Type II supernova spectral diversity, II: spectroscopic and photometric correlations

We present an analysis of observed trends and correlations between a large range of spectral and photometric parameters of more than 100 type II supernovae (SNe II), during the photospheric phase. We define a common epoch for all SNe of 50 days post-explosion, where the majority of the sample is likely to be under similar physical conditions. Several correlation matrices are produced to search for interesting trends between more than 30 distinct light-curve and spectral properties that characterize the diversity of SNe II. Overall, SNe with higher expansion velocities are brighter, have more rapidly declining light curves, shorter plateau durations, and higher 56Ni masses. Using a larger sample than previous studies, we argue that "Pd" - the plateau duration from the transition of the initial to "plateau" decline rates to the end of the "plateau" - is a better indicator of the hydrogen envelope mass than the traditionally used optically thick phase duration (OPTd: explosion epoch to end of plateau). This argument is supported by the fact that Pd also correlates with s 3, the light-curve decline rate at late times: lower Pd values correlate with larger s 3 decline rates. Large s 3 decline rates are likely related to lower envelope masses, which enables gamma-ray escape. We also find a significant anticorrelation between Pd and s 2 (the plateau decline rate), confirming the long standing hypothesis that faster declining SNe II (SNe IIL) are the result of explosions with lower hydrogen envelope masses and therefore have shorter Pd values.Fil: Gutiérrez, Claudia P.. Universidad de Chile; Chile. University of Southampton; Reino Unido. European Southern Observatory Santiago; Chile. Millennium Institute Of Astrophysics; ChileFil: Anderson, Joseph P.. European Southern Observatory Santiago; ChileFil: Hamuy, Mario. Millennium Institute Of Astrophysics; Chile. Universidad de Chile; ChileFil: González Gaitan, Santiago. Universidad de Chile; Chile. Universidade de Lisboa; Portugal. Millennium Institute Of Astrophysics; ChileFil: Galbany, Lluis. University of Pittsburgh at Johnstown; Estados Unidos. University of Pittsburgh; Estados UnidosFil: Dessart, Luc. Universidad de Chile; ChileFil: Stritzinger, Maximilian D.. University Aarhus; DinamarcaFil: Phillips, Mark M.. Las Campanas Observatory; ChileFil: Morrell, Nidia. Las Campanas Observatory; ChileFil: Folatelli, Gaston. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Type II Supernova Spectral Diversity. II. Spectroscopic and Photometric Correlations

We present an analysis of observed trends and correlations between a large range of spectral and photometric parameters of more than 100 type II supernovae (SNe II), during the photospheric phase. We define a common epoch for all SNe of 50 days post-explosion, where the majority of the sample is likely to be under similar physical conditions. Several correlation matrices are produced to search for interesting trends between more than 30 distinct light-curve and spectral properties that characterize the diversity of SNe II. Overall, SNe with higher expansion velocities are brighter, have more rapidly declining light curves, shorter plateau durations, and higher 56Ni masses. Using a larger sample than previous studies, we argue that "Pd" - the plateau duration from the transition of the initial to "plateau" decline rates to the end of the "plateau" - is a better indicator of the hydrogen envelope mass than the traditionally used optically thick phase duration (OPTd: explosion epoch to end of plateau). This argument is supported by the fact that Pd also correlates with s3, the light-curve decline rate at late times: lower Pd values correlate with larger s3 decline rates. Large s3 decline rates are likely related to lower envelope masses, which enables gamma-ray escape. We also find a significant anticorrelation between Pd and s2 (the plateau decline rate), confirming the long standing hypothesis that faster declining SNe II (SNe IIL) are the result of explosions with lower hydrogen envelope masses and therefore have shorter Pd values.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Type II Supernova Spectral Diversity. II. Spectroscopic and Photometric Correlations

We present an analysis of observed trends and correlations between a large range of spectral and photometric parameters of more than 100 type II supernovae (SNe II), during the photospheric phase. We define a common epoch for all SNe of 50 days post-explosion, where the majority of the sample is likely to be under similar physical conditions. Several correlation matrices are produced to search for interesting trends between more than 30 distinct light-curve and spectral properties that characterize the diversity of SNe II. Overall, SNe with higher expansion velocities are brighter, have more rapidly declining light curves, shorter plateau durations, and higher 56Ni masses. Using a larger sample than previous studies, we argue that "Pd" - the plateau duration from the transition of the initial to "plateau" decline rates to the end of the "plateau" - is a better indicator of the hydrogen envelope mass than the traditionally used optically thick phase duration (OPTd: explosion epoch to end of plateau). This argument is supported by the fact that Pd also correlates with s3, the light-curve decline rate at late times: lower Pd values correlate with larger s3 decline rates. Large s3 decline rates are likely related to lower envelope masses, which enables gamma-ray escape. We also find a significant anticorrelation between Pd and s2 (the plateau decline rate), confirming the long standing hypothesis that faster declining SNe II (SNe IIL) are the result of explosions with lower hydrogen envelope masses and therefore have shorter Pd values.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

A characterization of ASAS-SN core-collapse supernova environments with VLT+MUSE: I. Sample selection, analysis of local environments, and correlations with light curve properties

The analysis of core-collapse supernova (CCSN) environments can provide important information on the life cycle of massive stars and constrain the progenitor properties of these powerful explosions. The MUSE instrument at the VLT enables detailed local environment constraints of the progenitors of large samples of CCSNe. Using a homogeneous SN sample from the ASAS-SN survey has enabled us to perform a minimally biased statistical analysis of CCSN environments. We analyze 111 galaxies observed by MUSE that hosted 112 CCSNe detected or discovered by the ASAS-SN survey between 2014 and 2018. The majority of the galaxies were observed by the the AMUSING survey. Here we analyze the immediate environment around the SN locations and compare the properties between the different CCSN types and their light curves. We used stellar population synthesis and spectral fitting techniques to derive physical parameters for all HII regions detected within each galaxy, including the star formation rate (SFR), H$\alpha$ equivalent width (EW), oxygen abundance, and extinction. We found that stripped-envelope (SE) SNe occur in environments with a higher median SFR, H$\alpha$ EW, and oxygen abundances than SNe II and SNe IIn/Ibn. The distributions of SNe II and IIn are very similar, indicating that these events explode in similar environments. For the SESNe, SNe Ic have higher median SFRs, H$\alpha$ EWs, and oxygen abundances than SNe Ib. SNe IIb have environments with similar SFRs and H$\alpha$ EWs to SNe Ib, and similar oxygen abundances to SNe Ic. We also show that the postmaximum decline rate, $s$, of SNe II correlates with the H$\alpha$ EW, and that the luminosity and the $\Delta m_{15}$ parameter of SESNe correlate with the oxygen abundance, H$\alpha$ EW, and SFR at their environments. This suggests a connection between the explosion mechanisms of these events to their environment properties

Type II Supernova Spectral Diversity. I. Observations, Sample Characterization, and Spectral Line Evolution

We present 888 visual-wavelength spectra of 122 nearby type II supernovae (SNe II) obtained between 1986 and 2009, and ranging between 3 and 363 days post-explosion. In this first paper, we outline our observations and data reduction techniques, together with a characterization based on the spectral diversity of SNe II. A statistical analysis of the spectral matching technique is discussed as an alternative to nondetection constraints for estimating SN explosion epochs. The time evolution of spectral lines is presented and analyzed in terms of how this differs for SNe of different photometric, spectral, and environmental properties: velocities, pseudo-equivalent widths, decline rates, magnitudes, time durations, and environment metallicity. Our sample displays a large range in ejecta expansion velocities, from ∼9600 to ∼1500 km s-1 at 50 days post-explosion with a median Hα value of 7300 km s-1. This is most likely explained through differing explosion energies. Significant diversity is also observed in the absolute strength of spectral lines, characterized through their pseudo-equivalent widths. This implies significant diversity in both temperature evolution (linked to progenitor radius) and progenitor metallicity between different SNe II. Around 60% of our sample shows an extra absorption component on the blue side of the Hα P-Cygni profile ("Cachito" feature) between 7 and 120 days since explosion. Studying the nature of Cachito, we conclude that these features at early times (before ∼35 days) are associated with Si ii λ6355, while past the middle of the plateau phase they are related to high velocity (HV) features of hydrogen lines.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Type II Supernova Spectral Diversity. I. Observations, Sample Characterization, and Spectral Line Evolution

none26We present 888 visual-wavelength spectra of 122 nearby type II supernovae (SNe II) obtained between 1986 and 2009, and ranging between 3 and 363 days post-explosion. In this first paper, we outline our observations and data reduction techniques, together with a characterization based on the spectral diversity of SNe II. A statistical analysis of the spectral matching technique is discussed as an alternative to nondetection constraints for estimating SN explosion epochs. The time evolution of spectral lines is presented and analyzed in terms of how this differs for SNe of different photometric, spectral, and environmental properties: velocities, pseudo-equivalent widths, decline rates, magnitudes, time durations, and environment metallicity. Our sample displays a large range in ejecta expansion velocities, from ˜9600 to ˜1500 km s‑1 at 50 days post-explosion with a median {{{H}}}α value of 7300 km s‑1. This is most likely explained through differing explosion energies. Significant diversity is also observed in the absolute strength of spectral lines, characterized through their pseudo-equivalent widths. This implies significant diversity in both temperature evolution (linked to progenitor radius) and progenitor metallicity between different SNe II. Around 60% of our sample shows an extra absorption component on the blue side of the {{{H}}}α P-Cygni profile (“Cachito” feature) between 7 and 120 days since explosion. Studying the nature of Cachito, we conclude that these features at early times (before ˜35 days) are associated with Si II λ 6355, while past the middle of the plateau phase they are related to high velocity (HV) features of hydrogen lines.mixedGutiérrez, Claudia P.; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia; González-Gaitan, Santiago; Stritzinger, Maximilian D.; Phillips, Mark M.; Galbany, Lluis; Folatelli, Gastón; Dessart, Luc; Contreras, Carlos; Della Valle, Massimo; Freedman, Wendy L.; Hsiao, Eric Y.; Krisciunas, Kevin; Madore, Barry F.; Maza, José; Suntzeff, Nicholas B.; Prieto, Jose Luis; González, Luis; Cappellaro, Enrico; Navarrete, Mauricio; Pizzella, Alessandro; Ruiz, Maria T.; Smith, R. Chris; Turatto, MassimoGutiérrez, Claudia P.; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia; González-Gaitan, Santiago; Stritzinger, Maximilian D.; Phillips, Mark M.; Galbany, Lluis; Folatelli, Gastón; Dessart, Luc; Contreras, Carlos; Della Valle, Massimo; Freedman, Wendy L.; Hsiao, Eric Y.; Krisciunas, Kevin; Madore, Barry F.; Maza, José; Suntzeff, Nicholas B.; Prieto, Jose Luis; González, Luis; Cappellaro, Enrico; Navarrete, Mauricio; Pizzella, Alessandro; Ruiz, Maria T.; Smith, R. Chris; Turatto, Massim

Informe de Política Monetaria - Julio de 2020

De acuerdo con el mandato constitucional, el Banco de la República debe “velar por mantener el poder adquisitivo de la moneda, en coordinación con la política económica general”[1]. Para cumplir con este mandato, la Junta Directiva del Banco de la República (JDBR) adoptó como estrategia un esquema flexible de inflación objetivo, en el cual las acciones de política monetaria (PM) buscan conducir la inflación a una meta puntual y alcanzar el nivel máximo sostenible del producto y del empleo. La flexibilidad del esquema le permite a la JDBR mantener un balance apropiado entre el logro de la meta de inflación y el propósito de suavizar las fluctuaciones del producto y el empleo alrededor de su senda sostenible. La JDBR estableció una meta de inflación del 3%, planteada sobre la variación anual del índice de precios al consumidor (IPC). En el corto plazo la inflación puede ser afectada por factores que están fuera del control de la PM, como por ejemplo cambios en los precios de los alimentos debido a fenómenos climáticos. Para incorporar lo anterior, la JDBR anuncia, junto con la meta, un rango de ±1 punto porcentual (3 ±1 pp), el cual no es un objetivo de la PM, pero refleja el hecho de que la inflación puede fluctuar alrededor de la meta, sin pretender que sea siempre igual al 3%. El principal instrumento que tiene la JDBR para el control de la inflación es la tasa de interés de política (tasa repo a un día o tasa de interés de referencia). Dado que las acciones de PM toman tiempo en tener un efecto completo sobre la economía y la inflación[2], para fijar su valor la JDBR evalúa el pronóstico y las expectativas de la inflación frente a la meta, así como el estado actual y las perspectivas sobre la evolución de la economía. La JDBR se reúne una vez al mes, pero solo en ocho meses sesiona de forma ordinaria para tomar decisiones de PM (enero, marzo, abril, junio, julio, septiembre, octubre y diciembre). En los cuatro meses restantes (febrero, mayo, agosto y noviembre) no se toman, en principio, decisiones de este tipo[3]. Al finalizar las Juntas donde se toman decisiones de PM, se publica un comunicado y se hace una rueda de prensa a cargo del gerente general del Banco y el ministro de Hacienda. El siguiente día hábil se publican las minutas de la Junta, donde se describen las posturas que llevaron a adoptar la decisión. Adicionalmente, en enero, abril, julio y octubre se publica, junto con las minutas, el Informe de Política Monetaria (IPM)[4] realizado por el equipo técnico del Banco: el miércoles de la semana siguiente a la Junta el gerente general aclara inquietudes sobre las minutas y el gerente técnico del Banco presenta el IPM. Este esquema de comunicación busca entregar información relevante y actualizada que contribuya a la toma de mejores decisiones por parte de los agentes de la economía[5]. ___________ Constitución Política de Colombia (1991), artículo 373 y Sentencia C-481/99 de la Corte Constitucional. Para un mayor detalle véase M. Jalil y L. Mahadeva (2010). “Mecanismos de transmisión de la política monetaria en Colombia”, Universidad Externado de Colombia, Facultad de Finanzas, Gobierno y Relaciones Internacionales, ed. 1, vol. 1, núm. 69, octubre. Un miembro de la Junta puede solicitar en cualquier momento una reunión extraordinaria para tomar decisiones de PM. Antes conocido como Informe sobre Inflación. El actual esquema de comunicación fue aprobado por la JDBR en la reunión de agosto de 2019.Recuadro 1. Estimación del impacto de los alivios de precios sobre la inflación. Autores: Edgar Caicedo García - Nicolás Martínez CortésRecuadro 2. Nueva clasificación del Banco de la República de la canasta del IPC y revisión de medidas de inflación básica en Colombia. Autores: Edgar Caicedo-García - Nicolás Martínez-Cortés - Eliana R. González-Molano - Ramón Hernández-Ortega - José Vicente Romero - Anderson Grajales-Olart

Informe de Política Monetaria - Abril de 2020

De acuerdo con el mandato constitucional, el Banco de la República debe “velar por mantener el poder adquisitivo de la moneda, en coordinación con la política económica general”[1]. Para cumplir con este mandato, la Junta Directiva del Banco de la República (JDBR) adoptó como estrategia un esquema flexible de inflación objetivo, en el cual las acciones de política monetaria (PM) buscan conducir la inflación a una meta puntual y alcanzar el nivel máximo sostenible del producto y del empleo. La flexibilidad del esquema le permite a la JDBR mantener un balance apropiado entre el logro de la meta de inflación y el propósito de suavizar las fluctuaciones del producto y el empleo alrededor de su senda sostenible. La JDBR estableció una meta de inflación del 3%, planteada sobre la variación anual del índice de precios al consumidor (IPC). En el corto plazo la inflación puede ser afectada por factores que están fuera del control de la PM, como por ejemplo cambios en los precios de los alimentos debido a fenómenos climáticos. Para incorporar lo anterior, la JDBR anuncia, junto con la meta, un rango de ±1 punto porcentual (3 ±1 pp), el cual no es un objetivo de la PM, pero refleja el hecho de que la inflación puede fluctuar alrededor de la meta, sin pretender que sea siempre igual al 3%. El principal instrumento que tiene la JDBR para el control de la inflación es la tasa de interés de política (tasa repo a un día o tasa de interés de referencia). Dado que las acciones de PM toman tiempo en tener un efecto completo sobre la economía y la inflación[2], para fijar su valor la JDBR evalúa el pronóstico y las expectativas de la inflación frente a la meta, así como el estado actual y las perspectivas sobre la evolución de la economía. La JDBR se reúne una vez al mes, pero solo en ocho meses sesiona de forma ordinaria para tomar decisiones de PM (enero, marzo, abril, junio, julio, septiembre, octubre y diciembre). En los cuatro meses restantes (febrero, mayo, agosto y noviembre) no se toman, en principio, decisiones de este tipo[3]. Al finalizar las Juntas donde se toman decisiones de PM, se publica un comunicado y se hace una rueda de prensa a cargo del gerente general del Banco y el ministro de Hacienda. El siguiente día hábil se publican las minutas de la Junta, donde se describen las posturas que llevaron a adoptar la decisión. Adicionalmente, en enero, abril, julio y octubre se publica, junto con las minutas, el Informe de Política Monetaria (IPM)[4] realizado por el equipo técnico del Banco: el miércoles de la semana siguiente a la Junta el gerente general aclara inquietudes sobre las minutas y el gerente técnico del Banco presenta el IPM. Este esquema de comunicación busca entregar información relevante y actualizada que contribuya a la toma de mejores decisiones por parte de los agentes de la economía[5]. ___________ Constitución Política de Colombia (1991), artículo 373 y Sentencia C-481/99 de la Corte Constitucional. Para un mayor detalle véase M. Jalil y L. Mahadeva (2010). “Mecanismos de transmisión de la política monetaria en Colombia”, Universidad Externado de Colombia, Facultad de Finanzas, Gobierno y Relaciones Internacionales, ed. 1, vol. 1, núm. 69, octubre. Un miembro de la Junta puede solicitar en cualquier momento una reunión extraordinaria para tomar decisiones de PM. Antes conocido como Informe sobre Inflación. El actual esquema de comunicación fue aprobado por la JDBR en la reunión de agosto de 2019

Monetary Policy Report - April 2020

Banco de la República (the Central Bank of Colombia) is required by the Constitution to maintain the purchasing power of Colombia’s currency in coordination with general economic policy1. In order to fulfill this mandate, the Central Bank of Colombia’s Board of Directors (hereafter BDBR) has adopted a flexible inflation targeting scheme, by which monetary policy actions (MP) seek to lead inflation to a specific target and achieve maximum levels of sustainable output and employment. The flexibility of this scheme allows the BDBR to maintain an adequate balance between reaching its inflation target and smoothing output and employment fluctuations around their sustainable growth paths. The BDBR has set a 3.0% inflation target based on annual change in the consumer price index (CPI). In the short term, inflation may be affected by factors outside of monetary policy control, such as changes in food prices due to climate-related phenomena. To factor in this reality, the BDBR has also set a ±1 percentage point range outside its inflation target (i.e., 3.0 ± 1 pp). This range does not represent a monetary policy target, but rather reflects the fact that inflation can fluctuate around the target and will not always be equal to 3.0%. The main instrument of the BDBR to control inflation is the policy interest rate (overnight repo rate, or benchmark interest rate). Given that monetary policy actions take time to have their full effect on the economy and inflation2, the BDBR assesses the inflation forecast and inflation expectations vis-à-vis the inflation target, as well as the current situation and outlook of the economy, in order to determine their value. The BDBR meets once a month, producing monetary policy decisions in eight of its meetings (January, March, April, June, July, September, October, and December). In principle, no such decisions are made in the BDBR’s four remaining meetings (February, May, August, and November)3. At the end of the meetings in which monetary policy decisions are produced, a press release is published and a press conference held by the Governor of the Central Bank and the Minister of Finance. The minutes of the meeting describing the positions that led the BDBR to its decision are published on the following business day. Additionally, the Monetary Policy Report (MPR)4, produced by the Central Bank’s technical staff, is published in January, April, July, and October, together with the minutes. On the Wednesday of the week following the Board meeting, the Governor clarifies concerns about the minutes, and the Bank’s Deputy Technical Governor presents the MPR. This dissemination scheme5 seeks to deliver relevant and up-to-date information to contribute to better decision-making by the agents of the economy. 1 Political Constitution of Colombia (1991), Article 373 and Decision C-481/99 of the Constitutional Court. 2 For further details, see M. Jalil and L. Mahadeva (2010). “Transmission Mechanisms of Monetary Policy in Colombia”, Universidad Externado de Colombia, Faculty of Finance, Government, and International Relations, ed. 1, vol. 1, no. 69, October. 3 A Board Member may request an extraordinary meeting at any time to make MP decisions. 4 Formerly known as the Inflation Report. 5 The current communication scheme was approved by the BDBR in its August 2019 meeting