Nievas Rosillo, Mireia

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First Name
Last Name
Nievas Rosillo
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Estructura de la Materia, Física Térmica y Electrónica
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Now showing 1 - 10 of 62
  • Publication
    Constraining very-high-energy and optical emission from FRB 121102 with the MAGIC telescopes
    (Oxford Univ Press, 2018-12) Barrio Uña, Juan Abel; Contreras González, José Luis; Domínguez Díaz, Alberto; Carreto Fidalgo, David Friedrich; Fonseca Gonzáez, Victoria; Hoang, Kim Dinh; López Moya, Marcos; Nievas Rosillo, Mireia; Peñil del Campo, Pablo; Saha, Lab; otros, ...
    Fast radio bursts (FRBs) are bright flashes observed typically at GHz frequencies with millisecond duration, whose origin is likely extragalactic. Their nature remains mysterious, motivating searches for counterparts at other wavelengths. FRB 121102 is so far the only source known to repeatedly emit FRBs and is associated with a host galaxy at redshift z similar or equal to 0.193. We conducted simultaneous observations of FRB 121102 with the Arecibo and MAGIC telescopes during several epochs in 2016-2017. This allowed searches for millisecond time-scale burst emission in very-high-energy (VHE) gamma-rays as well as the optical band. While a total of five FRBs were detected during these observations, no VHE emission was detected, neither of a persistent nature nor burst-like associated with the FRBs. The average integral flux upper limits above 100 GeV at 95 percent confidence level are 6.6 x 10(-12) photons cm(-2) s(-1) (corresponding to luminosity L-VHE < 10 (45) erg s(-1)) over the entire observation period, and 1.2 x 10(-7) photons cm(-2) s(-1 )(L-VHE < 10 (49) erg s( -1)) over the total duration of the five FRBs. We constrain the optical U-band flux to be below 8.6 mJy at 5 sigma level for 1-ms intervals around the FRB arrival times. A bright burst with U-band flux 29 mJy and duration similar to 12 ms was detected 4.3 s before the arrival of one FRB. However, the probability of spuriously detecting such a signal within the sampled time space is 1.5 percent (2.2, post-trial), i.e. consistent with the expected background. We discuss the implications of the obtained upper limits for constraining FRB models.
  • Publication
    Zernike power spectra of clear and cloudy light-polluted urban night skies
    (Optical Society Of America, 2015-05-01) Bará, Salvador; Tilve, Victor; Nievas Rosillo, Mireia; Sánchez de Miguel, Alejandro; Zamorano Calvo, Jaime
    The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V, and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to -3 for clear nights and -2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained on clear nights, is described in the Zernike space.
  • Publication
    Report of the 2014 LoNNe intercomparison campaign
    (2015-08-31) Bará, Salvador; Espey, Brian; Falchi, Fabio; Kyba, Christopher C. M.; Nievas Rosillo, Mireia; Pescatori, Paolo; Ribas, Salvador; Sánchez de Miguel, Alejandro; Staubmann, Philipp; Tapia Ayuga, Carlos; Wuchterl, Günther; Zamorano Calvo, Jaime
    The 2014 LoNNe (Loss of the Night Network) intercomparison campaign is the second of four campaigns planned during EU COST Action ES1204. The goal of these campaigns is to understand systematic uncertainty inherent in observations of skyglow (light pollution). An innovation of this year’s campaign was to take measurements with many of the nstruments at two sites: an urban location and a location far from artificial lights. This report summarizes the eeting, and also provides three recommendations for obtaining and analyzing handheld SQM observations. The UCM group of Astronomical Instrumentation and Extragalactic Astronomy (GUAIX) hosted the meeting at the Physics building of Universidad Complutense de Madrid (UCM). A meeting room at Departamento de Astrofísica y CC. de la Atmósfera and the astronomical observatory (Observatorio UCM) were prepared in advance. In particular, a tailor made station to set the SQM and other photometer devices was installed on the roof of the Physics building. The Laboratorio de Investigación Científica Avanzada (LICA) was used to test and characterize a number of devices and filters.
  • Publication
    First NuSTAR observations of MRK 501 within a radio to TeV multi-instrument capaign
    (American Astronomical Society, 2015-10-10) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; López Moya, Marcos; Miranda Pantoja, José Miguel; Nievas Rosillo, Mireia; Satalecka, Konstanzja; Scapin, Valeria; Otros, ...
    We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 2013 April 1 and August 10, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby BL Lac object was observed in both a quiescent and an elevated state. The broadband campaign includes observations with NuSTAR, MAGIC, VERITAS, the Fermi Large Area Telescope, Swift X-ray Telescope and UV Optical Telescope, various ground-based optical instruments, including the GASPWEBT program, as well as radio observations by OVRO, Metsähovi, and the F-Gamma consortium. Some of the MAGIC observations were affected by a sand layer from the Saharan desert, and had to be corrected using eventby-event corrections derived with a Light Detection and Ranging (LIDAR) facility. This is the first time that LIDAR information is used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for the current and future ground-based gamma-ray instruments. The NuSTAR instrument provides unprecedented sensitivity in hard X-rays, showing the source to display a spectral energy distribution (SED) between 3 and 79 keV consistent with a log-parabolic spectrum and hard X-ray variability on hour timescales. None (of the four extended NuSTAR observations) show evidence of the onset of inverse-Compton emission at hard X-ray energies. We apply a single-zone equilibrium synchrotron selfCompton (SSC) model to five simultaneous broadband SEDs. We find that the SSC model can reproduce the observed broadband states through a decrease in the magnetic field strength coinciding with an increase in the luminosity and hardness of the relativistic leptons responsible for the high-energy emission.
  • Publication
    Very-high-energy gamma-ray observations of the Type Ia Supernova SN 2014J with the MAGIC telescopes
    (EDP Sciencies, 2017-06) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Bonnefoy, Simon Francois Albert; Contreras González, José Luis; Domínguez, A.; Fidalgo, D.; Fonseca González, Mª Victoria; López Moya, Marcos; Miranda Pantoja, José Miguel; Nievas Rosillo, Mireia
    Context. In this work we present data from observations with the MAGIC telescopes of SN 2014J detected in January 21 2014, the closest Type Ia supernova since Imaging Air Cherenkov Telescopes started to operate. Aims. We probe the possibility of very-high-energy (VHE; E ≥ 100 GeV) gamma rays produced in the early stages of Type Ia supernova explosions. Methods. We performed follow-up observations after this supernova explosion for 5 days, between January 27 and February 2 in 2014. We search for gamma-ray signal in the energy range between 100 GeV and several TeV from the location of SN 2014J using data from a total of ∼ 5.5 hours of observations. Prospects for observing gamma-rays of hadronic origin from SN 2014J in the near future are also being addressed. Results. No significant excess was detected from the direction of SN 2014J. Upper limits at 95% confidence level on the integral flux, assuming a power-law spectrum, dF/dE ∝ E −Γ , with a spectral index of Γ = 2.6, for energies higher than 300 GeV and 700 GeV, are established at 1.3 × 10−12 and 4.1 × 10−13 photons cm−2 s −1 , respectively. Conclusions. For the first time, upper limits on the VHE emission of a Type Ia supernova are established. The energy fraction isotropically emitted into TeV gamma rays during the first ∼ 10 days after the supernova explosion for energies greater than 300 GeV is limited to 10−6 of the total available energy budget (∼ 1051 erg). Within the assumed theoretical scenario, the MAGIC upper limits on the VHE emission suggest that SN 2014J will not be detectable in the future by any current or planned generation of Imaging Atmospheric Cherenkov Telescopes.
  • Publication
    Very high-energy gamma-ray follow-up program using neutrino triggers from IceCube
    (IOP Publishing LTD, 2016-11) Barrio Uña, Juan Abel; Bonnefoy, Simon Francois Albert; Contreras González, José Luis; Domínguez, A.; Fidalgo, D.; Fonseca González, Mª Victoria; López, M.; Nievas Rosillo, Mireia
    We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescopes (MAGIC and VERITAS). While IceCube is capable of monitoring the whole sky continuously, high-energy gamma-ray telescopes have restricted fields of view and in general are unlikely to be observing a potential neutrino-flaring source at the time such neutrinos are recorded. The use of neutrino-triggered alerts thus aims at increasing the availability of simultaneous multi-messenger data during potential neutrino flaring activity, which can increase the discovery potential and constrain the phenomenological interpretation of the high-energy emission of selected source classes (e. g. blazars). The requirements of a fast and stable online analysis of potential neutrino signals and its operation are presented, along with first results of the program operating between 14 March 2012 and 31 December 2015.
  • Publication
    Gamma-ray flaring activity of NGC 1275 in 2016-2017 measured by MAGIC
    (EDP Sciences S A, 2018-09-25) Barrio Uña, Juan Abel; Contreras González, José Luis; Domínguez Díaz, Alberto; Carreto Fidalgo, David Friedrich; Fonseca González, Victoria; Hoang, Kim Dinh; López Moya, Marcos; Nievas Rosillo, Mireia; Peñil del Campo, Pablo; Saha, Lab; otros, ...
    We report on the detection of flaring activity from the Fanaroff-Riley I radio galaxy NGC 1275 in very-high-energy (VHE, E> 100 GeV) gamma rays with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes. The observations were performed between 2016 September and 2017 February, as part of a monitoring programme. The brightest outburst, with similar to 1.5 times the Crab Nebula flux above 100 GeV (C.U.), was observed during the night between 2016 December 31 and 2017 January 1. The flux is fifty times higher than the mean flux previously measured in two observational campaigns between 2009 October and 2010 February and between 2010 August and 2011 February. Significant variability of the day-by-day light curve was measured. The shortest flux-doubling timescale was found to be of (611 +/- 101) min. The spectra calculated for this period are harder and show a significant curvature with respect to the ones obtained in the previous campaigns. The combined spectrum of the MAGIC data during the strongest flare state and simultaneous data from the Fermi-LAT around 2017 January 1 follows a power law with an exponential cutoff at the energy (492 +/- 35) GeV. We further present simultaneous optical flux density measurements in the R-band obtained with the Kungliga Vetenskaps Akademien (KVA) telescope and investigate the correlation between the optical and gamma-ray emission. Due to possible internal pair-production, the fast flux variability constrains the Doppler factor to values that are inconsistent with a large viewing angle as observed in the radio band. We investigate different scenarios for the explanation of fast gamma-ray variability, namely emission from magnetospheric gaps, relativistic blobs propagating in the jet (mini-jets), or an external cloud (or star) entering the jet. We find that the only plausible model to account for the luminosities here observed would be the production of gamma rays in a magnetospheric gap around the central black hole, only in the eventuality of an enhancement of the magnetic field threading the hole from its equipartition value with the gas pressure in the accretion flow. The observed gamma-ray flare therefore challenges all the discussed models for fast variability of VHE gamma-ray emission in active galactic nuclei.
  • Publication
    The broad-band properties of the intermediate synchrotron peaked BL Lac S2 0109+22 from radio to VHE gamma-rays
    (Oxford Univ Press, 2018-10) Barrio Uña, Juan Abel; Contreras González, José Luis; Domínguez Díaz, Alberto; Carreto Fidalgo, David Friedrich; Fonseca González, Victoria; Hoang, Kim Dinh; López Moya, Marcos; Nievas Rosillo, Mireia; Peñil del Campo, Pablo; Saha, Lab; otros, ...
    The Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes observed S2 0109+22 in 2015 July during its flaring activity in high-energy gamma-rays observed by Fermi-Large Area Telescope. We analyse the MAGIC data to characterize the very high energy (VHE) gamma-ray emission of S2 0109+22, which belongs to the subclass of intermediate synchrotron peak (ISP) BL Lacertae (BL Lac) objects. We study the multifrequency emission in order to investigate the source classification. Finally, we compare the source long-term behaviour to other VHE gamma-ray emitting (TeV) blazars. We performed a temporal and spectral analysis of the data centred around the MAGIC interval of observation (MJD 57225-57231). Long-term radio and optical data have also been investigated using the discrete correlation function. The redshift of the source is estimated through optical host-galaxy imaging and also using the amount of VHE gamma-ray absorption. The quasi-simultaneous multifrequency spectral energy distribution (SED) is modelled with the conventional one-zone synchrotron self-Compton (SSC) model. MAGIC observations resulted in the detection of the source at a significance level of 5.3 sigma. The VHE gamma-ray emission of S2 0109+22 is variable on a daily time scale. VHE gamma-ray luminosity of the source is lower than the average of TeV BL Lacs. The optical polarization and long-term optical/radio behaviour of the source are different from the general population of TeV blazars. All these findings agree with the classification of the source as an ISP BL Lac object. We estimate the source redshift as z = 0.36 +/- 0.07. The SSC parameters describing the SED are rather typical for blazars.
  • Publication
    Latest MAGIC discoveries pushing redshift boundaries in VHE astrophysics
    (IOP Publishing Ltd, 2016) Nievas Rosillo, Mireia; Domínguez, A.; otros, ...
    The search for detection of ?-rays from distant AGNs by Imaging Atmospheric Cherenkov Telescopes (IACTs) is challenging at high redshifts, not only because of lower flux due to the distance of the source, but also due to the consequent absorption of gamma-rays by the extragalactic background light (EBL). Before the MAGIC discoveries reported in this work, the farthest source ever detected in the VHE domain was the blazar PKS 1424+240, at z > 0.6. MAGIC, a system of two 17 m of diameter IACTs located in the Canary island of La Palma, has been able to go beyond that limit and push the boundaries for VHE detection to redshifts z similar to 1. The two sources detected and analyzed, the blazar QSO B0218+357 and the FSRQ PKS 1441+25 are located at redshift z = 0.944 and z = 0.939 respectively. QSO B0218+357 is also the first gravitational lensed blazar ever detected in VHE. The activity, triggered by Fermi-LAT in high energy ?-rays, was followed up by other instruments, such as the KVA telescope in the optical band and the Swift-XRT in X-rays. In the present work we show results on MAGIC analysis on QSO B0218+357 and PKS 1441+25 together with multiwavelength lightcurves. The collected dataset allowed us to test for the first time the present generation of EBL models at such distances.
  • Publication
    Periastron Observations of TeV Gamma-Ray Emission from a Binary System with a 50-year Period
    (IOP Publishing Ltd, 2018-11-01) Barrio Uña, Juan Abel; Contreras González, José Luis; Domínguez Díaz, Alberto; Carreto Fidalgo, David Friedrich; Fonseca González, Victoria; Hoang, Kim Dinh; López Moya, Marcos; Nievas Rosillo, Mireia; Peñil del Campo, Pablo; Saha, Lab
    We report on observations of the pulsar/Be star binary system PSR J2032+4127/MT91 213 in the energy range between 100 GeV and 20 TeV with the Very Energetic Radiation Imaging Telescope Array and Major Atmospheric Gamma Imaging Cherenkov telescope arrays. The binary orbit has a period of approximately 50 years, with the most recent periastron occurring on 2017 November 13. Our observations span from 18 months prior to periastron to one month after. A new point-like gamma-ray source is detected, coincident with the location of PSR J2032+4127/MT91 213. The gamma-ray light curve and spectrum are well characterized over the periastron passage. The flux is variable over at least an order of magnitude, peaking at periastron, thus providing a firm association of the TeV source with the pulsar/Be star system. Observations prior to periastron show a cutoff in the spectrum at an energy around 0.5 TeV. This result adds a new member to the small population of known TeV binaries, and it identifies only the second source of this class in which the nature and properties of the compact object are firmly established. We compare the gamma-ray results with the light curve measured with the X-ray Telescope on board the Neil Gehrels Swift Observatory and with the predictions of recent theoretical models of the system. We conclude that significant revision of the models is required to explain the details of the emission that we have observed, and we discuss the relationship between the binary system and the overlapping steady extended source, TeV J2032+4130.