Optical and high-energy monitoring of variable sources observed with INTEGRAL/OMC

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de la lectura: 11-05-2015Since the discovery of the first variable stars in the 16th century, their study has been one of the principal areas of astronomical research. During the 20th century and the beginning of the 21st, many optical photometric surveys have been carried out with the aim of understanding the physical mechanisms producing the observed variations of brightness. With the discovery of the first X-ray sources in the sky in the 60’s and the development of X-ray astronomy, several X-ray observatories have been launched into space in order to study the properties of these X-ray sources at higher energies. Multiwavelength analyses are required for a better knowledge of these systems. For this reason, an optical monitoring camera was included on the X- and gamma-ray space observatory INTEGRAL of the European Space Agency (ESA). In this thesis, the main results of the analysis of the optical photometric data obtained with the optical monitoring camera (OMC) on board INTEGRAL are presented. The major goal of this work was to classify the thousands of light curves obtained and to identify and study relevant scientific cases extracted from the large sample of data. In its 12 years of operations, OMC has observed a very large amount of classical variable sources, including pulsating stars, eclipsing binaries, rotating stars, AGN, etc. The compilation of the first catalog of optically variable sources observed by OMC, including information on their brightness, variability, periodicity, and object type classification, is presented. Within the sources in this catalog, a search for eclipsing binaries with one pulsating component has been carried out. One of the identified systems, DY Aqr, has been studied in detail. On the other hand, apart from these serendipitous observations, OMC was designed to provide optical monitoring of the sources observed by the main X- and gamma-ray instruments IBIS and JEM-X on board INTEGRAL. For the first time, simultaneous observations of the optical and X- and gamma-ray sky over more than 12 years are presented. In this thesis, two different works including multiwavelength information provided by INTEGRAL have been performed. In the first one the global properties of the emission of high-energy sources in different energy bands (hard X-rays, optical, IR, and MIR) have been studied. The emission from the different types of objects has been compared, looking for similarities and differences that could reveal information about the nature of their powerful sources. The second one consists of a multiwavelength long-term variability analysis, using light curves of the INTEGRAL instruments IBIS, JEM-X, and OMC, as well as from other highenergy missions and optical surveys, with a temporal coverage of more than 12 year

EXO 2030+375 Restarts in Reverse

The Be X-ray binary pulsar EXO 2030+375, first detected in 1985, has shown a significant detected X-ray outburst at nearly every periastron passage of its 46-day orbit for the past ~25 years, with one low state accompanied by a torque reversal in the 1990s. In early 2015 the outbursts progressively became fainter and less regular while the monotonic spin-up flattened. At the same time a decrease in the H$\alpha$ line equivalent width was reported, indicating a change in the disk surrounding the mass donor. In order to explore the source behaviour in the poorly explored low-flux state with a possible transition to a state of centrifugal inhibition of accretion we have undertaken an observing campaign with Swift/XRT, NuSTAR and the Nordic Optical Telescope (NOT). This conference contribution reports the preliminary results obtained from our campaign.Comment: 11th INTEGRAL Conference Gamma-Ray Astrophysics in Multi-Wavelength Perspective, 10-14 October 2016, Amsterdam, The Netherlands. 7 page

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies: III. the atlas of the stellar and ionized gas distribution

Context. Luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ∼1-2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. Local samples provide a unique opportunity to study these objects in detail. Aims. We aim to characterize the morphologies of the stellar continuum and the ionized gas (Hα) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. Methods. We use optical (5250-7450 Å) integral field spectroscopic (IFS) data for a representative sample of 38 sources (31 LIRGs and 7 ULIRGs), taken with the VIMOS instrument on the VLT. Results. We present an atlas of IFS images of continuum emission, Hα emission, and Hα equivalent widths for the sample. The morphologies of the Hα emission are substantially different from those of the stellar continuum. The Hα images frequently reveal extended structures that are not visible in the continuum, such as HII regions in spiral arms, tidal tails, rings, bridges, of up to few kpc from the nuclear regions. The morphologies of the continuum and Hα images are studied on the basis of the C2 kpc parameter, which measures the concentration of the emission within the central 2 kpc. The C2 kpc values found for the Hα images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (∼62%) have more than half of their Hα emission outside the central 2 kpc. No clear trends are found between the values of C2 kpc and the IR-luminosity of the sources. On the other hand, our results suggest that the star formation in advance mergers and early-stage interactions is more concentrated than in isolated objects. Finally, we compared the Hα and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the Hα luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects. © 2011 ESO.Based on observations carried out at the European Southern observatory, Paranal (Chile), Programs 076.B- 0479(A), 078.B-0072(A) and 081.B-0108(A).The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166.This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) under grant ESP2007-65475-C02-01. AM-I is supported by the Spanish Ministry of Science and Innovation (MICINN) under program “Specialization in International Organisms”, Ref. ES2006-0003.Peer Reviewe

Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions

High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies. In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system. We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields. We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations.The INTEGRALteams in the participating countries acknowledge the continuous support from their space agencies and funding organizations: the Italian Space Agency ASI (via different agreements including the latest one, 2019-35HH, and the ASIINAF agreement 2017-14-H.0), the French Centre national d’études spatiales (CNES), the Russian Foundation for Basic Research (KP, 19-02-00790), the Russian Science Foundation (ST, VD, AL; 19-12-00423), the Spanish State Research Agency (via different grants including ESP2017-85691-P, ESP2017-87676-C5-1-R and Unidad de Excelencia María de Maeztu – CAB MDM-2017-0737). IN is partially supported by the Spanish Government under grant PGC2018-093741-B-C21/C22 (MICIU/AEI/FEDER, UE). LD acknowledges grant 50 OG 1902

Advances in Understanding High-Mass X-ray Binaries with INTEGRALand Future Directions

High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies.In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system.We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields.We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations.</p

Optical counterpart to Swift J0243.6+6124

Context. Swift J0243.6+6124 is a unique system. It is the first and only ultra-luminous X-ray source in our Galaxy. It is the first and only high-mass Be X-ray pulsar showing radio jet emission. It was discovered during a giant X-ray outburst in October 2017. While there are numerous studies in the X-ray band, very little is known about the optical counterpart. Aims. Our aim is to characterize the variability timescales in the optical and infrared bands in order to understand the nature of this intriguing system. Methods. We performed optical spectroscopic observations to determine the spectral type. Long-term photometric light curves together with the equivalent width of the Hα line were used to monitor the state of the circumstellar disk. We used BVRI photometry to estimate the interstellar absorption and distance to the source. Continuous photometric monitoring in the B and V bands allowed us to search for intra-night variability. Results. The optical counterpart to Swift J0243.6+6124 is a V = 12.9, O9.5Ve star, located at a distance of ∼5 kpc. The optical extinction in the direction of the source is AV = 3.6 mag. The rotational velocity of the O-type star is 210 km s-1. The long-term optical variability agrees with the growth and subsequent dissipation of the Be circumstellar disk after the giant X-ray outburst. The optical and X-ray luminosity are strongly correlated during the outburst, suggesting a common origin. We did not detect short-term periodic variability that could be associated with nonradial pulsations from the Be star photosphere. Conclusions. The long-term optical and infrared pattern of variability of Swift J0243.6+6124 is typical of Be/X-ray binaries. However, the absence of nonradial pulsations is unusual and adds another peculiar trait to this unique source.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737

15 years of INTEGRAL/OMC monitoring

Highlights on Spanish Astrophysics X, Proceedings of the XIII Scientific Meeting of the Spanish Astronomical Society held on July 16-20, 2018, in Salamanca, Spain.OMC, the Optical Monitoring Camera onboard INTEGRAL, has been monitoring the optical emission of thousands of potentially variable astronomical objects during the latest 15 years. OMC takes one image of its 5°×5° field of view every 10, 50 or 200 seconds, downloading the photometric data for around 100 objects in each exposure. The OMC Archive, publicly available at http://sdc.cab.inta-csic.es/omc/, contains the light curves of around 90 000 scientific objects with more than at least 50 photometric points, including the optical emission of the high-energy targets being observed simultaneously by the other instruments on INTEGRAL: IBIS, SPI and JEM-X. The ¿First INTEGRAL-OMC catalogue of optically variable sources¿ contains already a complete analysis of more than 5000 variable sources. At the end of the INTEGRAL mission we will compile and publish the final catalogue containing the light curves and variability analysis of all the sources monitored by OMC during its lifetime

VIMOS-VLT Two-Dimensional Kinematics of Local Luminous Infrared Galaxies.

In this work, preliminary results of a kinematic study based on optical integral field spectroscopy with the VIMOS (Visible Multi-object Spectrograph) instrument on the VLT (Very Large Telescope) of some representative (U)LIRGs ((Ultra) Luminous Infrared Galaxies) is presented. Velocity fields and velocity dispersion distributions of the ionized gas are obtained from Hα 6,563Å emission line. Two representative examples, an isolated galaxy (NGC 3110) and a merger (IRAS F01159–4443), are shown. The isolated galaxy presents a velocity field typical of a rotating spiral galaxy with a peak to peak velocity difference of∼440kms-1. The merger shows a more perturbed kinematics although independent rotation for each individual galaxy has been found with a peak to peak velocity of∼260kms-1 in the northern galaxy and of∼250kms-1 in the southern one and a relative velocity between the two galaxies of∼130kms-