Search

The Burst Optical Observer and Transient Exploring System (BOOTES) is a world-wide automatic telescope network which aims to repaid follow-up of transient and astrophysical sources in the sky for which the first station was installed in 1998. With the advent in 2015 of the LIGO/Virgo interferometers, as part of the new generation of detectors designed for the detection of the signal of gravitational waves, a new window to explore the Universe has been opened. Here we present the status of the BOOTES network, the related strategies regarding the follow-up of gravitational wave events and the developments in the Gravitational Wave Era. Some preliminary results regarding the BOOTES follow-up observations are presented.

We performed optical spectroscopy of the candidates inside the gravitational wave errorboxes (S190408an, S190425z, S190426c, S190510g, S190728q, S190814bv). The spectral classification of 34 transients observed with the 10.4m Gran Telescopio de Canarias prior to 1 Sep 2019 is presented. We ruled out the association of these candidates with gravitational wave events.

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/., Gamma-ray bursts (GRBs) are flashes of high-energy radiation arising from energetic cosmic explosions. Bursts of long (greater than two seconds) duration are produced by the core-collapse of massive stars1, and those of short (less than two seconds) duration by the merger of compact objects, such as two neutron stars2. A third class of events with hybrid high-energy properties was identified3, but never conclusively linked to a stellar progenitor. The lack of bright supernovae rules out typical core-collapse explosions4,5,6, but their distance scales prevent sensitive searches for direct signatures of a progenitor system. Only tentative evidence for a kilonova has been presented7,8. Here we report observations of the exceptionally bright GRB 211211A, which classify it as a hybrid event and constrain its distance scale to only 346 megaparsecs. Our measurements indicate that its lower-energy (from ultraviolet to near-infrared) counterpart is powered by a luminous (approximately 1042 erg per second) kilonova possibly formed in the ejecta of a compact object merger. © 2022, The Author(s)., This work was supported by the European Research Council through the Consolidator grant BHianca (grant agreement ID 101002761) and by the National Science Foundation (under award number 12850). B.O’C. was partially supported by the National Aeronautics and Space Administration (NASA) through grants NNX16AB66G, NNX17AB18G and 80NSSC20K0389. N.K. was financially supported by Grants-in-Aid for Scientific Research 17H06362 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. This work was partially supported by the Optical and Near-Infrared Astronomy Inter-University Cooperation Program of the MEXT of Japan, and the joint research programme of the Institute for Cosmic Ray Research (ICRR), the University of Tokyo. Research at Perimeter Institute is supported in part by the Government of Canada through the Department of Innovation, Science and Economic Development and by the Province of Ontario through the Ministry of Colleges and Universities. The development of afterglow models used in this work was partially supported by the European Union Horizon 2020 programme under the AHEAD2020 project (grant agreement number 871158). C.L.F., E.A.C. and R.W. are supported by the US Department of Energy through the Los Alamos National Laboratory (LANL), operated by Triad National Security, LLC, for the National Nuclear Security Administration of US Department of Energy (contract no. 89233218CNA000001). This work includes observations obtained at the international Gemini Observatory (principal investigator (PI): B.O’C.; GS-2022A-Q-141), a programme of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the NSF on behalf of the Gemini Observatory partnership: the NSF (USA), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovacíon (Argentina), Ministério da Cieˆncia, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The HST data (ObsID: 16846; PI: E.T.) used in this work was obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This research is partially based on observations under our ToO proposal number DOT-2021-C2-P71 (PI: R.G.) and proposal number DOT-2021-C2-P54 (PI: S.B.P.) obtained at the 3.6-m Devasthal Optical Telescope (DOT), which is a National Facility run and managed by Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous Institute under the Department of Science and Technology, Government of India. R.G. and S.B.P. acknowledge all the observing and support staff of the 3.6-m DOT and 1.3-m DFOT for maintaining and running the observational facilities at Devasthal Nainital. R.G. is especially thankful to B. Kumar, A. K. Ror and M. Sarkar for the observations with the 3.6-m DOT and 1.3-m DFOT under the approved observing proposals: DOT-2021-C2-P71 (PI: R.G.), DFOT-2021B-P29 (PI: R.G.), and DOT-2021-C2-P54 (PI: S.B.P.). R.G., A.A., K.M. and S.B.P. acknowledge the BRICS grant (DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G)) for financial support. R.G. and S.B.P. also acknowledge the financial support of ISRO under the AstroSat archival data utilization programme (DS_2B-13013(2)/1/2021-Sec.2). A.A. acknowledges funds and assistance provided by the Council of Scientific & Industrial Research (CSIR), India with file no. 09/948(0003)/2020-EMR-I. M.D.C.-G. acknowledges support from the Ramón y Cajal Fellowship RYC2019-026465-I. Y.-D.H. acknowledges support under the additional funding from RYC2019-026465-I. A.J.C.-T. acknowledges support from the Spanish Ministry project PID2020-118491GB-I00, Junta de Andalucia project P20_01068 and the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). Based on observations collected at the Centro Astronómico Hispano-Alemán (CAHA) at Calar Alto (ToO Program 21B-2.2-028: PI: A.J.C.-T.), operated jointly by Junta de Andalucía and Consejo Superior de Investigaciones Científicas (IAA-CSIC). These results made use of the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. This research used resources provided by the LANL Institutional Computing Program. Figure 1 was created with the help of the NOIRLab/IPAC/ESA/STScI/CfA FITS Liberator. We made use of IRAF, which is distributed by the NSF NOIRLab. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.

Full list of authors: Amati, L.; O'Brien, P. T.; Götz, D.; Bozzo, E.; Santangelo, A.; Tanvir, N. ; Frontera, F.; Mereghetti, S.; Osborne, J. P.; Blain, A.; Basa, S.; Branchesi, M.; Burderi, L.; Caballero-García, M.; Castro-Tirado, A. J.; Christensen, L.; Ciolfi, R.; De Rosa, A.; Doroshenko, V.; Ferrara, A.; Ghirlanda, G.; Hanlon, L.; Heddermann, P.; Hutchinson, I.; Labanti, C.; Le Floch, E.; Lerman, H.; Paltani, S.; Reglero, V.; Rezzolla, L.; Rosati, P.; Salvaterra, R.; Stratta, G.; Tenzer, C.; Theseus Consortium.--This Open Access article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/., THESEUS, one of the two space mission concepts being studied by ESA as candidates for next M5 mission within its Comsic Vision programme, aims at fully exploiting Gamma-Ray Bursts (GRB) to solve key questions about the early Universe, as well as becoming a cornerstone of multi-messenger and time-domain astrophysics. By investigating the first billion years of the Universe through high-redshift GRBs, THESEUS will shed light on the main open issues in modern cosmology, such as the population of primordial low mass and luminosity galaxies, sources and evolution of cosmic re-ionization, SFR and metallicity evolution up to the “cosmic dawn” and across Pop-III stars. At the same time, the mission will provide a substantial advancement of multi-messenger and time-domain astrophysics by enabling the identification, accurate localisation and study of electromagnetic counterparts to sources of gravitational waves and neutrinos, which will be routinely detected in the late ‘20s and early ‘30s by the second and third generation Gravitational Wave (GW) interferometers and future neutrino detectors, as well as of all kinds of GRBs and most classes of other X/gamma-ray transient sources. Under all these respects, THESEUS will provide great synergies with future large observing facilities in the multi-messenger domain. A Guest Observer programme, comprising Target of Opportunity (ToO) observations, will expand the science return of the mission, to include, e.g., solar system minor bodies, exoplanets, and AGN. © 2021, The Author(s)., The authors, on behalf of the entire THESEUS consortium, are grateful to the ESA-appointed THESEUS Study Scientist Matteo Guainazzi, as well as the entire ESA Study Team for all their work and support across the mission assessment phase (2018-2021). Authors from the Italian National Institute of Astrophysics (INAF) are grateful for the support received through the agreement ASI-INAF n. 2n. 2018-29-HH.0. Open access funding provided by Istituto Nazionale di Astrofisica within the CRUI-CARE Agreement., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Aims. Gamma-ray burst (GRB) 190829A (z=0.0785) was detected by Fermi and Swift and also at very high energy (VHE) by the High-Energy Stereoscopic System (H.E.S.S.) telescopes. The prompt emission displayed two emission episodes separated by a quiescent gap of similar to 40 s. We present the 10.4 m Gran Telescopio Canarias (GTC) observations of the afterglow of GRB 190829A and its underlying supernova. We also compare GRB 190829A to GRB 180728A, a GRB with similar behaviour, and discuss the implications on underlying physical mechanisms producing these two GRBs.Methods. We present multi-band photometric data along with spectroscopic follow-up observations taken with the 10.4 m GTC telescope. Together with the data from the prompt emission, the 10.4 m GTC data are used to understand the emission mechanisms and possible progenitor.Results. A detailed analysis of the multi-band observations of the afterglow requires the cooling frequency to pass between the optical and X-ray bands at early epochs. The afterglow then transitions to the underlying supernova (SN) 2019oyw, which dominates later on.Conclusions. Although the prompt emission temporal properties of GRB 190829A and GRB 180728A are similar, the two pulses are different in the spectral domain. We find that SN 2019oyw associated with GRB 190829A is powered by Ni decay and is a Type Ic-BL SN. The spectroscopic and photometric properties of this SN are consistent with those observed for SN 1998bw, but evolved earlier. © ESO 2021., Based on observations made with the GTC telescope, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, part of them under Director's Discretionary Time. This work has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC) and the Leicester Database and Archive Service (LEDAS), provided by NASA's Goddard Space Flight Center and the Department of Physics and Astronomy, Leicester University, UK, respectively. Y.-D.H., A.J.C.-T., I.A. and D.A.K. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the `Center of Excellence Severo Ochoa' award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709). R.G, S.B.P., and A.A. acknowledge BRICS grant DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G) for part of the work. V.A.F. was supported by RFBR 18-29-21030 grant. S.B.P. also acknowledges DST/INT/JSPS/P/281/2018 for the present work. B.-B.Z. acknowledges the supported by the Fundamental Research Funds for the Central Universities (14380035). This work is supported by National Key Research and Development Programs of China (2018YFA0404204), the National Natural Science Foundation of China (Grant Nos. 11833003) and the Program for Innovative Talents, Entrepreneur in Jiangsu. D.A.K. acknowledges support from Spanish research project RTI2018-098104-J-I00 (GRBPhot). Finally, the authors extend their thanks to the anonymous referee for their valuable comments that helped to improve the manuscript substantially.

Full list of authors: Gupta, Rahul; Oates, S. R.; Pandey, S. B.; Castro-Tirado, A. J.; Joshi, Jagdish C.; Hu, Y. -D; Valeev, A. F.; Zhang, B. B.; Zhang, Z.; Kumar, Amit; Aryan, A.; Lien, A ; Kumar, B.; Cui, Ch; Wang, Ch; Dimple; Bhattacharya, D.; Sonbas, E.; Bai, J.; Tello, J. C.; Gorosabel, J.; Castro Ceron, J. M.; Porto, J. R. F.; Misra, K.; De Pasquale, M.; Caballero-Garcia, M. D.; Jelinek, M.; Kubanek, P.; Minaev, P.; Cunniffe, R.; Sanchez-Ramirez, R.; Guziy, S.; Jeong, S.; Tiwari, S. N.; Razzaque, S.; Bhalerao, V.; Pintado, V. C.; Sokolov, V. V.; Zhao, X.; Fan, Y.; Xin, Y.

Nature astronomy 387, 38 (2020). doi:10.1038/s41550-020-1183-3, LIGO and Virgo���s third observing run revealed the first neutron star���black hole (NSBH) merger candidates in gravitational waves. These events are predicted to synthesize r-process elements creating optical/near-infrared ���kilonova��� emission. The joint gravitational wave and electromagnetic detection of an NSBH merger could be used to constrain the equation of state of dense nuclear matter, and independently measure the local expansion rate of the Universe. Here, we present the optical follow-up and analysis of two of the only three high-significance NSBH merger candidates detected to date, S200105ae and S200115j, with the Zwicky Transient Facility. The Zwicky Transient Facility observed ~48% of S200105ae and ~22% of S200115j���s localization probabilities, with observations sensitive to kilonovae brighter than ���17.5 mag fading at 0.5 mag d$^{���1}$ in the g- and r-bands; extensive searches and systematic follow-up of candidates did not yield a viable counterpart. We present state-of-the-art kilonova models tailored to NSBH systems that place constraints on the ejecta properties of these NSBH mergers. We show that with observed depths of apparent magnitude ~22 mag, attainable in metre-class, wide-field-of-view survey instruments, strong constraints on ejecta mass are possible, with the potential to rule out low mass ratios, high black hole spins and large neutron star radii., Published by Nature Publishing Group, London

We present the results from an X-ray variability study of IRAS 13224-3809. This is probably the best source for X-ray reverberation studies since it is X-ray bright, extremely variable, and it has been extensively observed with XMM-Newton. We used all the archival XMM-Newton data from the three EPIC cameras (to increase the signal-to-noise) and, given the many observations of the source, we were able to compute the time-lags spectra in three different flux levels/periods. We fitted the time-lags and energy spectra, simultaneously, using a new X-ray reverberation code which computes the time dependent reflection spectra of the disc as a response to an X-ray flash from a point source located on the axis of the black-hole (BH) accretion disc (lamp-post geometry). To the best of our knowledge, this is the first time for an AGN that both time-lags and energy spectra are fitted by a model simultaneously in different flux periods. The model fits in the case when the BH is rapidly rotating are significantly better than the model fits in the case of a Schwarzschild BH. This result strongly favours the hypothesis of a rotating central BH in this source. We also detect significant variations in the height of the X-ray corona. The X-ray height appears to increase from 3-5 gravitational radii when the X-ray luminosity is of the order of 1.5-3 percent of the Eddington limit, up to 10 gravitational radii, when the luminosity doubles., Accepted for publication in MNRAS (18th Aug. 2020)

All authors: Kasliwal, Mansi M.; Anand, Shreya; Ahumada, Tomás; Stein, Robert; Carracedo, Ana Sagués; Andreoni, Igor; Coughlin, Michael W.; Singer, Leo P.; Kool, Erik C.; De, Kishalay; Kumar, Harsh; AlMualla, Mouza; Yao, Yuhan; Bulla, Mattia; Dobie, Dougal; Reusch, Simeon; Perley, Daniel A.; Cenko, S. Bradley; Bhalerao, Varun; Kaplan, David L.; Sollerman, Jesper; Goobar, Ariel; Copperwheat, Christopher M.; Bellm, Eric C.; Anupama, G. C.; Corsi, Alessandra; Nissanke, Samaya; Agudo, Iván; Bagdasaryan, Ashot; Barway, Sudhanshu; Belicki, Justin; Bloom, Joshua S.; Bolin, Bryce; Buckley, David A. H.; Burdge, Kevin B.; Burruss, Rick; Caballero-García, Maria D.; Cannella, Chris; Castro-Tirado, Alberto J.; Cook, David O.; Cooke, Jeff; Cunningham, Virginia; Dahiwale, Aishwarya; Deshmukh, Kunal; Dichiara, Simone; Duev, Dmitry A.; Dutta, Anirban; Feeney, Michael; Franckowiak, Anna; Frederick, Sara; Fremling, Christoffer; Gal-Yam, Avishay; Gatkine, Pradip; Ghosh, Shaon; Goldstein, Daniel A.; Golkhou, V. Zach; Graham, Matthew J.; Graham, Melissa L.; Hankins, Matthew J.; Helou, George; Hu, Youdong; Ip, Wing-Huen; Jaodand, Amruta; Karambelkar, Viraj; Kong, Albert K. H.; Kowalski, Marek; Khandagale, Maitreya; Kulkarni, S. R.; Kumar, Brajesh; Laher, Russ R.; Li, K. L.; Mahabal, Ashish; Masci, Frank J.; Miller, Adam A.; Mogotsi, Moses; Mohite, Siddharth; Mooley, Kunal; Mroz, Przemek; Newman, Jeffrey A.; Ngeow, Chow-Choong; Oates, Samantha R.; Patil, Atharva Sunil; Pandey, Shashi B.; Pavana, M.; Pian, Elena; Riddle, Reed; Sánchez-Ramírez, Rubén; Sharma, Yashvi; Singh, Avinash; Smith, Roger; Soumagnac, Maayane T.; Taggart, Kirsty; Tan, Hanjie; Tzanidakis, Anastasios; Troja, Eleonora; Valeev, Azamat F.; Walters, Richard; Waratkar, Gaurav; Webb, Sara; Yu, Po-Chieh; Zhang, Bin-Bin; Zhou, Rongpu; Zolkower, Jeffry, We present a systematic search for optical counterparts to 13 gravitational wave (GW) triggers involving at least one neutron star during LIGO/Virgo's third observing run (O3). We searched binary neutron star (BNS) and neutron star black hole (NSBH) merger localizations with the Zwicky Transient Facility (ZTF) and undertook follow-up with the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration. The GW triggers had a median localization area of 4480 deg2, a median distance of 267 Mpc, and false-alarm rates ranging from 1.5 to 10-25 yr-1. The ZTF coverage in the g and r bands had a median enclosed probability of 39%, median depth of 20.8 mag, and median time lag between merger and the start of observations of 1.5 hr. The O3 follow-up by the GROWTH team comprised 340 UltraViolet/Optical/InfraRed (UVOIR) photometric points, 64 OIR spectra, and three radio images using 17 different telescopes. We find no promising kilonovae (radioactivity-powered counterparts), and we show how to convert the upper limits to constrain the underlying kilonova luminosity function. Initially, we assume that all GW triggers are bona fide astrophysical events regardless of false-alarm rate and that kilonovae accompanying BNS and NSBH mergers are drawn from a common population; later, we relax these assumptions. Assuming that all kilonovae are at least as luminous as the discovery magnitude of GW170817 (-16.1 mag), we calculate that our joint probability of detecting zero kilonovae is only 4.2%. If we assume that all kilonovae are brighter than-16.6 mag (the extrapolated peak magnitude of GW170817) and fade at a rate of 1 mag day-1 (similar to GW170817), the joint probability of zero detections is 7%. If we separate the NSBH and BNS populations based on the online classifications, the joint probability of zero detections, assuming all kilonovae are brighter than-16.6 mag, is 9.7% for NSBH and 7.9% for BNS mergers. Moreover, no more than 10-4, or φ > 30° to be consistent with our limits. We look forward to searches in the fourth GW observing run; even 17 neutron star mergers with only 50% coverage to a depth of-16 mag would constrain the maximum fraction of bright kilonovae to, This work was supported by the Global Relay of Observatories Watching Transients Happen (GROWTH) project, funded by the National Science Foundation under PIRE grant No. 1545949. GROWTH is a collaborative project among the California Institute of Technology (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Texas Tech University (USA), San Diego State University (USA), University of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Indian Institute of Technology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (UK), and University of Sydney (Australia). Based on observations obtained with the Samuel Oschin Telescope 48 inch and the 60 inch telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. The ZTF is supported by the National Science Foundation under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. The ZTF forced photometry service was funded under Heising-Simons Foundation grant No. 12540303 (PI: Graham). The SED Machine is based upon work supported by the National Science Foundation under grant No. 1106171. The GROWTH-India telescope is a 70 cm telescope with a 0.7 degrees field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). The GROWTH-India project is supported by SERB and administered by IUSSTF under grant No. IUSSTF/PIRE Program/GROWTH/2015-16. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France (doi: 10.26093/cds/vizier). The original description of the VizieR service was published in A&AS 143, 23. These results made use of the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell is a private, nonprofit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University, and Yale University. The Large Monolithic Imager was built by Lowell Observatory using funds provided by the National Science Foundation (AST-1005313). The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale and a grant from the Mt. Cuba Astronomical Foundation. The KPED team thanks the National Science Foundation and the National Optical Astronomical Observatory for making the Kitt Peak 2.1 m telescope available. We thank the observatory staff at Kitt Peak for their efforts to assist Robo-AO KP operations. The KPED team thanks the National Science Foundation, the National Optical Astronomical Observatory, the Caltech Space Innovation Council, and the Murty family for support in the building and operation of KPED. In addition, they thank the CHIMERA project for use of the Electron Multiplying CCD (EMCCD). The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Some spectroscopic observations were obtained with the Southern African Large Telescope (SALT). The Photometric Redshifts for the Legacy Surveys (PRLS) catalog used in this paper was produced thanks to funding from the U.S. Department of Energy Office of Science, Office of High Energy Physics, via grant DE-SC0007914. This publication has made use of data collected at Lulin Observatory, partly supported by MoST grant 108-2112-M-008-001. Based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias on the island of La Palma. M.M.K. acknowledges generous support from the David and Lucille Packard Foundation. M.W.C. acknowledges support from the National Science Foundation with grant No. PHY-2010970. A.G. and J.S. acknowledge support from the Knut and Alice Wallenberg Foundation and GREAT research environment grant 2016-06012, funded by the Swedish Research Council. Some of the work by D.A.P. was performed at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. D.A.P. was partially supported by a grant from the Simons Foundation. H.K. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. This work has been supported by the Spanish Science Ministry Centro de Excelencia Severo Ochoa Program under grant SEV-2017-0709. A.J.C.T. acknowledges support from the Junta de Andalucia (Project P07-TIC-03094) and Spanish Ministry Projects AYA2012-39727-C03-01, AYA2015-71718R, and PID-019-109974RB-I00. V.A.F. was supported by grant RFBR 19-02-00432. I.A. acknowledges support by a Ramon y Cajal grant (RYC-2013-14511) of the Ministerio de Ciencia, Innovacion, y Universidades (MICIU) of Spain. He also acknowledges financial support from MCIU through grant AYA2016-80889-P. A.A.M. is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow by the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). A.C. acknowledges support from the National Science Foundation with grant No. 1907975. W.-H.I., A. K., K.-L.L., C.-C.N., A.P., H.T., and P.-C.Y. acknowledge support from Ministry of Science and Technology (MoST) Taiwan grants 104-2923-M-008-004-MY5, 107-2119-M-008-012, 108-2628-M-007-005-RSP, and 108-2112-M-007-025-MY3. D.D. is supported by an Australian Government Research Training Program Scholarship. S.A. is supported by the GROWTH project, funded by the National Science Foundation under PIRE grant No. 1545949. A.S.C. is supported by GREAT research environment grant 2016-06012, funded by the Swedish Research Council. E.C.K. acknowledges support from the G.R.E.A.T. research environment and the Wenner-Gren Foundations. A.J.C.T. is thankful for fruitful discussions with J. Cepa, E. Fernandez-Garcia, J. A. Font, S. Jeong, A. Martin-Carrillo, A. M. Sintes, and S. Sokolov. D.A.H.B. acknowledges research support from the National Research Foundation of South Africa. S.B.P. and V.B. acknowledge BRICS grant No. "DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G)" for part of the present work. J.S.B. was partially supported by a Gordon and Betty Moore Foundation Data-Driven Discovery grant and a grant from the National Science Foundation, "Conceptualization of a Scalable Cyberinfrastructure Center for Multimessenger Astrophysics."

X-ray reverberation echoes are assumed to be produced in the strongly distorted spacetime around accreting supermassive black holes. This signal allows us to spatially map the geometry of the inner accretion flow - a region which cannot yet be spatially resolved by any telescope - and provides a direct measure of the black hole mass and spin. The reverberation timescale is set by the light travel path between the direct emission from a hot X-ray corona and the reprocessed emission from the inner edge of the accretion disc. However, there is an inherent degeneracy in the reverberation signal between black hole mass, inner disc radius and height of the illuminating corona above the disc. Here, we use a long X-ray observation of the highly-variable active galaxy, IRAS 13224-3809, to track the reverberation signal as the system evolves on timescales of a day. With the inclusion of all the relativistic effects, modelling reveals that the height of the X-ray corona increases with increasing luminosity, providing a dynamic view of the inner accretion region. This simultaneous modelling allows us to break the inherent degeneracies and obtain an independent timing-based estimate for the mass and spin of the black hole. The uncertainty on black hole mass is comparable to the leading optical reverberation method, making X-ray reverberation a powerful technique, particularly for sources with low optical variability., Comment: Accepted Nat. Ast. version

Space Telescopes and Instrumentation 2020: Ultraviolet to Gamma Ray; Virtual, Online; United States; 14 December 2020 through 18 December 2020; Code 166330.--Proceedings of SPIE - The International Society for Optical Engineering Volume 11444, 2020, Article number 114448S.--Full list of authors: Gasent-Blesa, J. L.; Reglero, V.; Connell, P.; Pinazo-Herrero, B.; Navarro-González, J.; Rodríguez-Martínez, P.; Castro-Tirado, A. J.; Caballero-García, M. D.; Amati, L.; Labanti, C.; Mereghetti, S.; Frontera, F.; Campana, R.; Orlandini, M.; Stephen, J.; Terenzi, L.; Evangelisti, F.; Squerzanti, S.; Melchiorri, M.; Fuschino, F. De Rosa, A.; Morgante, G., Within the scientific goals of the THESEUS ESA/M5 candidate mission, a critical item is a fast (within a few s) and accurate (, THESEUS/XGIS instrument is supported by: the ASI-INAF Agreement n. 2018-29-HH.0; the OHB Italia/INAF-OASBo Agreement n.2331/2020/01; the European Space Agency ESA through the M5/NPMC Programme; the AHEAD2020 project funded by the UE through H2020-INFRAIA-2018-2020; the Spanish Ministerio de Ciencia e Innovaci?n, PID2019 109269RB-C41; the Polish National Science Centre, Project 2019/35/B/ST9/03944 and Foundation for Polish Science, Project POIR.04.04.00-00-5C65/17-00. The authors thank all the members of the THESEUS team involved in the development of XGIS instrument.

On 2019 August 14, the Advanced LIGO and Virgo interferometers detected the high-significance gravitational wave (GW) signal S190814bv. The GW data indicated that the event resulted from a neutron star-black hole (NSBH) merger, or potentially a low-mass binary BH merger. Due to the low false-alarm rate and the precise localization (23 deg at 90%), S190814bv presented the community with the best opportunity yet to directly observe an optical/near-infrared counterpart to an NSBH merger. To search for potential counterparts, the GROWTH Collaboration performed real-time image subtraction on six nights of public Dark Energy Camera images acquired in the 3 weeks following the merger, covering >98% of the localization probability. Using a worldwide network of follow-up facilities, we systematically undertook spectroscopy and imaging of optical counterpart candidates. Combining these data with a photometric redshift catalog, we ruled out each candidate as the counterpart to S190814bv and placed deep, uniform limits on the optical emission associated with S190814bv. For the nearest consistent GW distance, radiative transfer simulations of NSBH mergers constrain the ejecta mass of S190814bv to be M < 0.04 M at polar viewing angles, or M < 0.03 M if the opacity is κ < 2 cmg. Assuming a tidal deformability for the NS at the high end of the range compatible with GW170817 results, our limits would constrain the BH spin component aligned with the orbital momentum to be χ < 0.7 for mass ratios Q < 6, with weaker constraints for more compact NSs., This work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation under PIRE grant No. 1545949. GROWTH is a collaborative project among California Institute of Technology (USA), University of Maryland College Park (USA), University of Wisconsin Milwaukee (USA), Texas Tech University (USA), San Diego State University (USA), University of Washington (USA), Los Alamos National Laboratory (USA), Tokyo Institute of Technology (Japan), National Central University (Taiwan), Indian Institute of Astrophysics (India), Indian Institute of Technology Bombay (India), Weizmann Institute of Science (Israel), The Oskar Klein Centre at Stockholm University (Sweden), Humboldt University (Germany), Liverpool John Moores University (UK), and University of Sydney (Australia). D.A.G. acknowledges support from Hubble Fellowship grant HST-HF2-51408.001-A. Support for program No. HST-HF251408.001-A is provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. We gratefully acknowledge Amazon Web Services, Inc., for a generous grant (PS_IK_ FY2019_Q3_ Caltech_Gravitational_Wave) that funded our use of the Amazon Web Services cloud computing infrastructure to process the DECam data. P.E.N. acknowledges support from the DOE through DE-FOA-0001088, Analytical Modeling for Extreme-Scale Computing Environments. D.A.P. and D.A.G. performed the work associated with this project at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. This work was partially supported by a grant from the Simons Foundation. A.J.C.-T. thanks I. Agudo, J. Cepa, V. Dhillon, J. A. Font, A. MartinCarrillo, S. R. Oates, S. B. Pandey, E. Pian, R. Sanchez-Ramirez, A. M. Sintes, V. Sokolov, and B.-B. Zhang for fruitful conversations. F.F. gratefully acknowledges support from NASA through grant 80NSSC18K0565 and from the NSF through grant PHY1806278. M.B., A.G., E.K., S.D., and J.S. acknowledge support from the G.R.E.A.T research environment funded by the Swedish National Science Foundation. J.S. acknowledges support from the Knut and Alice Wallenberg Foundation. J.S.B. and K.Z. are partially supported by a Gordon and Betty Moore Foundation Data-Driven Discovery grant. D.A.H.B. acknowledges research support from the National Research Foundation of South Africa. M.W.C. is supported by the David and Ellen Lee Postdoctoral Fellowship at the California Institute of Technology. S.N. and G.R. are grateful for support from VIDI, Projectruimte, and TOP Grants of the Innovational Research Incentives Scheme (Vernieuwingsimpuls) financed by the Netherlands Organization for Scientific Research (NWO). H.K. and K.Z. thank the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. D.D. is supported by an Australian Government Research Training Program Scholarship. P.G. is supported by NASA Earth and Space Science Fellowship (ASTRO18F-0085). D.L.K. was supported by NSF grant AST-1816492. Y.D.H. thanks the support by the program of China Scholarships Council (CSC) under grant No. 201406660015. A.K.H.K. acknowledges support from the Ministry of Science and Technology of the Republic of China (Taiwan) through grants 107-2628-M-007-003 and 1082628-M-007-005-RSP. V.Z.G. acknowledges support from the University of Washington College of Arts and Sciences, Department of Astronomy, and the DIRAC Institute. University of Washington's DIRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences and the Washington Research Foundation. M.J. and A.C. acknowledge the support of the Washington Research Foundation Data Science Term Chair fund and the UW Provost's Initiative in Data-Intensive Discovery. S.M. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant-1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. M.G. is supported by the Polish NCN MAESTRO grant 2014/14/A/ST9/00121. This research has made use of the VizieR catalog access tool, CDS, Strasbourg, France (doi:10.26093/cds/vizier). The original description of the VizieR service was published in A&AS 143, 23. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaborating institutions: Argonne National Lab, University of California Santa Cruz, University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, University of Chicago, University College London, DES-Brazil consortium, University of Edinburgh, ETH-Zurich, University of Illinois at Urbana-Champaign, Institut de Ciencies de l'Espai, Institut de Fisica d'Altes Energies, Lawrence Berkeley National Lab, Ludwig-Maximilians Universitat, University of Michigan, National Optical Astronomy Observatory, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Lab, Stanford University, University of Sussex, and Texas A&M University. Funding for DES, including DECam, has been provided by the U.S. Department of Energy, National Science Foundation, Ministry of Education and Science (Spain), Science and Technology Facilities Council (UK), Higher Education Funding Council (England), National Center for Supercomputing Applications, Kavli Institute for Cosmological Physics, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo a Pesquisa, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Ministerio da Ciencia e Tecnologia (Brazil), the German Research Foundation-sponsored cluster of excellence "Origin and Structure of the Universe," and the DES collaborating institutions. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. This work is partly based on data obtained with the instrument OSIRIS, built by a Consortium led by the Instituto de Astrofisica de Canarias in collaboration with the Instituto de Astronomia of the Universidad Autonoma de Mexico. OSIRIS was funded by GRANTECAN and the National Plan of Astronomy and Astrophysics of the Spanish Government. Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT). Polish participation in SALT is funded by grant No. MNiSW DIR/WK/2016/07.

GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at z = 0.1613, at a projected physical offset of 16 kpc from the galaxy's center. We present X-ray, optical/nIR, and radio observations of its counterpart and model them with two distinct components of emission: a standard afterglow, arising from the interaction of the relativistic jet with the surrounding medium, and a kilonova, powered by the radioactive decay of the sub-relativistic ejecta. Broadband modelling of the afterglow data reveals a weak reverse shock propagating backward into the jet, and a likely jet-break at 3.5 d. This is consistent with a structured jet seen slightly off-axis (theta(view) similar to theta(core)) while expanding into a low-density medium (n approximate to 10(-3) cm(-3)). Analysis of the kilonova properties suggests a rapid evolution towards red colours, similar to AT2017gfo, and a low-nIR luminosity, possibly due to the presence of a long-lived neutron star. The global properties of the environment, the inferred low mass (M-ej less than or similar to 0.006 M-circle dot) and velocities (v(ej) greater than or similar to 0.05c) of lanthanide-rich ejecta are consistent with a binary neutron star merger progenitor.© 2019 The Authors., Partial support of the DCT was provided by Discovery Communications. LMI was built by Lowell Observatory using funds from the National Science Foundation (AST-1005313). The work is partly based on the observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. ET acknowledges financial support provided by the National Aeronautics and Space Administration through HST-GO14357, HST-GO14087, HST-GO14607, and HST-GO14850 grants from the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Incorporated. AJCT, YDH e IM acknowledge financial support from the State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). The development of CIRCE at GTC was supported by the University of Florida and the National Science Foundation (grant AST-0352664), in collaboration with IUCAA. RSR acknowledges support by Italian Space Agency (ASI) through the Contract no. 2015-046-R.0 and by AHEAD the European Union Horizon 2020 Programme under the AHEAD project (grant agreement no. 654215). YDH also acknowledges the support by the program of China Scholarships Council (CSC) under the grant no. 201406660015. JBG acknowledges the support of the Viera y Clavijo program funded by ACIISI and ULL. GN and AT acknowledge funding in the framework of the project ULTraS (ASI-INAF contract no. 2017-14-H.0). GR acknowledges the support of the University of Maryland through the Joint Space Science Institute Prize Postdoctoral Fellowship.

We investigate the prompt emission and the afterglow properties of short-duration gamma-ray burst (sGRB) 130603B and another eight sGRB events during 2012-2015, observed by several multiwavelength facilities including the Gran Canarias Telescope 10.4 m telescope. Prompt emission high energy data of the events were obtained by INTEGRAL-SPI-ACS, Swift-BAT, and Fermi-GBM satellites. The prompt emission data by INTEGRAL in the energy range of 0.1-10 MeV for sGRB 130603B, sGRB 140606A, sGRB 140930B, sGRB 141212A, and sGRB 151228A do not show any signature of the extended emission or precursor activity and their spectral and temporal properties are similar to those seen in case of other short bursts. For sGRB 130603B, our new afterglow photometric data constrain the pre-jet-break temporal decay due to denser temporal coverage. For sGRB 130603B, the afterglow light curve, containing both our new and previously published photometric data is broadly consistent with the ISM afterglow model. Modeling of the host galaxies of sGRB 130603B and sGRB 141212A using the LePHARE software supports a scenario in which the environment of the burst is undergoing moderate star formation activity. From the inclusion of our late-time data for eight other sGRBs we are able to: place tight constraints on the non-detection of the afterglow, host galaxy, or any underlying 'kilonova' emission. Our late-time afterglow observations of the sGRB 170817A/GW170817 are also discussed and compared with the sub-set of sGRBs.© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, AJCT acknowledges support from the Junta de Andalucia (Project P07-TIC-03094) and support from the Spanish Ministry Projects AYA2012-39727-C03-01 and 201571718R. This work has been supported by the Spanish Science Ministry 'Centro de Excelencia SeveroOchoa' Program under grant SEV-2017-0709. FEDER funds are acknowledged. E.S. acknowledges assistance from the Scientific and Technological Research Council of Turkey (TUBITAK) through project 112T224. We thank TUBITAK for a partial support in using T100 telescope with project number 10CT100-95. A.S.P acknowledges partial support grants RFBR 17-02-01388, 17-51-44018, and 1752-80139. E.D.M., A.A.V., and P.Yu.M. are grateful to RSCF grant 18-12-00522 for support. B.-B.Z. acknowledges support from National Thousand Young Talents program of China and National Key Research and Development Program of China (2018YFA0404204). R.Ya.I. is grateful for partial support by the grant RUSTAVELI/FR/379/6-300/14. R.S.R. acknowledges support from ASI (Italian Space Agency) through the Contract No. 2015-046R.0 and from European Union Horizon 2020 Programme under the AHEAD project (grant agreement No. 654215). SJ acknowledges the support of the Korea Basic Science Research Program through NRF-2015R1D1A4A01020961.

We analyzed the X-ray power density spectra of five ultraluminous X-ray sources (ULXs) NGC5408 X-1, NGC6946 X-1, M82 X-1, NGC1313 X-1 and IC342 X-1 that are the only ULXs which display both flat-topped noise (FTN) and quasi-periodic oscillations (QPO). We studied the QPO frequencies, fractional root-mean-square (rms) variability, X-ray luminosity and spectral hardness. We found that the level of FTN is anti-correlated with the QPO frequency. As the frequency of the QPO and brightness of the sources increase, their fractional variability decreases. We propose a simple interpretation using the spherizarion radius, viscosity time and $\alpha$-parameter as basic properties of these systems. The main physical driver of the observed variability is the mass accretion rate which varies >3 between different observations of the same source. As the accretion rate decreases the spherization radius reduces and the FTN plus the QPO move toward higher frequencies resulting in a decrease of the fractional rms variability. We also propose that in all ULXs when the accretion rate is low enough (but still super-Eddington) the QPO and FTN disappear. Assuming that the maximum X-ray luminosity depends only on the black hole (BH) mass and not on the accretion rate (not considering the effects of either the inclination of the super-Eddington disc nor geometrical beaming of radiation) we estimate that all the ULXs have about similar BH masses, with the exception of M82 X-1, which might be 10 times more massive., Comment: 15 pages, 7 figures, accepted for publication in MNRAS

Ultra-Luminous X-ray sources (ULXs) are accreting black holes for which their X-ray properties have been seen to be different to the case of stellar-mass black hole binaries. For most of the cases their intrinsic energy spectra are well described by a cold accretion disc (thermal) plus a curved high-energy emission components. The mass of the black hole (BH) derived from the thermal disc component is usually in the range of 100-105 solar masses, which have led to the idea that this can represent strong evidence of the Intermediate Mass Black Holes (IMBH), proposed to exist by theoretical studies but with no firm detection (as a class) so far. Recent theoretical and observational developments are leading towards the idea that these sources are instead compact objects accreting at an unusual super-Eddington regime instead. On the other hand, gravitational waves have been seen to be a useful tool for finding (some of these) IMBHs. We give a brief overview about the recent advent of the discovery of gravitational waves and their relationship with these so far elusive IMBHs.© 2017 Universidad Nacional Autonoma de Mexico. All rights reserved, MCG, MB and MD acknowledge support provided by the European Seventh Frame -work Programme (FP7/2007-2013) under grant agreement no 312789 and GA CR grant 18-005335. SF acknowledges support by the Russian Science Foundation (N 14-50-00043) and the Russian Government Program of Competitive Growth of KFU. AJCT acknowledges support from the Spanish MINECO Ministry project: AYA2015-71718-R.

The ejecta composition is an open question in gamma-ray burst (GRB) physics . Some GRBs possess a quasi-thermal spectral component in the time-resolved spectral analysis , suggesting a hot fireball origin. Others show a featureless non-thermal spectrum known as the Band function , consistent with a synchrotron radiation origin and suggesting that the jet is Poynting-flux dominated at the central engine and probably in the emission region as well . There are also bursts showing a sub-dominant thermal component and a dominant synchrotron component , suggesting a probable hybrid jet composition . Here, we report an extraordinarily bright GRB 160625B, simultaneously observed in gamma-ray and optical wavelengths, whose prompt emission consists of three isolated episodes separated by long quiescent intervals, with the durations of each sub-burst being approximately 0.8 s, 35 s and 212 s, respectively. Its high brightness (with isotropic peak luminosity L ≈ 4 × 10 erg s) allows us to conduct detailed time-resolved spectral analysis in each episode, from precursor to main burst and to extended emission. The spectral properties of the first two sub-bursts are distinctly different, allowing us to observe the transition from thermal to non-thermal radiation between well-separated emission episodes within a single GRB. Such a transition is a clear indication of the change of jet composition from a fireball to a Poynting-flux-dominated jet., B.-B.Z. thanks Y.-Z. Fan, Y.-Z. Wang, H. Wang, K. D. Alexander and D. Lazzati for helpful discussions. We are grateful to K. Hurley, I. Mitrofanov, A. Sanin, M. Litvak and W. Boynton for the use of Mars Odyssey data in the triangulation. We acknowledge the use of the public data from the Swift and Fermi data archives. B.-B. Z. and A.J. C.-T. acknowledge support from the Spanish Ministry Projects AYA2012-39727-C03-01 and AYA2015-71718-R. Part of this work made use of B.-B.Z.'s personal Interactive Data Language (IDL) code library ZBBIDL and personal Python library ZBBPY. The computation resources used in this work are owned by Scientist Support LLC. B.Z. acknowledges NASA NNX14AF85G and NNX15AK85G for support. Z. G. D. acknowledges the National Natural Science Foundation of China(NSFC) (grant 11573014). Y.-D. H. acknowledges support by China Scholarships Council (grant 201406660015). Mini-MegaTORTORA belongs to Kazan Federal University, and the work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University. A. P., E.M., P. M. and A.V. are grateful to the Russian Foundation for Basic Research (grant 17-02-01388) for partial support. A. P. and S.B.P. acknowledge joint BRICS (Brazil, Russia, India, China and South Africa) grant RFBR 17-52-80139 and 388-ProFChEAP for partial support. R. I. is grateful to grant RUSTAVELI FR/379/6300/ 14 for partial support. Observations on Mini-MegaTORTORA are supported by the Russian Science Foundation (grant 14-50-00043). A.V.F. and A. M. thank the Russian Science Foundation (grant 14-50-00043). L.M. and A.F.Z. acknowledge support from INTA-CEDEA ESAt personnel hosting the Pi of the Sky facility at the BOOTES-1 station. H. G. and X.-Y.W. acknowledge NSFC (grants 11603003 and 11625312, respectively). Z. G. D., X.-F. W., B.Z., X.-Y. W.,L.S. and F.-W.Z. are also supported by the 973 program (grant 2014CB845800). F.-W.Z. is also supported in part by the NSFC (grants U1331101 and 11163003), the Guangxi Natural Science Foundation (grant 2013GXNSFAA019002) and the project of outstanding young teachers' training in higher education institutions of Guangxi. L.S. acknowledges support by the NSFC (grant 11103083) and the Joint NSFC-ISF Research Program (grant 11361140349). S.O. acknowledges the support of the Leverhulme Trust. S.J. acknowledges support from Korea Basic Science Research Program through NRF-2014R1A6A3A03057484 and NRF-2015R1D1A4A01020961, and I. H. P. through NRF-2015R1A2A1A01006870 and NRF-2015R1A2A1A15055344. R. A., D. F. and D. S. acknowledge support from RSF (grant 17-12-01378). A. K. acknowledges the Science and Education Ministry of Kazakhstan (grant 0075/GF4).

We present briefly the first results obtained by the application of the KYNREFREV-reverberation model, which is ready for its use in XSPEC. This model computes the time dependent reflection spectra of the disc as a response to a flash of primary power-law radiation from a point source corona located on the axis of the black-hole accretion disc. The assumptions of the model are: central Kerr black hole, surrounded by a Keplerian, geometrically thin, optically thick, ionised disc with the possibility of defining the radial density profile and a stationary hot point-like patch of plasma located on the system rotation axis and emitting isotropic power-law radiation (lamp-post geometry). Full relativistic ray-tracing code in vacuum is used for photon paths from the corona to the disc and to the observer and from the disc to the observer. The ionisation of the disc is set for each radius according to the amount of the incident primary flux and the density of the accretion disc. In this paper we comment on some preliminary results obtained through the analysis of X-ray reverberation time-lags from 1H 0707-495 and IRAS 13224-3809., Comment: 10 pages, 5 figures and 2 tables. Submitted to Proceedings of Science ("APCS2016: Accretion Processes in Cosmic Sources" held at S. Petersburg, Eds. Franco Giovannelli & Lola Sabau-Graziati)

This is an erratum to the paper 'The afterglow and kilonova of the short GRB 160821B' (2019, MNRAS, 489, 2104-2116). In the original version of this article, the affiliations of K. Ackley were incorrect. They have now been corrected to: i) Monash Centre for Astrophysics, School of Physics and Astronomy, Monash University, VIC 3800, Australia ii) OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery, Clayton VIC 3800, Australia The authors apologise for this error.

Ultra-Luminous X-ray sources are thought to be accreting black holes that might host Intermediate Mass Black Holes (IMBH), proposed to exist by theoretical studies, even though a firm detection (as a class) is still missing. The brightest ULX in M82 (M82 X-1) is probably one of the best candidates to host an IMBH. In this work we analyzed the data of the recent release of observations obtained from M82 X-1 taken by XMM-Newton. We performed a study of the timing and spectral properties of the source. We report on the detection of (46+-2) mHz Quasi-Periodic Oscillations (QPOs) in the power density spectra of two observations. A comparison of the frequency of these high-frequency QPOs with previous detections supports the 1:2:3 frequency distribution as suggested in other studies. We discuss the implications if the (46+-2) mHz QPO detected in M82 X-1 is the fundamental harmonic, in analogy with the High-Frequency QPOs observed in black hole binaries. For one of the observations we have detected for the first time a QPO at 8 mHz (albeit at a low significance), that coincides with a hardening of the spectrum. We suggest that the QPO is a milli-hertz QPO originating from the close-by transient ULX M82 X-2, with analogies to the Low-Frequency QPOs observed in black hole binaries., 9 pages (with 4 figures and 4 tables). Accepted for publication in MNRAS (26/09/13)

The notion of source states characterizing the X-ray emission from black hole binaries has revealed to be a very useful tool to disentangle the complex spectral and aperiodic phenomenology displayed by those classes of accreting objects. We seek to use the same tools for Ultra-Luminous X-ray (ULX) sources. We analyzed the data from the longest observations obtained from the ULX source in NGC 5408 (NGC 5408 X-1) taken by XMM-Newton. We performed a study of the timing and spectral properties of the source. In accordance with previous studies on similar sources, the intrinsic energy spectra of the source are well described by a cold accretion disc emission plus a curved high-energy emission component. We studied the broad-band noise variability of the source and found an anti-correlation between the root mean square variability in the 0.0001-0.2Hz and intensity, similarly to what is observed in black-hole binaries during the hard states. We discuss the physical processes responsible for the X-ray features observed and suggest that NGC 5408 X-1 harbors a black hole accreting in an unusual bright hard-intermediate state., Comment: 12 pages, including 6 figures and 3 tables. Accepted for publication in MNRAS (06/08/13)

We present observations of rapid (sub-second) optical flux variability in V404 Cyg during its 2015 June outburst. Simultaneous three-band observations with the ULTRACAM fast imager on four nights show steep power spectra dominated by slow variations on ~100-1000s timescales. Near the peak of the outburst on June 26, a dramatic change occurs and additional, persistent sub-second optical flaring appears close in time to giant radio and X-ray flaring. The flares reach peak optical luminosities of ~few x 10^{36} erg/s. Some are unresolved down to a time resolution of 24 milliseconds. Whereas the fast flares are stronger in the red, the slow variations are bluer when brighter. The redder slopes, emitted power, and characteristic timescales of the fast flares can be explained as optically-thin synchrotron emission from a compact jet arising on size scales ~140-500 Gravitational radii (with a possible additional contribution by a thermal particle distribution). The origin of the slower variations is unclear. The optical continuum spectral slopes are strongly affected by dereddening uncertainties and contamination by strong H{alpha} emission, but the variations of these slopes follow relatively stable loci as a function of flux. Cross-correlating the slow variations between the different bands shows asymmetries on all nights consistent with a small red skew (i.e., red lag). X-ray reprocessing and non-thermal emission could both contribute to these. These data reveal a complex mix of components over five decades in timescale during the outburst., MNRAS in press (Accepted Mar 04 2016; Revised Mar 03; Reviewed Feb 22; Received Dec 22 2015), Advance Access: http://mnras.oxfordjournals.org/content/early/2016/03/14/mnras.stw571.abstract

In this paper we present the best quality XMM-Newton and Suzaku data from M82 X-1 so far. We analyze the spectra of this remarkable Ultra-Luminous X-ray Source in a self-consistent manner. We have disentangled emission from the host galaxy, responsible for the soft X-ray emission (E

We present the previously unanalysed high quality XMM-Newton spectrum of an ultraluminous X-ray source candidate in NGC 4517. As with other high quality ULX spectra, a downturn in the spectrum is observed at ~6 keV. Both of the recent disc reflection and Comptonisation interpretations of this feature are applied, in order to present a direct comparison, and are found to provide statistically equivalent representations of the current data. We find that the reflection model requires the accretion disc to have a highly super-solar iron abundance, while the Comptonisation model requires low temperature Comptonising electrons, and for the corona to be optically thick. These physical requirements are discussed in detail, and physically motivated scenarios are highlighted in which each model can be considered a viable explanation for the observed emission. By extending our consideration of these two interpretations to high energies, we demonstrate that observations of ULXs at energies above ~10 keV should be extremely useful when attempting to distinguish between them. With current instrumentation, it is only viable to perform these observations for M82 X-1, but future high angular resolution hard X-ray imaging spectrometers, such as the Hard X-ray Imaging System due to fly on Astro-H, should go a long way to resolving this issue.

We present a systematic search for radio counterparts to Ultra Luminous X-ray (ULX) source candidates based on a cross-correlation of the Swartz et al. (2004) ULX catalogue based on Chandra data and the FIRST radio survey. We find seven cases of conspiscuous peaks of radio emission that could be associated to ULX sources. Among these seven ULX radio candidates, three X-ray sources are located within 5" of the FIRST radio peaks. These three cases are shown and discussed individually., 5 pages, 3 figures. Accepted for publication in the Astronomische Nachrichten, to appear in the proceedings of the conference "Ultra-Luminous X-ray sources and Middle Weight Black Holes" (Madrid, May 24-26, 2010). Resubmission corrects the Authors list and the acknowledgements

We apply a reflection-based model to the best available XMM-Newton spectra of X-ray bright UltraLuminous X-ray (ULX) sources (NGC 1313 X-1, NGC 1313 X-2, M 81 X-6, Holmberg IX X-1, NGC 5408 X-1 and Holmberg II X-1). A spectral drop is apparent in the data of all the sources at energies 6-7 keV. The drop is interpreted here in terms of relativistically-blurred ionized reflection from the accretion disk. A soft-excess is also detected from these sources (as usually found in the spectra of AGN), with emission from O K and Fe L, in the case of NGC 5408 X-1 and Holmberg II X-1, which can be understood as features arising from reflection of the disk. Remarkably, ionized disk reflection and the associated powerlaw continuum provide a good description of the broad-band spectrum, including the soft-excess. There is no requirement for thermal emission from the inner disk in the description of the spectra. The black holes of these systems must then be highly spinning, with a spin close to the maximum rate of a maximal spinning black hole. The results require the action of strong light bending in these sources. We suggest that they could be strongly accreting black holes in which most of the energy is extracted from the flow magnetically and released above the disc thereby avoiding the conventional Eddington limit., Accepted for publication in MNRAS

In the version of this Letter originally published, the letter i was mistakenly omitted from the surname of the author R. Sanchez-Ramirez. This has now been corrected.

12 pages, 10 figures, 3 tables.-- ISI Article Identifier: 000250480600041.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.1302, We present broadband (3-500 keV) INTEGRAL X-ray spectra and X-ray/optical light curves of the luminous black hole X-ray transient and relativistic jet source GRO J1655-40. Our analysis covers four Target of Opportunity observations of the outburst that started in 2005 February. We find that the high-energy emission of GRO J1655-40 can be modeled well with an unbroken power law (with photon indices Γ of 1.72 ± 0.03 and 2.21 ± 0.04 for the first and second observations). These correspond to hard and thermal-dominant states, respectively. In contrast to many other black hole spectra, high-energy complexity in the form of a break or cutoff is not required for the hard state, contrary to previous expectations. We show for the first time that Comptonization by nonthermal electrons is the dominant process behind the high-energy emission in the hard state. We discuss our results in terms of models for broadband emission and accretion flows in stellar-mass black holes., MDCG is a MEC funded PhD student supported under grants PNE2003-04352+ESP2005-07714-C03-03. This work is based on observations made with INTEGRAL, an ESA science mission with instruments and science data centre funded by ESA member states and with the participation of Russia and the USA.

Aims: We present a study of the Be/X-ray binary system V 0332+53 with the main goal of characterizing its behavior mainly during the intermediate-luminosity X-ray event on 2008. In addition, we aim to contribute to the understanding of the global behavior of the donor companion by including optical data from our dedicated campaign starting on 2006. Methods: V 0332+53 was observed by RXTE and Swift during the decay of the intermediate-luminosity X-ray outburst of 2008, as well as with Suzaku before the rising of the third normal outburst of the 2010 series. In addition, we present recent data from the Spanish ground-based astronomical observatories of El Teide (Tenerife), Roque de los Muchachos (La Palma), and Sierra Nevada (Granada), and since 2006 from the Turkish TUBITAK National Observatory (Antalya). We have performed temporal analyses to investigate the transient behaviour of this system during several outbursts. Results: Our optical study revealed that continuous mass ejection episodes from the Be star have been taking place since 2006 and another one is currently ongoing. The broad-band 1-60 keV X-ray spectrum of the neutron star during the decay of the 2008 outburst was well fitted with standard phenomenological models, enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron K-alpha fluorescence line at 6.4 keV. For the first time in V 0332+53 we tentatively see an increase of the cyclotron line energy with increasing flux (although further and more sensitive observations are needed to confirm this). Regarding the fast aperiodic variability, we detect a Quasi-Periodic Oscillation (QPO) at 227+-9 mHz only during the lowest luminosities. The latter fact might indicate that the inner regions surrounding the magnetosphere are more visible during the lowest flux states., Comment: Accepted for publication in A&A (13/01/16)

The Burst Observer and Optical Transient Exploring System (BOOTES) is a network of telescopes that allows the continuous monitoring of transient astrophysical sources. It was originally devoted to the study of the optical emission from gamma-ray bursts (GRBs) that occur in the Universe. In this paper we show the initial results obtained using the spectrograph COLORES (mounted on BOOTES-2), when observing optical transients (OTs) of diverse nature.© Czech Technical University in Prague, 2015., MCG is supported by the European social fund within the framework of realizing the project >Support of inter-sectoral mobility and quality enhancement of research teams at Czech Technical University in Prague>, CZ.1.07/2.3.00/30.0034. MJ and AJCT thank the support of the Spanish Ministry Projects AYA2009-14000-C03-01 and AYA2012-39727-C03-01. RH acknowledges GACR grant 13-33324S.

Aims. We present a multiwavelength study of the Be/X-ray binary system SAX J2103.5+4545 with the goal of better characterizing the transient behaviour of this source. Methods. SAX J2103.5+4545 was observed by Swift-XRT four times in 2007 from April 25 to May 5, and during quiescence in 2012 August 31. In addition, this source has been monitored from the ground-based astronomical observatories of El Teide (Tenerife, Spain), Roque de los Muchachos (La Palma, Spain) and Sierra Nevada (Granada, Spain) since 2011 August, and from the TUBITAK National Observatory (Antalya, Turkey) since 2009 June. We have performed spectral and photometric temporal analyses in order to investigate the different states exhibited by SAX J2103.5+4545. Results. In X-rays, an absorbed power law model provided the best fit for all the XRT spectra. An iron-line feature at ~6.42 keV was present in all the observations except for that taken during quiescence in 2012. The photon indexes are consistent with previous studies of SAX J2103.5+4545 in high/low luminosity states. Pulsations were found in all the XRT data from 2007 (2.839(2) mHz; MJD 54222.02), but not during quiescence. Both optical outbursts in 2010 and 2012 lasted for about 8/9 months (as the one in 2007 probably did and the current one in 2014 might do) and were most probably caused by mass ejection events from the Be star that eventually fed the circumstellar disc. All of these outbursts started about 3 months before the triggering of the X-ray activity, and about the same period before the maximum of the H_alpha line equivalent width (in emission) was reached at only ~ -5 \AA. In this work we found that the global correlation between the BV variability and the X-ray intensity was also observed at longer wavelengths in the IR domain., Comment: 11 pages, 7 figures, and online material (2 tables). Submitted to A&A in 2014 January

Ultra-Luminous X-ray sources are accreting black holes that might represent strong evidence of the Intermediate Mass Black Holes (IMBH), proposed to exist by theoretical studies but with no firm detection (as a class) so far. We analyze the best X-ray timing and spectral data from the ULX in NGC 5408 provided by XMM-Newton. The main goal is to study the broad-band noise variability of the source. We found an anti-correlation of the fractional root-mean square variability versus the intensity of the source, similar to black-hole binaries during hard states., Revised version. Proceedings of IAUS 290 "Feeding Compact Objects: Accretion on All Scales", C. M. Zhang, T. Belloni, M. Mendez & S. N. Zhang (eds.)

Aims: We used data from the 58 month long, continuous Swift/Burst Alert Telescope (BAT) observations of the five brightest Seyfert galaxies at hard X-rays, to study their flux and spectral variability in the 20-100 keV energy band. The column density in these objects is less than 10^24 cm-2, which implies that the Swift/BAT data allow us to study the "true" variability of the central source. Results: All objects show significant variations, with an amplitude which is similar to the AGN variability amplitude at energies below 10 keV. We found evidence for an anti-correlation between variability amplitude and black hole mass. The light curves in both bands are well correlated, with no significant delays on time scales as short as 2 days. NGC 4151 and NGC 2110 do not show spectral variability, but we found a significant anti-correlation between hardness ratios and source flux in NGC 4388 (and NGC 4945, IC 4329, to a lesser extent). This "softer when brighter" behaviour is similar to what has been observed at energies below 10 keV, and cannot be explained if the continuum varies only in flux; the intrinsic shape should also steepen with increasing flux. Conclusions: The presence of significant flux variations indicate that the central source in these objects is intrinsically variable on time scales as short as 1-2 days. The intrinsic slope of the continuum varies with the flux (at least in NGC 4388). The positive "spectral slope-flux" correlation can be explained if the temperature of the hot corona decreases with increasing flux. The lack of spectral variations in two objects, could be due to the fact that they may operate in a different "state", as their accretion rate is less than 1% of the Eddington limit (significantly smaller than the rate of the other three objects in the sample)., Comment: Accepted (29/10/11) for publication in A&A (12 pages, containing 14 figures and 2 tables). (Abstract shortened --see link for the complete one)

The Optical Monitoring Camera (OMC) on-board the INTEGRAL satellite has, as one of its scientific goals, the observation of a large number of variable sources previously selected. After almost 6 years of operations, OMC has monitored more than 100 000 sources of scientific interest. In this contribution we present the OMC Scientific Archive (this http URL) which has been developed to provide the astronomical community with a quick access to the light curves generated by this instrument.We describe the main characteristics of this archive, as well as important aspects for the users: object types, temporal sampling of light curves and photometric accuracy.

We report on the first deeper X-ray broad-band observation of the hot spot galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the spiral barred galaxy were obtained from XMM-Newton archival data to study its X-ray population and the conditions of the hot gas in its central region. We investigate the spectral properties of the discrete point-source population and give estimates of their X-ray spectral parameters. By analysing the RGS spectra, we derive temperature and abundances for the hot gas located in its central region. A total of six X-ray point sources (four of them ULX candidates) were detected in the energy range of 0.3-10.0 keV located within the galaxy D25 optical disk. Three of these sources are detected for the first time, and one of them with a luminosity of higher than 10^39 erg/s. After fitting three different models, we were able to estimate their luminosities, which are compatible with those of binaries with a compact object in the form of black holes (BHs) rather than neutron stars (NSs). We extracted the combined first-order RGS1 and RGS2 spectra of its central region, which display several emission lines. Both O\,{\sc vii} $f$ and $r$ lines seem to be of similar strength, which is consistent with the presence of the collisionally ionized gas that is typical of starburst galaxies. We fitted the spectrum to a model for a plasma in collisional ionization equilibrium (CIE) and the continuum was modelled with a power law, resulting in a plasma temperature of T = 0.31 \pm 0.01 keV and an emission measure EM \equiv n_Hn_eV =6.4_{-0.4}^{+0.5}\times 10^{61}$~cm$^{-3}. We also estimated abundances that are consistent with solar values., Comment: 5 pages, 2 figures, accepted for publication in A&A, resubmission corrects typographical errors and improves exposition according to the referee's suggestions

GX 339–4 is a well-known microquasar. In this contribution we show the obtained results with the INTEGRAL and XMM-Newton observatories of the outburst undertaken on 2007. The observations cover spectral evolution from the hard, soft intermediate states to the high/soft state. Spectral hardening correlated with the appearance of an skewed Fe line is detected during one of the observations during the soft intermediate state. In all spectral states joint XMM/EPIC-pn, JEM-X, ISGRI and SPI data were fit with the hybrid thermal/non-thermal Comptonization model (EQPAIR). With this model a non-thermal component seems to be required by the data in all the observations. Our results imply evolution in the coronal properties, the most important one being the transition from a compact corona in the first observation to the disappearance of coronal material in the second and re-appearance in the third. We discuss the results obtained in the context of possible physical scenarios for the origin and geometry of the corona and its relation to black hole states.

We present simultaneous XMM-Newton and INTEGRAL observations of the luminous black hole transient and relativistic jet source GX 339-4. GX 339-4 started an outburst on November of 2006 and our observations were undertaken from January to March of 2007. We triggered five INTEGRAL and three XMM-Newton target of Opportunity observations within this period. Our data cover different spectral states, namely Hard Intermediate, Soft Intermediate and High/Soft. We performed spectral analysis to the data with both phenomenological and more physical models and find that a non-thermal component seems to be required by the data in all the observations. We find a hardening of the spectrum in the third observation coincident with appearance of a broad and skewed Fe K alpha line. In all spectral states joint XMM/EPIC-pn,JEM-X, ISGRI and SPI data were fit with the hybrid thermal/non-thermal Comptonization model (EQPAIR). While this model accounts very well for the high/energy emission observed, it has several drawbacks in the description of the lower energy channels. Our results imply evolution in the coronal properties, the most important one being the transition from a compact corona in the first observation to the disappearance of coronal material in the second and re-appearance in the third. This fact, accompanied by the plasma ejection events detected in radio on February 4 to 18, suggest that the ejected medium is the coronal material responsible for the hard X-ray emission., Comment: 42 pages in the 1 column version, 17 figures. Accepted for publication in ApJ

The emission line arising from a transition of an electron from the iron K shell to the ground state (the K line) is prominent in the reflection spectrum of the hard X-ray continuum irradiating dense accreting matter around a black hole. The corresponding iron L-line emission should be detectable when iron abundance is high. That's the theory, and now broad iron L-line emission has been observed, together with the broad K line in the narrow-line Seyfert galaxy 1H0707. There is a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the hole, a timescale comparable to the light-crossing time of the innermost radii around a supermassive black hole. This discovery opens a window on events close to the black hole event horizon in these objects. Emission arising from a transition of an electron from the iron K shell to the ground state (the K line) is prominent in the reflection spectrum created by the hard X-ray continuum irradiating the dense accreting matter around a black hole. Here the presence of both iron K and L emission is reported in the spectrum of the active galaxy 1H 0707-495. There is a 'reverberation lag' with a timescale comparable to the light-crossing time of the innermost radii around a supermassive black hole. Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG–6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies2, from accreting stellar-mass black holes3 and even from accreting neutron stars4. The iron K line is prominent in the reflection spectrum5,6 created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion7 of the line makes it sensitive to the strong gravity and spin of the black hole8. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy9 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole.

Aims: The nature of Cygnus X-3 is still not understood well. This binary system might host a black hole or a neutron star. Recent observations by INTEGRAL have shown that Cygnus X-3 was again in an extremely ultrasoft state. Here we present our analysis of the transition from the ultrasoft state, dominated by blackbody radiation at soft X-rays plus non-thermal emission in the hard X-rays, to the low hard state. Methods: INTEGRAL observed Cyg X-3 six times during three weeks in late May and early June 2007. Data from IBIS/ISGRI and JEM-X1 were analysed to show the spectral transition. Results: During the ultrasoft state, the soft X-ray spectrum is well-described by an absorbed (NH = 1.5E22 1/cm**2) black body model, whereas the X-ray spectrum above 20 keV appears to be extremely low and hard (Gamma = 1.7). During the transition, the radio flux rises to a level of >1 Jy, and the soft X-ray emission drops by a factor of 3, while the hard X-ray emission rises by a factor of 14 and becomes steeper (up to Gamma = 4). Conclusions: The ultrasoft state apparently precedes the emission of a jet, which is apparent in the radio and hard X-ray domain., 4 pages, 3 figures, accepted for publication as A&A Research Note

We report on two simultaneous XMM-Newton and INTEGRAL observations of the microquasar GRO J1655-40 during the 2005 outburst when the source was in its high-soft state. The 0.3-200 keV spectra are complex with an overall continuum which may be modeled using an absorbed blackbody together with a weak, steep, power-law component. In addition, there is evidence for the presence of both a relativistically broadened Fe K line and a highly photo-ionized absorber. The photo-ionized absorber is responsible for strong K absorption lines of Fe XXV and Fe XXVI in the EPIC pn spectra and blue-shifted (v = -540 +/- 120 km/s) Ne X and Fe XXIV features in the RGS spectra. The parameters of the photo-ionized absorber were different during the two observations with the ionization parameter, logxi, decreasing from 3.60 +/- 0.04 to 3.30 +/- 0.04 erg cm/s and the column density decreasing from (5.2 +/- 1.0) x 10^22 atom cm-2 to (1.5 +/- 1.0) x 10^22 atom cm-2 during the first and second observations as the 0.5-200 keV GRO J1655-40 luminosity decreased by around a half. At 90% confidence the INTEGRAL data show no evidence of a break in the power-law component up to energies of 380 keV and 90 keV for the first and second observations, respectively., Comment: Accepted for publication in A&A (submitted: 11 April 2006). 12 pages, 7 figures

The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray source, and shows properties in the optical that are similar to the W UMa systems, but are somewhat unusual compared to what is seen in other contact binary systems. The goal of this work is to characterize its properties and investigate its nature by means of detailed photometric and spectroscopic observations. We have performed extensive V-band photometric measurements with the INTEGRAL satellite along with ground-based multi-band photometric observations, as well as high-resolution spectroscopic monitoring from which we have measured the radial velocities of the components. These data have been analysed to determine the stellar properties, including the absolute masses and radii. Additional low-resolution spectroscopy was obtained to investigate spectral features. From the measured eclipse timings we determine an orbital period for the binary of P=0.4223576+-0.0000009 days. The light-curve and spectroscopic analyses reveal the observations to be well represented by a model of an overcontact system composed of main-sequence F5 and G7 stars (temperature difference of nearly 1000 K), with the possible presence of a third star. Low-resolution optical spectroscopy reveals a complex H alpha emission, and other features that are not yet understood. The unusually large mass ratio of q=0.81+-0.05 places it in the rare "H" (high mass ratio) subclass of the W UMa systems, which are presumably on their way to coalescence., 12 pages in double column format. Accepted for publication in Astronomy and Astrophysics

The Optical Monitoring Camera on-board INTEGRAL (OMC) provides Johnson V band photometry of any potentially variable source within its field of view. Taking advantage of the INTEGRAL capabilities allowing the simultaneous observation of different kind of objects in the optical, X and gamma rays bands, we have performed a study of the optical counterparts of different high-energy sources. Up to now, OMC has detected the optical counterpart for more than 100 sources from the High Energy Catalog (Ebisawa et al., 2003). The photometrically calibrated light curves produced by OMC can be accessed through our web portal at: http://sdc.laeff.inta.es/omc, 4 pages, 4 figures, proceeding included in VIII Reunion Cientifica de la Sociedad Espanyola de Astronomia (Santander, 2008)

We present the first results obtained by the application of the KYNREFREV-reverberation model, which is ready for its use in XSPEC. This model computes the time dependent reflection spectra of the disc as a response to a flash of primary power-law radiation from a point source corona located on the axis of the black hole accretion disc (lamp-post geometry). Full relativistic effects are taken into account. The ionisation of the disc is set for each radius according to the amount of the incident primary flux and the density of the accretion disc. We tested the model by fitting model predictions to the observed time-lag spectra of three Narrow-Line Seyfert 1 galaxies (ARK 564, MCG-6-30-15 and 1H 0707-495), assuming either a rapidly or zero spinning black hole (BH). The time-lags strongly suggest a compact X-ray source, located close to the BH, at a height of approx. 4 gravitational radii. This result does not depend either on the BH spin or the disc ionization. There is no significant statistical difference between the quality of the best-fits in the rapidly and zero spinning BH scenarios in Ark 564 and MCG-6-30-15. But there is an indication that the hypothesis of a non-rotating BH in 1H 0707-495 is not consistent with its time-lag spectrum. Finally, the best-fits to the Ark 564 and 1H 0707-495 data are of rather low quality. We detect wavy-residuals around the best-fit reverberation model time-lags at high frequencies. This result suggests that the simple lamp-post geometry does not fully explain the X-ray source/disc configuration in Active Galactic Nuclei., Comment: Accepted in MNRAS after minor revision (23/Jul./2018). 10 pages

The black hole transient V404 Cygni exhibited a bright outburst in June 2015 that was intensively followed over a wide range of wavelengths. Our team obtained high time resolution optical spectroscopy (~90 s), which included a detailed coverage of the most active phase of the event. We present a data base consisting of 651 optical spectra obtained during this event, that we combine with 58 spectra gathered during the fainter December 2015 sequel outburst, as well as with 57 spectra from the 1989 event.We previously reported the discovery of windrelated features (P-Cygni and broad-wing line profiles) during both 2015 outbursts. Here, we build diagnostic diagrams that enable us to study the evolution of typical emission line parameters, such as line fluxes and equivalent widths, and develop a technique to systematically detect outflow signatures. We find that these are present throughout the outburst, even at very low optical fluxes, and that both types of outflow features are observed simultaneously in some spectra, confirming the idea of a common origin. We also show that the nebular phases depict loop patterns in many diagnostic diagrams, while P-Cygni profiles are highly variable on time-scales of minutes. The comparison between the three outbursts reveals that the spectra obtained during June and December 2015 share many similarities, while those from 1989 exhibit narrower emission lines and lower wind terminal velocities. The diagnostic diagrams presented in this work have been produced using standard measurement techniques and thus may be applied to other active low-mass X-ray binaries. © 2018 The Author(s)., DMS acknowledges Fundacion La Caixa for the financial support received in the form of a PhD contract. TMD acknowledges support via a Ramon y Cajal Fellowship (RYC-2015-18148) and the Spanish MINECO project AYA2017-83216-P. JC acknowledges financial support from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) under the 2015 Severo Ochoa Program MINECO SEV-2015-0548, and to the Leverhulme Trust through grant VP2-2015-046. PAC gratefully acknowledges the receipt of a Leverhulme Emeritus Fellowship from the Leverhulme Trust. MAP's research is funded under the Juan de la Cierva Fellowship Programme (IJCI-2016-30867) from MINECO. ML is supported by EU's Horizon 2020 programme through a Marie Sklodowska-Curie Fellowship (grant nr. 702638). MAPT acknowledges support via a Ramon y Cajal Fellowship (RYC-2015-17854). AWS is supported by an NSERC Discovery Grant and a Discovery Accelerator Supplement. AJCT acknowledges support from the Spanish Ministry MINECO Project AYA 2015-71718-R (including FEDER funds). We thank Javier Mendez (head of the ING Service Program), Chris Benn (head of Astronomy), Marc Balcells (director of ING) and all the ING SAs for their help in monitoring this unique event during ING Service and Discretionary time. We also thank Romano Corradi (director of GTC), Antonio Cabrera (head of science operations) and the GTC support team for the quick response during the multiples triggers of our program. This research has been carried out with telescope time awarded by the CCI International Time Programme at the Canary Islands observatories (program ITP13-8). We also thank the GTC DDT committee (coordinated by the IAC director, Rafael Rebolo) for the awarded time to our observing program. This paper is partially based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), and Poland, and with the participation of Russia and the USA. MOLLY software developed by T. R. Marsh is gratefully acknowledged.