: https://ui.adsabs.harvard.edu/abs/2017A%26A...608A.143G/abstract & https://ui.adsabs.harvard.edu/abs/2020A%26A...641A.144L/abstract & https://ui.adsabs.harvard.edu/abs/2021A%26A...648A.105A/abstract#VicisAstro5/11
(DIR) Post #AiKLRGRsh08WyFqNqy by vicgrinberg@mastodon.social
2023-08-26T14:54:53Z
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Why study HMXBs? They are key sources that touch all kind of astro areas (high energy, stellar, accretion physics) + we can often use data taken for other purposes to study the winds (absorption is noise for accretion physics studies).They are systems where one supernova has happened & another will and are progenitors for gravitational wave events. We also want to know about accretion history of HMXBs (their total energy output) & use them as unique labs for complex physics.#VicisAstro6/11
(DIR) Post #AiKLRJ9CetyjLC80em by vicgrinberg@mastodon.social
2023-08-26T14:55:57Z
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That's why a few years ago - well, more like 5 or 6 by now - a few of us (including @fuerst and @pkretsch) started the X-Wind collaboration, aiming to bring together X-ray astronomers and experts in winds from massive stars from other wavelength & from theory in order to better understand winds in HMXBs: https://www.sternwarte.uni-erlangen.de/~grinberg/x-wind/#VicisAstro7/11
(DIR) Post #AiKLRLyg8ULI7QE9AW by vicgrinberg@mastodon.social
2023-08-26T14:57:55Z
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The problem is that the winds are complex and clumpiness and with them short-term variability we observe depends on e.g. line of sight, clump properties such as mass and radius, clump movement, wind ionisiation ... Enough parameters to feel totally lost and drowning!So what I've done with my amazing colleague I. El Mellah is to try to disentangle a part of this complexity via simulations! Careful, we'll now be diving into this rather complex paper: https://ui.adsabs.harvard.edu/abs/2020A%26A...643A...9E/abstract#VicisAstro8/11
(DIR) Post #AiKLROs3NZpF5k9Ol6 by vicgrinberg@mastodon.social
2023-08-26T15:00:08Z
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We simulate "absorption light curves", i.e. measurement of how much material is along the line of sight. Such lightcurves have two main properties: a typical timescale and a typical absorption variability.We can get the typical timescales from the autocorrelation function and it's a good estimate for the clump radius. If we can measure absorption variability, we can then also get clump muss. But how measure that?#VicisAstro9/11
(DIR) Post #AiKLRRSzjCYz8tRvcG by vicgrinberg@mastodon.social
2023-08-26T15:01:26Z
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What we want are measurements of how absorption changes with time as clumps pass through our line of sight towards the compact object.The usual way is to use spectral modelling - this allows exact measurements but needs long exposures. Bad for time resolution!Instead, we can use colors. They need short exposures, but are noisy & harder to model. I did develop an approach how to make use of the typical patterns in color space to do so: https://ui.adsabs.harvard.edu/abs/2020A%26A...643A.109G/abstract#VicisAstro10/11
(DIR) Post #AiKLRUC5aVp5bKYyBM by vicgrinberg@mastodon.social
2023-08-26T15:02:15Z
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What next for this research?1. Apply methods to more sources! Also to build a sample and test different star & binary properties e.g. https://ui.adsabs.harvard.edu/abs/2023A%26A...674A.147D/abstract & https://ui.adsabs.harvard.edu/abs/2021MNRAS.501.5646M/abstract2. Refine methods (better statistics tools, take more effects into account ...) - e.g. https://ui.adsabs.harvard.edu/abs/2023arXiv230414201H/abstract3. And of course we hope for better data with #XRISM and #Athena missions!#VicisAstro #XraysAreTheBestRays #SciArt #scicomm #wisskomm #VicisArt11/11