Ronald Mennickent - Academia.edu (original) (raw)

Papers by Ronald Mennickent

Astronomische Nachrichten, Oct 2, 2009

We summarize our optical monitoring program of VY Scl stars with the SMARTS telescopes, and trigg... more We summarize our optical monitoring program of VY Scl stars with the SMARTS telescopes, and triggered X-ray as well as optical observations after/during state transitions of V504 Cen and VY Scl.

Astronomy and Astrophysics, 2008

Context. The supersoft X-ray binary RX J0513.9-6951 shows cyclic changes between optical-low / X-... more Context. The supersoft X-ray binary RX J0513.9-6951 shows cyclic changes between optical-low / X-ray-on states and opticalhigh / X-ray-off states. It is supposed to be accreting close to the Eddington-critical limit and driven by "accretion wind evolution". Aims. We seek to derive the variations in the characteristic time scales of the long-term optical light curve and to determine the implications for the physical parameters of the system. Methods. We used existing and new optical monitoring observations covering a total time span of 14 years and compared the durations of the low and high states with the model calculations of Hachisu & Kato.

Revista Mexicana De Astronomia Y Astrofisica Conference Series, Jun 1, 2006

We present an update on our project to provide new input on the period distribution of pre-CVs by... more We present an update on our project to provide new input on the period distribution of pre-CVs by taking photometric light curves of candidate pre-CVs to detect sinusoidal (due to reflection effect) or ellipsoidal (due to Roche deformation) variability, and to determine the orbital period in positive cases. Having analysed data for 18 objects we find 6 confirmed pre-CVs or very probable candidates, 7 discarded systems, and 5 with still insufficient data. With the exception of the previously reported system LTT 560 with an orbital period P = 3.54 h, all confirmed pre-CVs have periods > 8 h, that still have to be confirmed by further observations. Among these, the clearest case is that of EC 14329-1625 with possible values of either 8.42 h or 16.84 h, depending on the variation being of sinusoidal or ellipsoidal nature, respectively. This research was supported by Fondecyt grant 1051078.

We have taken near-infrared (JHK) spectroscopic data of a sample of pre-CVs, in order to examine ... more We have taken near-infrared (JHK) spectroscopic data of a sample of pre-CVs, in order to examine them for signatures of nuclear evolution. Here we present preliminary results for the three systems BPM 71214, RR Cae, and RE 1016−053.

Na década de 90 iniciaram-se vários programas para a pesquisa de matéria escura na Galáxia usando... more Na década de 90 iniciaram-se vários programas para a pesquisa de matéria escura na Galáxia usando o efeito de microlentes gravitacionais. Entre os projetos mais bem conhecidos podemos mencionar o OGLE (Optical Gravitational Lensing Experiment) e o MACHO (MAssive Compact Halo Objects). A estratégia usada por eles consiste em fazer fotometria de banda larga (normalmente B, R e I) de

We present the results of the UBVRI photometry of the old (tau=17.3 Myr) radio pulsar PSR B0950+0... more We present the results of the UBVRI photometry of the old (tau=17.3 Myr) radio pulsar PSR B0950+08 obtained with the FORS1 at the VLT UT1. We detected a faint point-like object, B=27.06+/-0.35, V=27.05+/-0.15, Rc=26.49+/-0.10, Ic=26.20+/-0.17 coinciding with the radio pulsar by position with the accuracy better than 0.12". The broadband spectrum of PSR B0950+08 cannot be explained by the thermal radiation from the surface of the neutron star. It can be fitted by a single power law with the spectral index 0.65+/-0.40, revealing nonthermal origin of the detected optical emission.

In order to obtain the main stellar and orbital parameters of the Double Periodic Variable DQ Vel... more In order to obtain the main stellar and orbital parameters of the Double Periodic Variable DQ Velorum, we have carried out a series of spectroscopic and photometric observations covering several orbital cycles. We disentangle DQ Vel composite spectra and measure radial velocities using an iterative method for double spectroscopic binaries. We obtain the spectroscopic mass ratio q=0.31±0.03 from the radial velocity curves. We compare our single-lined spectra with a grid of synthetic spectra and estimate the temperature of the stars. We also model the V-band light curve using a fitting method based on the simplex algorithm including an accretion disc. We find that DQ Vel is a semi-detached system consisting on a B3V gainer (T_{g}=18500±500 K) and an A1III donor star (T_{d}=9400±100 K) plus an extended accretion disc around the gainer. We compare the stellar and disc parameters of DQ Vel with the DPV V393 Sco to investigate the nature and evolution of these two similar DPV systems.

Catalogues of Be star candidates in the SMC and the LMC as identified by Mennickent et al. (2002A... more Catalogues of Be star candidates in the SMC and the LMC as identified by Mennickent et al. (2002A&A...393..887M) (~1000 stars) and Sabogal et al. (2005, Cat. J/MNRAS/361/1055) (2446 stars), respectively, were used. In order to obtain their NIR properties, we used the NIR IRSF catalogue (Kato et al. 2007, Cat. II/288) which has JHKs photometric data for about 15 million point sources spread over a 40deg2 area of the LMC and 2.7 million sources spread over a 11deg2 area of the SMC. (11 data files).

Monthly Notices of the Royal Astronomical Society, 2015

We present a spectroscopic and photometric study of the Double Period Variable HD 170582. Based o... more We present a spectroscopic and photometric study of the Double Period Variable HD 170582. Based on the study of the ASAS V-band light curve we determine an improved orbital period of 16.87177 ± 0.02084 days and a long period of 587 days. We disentangled the light curve into an orbital part, determining ephemerides and revealing orbital ellipsoidal variability with unequal maxima, and a long cycle, showing quasi-sinusoidal changes with amplitude ∆V= 0.1 mag. Assuming synchronous rotation for the cool stellar component and semi-detached configuration we find a cool evolved star of M 2 = 1.9 ± 0.1 M , T 2 = 8000 ± 100 K and R 2 = 15.6 ± 0.2 R , and an early B-type dwarf of M 1 = 9.0 ± 0.2 M . The B-type star is surrounded by a geometrically and optically thick accretion disc of radial extension 20.8 ± 0.3 R contributing about 35% to the system luminosity at the V band. Two extended regions located at opposite sides of the disc rim, and hotter than the disc by 67% and 46%, fit the light curve asymmetries. The system is seen under inclination 67.4 ± 0.4 degree and it is found at a distance of 238 ± 10 pc. Specially interesting is the double line nature of H  5875; two absorption components move in anti-phase during the orbital cycle; they can be associated with the shock regions revealed by the photometry. The radial velocity of one of the H  5875 components closely follows the donor radial velocity, suggesting that the line is formed in a wind emerging near the stream-disc interacting region.

ABSTRACT We present the spectra of 29 carbon stars, 25 Be stars and 6 Be or Ce candidates which w... more ABSTRACT We present the spectra of 29 carbon stars, 25 Be stars and 6 Be or Ce candidates which were serendipitously found in a survey aiming to identify new symbiotic stars in the Magellanic Clouds. A short description of the spectral characteristics of each individual object is given, indicating the ones which are suitable for posterior follow-up.

Proceedings of the International Astronomical Union, 2010

We present preliminary results of our spectroscopic campaign of a group of intermediate mass inte... more We present preliminary results of our spectroscopic campaign of a group of intermediate mass interacting binaries dubbed "Double Periodic Variables" (DPVs), characterized by orbital light curves and additional long photometric cycles recurring roughly after 33 orbital periods . They have been interpreted as interacting, semi-detached binaries showing cycles of mass loss into the interstellar medium . High resolution Balmer and helium line profiles of DPVs can be interpreted in terms of mass flows in these systems. A system solution is given for LP Ara, based on modeling of the ASAS V-band orbital light curve and the radial velocity of the donor star.

Proceedings of the International Astronomical Union, 2009

We give a brief report on spectroscopic properties of V 393 Scorpii. Hα emission and shape and ra... more We give a brief report on spectroscopic properties of V 393 Scorpii. Hα emission and shape and radial velocity of He I 5875 are modulated with the long cycle. The long cycle is explained as a relaxation cycle in the circumprimary disc, that cumulates the mass transferred from the donor until certain instability produces disc depletion.

The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now i... more The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now in its 4th year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variables stars, microlensing events, new star clusters), others concerning more exotic objects, e.g. novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the actual status of the survey, as well some of the results based on the VVV data, are presented.

Proceedings of the International Astronomical Union, 2010

We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the p... more We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the physical properties of the circumstellar envelopes of Be stars classified in Groups I and II ). We find that while Humphreys and Pfund lines of Group I stars form in an optically thick envelope/disk, Group II stars show Pfund lines that form in an optically thick medium and Humphreys lines originating in optically thinner regions. The transition between Groups I and II could be understood in terms of the evolution of the circumstellar disk of the star and might bring clues on the mechanism originating the Be phenomenon.

Proceedings of the International Astronomical Union, 2010

Photometric searches for Be stars in environments with different metallicities have led to the di... more Photometric searches for Be stars in environments with different metallicities have led to the discovery of many Be-like star variables. The knowledge of these types of variables is still fragmentary. This work presents the preliminary results of analyzing FLAMES+GIRAFFE spectra of a sample of these Be-like stars that we have found in the Small Magellanic Cloud (SMC).

Proceedings of the International Astronomical Union, 2010

The Astronomical Journal, 2007

1 Based on observations obtained with the 1.3 m telescope at the Las Campanas Observatory.

Publications of the Astronomical Society of the Pacific, 2003

... Publisher: Issue Date: 2003. ???metadata.dc.subject.productividad???: ARTICULOS INTERNACIONAL... more ... Publisher: Issue Date: 2003. ???metadata.dc.subject.productividad???: ARTICULOS INTERNACIONALES-1000324. ???metadata.dc.creator.projectrelation???: RONALD ENRIQUE MENNICKENT CID. Description: Completo. URI: http://hdl.handle.net/10533/20466. ...

Astronomische Nachrichten, Oct 2, 2009

We summarize our optical monitoring program of VY Scl stars with the SMARTS telescopes, and trigg... more We summarize our optical monitoring program of VY Scl stars with the SMARTS telescopes, and triggered X-ray as well as optical observations after/during state transitions of V504 Cen and VY Scl.

Astronomy and Astrophysics, 2008

Context. The supersoft X-ray binary RX J0513.9-6951 shows cyclic changes between optical-low / X-... more Context. The supersoft X-ray binary RX J0513.9-6951 shows cyclic changes between optical-low / X-ray-on states and opticalhigh / X-ray-off states. It is supposed to be accreting close to the Eddington-critical limit and driven by "accretion wind evolution". Aims. We seek to derive the variations in the characteristic time scales of the long-term optical light curve and to determine the implications for the physical parameters of the system. Methods. We used existing and new optical monitoring observations covering a total time span of 14 years and compared the durations of the low and high states with the model calculations of Hachisu & Kato.

Revista Mexicana De Astronomia Y Astrofisica Conference Series, Jun 1, 2006

We present an update on our project to provide new input on the period distribution of pre-CVs by... more We present an update on our project to provide new input on the period distribution of pre-CVs by taking photometric light curves of candidate pre-CVs to detect sinusoidal (due to reflection effect) or ellipsoidal (due to Roche deformation) variability, and to determine the orbital period in positive cases. Having analysed data for 18 objects we find 6 confirmed pre-CVs or very probable candidates, 7 discarded systems, and 5 with still insufficient data. With the exception of the previously reported system LTT 560 with an orbital period P = 3.54 h, all confirmed pre-CVs have periods > 8 h, that still have to be confirmed by further observations. Among these, the clearest case is that of EC 14329-1625 with possible values of either 8.42 h or 16.84 h, depending on the variation being of sinusoidal or ellipsoidal nature, respectively. This research was supported by Fondecyt grant 1051078.

We have taken near-infrared (JHK) spectroscopic data of a sample of pre-CVs, in order to examine ... more We have taken near-infrared (JHK) spectroscopic data of a sample of pre-CVs, in order to examine them for signatures of nuclear evolution. Here we present preliminary results for the three systems BPM 71214, RR Cae, and RE 1016−053.

Na década de 90 iniciaram-se vários programas para a pesquisa de matéria escura na Galáxia usando... more Na década de 90 iniciaram-se vários programas para a pesquisa de matéria escura na Galáxia usando o efeito de microlentes gravitacionais. Entre os projetos mais bem conhecidos podemos mencionar o OGLE (Optical Gravitational Lensing Experiment) e o MACHO (MAssive Compact Halo Objects). A estratégia usada por eles consiste em fazer fotometria de banda larga (normalmente B, R e I) de

We present the results of the UBVRI photometry of the old (tau=17.3 Myr) radio pulsar PSR B0950+0... more We present the results of the UBVRI photometry of the old (tau=17.3 Myr) radio pulsar PSR B0950+08 obtained with the FORS1 at the VLT UT1. We detected a faint point-like object, B=27.06+/-0.35, V=27.05+/-0.15, Rc=26.49+/-0.10, Ic=26.20+/-0.17 coinciding with the radio pulsar by position with the accuracy better than 0.12". The broadband spectrum of PSR B0950+08 cannot be explained by the thermal radiation from the surface of the neutron star. It can be fitted by a single power law with the spectral index 0.65+/-0.40, revealing nonthermal origin of the detected optical emission.

In order to obtain the main stellar and orbital parameters of the Double Periodic Variable DQ Vel... more In order to obtain the main stellar and orbital parameters of the Double Periodic Variable DQ Velorum, we have carried out a series of spectroscopic and photometric observations covering several orbital cycles. We disentangle DQ Vel composite spectra and measure radial velocities using an iterative method for double spectroscopic binaries. We obtain the spectroscopic mass ratio q=0.31±0.03 from the radial velocity curves. We compare our single-lined spectra with a grid of synthetic spectra and estimate the temperature of the stars. We also model the V-band light curve using a fitting method based on the simplex algorithm including an accretion disc. We find that DQ Vel is a semi-detached system consisting on a B3V gainer (T_{g}=18500±500 K) and an A1III donor star (T_{d}=9400±100 K) plus an extended accretion disc around the gainer. We compare the stellar and disc parameters of DQ Vel with the DPV V393 Sco to investigate the nature and evolution of these two similar DPV systems.

Catalogues of Be star candidates in the SMC and the LMC as identified by Mennickent et al. (2002A... more Catalogues of Be star candidates in the SMC and the LMC as identified by Mennickent et al. (2002A&A...393..887M) (~1000 stars) and Sabogal et al. (2005, Cat. J/MNRAS/361/1055) (2446 stars), respectively, were used. In order to obtain their NIR properties, we used the NIR IRSF catalogue (Kato et al. 2007, Cat. II/288) which has JHKs photometric data for about 15 million point sources spread over a 40deg2 area of the LMC and 2.7 million sources spread over a 11deg2 area of the SMC. (11 data files).

Monthly Notices of the Royal Astronomical Society, 2015

We present a spectroscopic and photometric study of the Double Period Variable HD 170582. Based o... more We present a spectroscopic and photometric study of the Double Period Variable HD 170582. Based on the study of the ASAS V-band light curve we determine an improved orbital period of 16.87177 ± 0.02084 days and a long period of 587 days. We disentangled the light curve into an orbital part, determining ephemerides and revealing orbital ellipsoidal variability with unequal maxima, and a long cycle, showing quasi-sinusoidal changes with amplitude ∆V= 0.1 mag. Assuming synchronous rotation for the cool stellar component and semi-detached configuration we find a cool evolved star of M 2 = 1.9 ± 0.1 M , T 2 = 8000 ± 100 K and R 2 = 15.6 ± 0.2 R , and an early B-type dwarf of M 1 = 9.0 ± 0.2 M . The B-type star is surrounded by a geometrically and optically thick accretion disc of radial extension 20.8 ± 0.3 R contributing about 35% to the system luminosity at the V band. Two extended regions located at opposite sides of the disc rim, and hotter than the disc by 67% and 46%, fit the light curve asymmetries. The system is seen under inclination 67.4 ± 0.4 degree and it is found at a distance of 238 ± 10 pc. Specially interesting is the double line nature of H  5875; two absorption components move in anti-phase during the orbital cycle; they can be associated with the shock regions revealed by the photometry. The radial velocity of one of the H  5875 components closely follows the donor radial velocity, suggesting that the line is formed in a wind emerging near the stream-disc interacting region.

ABSTRACT We present the spectra of 29 carbon stars, 25 Be stars and 6 Be or Ce candidates which w... more ABSTRACT We present the spectra of 29 carbon stars, 25 Be stars and 6 Be or Ce candidates which were serendipitously found in a survey aiming to identify new symbiotic stars in the Magellanic Clouds. A short description of the spectral characteristics of each individual object is given, indicating the ones which are suitable for posterior follow-up.

Proceedings of the International Astronomical Union, 2010

We present preliminary results of our spectroscopic campaign of a group of intermediate mass inte... more We present preliminary results of our spectroscopic campaign of a group of intermediate mass interacting binaries dubbed "Double Periodic Variables" (DPVs), characterized by orbital light curves and additional long photometric cycles recurring roughly after 33 orbital periods . They have been interpreted as interacting, semi-detached binaries showing cycles of mass loss into the interstellar medium . High resolution Balmer and helium line profiles of DPVs can be interpreted in terms of mass flows in these systems. A system solution is given for LP Ara, based on modeling of the ASAS V-band orbital light curve and the radial velocity of the donor star.

Proceedings of the International Astronomical Union, 2009

We give a brief report on spectroscopic properties of V 393 Scorpii. Hα emission and shape and ra... more We give a brief report on spectroscopic properties of V 393 Scorpii. Hα emission and shape and radial velocity of He I 5875 are modulated with the long cycle. The long cycle is explained as a relaxation cycle in the circumprimary disc, that cumulates the mass transferred from the donor until certain instability produces disc depletion.

The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now i... more The VISTA Variables in the Vía Láctea (VVV) survey is one of six public ESO surveys, and is now in its 4th year of observing. Although far from being complete, the VVV survey has already delivered many results, some directly connected to the intended science goals (detection of variables stars, microlensing events, new star clusters), others concerning more exotic objects, e.g. novae. Now, at the end of the fourth observing period, and comprising roughly 50% of the proposed observations, the actual status of the survey, as well some of the results based on the VVV data, are presented.

Proceedings of the International Astronomical Union, 2010

We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the p... more We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the physical properties of the circumstellar envelopes of Be stars classified in Groups I and II ). We find that while Humphreys and Pfund lines of Group I stars form in an optically thick envelope/disk, Group II stars show Pfund lines that form in an optically thick medium and Humphreys lines originating in optically thinner regions. The transition between Groups I and II could be understood in terms of the evolution of the circumstellar disk of the star and might bring clues on the mechanism originating the Be phenomenon.

Proceedings of the International Astronomical Union, 2010

Photometric searches for Be stars in environments with different metallicities have led to the di... more Photometric searches for Be stars in environments with different metallicities have led to the discovery of many Be-like star variables. The knowledge of these types of variables is still fragmentary. This work presents the preliminary results of analyzing FLAMES+GIRAFFE spectra of a sample of these Be-like stars that we have found in the Small Magellanic Cloud (SMC).

Proceedings of the International Astronomical Union, 2010

The Astronomical Journal, 2007

1 Based on observations obtained with the 1.3 m telescope at the Las Campanas Observatory.

Publications of the Astronomical Society of the Pacific, 2003

... Publisher: Issue Date: 2003. ???metadata.dc.subject.productividad???: ARTICULOS INTERNACIONAL... more ... Publisher: Issue Date: 2003. ???metadata.dc.subject.productividad???: ARTICULOS INTERNACIONALES-1000324. ???metadata.dc.creator.projectrelation???: RONALD ENRIQUE MENNICKENT CID. Description: Completo. URI: http://hdl.handle.net/10533/20466. ...