المؤلفون: Ballhausen, R., Thalhammer, P., Pradhan, P., Sokolova-Lapa, E., Stierhof, J., Pottschmidt, K., Wilms, J., Coley, J. B., Kretschmar, P., Fuerst, F., Becker, P., West, B., Malacaria, C., Wolff, M. T., Rothschild, R., Staubert, R.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: In 2021, the high-mass X-ray binary EXO 2030+375 underwent a giant X-ray outburst, the first since 2006, that reached a peak flux of ${\sim}600\,\mathrm{mCrab}$ (3-50\,keV). The goal of this work is to study the spectral evolution over the course of the outburst, search for possible cyclotron resonance scattering features (CRSFs), and to associate spectral components with the emission pattern of the accretion column. We used broadband spectra taken with the Nuclear Spectroscopic Telescope Array (NuSTAR), the Neutron Star Interior Composition Explorer (NICER), and Chandra near the peak and during the decline phase of the outburst. We describe the data with established empirical continuum models and perform pulse-phase-resolved spectroscopy. We compare the spectral evolution with pulse phase using a proposed geometrical emission model. We find a significant spectral hardening toward lower luminosity, a behavior that is expected for super-critical sources. The continuum shape and evolution cannot be described by a simple power-law model with exponential cutoff; it requires additional absorption or emission components. We can confirm the presence of a narrow absorption feature at ${\sim}10\,\mathrm{keV}$ in both NuSTAR observations. The absence of harmonics puts into question the interpretation of this feature as a CRSF. The empirical spectral components cannot be directly associated with identified emission components from the accretion column.
Comment: 12 pages, 8 figures, accepted in A&A

الوصول الحر: http://arxiv.org/abs/2406.13029Test

المؤلفون: Wolf, J., Salvato, M., Belladitta, S., Arcodia, R., Ciroi, S., Di Mille, F., Sbarrato, T., Buchner, J., Hämmerich, S., Wilms, J., Collmar, W., Dwelly, T., Merloni, A., Urrutia, T., Nandra, K.

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena

الوصف: The SRG/eROSITA All-Sky Survey (eRASS) is expected to contain ~100 quasars that emitted their light when the universe was less than a billion years old, i.e. at z>5.6. By selection, these quasars populate the bright end of the AGN X-ray luminosity function and their count offers a powerful demographic diagnostic of the parent super-massive black hole population. Of the >~ 400 quasars that have been discovered at z>5.6 to date, less than 15 % have been X-ray detected. We present a pilot survey to uncover the elusive X-ray luminous end of the distant quasar population. We have designed a quasar selection pipeline based on optical, infrared and X-ray imaging data from DES DR2, VHS DR5, CatWISE2020 and the eRASS. The core selection method relies on SED template fitting. We performed optical follow-up spectroscopy with the Magellan/LDSS3 instrument for the redshift confirmation of a subset of candidates. We have further obtained a deeper X-ray image of one of our candidates with Chandra ACIS-S. We report the discovery of five new quasars in the redshift range 5.6 < z < 6.1. Two of these quasars are detected in eRASS and are by selection X-ray ultra-luminous. These quasars are also detected at radio frequencies. The first one is a broad absorption line quasar which shows significant X-ray dimming over 3.5 years, i.e. about 6 months in the quasar rest frame. The second radio-detected quasar is a jetted source with compact morphology. We show that a blazar configuration is likely for this source, making it the second most distant blazar known to date. With our pilot study, we demonstrate the power of eROSITA as a discovery machine for luminous quasars in the epoch of reionization. The X-ray emission of the two eROSITA detected quasars are likely to be driven by different high-energetic emission mechanisms a diversity which will be further explored in a future systematic full-hemisphere survey.
Comment: Submitted to A&A, June 7, 2024

الوصول الحر: http://arxiv.org/abs/2406.05118Test

المؤلفون: Thalhammer, P., Ballhausen, R., Sokolova-Lapa, E., Stierhof, J., Zainab, A., Staubert, R., Pottschmidt, K., Coley, J. B., Rothschild, R. E., Jaisawal, G. K., West, B., Becker, P. A., Pradhan, P., Kretschmar, P., Wilms, J.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The Be X-ray binary EXO 2030+375 went through its third recorded giant outburst from June 2021 to early 2022. We present the results of both spectral and timing analysis based on NICER monitoring, covering the 2-10 keV flux range from 20 to 310 mCrab. Dense monitoring with observations carried out about every second day and a total exposure time of 160 ks allowed us to closely track the source evolution over the outburst. Changes in spectral shape and pulse profiles showed a stable luminosity dependence during the rise and decline. The same type of dependence has been seen in past outbursts. The pulse profile is characterized by several distinct peaks and dips. The profiles show a clear dependence on luminosity with a stark transition at a luminosity of 2x10^36 erg/s, indicating a change in the emission pattern. Using relativistic ray-tracing, we demonstrate how anisotropic beaming of emission from an accretion channel with constant geometrical configuration can give rise to the observed pulse profiles over a range of luminosities.
Comment: 15 pages, 16 figures, accepted by A&A

الوصول الحر: http://arxiv.org/abs/2405.20734Test

المؤلفون: Albert, A., Alves, S., André, M., Ardid, M., Ardid, S., Aubert, J. -J., Aublin, J., Baret, B., Basa, S., Becherini, Y., Belhorma, B., Bendahman, M., Benfenati, F., Bertin, V., Biagi, S., Boumaaza, J., Bouta, M., Bouwhuis, M. C., Brânzaş, H., Bruijn, R., Brunner, J., Busto, J., Caiffi, B., Calvo, D., Campion, S., Capone, A., Carenini, F., Carr, J., Carretero, V., Celli, S., Cerisy, L., Chabab, M., Moursli, R. Cherkaoui El, Chiarusi, T., Circella, M., Coelho, J. A. B., Coleiro, A., Coniglione, R., Coyle, P., Creusot, A., Díaz, A. F., De Martino, B., Distefano, C., Di Palma, I., Donzaud, C., Dornic, D., Drouhin, D., Eberl, T., Eddymaoui, A., van Eeden, T., van Eijk, D., Hedri, S. El, Khayati, N. El, Enzenhöfer, A., Fermani, P., Ferrara, G., Filippini, F., Fusco, L., Gagliardini, S., García, J., Oliver, C. Gatius, Gay, P., Geißelbrecht, N., Glotin, H., Gozzini, R., Ruiz, R. Gracia, Graf, K., Guidi, C., Haegel, L., van Haren, H., Heijboer, A. J., Hello, Y., Hennig, L., Hernández-Rey, J. J., Hößl, J., Huang, F., Illuminati, G., Jisse-Jung, B., de Jong, M., de Jong, P., Kadler, M., Kalekin, O., Katz, U., Kouchner, A., Kreykenbohm, I., Kulikovskiy, V., Lahmann, R., Lamoureux, M., Lazo, A., Lefèvre, D., Leonora, E., Levi, G., Stum, S. Le, Loucatos, S., Manczak, J., Marcelin, M., Margiotta, A., Marinelli, A., Martínez-Mora, J. A., Migliozzi, P., Moussa, A., Muller, R., Navas, S., Nezri, E., Fearraigh, B. Ó, Oukacha, E., Păun, A., Păvălaş, G. E., Peña-Martínez, S., Perrin-Terrin, M., Piattelli, P., Poirè, C., Popa, V., Pradier, T., Randazzo, N., Real, D., Riccobene, G., Romanov, A., Sánchez-Losa, A., Saina, A., Greus, F. Salesa, Samtleben, D. F. E., Sanguineti, M., Sapienza, P., Schüssler, F., Seneca, J., Spurio, M., Stolarczyk, Th., Taiuti, M., Tayalati, Y., Vallage, B., Vannoye, G., Van Elewyck, V., Viola, S., Vivolo, D., Wilms, J., Zavatarelli, S., Zegarelli, A., Zornoza, J. D., Zúñiga, J.

مصطلحات موضوعية: Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors

الوصف: Position calibration in the deep sea is typically done by means of acoustic multilateration using three or more acoustic emitters installed at known positions. Rather than using hydrophones as receivers that are exposed to the ambient pressure, the sound signals can be coupled to piezo ceramics glued to the inside of existing containers for electronics or measuring instruments of a deep sea infrastructure. The ANTARES neutrino telescope operated from 2006 until 2022 in the Mediterranean Sea at a depth exceeding 2000m. It comprised nearly 900 glass spheres with 432mm diameter and 15mm thickness, equipped with photomultiplier tubes to detect Cherenkov light from tracks of charged elementary particles. In an experimental setup within ANTARES, piezo sensors have been glued to the inside of such - otherwise empty - glass spheres. These sensors recorded signals from acoustic emitters with frequencies from 46545 to 60235Hz. Two waves propagating through the glass sphere are found as a result of the excitation by the waves in the water. These can be qualitatively associated with symmetric and asymmetric Lamb-like waves of zeroth order: a fast (early) one with $v_e \approx 5$mm/$\mu$s and a slow (late) one with $v_\ell \approx 2$mm/$\mu$s. Taking these findings into account improves the accuracy of the position calibration. The results can be transferred to the KM3NeT neutrino telescope, currently under construction at multiple sites in the Mediterranean Sea, for which the concept of piezo sensors glued to the inside of glass spheres has been adapted for monitoring the positions of the photomultiplier tubes.
Comment: submitted to "Experimental Astronomy"

الوصول الحر: http://arxiv.org/abs/2405.07230Test

المؤلفون: Aiello, S., Albert, A., Alshamsi, M., Garre, S. Alves, Ambrosone, A., Ameli, F., Andre, M., Androutsou, E., Anguita, M., Aphecetche, L., Ardid, M., Ardid, S., Atmani, H., Aublin, J., Badaracco, F., Bailly-Salins, L., Bardačová, Z., Baret, B., Bariego-Quintana, A., Pree, S. Basegmez du, Becherini, Y., Bendahman, M., Benfenati, F., Benhassi, M., Benoit, D. M., Berbee, E., Bertin, V., Biagi, S., Boettcher, M., Bonanno, D., Boumaaza, J., Bouta, M., Bouwhuis, M., Bozza, C., Bozza, R. M., Brânzaş, H., Bretaudeau, F., Breuhaus, M., Bruijn, R., Brunner, J., Bruno, R., Buis, E., Buompane, R., Busto, J., Caiffi, B., Calvo, D., Campion, S., Capone, A., Carenini, F., Carretero, V., Cartraud, T., Castaldi, P., Cecchini, V., Celli, S., Cerisy, L., Chabab, M., Chadolias, M., Chen, A., Cherubini, S., Chiarusi, T., Circella, M., Cocimano, R., Coelho, J. A. B., Coleiro, A., Condorelli, A., Coniglione, R., Coyle, P., Creusot, A., Cuttone, G., Dallier, R., Darras, Y., De Benedittis, A., De Martino, B., Decoene, V., Del Burgo, R., Del Rosso, I., Di Mauro, L. S., Di Palma, I., Díaz, A. F., Diaz, C., Diego-Tortosa, D., Distefano, C., Domi, A., Donzaud, C., Dornic, D., Dörr, M., Drakopoulou, E., Drouhin, D., Ducoin, J. G., Dvornický, R., Eberl, T., Eckerová, E., Eddymaoui, A., van Eeden, T., Eff, M., van Eijk, D., Bojaddaini, I. El, Hedri, S. El, Enzenhöfer, A., Ferrara, G., Filipović, M. D., Filippini, F., Franciotti, D., Fusco, L. A., Gagliardini, S., Gal, T., Méndez, J. García, Soto, A. Garcia, Oliver, C. Gatius, Geißelbrecht, N., Ghaddari, H., Gialanella, L., Gibson, B. K., Giorgio, E., Goos, I., Goswami, P., Gozzini, S. R., Gracia, R., Graf, K., Guidi, C., Guillon, B., Gutiérrez, M., Haack, C., van Haren, H., Heijboer, A., Hekalo, A., Hennig, L., Hernández-Rey, J. J., Ibnsalih, W. Idrissi, Illuminati, G., Joly, D., de Jong, M., de Jong, P., Jung, B. J., Kalekin, O., Katz, U. F., Kharkhelauri, L., Kistauri, G., Kopper, C., Kouchner, A., Kueviakoe, V., Kulikovskiy, V., Kvatadze, R., Labalme, M., Lahmann, R., Larosa, G., Lastoria, C., Lazo, A., Stum, S. Le, Lehaut, G., Leonora, E., Lessing, N., Levi, G., Longhitano, F., Magnani, F., Majumdar, J., Malerba, L., Mamedov, F., Mańczak, J., Manfreda, A., Marconi, M., Margiotta, A., Marinelli, A., Markou, C., Martin, L., Marzaioli, F., Mastrodicasa, M., Mastroianni, S., Miccichè, S., Miele, G., Migliozzi, P., Migneco, E., Mitsou, M. L., Mollo, C. M., Morales-Gallegos, L., Moretti, G., Moussa, A., Mateo, I. Mozun, Muller, R., Musone, M. R., Musumeci, M., Navas, S., Nayerhoda, A., Nicolau, C. A., Nkosi, B., Fearraigh, B. Ó, Oliviero, V., Orlando, A., Oukacha, E., Paesani, D., González, J. Palacios, Papalashvili, G., Parisi, V., Gomez, E. J. Pastor, Păun, A. M., Păvălaş, G. E., Pelegris, I., Martínez, S. Pena, Perrin-Terrin, M., Perronnel, J., Pestel, V., Pestes, R., Piattelli, P., Poirè, C., Popa, V., Pradier, T., Prado, J., Pulvirenti, S., Quiroz-Rangel, C. A., Rahaman, U., Randazzo, N., Razzaque, S., Rea, I. C., Real, D., Riccobene, G., Robinson, J., Romanov, A., Šaina, A., Greus, F. Salesa, Samtleben, D. F. E., Losa, A. Sánchez, Sanfilippo, S., Sanguineti, M., Santonastaso, C., Santonocito, D., Sapienza, P., Schnabel, J., Schumann, J., Schutte, H. M., Seneca, J., Sennan, N., Setter, B., Sgura, I., Shanidze, R., Sharma, A., Shitov, Y., Šimkovic, F., Simonelli, A., Sinopoulou, A., Smirnov, M. V., Spisso, B., Spurio, M., Stavropoulos, D., Štekl, I., Taiuti, M., Tangorra-Cascione, R., Tayalati, Y., Thiersen, H., Melo, I. Tosta e, Tragia, E., Trocmé, B., Tsourapis, V., Tudorache, A., Tzamariudaki, E., Ukleja, A., Vacheret, A., Melchor, A. Valer, Valsecchi, V., Van Elewyck, V., Vannoye, G., Vasileiadis, G., de Sola, F. Vazquez, Veutro, A., Viola, S., Vivolo, D., Wilms, J., de Wolf, E., Yepes-Ramirez, H., Yvon, I., Zarpapis, G., Zavatarelli, S., Zegarelli, A., Zito, D., Zornoza, J. D., Zúñiga, J., Zywucka, N.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Gamma-ray bursts are promising candidate sources of high-energy astrophysical neutrinos. The recent GRB 221009A event, identified as the brightest gamma-ray burst ever detected, provides a unique opportunity to investigate hadronic emissions involving neutrinos. The KM3NeT undersea neutrino detectors participated in the worldwide follow-up effort triggered by the event, searching for neutrino events. In this letter, we summarize subsequent searches, in a wide energy range from MeV up to a few PeVs. No neutrino events are found in any of the searches performed. Upper limits on the neutrino emission associated with GRB 221009A are computed.
Comment: 11 pages, 2 PDF figures. Submitted to JCAP

الوصول الحر: http://arxiv.org/abs/2404.05354Test

المؤلفون: Gokus, A., Wilms, J., Kadler, M., Dorner, D., Nowak, M. A., Kreikenbohm, A., Leiter, K., Bretz, T., Schleicher, B., Markowitz, A. G., Pottschmidt, K., Mannheim, K., Kreykenbohm, I., Langejahn, M., McBride, F., Beuchert, T., Dauser, T., Kreter, M., Abhir, J., Baack, D., Balbo, M., Biland, A., Brand, K., Buss, J., Eisenberger, L., Elsaesser, D., Guenther, P., Hildebrand, D., Linhoff, M., Paravac, A., Rhode, W., Sliusar, V., Hasan, S., Walter, R.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: By studying the variability of blazars across the electromagnetic spectrum, it is possible to resolve the underlying processes responsible for rapid flux increases, so-called flares. We report on an extremely bright X-ray flare in the high-peaked BL Lacertae object Mrk 421 that occurred simultaneously with enhanced $\gamma$-ray activity detected at very high energies (VHE) by FACT on 2019 June 9. We triggered an observation with XMM-Newton, which observed the source quasi-continuously for 25 hours. We find that the source was in the brightest state ever observed using XMM-Newton, reaching a flux of $2.8\times10^{-9}$ erg cm$^{-2}$ s$^{-1}$ over an energy range of 0.3 - 10 keV. We perform a spectral and timing analysis to reveal the mechanisms of particle acceleration and to search for the shortest source-intrinsic time scales. Mrk 421 exhibits the typical harder-when-brighter behaviour throughout the observation and shows a clock-wise hysteresis pattern, which indicates that the cooling dominates over the acceleration process. While the X-ray emission in different sub-bands is highly correlated, we can exclude large time lags as the computed zDCFs are consistent with a zero lag. We find rapid variability on time scales of 1 ks for the 0.3 - 10 keV band and down to 300s in the hard X-ray band (4 - 10 keV). Taking these time scales into account, we discuss different models to explain the observed X-ray flare, and find that a plasmoid-dominated magnetic reconnection process is able to describe our observation best.
Comment: 13 pages, 7 figures, accepted for publication in MNRAS

الوصول الحر: http://arxiv.org/abs/2402.19377Test

المؤلفون: Albert, A., Alves, S., André, M., Ardid, M., Ardid, S., Aubert, J. -J., Aublin, J., Baret, B., Basa, S., Becherini, Y., Belhorma, B., Bendahman, M., Benfenati, F., Bertin, V., Biagi, S., Bissinger, M., Boumaaza, J., Bouta, M., Bouwhuis, M. C., Brânzas, H., Bruijn, R., Brunner, J., Busto, J., Caiffi, B., Calvo, D., Campion, S., Capone, A., Caramete, L., Carenini, F., Carr, J., Carretero, V., Celli, S., Cerisy, L., Chabab, M., Moursli, R. Cherkaoui El, Chiarusi, T., Circella, M., Coelho, J. A. B., Coleiro, A., Coniglione, R., Coyle, P., Creusot, A., Cruz, A. S. M., Díaz, A. F., De Martino, B., Distefano, C., Di Palma, I., Donzaud, C., Dornic, D., Drouhin, D., Eberl, T., van Eeden, T., van Eijk, D., Hedri, S. El, Khayati, N. El, Enzenhöfer, A., Fermani, P., Ferrara, G., Filippini, F., Fusco, L., Gagliardini, S., García, J., Oliver, C. Gatius, Gay, P., Geißelbrecht, N., Glotin, H., Gozzini, R., Ruiz, R. Gracia, Graf, K., Guidi, C., Haegel, L., Hallmann, S., van Haren, H., Heijboer, A. J., Hello, Y., Hennig, L., Hernández-Rey, J. J., Hößl, J., Hofestädt, J., Huang, F., Illuminati, G., James, C. W., Jisse-Jung, B., de Jong, M., de Jong, P., Kadler, M., Kalekin, O., Katz, U., Kouchner, A., Kreykenbohm, I., Kulikovskiy, V., Lahmann, R., Lamoureux, M., Lazo, A., Lefèvre, D., Leonora, E., Levi, G., Stum, S. Le, Loucatos, S., Maderer, L., Manczak, J., Marcelin, M., Margiotta, A., Marinelli, A., Martínez-Mora, J. A., Migliozzi, P., Moussa, A., Muller, R., Navas, S., Nezri, E., Fearraigh, B. Ó, Oukacha, E., Pāun, A., Pāvālas, G. E., Peña-Martínez, S., Perrin-Terrin, M., Piattelli, P., Popa, V., Pradier, T., Randazzo, N., Real, D., Riccobene, G., Romanov, A., Sánchez-Losa, A., Saina, A., Greus, F. Salesa, Samtleben, D. F. E., Sanguineti, M., Sapienza, P., Schnabel, J., Schumann, J., Schüssler, F., Seneca, J., Spurio, M., Stolarczyk, Th., Taiuti, M., Tayalati, Y., Tingay, S. J., Vallage, B., Vannoye, G., Van Elewyck, V., Viola, S., Vivolo, D., Wilms, J., Zavatarelli, S., Zegarelli, A., Zornoza, J. D., Zúñiga, J., Lipunov, V., Antipov, G., Balanutsa, P., Buckley, D., Budnev, N., Chasovnikov, A., Cheryasov, D., Francile, C., Gabovich, A., Gorbovskoy, E., Gorbunov, I., Gress, O., Kornilov, V., Kuznetsov, A., Iyudin, A., Podesta, R., Podesta, F., Lopez, R. Rebolo, Senik, V., Sierra-Rucart, M., Svertilov, S., Tiurina, N., Vlasenko, D., Yashin, I., Zhirkov, K., Croft, S., Kaplan, D. L., Anderson, G. E., Williams, A., Dobie, D., Bannister, K. W., Hancock, P. J., Evans, P. A., Kennea, J. A., Osborne, J. P., Cenko, S. B., Antier, S., Atteia, J. L., Boër, M., Klotz, A., Chaty, S., Hodapp, K., Savchenko, V.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES Collaboration since 2009. This program, named TAToO, has triggered robotic optical telescopes (MASTER, TAROT, ROTSE and the SVOM ground based telescopes) immediately after the detection of any relevant neutrino candidate and scheduled several observations in the weeks following the detection. A subset of ANTARES events with highest probabilities of being of cosmic origin has also been followed by the Swift and the INTEGRAL satellites, the Murchison Widefield Array radio telescope and the H.E.S.S. high-energy gamma-ray telescope. The results of twelve years of observations are reported. No optical counterpart has been significantly associated with an ANTARES candidate neutrino signal during image analysis. Constraints on transient neutrino emission have been set. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift and MASTER. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. The return of experience is particularly important for the design of the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea.
Comment: 27 pages, 14 figures, submitted to JCAP

الوصول الحر: http://arxiv.org/abs/2402.16498Test

المؤلفون: Iwasawa, K., Liu, T., Boller, Th., Buchner, J., Li, J., Kawaguchi, T., Nagao, T., Terashima, Y., Toba, Y., Silverman, J. D., Arcodia, R., Dauser, Th., Krumpe, M., Nandra, K., Wilms, J.

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena

الوصف: We selected sources with a steep soft-X-ray-band spectrum with a photon index larger than 2.5 -- measured by eROSITA on board the Spectrum-Roentgen-Gamma (SRG) -- from the eFEDS AGN catalogue as candidates of highly accreting supermassive black holes, and investigated their multi-wavelength properties. Among 601 bright AGN with 0.2-5 keV counts of greater than 100, 83 sources (~14%) are classified as steep-spectrum sources. These sources have typical 0.5-2 keV luminosities of L(SX) ~ 1e44 erg/s and the majority of them are found at redshifts below z=1. In comparison with sources with flatter spectra, these sources have, on average, a UV (or optical) to 2 keV luminosity ratio that is larger by ~0.3 dex and bluer optical-to-UV continuum emission. They also appear to be radio quiet based on the detection rate in the FIRST and VLASS surveys. Their host galaxies -- at least in the redshift range of z=0.2-0.8, where the AGN-galaxy decomposition results from the Subaru Hyper Suprime-Cam imaging are available -- tend to be late-type and have smaller stellar masses than those of sources with flatter spectra. These properties are similar to those found in nearby narrow-line Seyfert 1 galaxies, in agreement with the picture that they are AGN with elevated accretion rates and are in the early growth phase of black hole and galaxy co-evolution. However, the steep-spectrum sources are not exclusively narrow-line Seyfert 1 galaxies; indeed many are broad-line Seyfert 1 galaxies, as found by a catalogue search. This suggests that these steep-spectrum sources may be black holes generally with high accretion rates but of a wide mass range, including a few objects emitting at L(SX)>1e45 erg/s, of which black hole masses can be close to 10^9 M_sun.
Comment: 8 pages, accepted for publication in A&A

الوصول الحر: http://arxiv.org/abs/2402.14135Test

المؤلفون: Kyritsis, E., Zezas, A., Haberl, F., Weber, P., Basu-Zych, A., Vulic, N., Maitra, C., Hämmerich, S., Wilms, J., Sasaki, M., Hornschemeier, A., Ptak, A., Merloni, A., Comparat, J.

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena

الوصف: We present a study of X-ray normal galaxies using data from the first all-sky scan of the eROSITA X-ray survey. eRASS1 provides the first unbiased X-ray census of normal galaxies allowing us to study the X-ray emission from XRBs and the hot ISM in the full range of stellar population parameters present in the local Universe. By combining the HECATE value-added galaxy catalogue with the eRASS1, we study the X-ray emission from normal galaxies as a function of their SFR, M$_{*}$, Metallicity, and stellar population age. After applying optical and mid-IR activity classification criteria, we constructed a sample of 18790 star-forming galaxies with measurements of their L$_{X}$. By stacking the X-ray data in SFR-M$_{*}$-distance bins we study the correlation between the average L$_{X}$ and stellar population parameters. We also present updated L$_{\rm{X}}$-SFR and L$_{\rm{X}}$/SFR-Metallicity scaling relations accounting for the scatter dependence on the SFR. We find that the integrated L$_{X}$ of the HEC-eR1 star-forming galaxies is significantly elevated with respect to that expected from the current scaling relations. The observed scatter is also significantly larger. This excess persists even when we measure the average L$_{X}$ of galaxies in SFR-M$_{*}$-distance and metallicity bins and it is stronger in lower SFRs. The excess is not the result of hot gas, LMXBs, background AGN, LLAGN (including TDEs), or stochastic sampling of the XRB XLF. We find that while the excess correlates with lower metallicity, its primary driver is the age of the stellar populations. Our analysis reveals a sub-population of X-ray luminous starbursts with high sSFRs, low metallicities, and young stellar populations. This population drives upwards the X-ray scaling relations for star-forming galaxies, and has important implications for understanding the population of XRBs in the local and high-z Universe.
Comment: Submitted to A&A

الوصول الحر: http://arxiv.org/abs/2402.12367Test

المؤلفون: Clerc, N., Comparat, J., Seppi, R., Artis, E., Bahar, Y. E., Balzer, F., Bulbul, E., Dauser, T., Garrel, C., Ghirardini, V., Grandis, S., Kirsch, C., Kluge, M., Liu, A., Pacaud, F., Ramos-Ceja, M. E., Reiprich, T. H., Sanders, J. S., Wilms, J., Zhang, X.

مصطلحات موضوعية: Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: Characterising galaxy cluster populations from catalog of sources selected in astronomical surveys requires knowledge of sample incompleteness, known as selection function. The first All-Sky Survey (eRASS1) by eROSITA onboard Spectrum Roentgen Gamma (SRG) has enabled the collection of large samples of galaxy clusters detected in the soft X-ray band over the Western Galactic hemisphere. The driving goal consists in constraining cosmological parameters, which puts stringent requirements on accuracy, flexibility and explainability of the selection function models. We use a large set of mock observations of the eRASS1 survey and we process simulated data identically to the real eRASS1 events. We match detected sources to simulated clusters and we associate detections to intrinsic cluster properties. We train a series of models to build selection functions depending only on observable surface brightness data. We develop a second series of models relying on global cluster characteristics such as X-ray luminosity, flux, and expected instrumental count-rate as well as on morphological properties. We validate our models using our simulations and we rank them according to selected performance metrics. We validate the models with datasets of clusters detected in X-rays and via the Sunyaev-Zeldovich effect. We present the complete Bayesian population modelling framework developed for this purpose. Our results reveal the surface brightness characteristics most relevant to cluster selection in the eRASS1 sample, in particular the ambiguous role of central surface brightness at the scale of the instrument resolution. We have produced a series of user-friendly selection function models and demonstrated their validity and their limitations. Our selection function for bright sources reproduces well the catalog matches with external datasets. (abridged)
Comment: 24 pages, 31 figures, 2 tables. Submitted to A&A

الوصول الحر: http://arxiv.org/abs/2402.08457Test