Panning for gold, but finding helium: Discovery of the ultra-stripped supernova SN 2019wxt from gravitational-wave follow-up observations

IA acknowledges support from the Spanish MCINN through the “Center of Excellence Severo Ochoa” award for IAA-CSIC (SEV-2017-0709), and through grants AYA2016-80889-P and PID2019-107847RB-C44. LA acknowledges support from the Italian Ministry of Research through grant PRIN MIUR 2020 – 2020KB33TP METE. FEB acknowledges support from CONICYT Basal AFB-170002 and the Ministry of Economy through grant IC120009 to The Millennium Institute of Astrophysics (MAS). MGB acknowledges support from ASI grant I/004/11/5. MB acknowledges support from MIUR PRIN 2017, grant 20179ZF5KS. SJB thanks the Science Foundation Ireland and the Royal Society (RS-EA/3471). EB acknowledges support from the GRAWITA grant funded by INAF. MDC-G and YDH acknowledge support from the Ramón y Cajal Fellowship RYC2019-026465-I (funded by the MCIN/AEI/ 10.13039/501100011033 and the European Social Funding). EC acknowledges support from MIUR PRIN 2017. TWC acknowledges Marie Sklodowska-Curie grant H2020-MSCA-IF-2018-842471. AJCT acknowledges support from the Spanish Ministry project PID2020-118491GB-I00 and Junta de Andalucia grant P20_010168. PDA acknowledges support from ASI grant I/004/11/5 and from MIUR PRIN 2017, grant 20179ZF5KS. AF acknowledges the support of the ERC under the EU Horizon 2020 research and innovation program (ERC Advanced Grant KILONOVA No. 885281). MFr is supported by a Royal Society - Science Foundation Ireland University Research Fellowship. LG acknowledges RYC2019-027683-I, PID2020-115253GA-I00 & PIE20215AT016 grants. CG is supported by a VILLUM FONDEN Young Investor Grant (project number 25501). JG-R acknowledges support from Spanish AEI under Severo Ochoa Centres of Excellence Programme 2020-2023 (CEX2019-000920-S), and from ACIISI and ERDF under grant ProID2021010074. GG acknowledges the PRIN MIUR ‘Figaro’ for financial support. MG is supported by EU Horizon 2020 programme under grant No 101004719. KEH acknowledges support by a Project Grant (217690-051) from The Icelandic Research Fund. JH was supported by a VILLUM FONDEN Investigator grant (project number 16599). AI acknowledges the research programme Athena with project number 184.034.002, which is financed by the Dutch Research Council (NWO). LI was supported by research grants from VILLUM FONDEN (proj. 16599, 25501). ZPJ has been supported by NSFC under grant No. 11933010. DAK acknowledges support from Spanish National Research Project RTI2018-098104-J-I00 (GRBPhot). ECK acknowledges support from the G.R.E.A.T. research environment funded by the Vetenskapsrådet, and from The Wenner-Gren Foundations. GL was supported by a research grant (19054) from VILLUM FONDEN. AJL has received funding from the European Research Council search Council (ERC) via grant number 725246. JDL acknowledges support from a UK Research and Innovation Future Leaders Fellowship (MR/T020784/1). KM EU H2020 ERC grant no. 758638. IM is partially supported by OzGrav (ARC project CE17010000). BM acknowledges support from the Spanish MCINN under grant PID2019-105510GB-C31 and through the María de Maeztu award CEX2019-000918-M. DMS acknowledges support from the ERC under Horizon 2020 programme (No. 715051), as well as the Gobierno de Canarias and ERDF (ProID2020010104). AM acknowledge support from ASI grant I/004/11/3. MJM acknowledges the National Science Centre, Poland grant 2018/30/E/ST9/00208. DMS acknowledges support from the Gobierno de Canarias and ERDF (ProID2021010132); as well as from the Spanish Ministry of Science and Innovation via an Europa Excelencia grant (EUR2021-122010). JM acknowledges support from the Spanish MCINN through the “Center of Excellence Severo Ochoa” award to the IAA-CSIC (SEV-2017-0709), from the grant RTI2018-096228-B-C31 (MICIU/FEDER, EU) and the grant IAA4SKA P18-RT-3082 (Reg. Govt. of Andalusia). MN is supported by ERC grant 948381 and by a Turing Fellowship. ANG acknowledges support to TLS. FO acknowledges support from the GRAWITA/PRIN project ‘The new frontiers of the Multi-Messenger Astrophysics’ and from the H2020 grant 871158. MAPT was supported by grants RYC-2015-17854 and AYA2017-83216-P. GP is supported by ANID - Millennium Science Initiative - ICN12_009. JQV acknowledges support from ANID folio 21180886. AR acknowledges support from Premiale LBT 2013. OSS acknowledges the Italian MUR grant 1.05.06.13 and INAF-Prin 1.05.06.13. RS-R acknowledges support under the CSIC-MURALES project with reference 20215AT009. SS acknowledges support from the G.R.E.A.T. research environment, funded by Vetenskapsrådet project number 2016-06012. SJS sTFC Grant ST/P000312/1 and ST/N002520/1. RLCS acknowledges funding from STFC. HFS acknowledge the support of the Marsden Fund Council managed through Royal Society Te Aparangi. SDV aknowledges fundings from PNHE of INSU/AA. DV acknowledges the financial support of the German-Israeli Foundation (GIF No. I-1500-303.7/2019). DW is supported by Independent Research Fund Denmark grant DFF-7014-00017. The Cosmic Dawn Center is funded by the Danish National Research Foundation. LW acknowledges support from the Polish NCN DAINA No. 2017/27/L/ST9/03221, EC H2020 OPTICON No. 730890 and ORP No. 101004719. SY has been supported by the Knut and Alice Wallenberg Foundation, and the G.R.E.A.T. research environment funded by the Swedish Research Council. Based on observations collected by the ENGRAVE collaboration at the European Southern Observatory under ESO programmes 1102.D-0353, 0102.D-0348, 0102.D-0350; also on observations collected at the European Southern Observatory under ESO programmes 1103.D-0328 (ePESSTO+) and 1104.A-0380 (by the adH0cc team). Data for this paper has been obtained under the International Time Programme of the CCI (International Scientific Committee of the Observatorios de Canarias of the IAC) with the GTC operated on the island of La Palma in the Roque de los Muchachos. This research made use of TARDIS, a community-developed software package for spectral synthesis in supernovae. The development of TARDIS received support from the Google Summer of Code initiative and from ESA’s Summer of Code in Space program. TARDIS makes extensive use of Astropy and PyNE. We are grateful for use of the computing resources from the Northern Ireland High Performance Computing (NI-HPC) service funded by EPSRC (EP/T022175). This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated with program 15980. GROND observations at La Silla were performed as part of the program 0104.A-9099. Part of the funding for GROND (both hardware as well as personnel) was generously granted from the Leibniz-Prize to Prof. G. Hasinger (DFG grant HA 1850/28-1). Based (in part) on observations made in the Observatorios de Canarias del IAC with the GTC operated on the Island of La Palma in the Roque de los Muchachos Observatory. This research used telescope time awarded by the CCI International Time Programme ("GTC1-18ITP; Coordinated European follow-up of gravitational wave events"). This work was enabled by observations made from the Gemini North telescope and UKIRT telescopes, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance. UKIRT is owned by the University of Hawaii (UH) and operated by the UH Institute for Astronomy. When the data reported here were obtained, the operations were enabled through the cooperation of the East Asian Observatory (EAO). The international Gemini Observatory is a program of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2019.1.01406.T. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. Author contributions: IA, TA, RB, SF, SG, MGi, BM, JM, MO, ZP, MP-T and JY were co-investigators (PI: MGi) of the e-MERLIN proposal and contributed to radio data analysis and interpretation. LA contributed to the discussion and manuscript review. FEB helped with the interpretation and contributed to the manuscript. SB served as on-call team member for ENGRAVE during O3 and provided comments and inputs to the preparation of the manuscript. MGB coordinated the working group that interfaces with external facilities and contributed to operations. KB served in the ENGRAVE/HST team. TDB, CCL, EAM and RW contributed PS1 data and processing. MB contributed to governance as a member of the ENGRAVE Governing Council and provided comments on the manuscript. SJB performed photometry on optical and IR images with autophot. EB served in the Governing Council of ENGRAVE contributing in the governance activities. EC performed data reduction and presentation. KCC and MEH led the PS1, Gemini and UKIRT observing, proposals and data management. SC contributed to the revision of the manuscript and to scientific discussions. TWC coordinated the reduction and analysis of GROND data, compared bolometric light curves and joined the weekly discussion meetings during the preparation of the draft. AC served on the on-call operations team triggering VLT observations. SC contributed to the revision of the final text and to scientific discussions. FD provided comments to the paper during the second circulation. PDA contributed to governance as a Governing Council member, served on the operations team and reduced the TNG data. VD contributed to triggering, worked in the ENGRAVE WG-2 spec and reviewed the paper. AFi reduced the FORS2 and GNIRS spectra and contributed to discussions and editing of the paper. AFl served during his PhD programme for 6 ENGRAVE observing subruns as on-call or writing team member. MFr co-led the writing team, produced Figures 2–5, 15 and B.1, contributed to spectroscopic and photometric analysis, interpretation and paper writing. MFu run the kilonova models and produced Fig. 14. LG served on the on-call operations team and contributed to the revision of the final text. CG contributed to discussion and modelling of dust. JG-R contributed with reduction of MEGARA data. GG participated to the discussion on event rates. JHG led the spectroscopic modelling with TARDIS, and assisted with writing the manuscript. In addition to analysing and interpreting the e-MERLIN data, MGi inspected the VLASS and Aperitif survey data and used it to estimate the host galaxy SFR. BPG calculated the GOTO statistics used in Sect. 2.1. MGr contributed to observations and data reduction. KEH contributed to NOT and VLT observations and data reduction. JH is a member of the ENGRAVE Governing Council and contributed to discussions on dust. YDH performed optical observations with GTC. AI carried out ACAM and LIRIS observations and data reduction. LI contributed to the data analysis of the NOT spectrum and provided comments to the manuscript. ZPJ did observation-related duties and participated in early discussions. PGJ is a Governing Council member and PI of part of the WHT and GTC data, helped in reducing the data and contributed to the analysis. DAK provided comments and proofread the paper. ECK analysed the WISE data and provided comments. RK served as a member of the writing team and provided inputs on draft. GL coordinated the WG-POL and provided comments on the manuscript. AJL chairs the Executive Committee, contributed to data collection and led HST observations. JDL is a member of the ENGRAVE operations and spectroscopy teams. KM coordinated the on-call team, scheduled observations and provided scientific interpretation. IM contributed to astrophysical modelling and interpretation. DMS contributed to EMBOSS/ENGRAVE efforts in WHT and GTC data reduction. SM contributed to ENGRAVE and provided comments on the manuscript. AM is a member of the imaging working group and contributed to observations and data reduction. MJM measured and interpreted the molecular gas properties of the host (Table 6) and produced the CO spectra (Fig. 13). MN carried out light curve modelling and worked in the operations team. ANG has been involved in the GROND observations and data reduction. SRO performed the Swift/UVOT data analysis. FO is a member of the operation team and of the WG-SPEC and contributed to the paper review process. SP is a member of the spectroscopy team and provided comments on the manuscript. RP contributed to ALMA data reduction and analysis. MAPT contributed to coordinate the EMBOSS WHT observations and part of the EMIR and OSIRIS data analysis. EP is a member of the ENGRAVE Governing Council. GP served on the on-call operations team. JQ-V provided comments and suggestions to the writing team. FR has contributed with comments in the first circulation of the paper draft. ARa is the PI of the GROND ToO time project. SR contributed to revise the manuscript. ARo provided comments to the draft. OSS co-led the writing team, produced Figures 1 (together with AJL), 9, 7, 16, C.1, D.1 and D.2 (and the corresponding pieces of analysis) and derived the SN2019wxt-like transient volumetric rate estimate in Sect. 7.1. SSc reduced the X-shooter data and was involved in the ALMA observation. SJS contributed to the PS1 data, light curve and spectral analysis, text and interpretation. KWS is developer and operator of the QUB Pan-STARRS transient science server. MDF contributed to the KN comparison analysis. JS contributed to the text and discussion. SSr contributed with calibrating the Pan-STARRS and UKIRT photometry and modelling the bolometric light curve. RLCS provided comments on and contributed to editing the manuscript. DS is a member of the ENGRAVE governing council and was involved in discussions around this object from the start. HFS conducted the search within the BPASS fiducial models and contributed text. VT participated to pipelines development, paper layout drafting and is an on-duty operations member. SDV is a member of the ENGRAVE Executive Committee and provided comments to the manuscript. DV contributed to the astrophysical interpretation. DW provided comments on the manuscript. KW served on the on-call operations team. LW was part of the on call operation team. SY served on the on-call operations team. DRY developed and maintains many of the software tools essential to the work of the consortium.We present the results from multi-wavelength observations of a transient discovered during an intensive follow-up campaign of S191213g, a gravitational wave (GW) event reported by the LIGO-Virgo Collaboration as a possible binary neutron star merger in a low latency search. This search yielded SN 2019wxt, a young transient in a galaxy whose sky position (in the 80% GW contour) and distance (∼150 Mpc) were plausibly compatible with the localisation uncertainty of the GW event. Initially, the transienta's tightly constrained age, its relatively faint peak magnitude (Mi ∼ -16.7 mag), and the r-band decline rate of ∼1 mag per 5 days appeared suggestive of a compact binary merger. However, SN 2019wxt spectroscopically resembled a type Ib supernova, and analysis of the optical-near-infrared evolution rapidly led to the conclusion that while it could not be associated with S191213g, it nevertheless represented an extreme outcome of stellar evolution. By modelling the light curve, we estimated an ejecta mass of only ∼0.1 M·, with 56Ni comprising ∼20% of this. We were broadly able to reproduce its spectral evolution with a composition dominated by helium and oxygen, with trace amounts of calcium. We considered various progenitor channels that could give rise to the observed properties of SN 2019wxt and concluded that an ultra-stripped origin in a binary system is the most likely explanation. Disentangling genuine electromagnetic counterparts to GW events from transients such as SN 2019wxt soon after discovery is challenging: in a bid to characterise this level of contamination, we estimated the rate of events with a volumetric rate density comparable to that of SN 2019wxt and found that around one such event per week can occur within the typical GW localisation area of O4 alerts out to a luminosity distance of 500 Mpc, beyond which it would become fainter than the typical depth of current electromagnetic follow-up campaigns.Spanish MCINN: IAA-CSIC (SEV-2017-0709), AYA2016-80889-P, PID2019-107847RB-C44MCIN/AEI/ 10.13039/501100011033European Social Funding: Ramón y Cajal Fellowship RYC2019-026465-IMarie Sklodowska-Curie grant H2020-MSCA-IF-2018-842471Spanish Ministry PID2020-118491GB-I00Junta de Andalucia P20_010168EU Horizon 2020: ERC KILONOVA No. 885281Spanish AEI CEX2019-000920-SACIISIERDF ProID2021010074EU Horizon 2020: 101004719European Research Council (ERC) 725246Spanish MCINN PID2019-105510GB-C31María de Maeztu award CEX2019-000918-MERC Horizon 2020: 715051Gobierno de CanariasERDF ProID2021010132Spanish Ministry of Science and Innovation, Europa Excelencia EUR2021-122010MICIU/FEDER, EU RTI2018-096228-B-C31Reg. Govt. of Andalusia IAA4SKA P18-RT-3082H2020 871158Millennium Science Initiative - ICN12_009CSIC-MURALES 20215AT009European Southern Observatory 1102.D-0353, 0102.D-0348, 0102.D-0350, 1103.D-0328, 1104.A-0380NASA NAS 5–26555, 15980CCI International Time Programme ("GTC1-18ITP; Coordinated European follow-up of gravitational wave events")ERDF ProID202001010

A recollimation shock 80 mas from the core in the jet of the radio galaxy 3C120: Observational evidence and modeling

We present Very Long Baseline Array observations of the radio galaxy 3C120 at 5, 8, 12, and 15 GHz designed to study a peculiar stationary jet feature (hereafter C80) located ~80 mas from the core, which was previously shown to display a brightness temperature ~600 times lager than expected at such distances. The high sensitivity of the images -- obtained between December 2009 and June 2010 -- has revealed that C80 corresponds to the eastern flux density peak of an arc of emission (hereafter A80), downstream of which extends a large (~20 mas in size) bubble-like structure that resembles an inverted bow shock. The linearly polarized emission closely follows that of the total intensity in A80, with the electric vector position angle distributed nearly perpendicular to the arc-shaped structure. Despite the stationary nature of C80/A80, superluminal components with speeds up to ~3 c have been detected downstream from its position, resembling the behavior observed in the HST-1 emission complex in M87. The total and polarized emission of the C80/A80 structure, its lack of motion, and brightness temperature excess are best reproduced by a model based on synchrotron emission from a conical shock with cone opening angle \eta=10 degrees, jet viewing angle \theta=16 degrees, a completely tangled upstream magnetic field, and upstream Lorentz factor \gamma=8.4. The good agreement between our observations and numerical modeling leads us to conclude that the peculiar feature associated with C80/A80 corresponds to a conical recollimation shock in the jet of 3C120 located at a de-projected distance of ~190 pc downstream from the nucleus.Comment: Accepted for publication in Ap

Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behavior rules out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow; perhaps related to turbulence in the accretion disk; coupled with hydrodynamic instabilities, leads to the non-ballistic dynamics that cause the observed non-periodic changes in the direction of the inner jet.Comment: Accepted for Publication in The Astrophysical Journal. 11 pages, 6 figures, 4 tables. High resolution images on figure 1 and complete tables 1 and 2 may be provided on reques

IAA : Información y actualidad astronómica (10)

Sumario : Investigación: Chorros relativistas en núcleos activos de galaxias.-- Materia oscura: a tientas por el Universo.-- Ventana Abierta: Físico teórico autónomo se ofrece para.-- Charlas con… Robert Haberle.-- Actualidad Científica: La búsqueda de las estrellas más viejas de la Galaxia.-- Un superbólido más brillante que la Luna llena surcó el cielo argelino.-- Actividades IAA.-- Agenda.Esta revista se publica con la ayuda de la Acción Especial DIF 2001-4284-E del Programa Nacional de Difusión de la Ciencia y la Tecnología, del Ministerio de Ciencia y TecnologíaN

A multi-wavelength polarimetric study of the blazar CTA 102 during A gamma-ray flare in 2012

Casadio, Carolina et. al.We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright γ-ray outburst detected by the Fermi Large Area Telescope in 2012 September-October when the source reached a flux of F = 5.2 ± 0.4 × 10 photons cm s. At the same time, the source displayed an unprecedented optical and near-infrared (near-IR) outburst. We study the evolution of the parsec-scale jet with ultra-high angular resolution through a sequence of 80 total and polarized intensity Very Long Baseline Array images at 43 GHz, covering the observing period from 2007 June to 2014 June. We find that the γ-ray outburst is coincident with flares at all the other frequencies and is related to the passage of a new superluminal knot through the radio core. The powerful γ-ray emission is associated with a change in direction of the jet, which became oriented more closely to our line of sight (θ ∼ 1.°2) during the ejection of the knot and the γ-ray outburst. During the flare, the optical polarized emission displays intra-day variability and a clear clockwise rotation of electric vector position angles (EVPAs), which we associate with the path followed by the knot as it moves along helical magnetic field lines, although a random walk of the EVPA caused by a turbulent magnetic field cannot be ruled out. We locate the γ-ray outburst a short distance downstream of the radio core, parsecs from the black hole. This suggests that synchrotron self-Compton scattering of NIR to ultraviolet photons is the probable mechanism for the γ-ray production.This research has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) grant AYA2013-40825-P. The research at Boston University (BU) was funded in part by NASA Fermi Guest Investigator grants NNX14AQ58G and NNX13AO99G, and Swift Guest Investigator grant NNX14AI96G. I. A. acknowledges support by a Ramon y Cajal grant of the MINECO. The VLBA is operated by the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The PRISM camera at Lowell Observatory was developed by K. Janes et al. at BU and Lowell Observatory, with funding from the NSF, BU, and Lowell Observatory. St. Petersburg University team acknowledges support from Russian RFBR grant 15-02-00949 and St. Petersburg University research grant 6.38.335.2015. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF, and the W.M. Keck Foundation. The Mimir observations were performed by Lauren Cashman, Jordan Montgomery, and Dan Clemens, all from Boston University. This research is partly based on data taken at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Data from the Steward Observatory spectropolarimetric monitoring project were used. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, and NNX12AO93G. The Metsahovi team acknowledges the support from the Academy of Finland to our observing projects (numbers 212656, 210338, 121148, and others).Peer Reviewe

Polarization angle swings in blazars: the case of 3C 279

Kiehlmann, S. et. al.Context. Over the past few years, on several occasions, large, continuous rotations of the electric vector position angle (EVPA) of linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy gamma-ray flares and they have attracted considerable attention, since they could allow us to probe the magnetic field structure in the gamma-ray emitting region of the jet. The flat-spectrum radio quasar 3C 279 is one of the most prominent examples showing this behaviour. Aims. Our goal is to study the observed EVPA rotations and to distinguish between a stochastic and a deterministic origin of the polarization variability. Methods. We have combined multiple data sets of R-band photometry and optical polarimetry measurements of 3C 279, yielding exceptionally well-sampled flux density and polarization curves that cover a period of 2008-2012. Several large EVPA rotations are identified in the data. We introduce a quantitative measure for the EVPA curve smoothness, which is then used to test a set of simple random walk polarization variability models against the data. Results. 3C 279 shows different polarization variation characteristics during an optical low-flux state and a flaring state. The polarization variation during the flaring state, especially the smooth similar to 360 degrees rotation of the EVPA in mid-2011, is not consistent with the tested stochastic processes. Conclusions. We conclude that, during the two different optical flux states, two different processes govern polarization variation, which is possibly a stochastic process during the low-brightness state and a deterministic process during the flaring activity.S.K. was supported for this research through a stipend from the International Max Planck Research School (IMPRS) for Astronomy and Astrophysics at the Max Planck Institute for Radio Astronomy in cooperation with the Universities of Bonn and Cologne. T.S. was partly supported by the Academy of Finland project 274477. The research at Boston University was partly funded by NASA Fermi GI grant NNX11AQ03G. K.V.S. is partly supported by the Russian Foundation for Basic Research grants 13-02-12103 and 14-02-31789. N.G.B. was supported by the RFBR grant 12-02-01237a. E.B., M.S. and D.H. thank financial support from UNAM DGAPA-PAPIIT through grant IN116211-3. I. A. acknowledges support by a Ramon y Cajal grant of the Spanish Ministry of Economy and Competitiveness (MINECO). The research at the IAA-CSIC and the MAPCAT program are supported by the Spanish Ministry of Economy and Competitiveness and the Regional Government of Andalucia (Spain) through grants AYA2010-14844, AYA2013-40825-P, and P09-FQM-4784. The Calar Alto Observatory is jointly operated by the Max-Planck-Institut fur Astronomie and the Instituto de Astrofisica de Andalucia-CSIC. Data from the Steward Observatory spectropolarimetric monitoring project were used. This program is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX14AQ58G. St. Petersburg University team acknowledges support from Russian RFBR grant 15-02-00949 and St. Petersburg University research grant 6.38.335.2015. The Abastumani team acknowledges financial support of the project FR/638/6-320/12 by the Shota Rustaveli National Science Foundation under contract 31/77.Peer reviewe

Análisis financiero y bursátil del Bitcoin y otras criptomonedas

El mercado de las criptomonedas ha evolucionado a un ritmo sin precedentes a lo largo de su corto periodo de vida, desde que bajo el pseudónimo de Satoshi Nakatomo se publicase el artículo Bitcoin: A Peer-to-Peer Electronic Cash System. El presente trabajo, sigue una línea novedosa ya que las investigaciones en este campo son de escasa relevancia. Nos proporciona un análisis financiero, bursátil y fiscal del bitcoin analizando las implicaciones surgidas desde esta triple perspectiva. Se llevará a cabo un análisis exhaustivo de los rasgos definitorios de estas criptomonedas, atendiendo a la posibilidad de establecimiento de las mismas como medio de pago, impulsado por el auge del e-commerce. También se analizará su afianzamiento como instrumento habitual de financiación de nuevos proyectos de empresas, a través de las Inittial Coins Offerings. Por último, se estudiará como activo de inversión, obteniendo conclusiones sobre el estudio de las variables de precio, rentabilidad, volatilidad y correlación con otros activos comparables de diversa naturaleza (materias primas, divisas, metales preciosos, acciones y otras criptomonedas) en la serie temporal 2014-2020.<br /

Multiwavelength Variations of 3C 454.3 during the November 2010 to January 2011 Outburst

We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from November 2010 through January 2011. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at gamma-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies, and the Submillimeter Array at 1.3 mm. From this dataset, we form a series of 52 spectral energy distributions (SEDs) spanning nearly two months that are unprecedented in time coverage and breadth of frequency. Discrete correlation anlaysis of the millimeter, far-infrared, and gamma-ray light curves show that the variations were essentially simultaneous, indicative of co-spatiality of the emission, at these wavebands. In contrast, differences in short-term fluctuations at various wavelengths imply the presence of inhomegeneities in physical conditions across the source. We locate the site of the outburst in the parsec-scale core, whose flux density as measured on 7 mm Very Long Baseline Array images increased by 70 percent during the first five weeks of the outburst. Based on these considerations and guided by the SEDs, we propose a model in which turbulent plasma crosses a conical standing shock in the parsec-scale region of the jet. Here, the high-energy emission in the model is produced by inverse Compton scattering of seed photons supplied by either nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for X-rays) synchrotron radiation from plasma that crosses the standing shock. For the two dates on which we fitted the model SED to the data, the model corresponds very well to the observations at all bands except at X-ray energies, where the spectrum is flatter than observed.Comment: Accepted for publication in Astrophysical Journal. 82 pages, 13 figure

Jet stability and the generation of superluminal and stationary components

We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component, instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness, and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component.Comment: Accepted by ApJ Letters. LaTeX, 19 pages, 4 PostScript figure