Pub Date : 2019-12-01DOI: 10.32023/0001-5237/69.4.4
Y. Nikolov, R. Zamanov, K. Stoyanov
{"title":"Spectropolarimetric Observations of the Recurrent Nova RS Oph","authors":"Y. Nikolov, R. Zamanov, K. Stoyanov","doi":"10.32023/0001-5237/69.4.4","DOIUrl":"https://doi.org/10.32023/0001-5237/69.4.4","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"69 1","pages":"361-368"},"PeriodicalIF":2.2,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47818088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-01DOI: 10.32023/0001-5237/69.3.3
K. Gazeas, S. Palafouta
{"title":"DV Psc: A Magnetically Active Hierarchical Triple System","authors":"K. Gazeas, S. Palafouta","doi":"10.32023/0001-5237/69.3.3","DOIUrl":"https://doi.org/10.32023/0001-5237/69.3.3","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"43 9 1","pages":"261-282"},"PeriodicalIF":2.2,"publicationDate":"2019-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69520909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-15DOI: 10.32023/0001-5237/69.1.1
J. Clari'a, M. C. Parisi, T. Palma, A. Ahumada, C. G. Oviedo
We present high-quality CCD photometry in the Washington system C and T1 passbands down to T1 ~ 19.5 mag in the fields of 10 Galactic open clusters (OCs) or candidates projected close to the Galactic plane, namely: ESO 313-SC03, BH 54, Ruprecht 87, ESO 129-SC32, BH 217, Collinder 347, Basel 5, Ruprecht 144, Archinal 1 and Berkeley 82. Four of these objects are located toward the Galactic centre direction within a solid angle of 21 deg. No photoelectric or CCD photometry in the optical domain has been so far reported for five of these objects. Cluster radii are estimated from radial density profiles (RDPs) in the cluster fields. Using the cluster Washington (C-T1,T1) colour-magnitude diagrams (CMDs), statistically cleaned from field star contamination, we estimate reddening, heliocentric distance and age of the clusters by fitting Padova theoretical isochrones computed for the Washington system. In all cases, the best fittings were obtained with nearly solar metal content isochrones. Both RDPs and CMDs show that we are dealing with real OCs, except for Ruprecht 87 and Archinal,1 that are found to be probably not physical systems. Differential reddening appears to be present across the fields of ESO313-SC03, ESO129-SC32, BH 217, Collinder 347 and Basel 5. The studied OCs are located at d = 1.0-5.0 kpc from the Sun and at Galactocentric distances R_GC = 6.0-10.6 kpc, with mean reddening E(B-V) in the range 0.10-1.30 mag and ages between 5 Myr (Collinder 347) and ~ 1000 Myr (Basel 5). The estimated linear cluster radii are in the range of 0.4-3.2 pc. In general terms, the results obtained show fairly good agreement with previous photometric results. In some clusters, however, considerable differences are found between the present results and previous ones determined using near-infrared photometric data. The current study provides new OC parameters and some revisions to the OC catalogues.
{"title":"CCD Washington Photometry of Ten Open Clusters or Candidates Projected Close to the Galactic Plane","authors":"J. Clari'a, M. C. Parisi, T. Palma, A. Ahumada, C. G. Oviedo","doi":"10.32023/0001-5237/69.1.1","DOIUrl":"https://doi.org/10.32023/0001-5237/69.1.1","url":null,"abstract":"We present high-quality CCD photometry in the Washington system C and T1 passbands down to T1 ~ 19.5 mag in the fields of 10 Galactic open clusters (OCs) or candidates projected close to the Galactic plane, namely: ESO 313-SC03, BH 54, Ruprecht 87, ESO 129-SC32, BH 217, Collinder 347, Basel 5, Ruprecht 144, Archinal 1 and Berkeley 82. Four of these objects are located toward the Galactic centre direction within a solid angle of 21 deg. No photoelectric or CCD photometry in the optical domain has been so far reported for five of these objects. Cluster radii are estimated from radial density profiles (RDPs) in the cluster fields. Using the cluster Washington (C-T1,T1) colour-magnitude diagrams (CMDs), statistically cleaned from field star contamination, we estimate reddening, heliocentric distance and age of the clusters by fitting Padova theoretical isochrones computed for the Washington system. In all cases, the best fittings were obtained with nearly solar metal content isochrones. Both RDPs and CMDs show that we are dealing with real OCs, except for Ruprecht 87 and Archinal,1 that are found to be probably not physical systems. Differential reddening appears to be present across the fields of ESO313-SC03, ESO129-SC32, BH 217, Collinder 347 and Basel 5. The studied OCs are located at d = 1.0-5.0 kpc from the Sun and at Galactocentric distances R_GC = 6.0-10.6 kpc, with mean reddening E(B-V) in the range 0.10-1.30 mag and ages between 5 Myr (Collinder 347) and ~ 1000 Myr (Basel 5). The estimated linear cluster radii are in the range of 0.4-3.2 pc. In general terms, the results obtained show fairly good agreement with previous photometric results. In some clusters, however, considerable differences are found between the present results and previous ones determined using near-infrared photometric data. The current study provides new OC parameters and some revisions to the OC catalogues.","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48255115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-12-01DOI: 10.32023/0001-5237/68.4.5
A. Frasca, D. Montes, J. Alcalá, A. Klutsch, P. Guillout
{"title":"Contemporaneous Broad-Band Photometry and Hα Observations of T Tau Stars","authors":"A. Frasca, D. Montes, J. Alcalá, A. Klutsch, P. Guillout","doi":"10.32023/0001-5237/68.4.5","DOIUrl":"https://doi.org/10.32023/0001-5237/68.4.5","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"403-424"},"PeriodicalIF":2.2,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69520891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-01DOI: 10.32023/0001-5237/68.3.6
W. Dimitrov, Natalia Żywucka-Hejzner, M. Polińska, K. Kamiński, M. Kamińska
{"title":"Spectroscopy of the eclipsing binary BD-00°2862 : possible multiplicity","authors":"W. Dimitrov, Natalia Żywucka-Hejzner, M. Polińska, K. Kamiński, M. Kamińska","doi":"10.32023/0001-5237/68.3.6","DOIUrl":"https://doi.org/10.32023/0001-5237/68.3.6","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"269-284"},"PeriodicalIF":2.2,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42020671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.32023/0001-5237/68.2.1
I. Soszyński, A. Udalski, M. Szymański, Ł. Wyrzykowski, K. Ulaczyk, R. Poleski, P. Pietrukowicz, S. Kozłowski, D. Skowron, J. Skowron, P. Mr'oz, K. Rybicki, P. Iwanek
We present a nearly complete collection of type II Cepheids in the Magellanic System. The sample consists of 338 objects: 285 and 53 variables in the Large and Small Magellanic Clouds, respectively. Based on the pulsation periods and light-curve morphology, we classified 118 of our type II Cepheids as BL Herculis, 120 as W Virginis, 34 as peculiar W Virginis, and 66 as RV Tauri stars. For all objects, we publish time-series VI photometry obtained during the OGLE-IV survey, from 2010 to the end of 2017. We present the most interesting individual objects in our collection: 16 type II Cepheids showing additional eclipsing or ellipsoidal variability, two RV Tau variables more than 2.5 mag fainter than other stars of this type in the LMC, an RVb star that drastically decreased the amplitude of the long-period modulation, type II Cepheids exhibiting significant amplitude and period changes, and an RV Tau star which experiences interchanges of deep and shallow minima. We show that peculiar W Vir stars have markedly different spatial distribution than other subclasses of type II Cepheids, which indicates different evolutionary histories of these objects.
{"title":"The OGLE Collection of Variable Stars. Type II Cepheids in the Magellanic System","authors":"I. Soszyński, A. Udalski, M. Szymański, Ł. Wyrzykowski, K. Ulaczyk, R. Poleski, P. Pietrukowicz, S. Kozłowski, D. Skowron, J. Skowron, P. Mr'oz, K. Rybicki, P. Iwanek","doi":"10.32023/0001-5237/68.2.1","DOIUrl":"https://doi.org/10.32023/0001-5237/68.2.1","url":null,"abstract":"We present a nearly complete collection of type II Cepheids in the Magellanic System. The sample consists of 338 objects: 285 and 53 variables in the Large and Small Magellanic Clouds, respectively. Based on the pulsation periods and light-curve morphology, we classified 118 of our type II Cepheids as BL Herculis, 120 as W Virginis, 34 as peculiar W Virginis, and 66 as RV Tauri stars. For all objects, we publish time-series VI photometry obtained during the OGLE-IV survey, from 2010 to the end of 2017. \u0000We present the most interesting individual objects in our collection: 16 type II Cepheids showing additional eclipsing or ellipsoidal variability, two RV Tau variables more than 2.5 mag fainter than other stars of this type in the LMC, an RVb star that drastically decreased the amplitude of the long-period modulation, type II Cepheids exhibiting significant amplitude and period changes, and an RV Tau star which experiences interchanges of deep and shallow minima. We show that peculiar W Vir stars have markedly different spatial distribution than other subclasses of type II Cepheids, which indicates different evolutionary histories of these objects.","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"89-109"},"PeriodicalIF":2.2,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46042828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.32023/0001-5237/68.2.4
W. Dimitrov, T. Tomov, K. Kamiński, M. Polińska, I. Iliev, M. Kamińska
{"title":"GT Ursae Majoris AB - a Possible Quadruple System","authors":"W. Dimitrov, T. Tomov, K. Kamiński, M. Polińska, I. Iliev, M. Kamińska","doi":"10.32023/0001-5237/68.2.4","DOIUrl":"https://doi.org/10.32023/0001-5237/68.2.4","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"141-158"},"PeriodicalIF":2.2,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43825504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-02-27DOI: 10.32023/0001-5237/68.1.2
J. Skowron, Y. Ryu, K. Hwang, A. Udalski, P. Mr'oz, S. Kozłowski, I. Soszy'nski, P. Pietrukowicz, M. Szyma'nski, R. Poleski, K. Ulaczyk, M. Pawlak, K. Rybicki, P. Iwanek, M. Albrow, S. Chung, A. Gould, C. Han, Y. Jung, I. Shin, Y. Shvartzvald, J. Yee, W. Zang, W. Zhu, S. Cha, D.-J. Kim, H.-W. Kim, S.-L. Kim, C.‐U. Lee, D.-J. Lee, Y. Lee, B.-G. Park, R. Pogge
We report the discovery of microlensing planet OGLE-2017-BLG-0373Lb. We show that while the planet-host system has an unambiguous microlens topology, there are two geometries within this topology that fit the data equally well, which leads to a factor 2.5 difference in planet-host mass ratio, i.e., $q=1.5times 10^{-3}$ versus $q=0.6times 10^{-3}$. We show that this is an "accidental degeneracy" in the sense that it is due to a gap in the data. We dub it "the caustic-chirality degeneracy". We trace the mathematical origins of this degeneracy, which should enable similar degenerate solutions to be easily located in the future. A Bayesian estimate, based on a Galactic model, yields a host mass $M=0.25^{+0.30}_{-0.15} M_odot$ at a distance $D_L=5.9^{+1.3}_{-1.95}$ kpc. The lens-source relative proper motion is relatively fast, $mu=9$ mas/yr, which implies that the host mass and distance can be determined by high-resolution imaging after about 10 years. The same observations could in principle resolve the discrete degeneracy in $q$, but this will be more challenging.
{"title":"OGLE-2017-BLG-0373Lb: A Jovian Mass-Ratio Planet Exposes A New Accidental Microlensing Degeneracy","authors":"J. Skowron, Y. Ryu, K. Hwang, A. Udalski, P. Mr'oz, S. Kozłowski, I. Soszy'nski, P. Pietrukowicz, M. Szyma'nski, R. Poleski, K. Ulaczyk, M. Pawlak, K. Rybicki, P. Iwanek, M. Albrow, S. Chung, A. Gould, C. Han, Y. Jung, I. Shin, Y. Shvartzvald, J. Yee, W. Zang, W. Zhu, S. Cha, D.-J. Kim, H.-W. Kim, S.-L. Kim, C.‐U. Lee, D.-J. Lee, Y. Lee, B.-G. Park, R. Pogge","doi":"10.32023/0001-5237/68.1.2","DOIUrl":"https://doi.org/10.32023/0001-5237/68.1.2","url":null,"abstract":"We report the discovery of microlensing planet OGLE-2017-BLG-0373Lb. We show that while the planet-host system has an unambiguous microlens topology, there are two geometries within this topology that fit the data equally well, which leads to a factor 2.5 difference in planet-host mass ratio, i.e., $q=1.5times 10^{-3}$ versus $q=0.6times 10^{-3}$. We show that this is an \"accidental degeneracy\" in the sense that it is due to a gap in the data. We dub it \"the caustic-chirality degeneracy\". We trace the mathematical origins of this degeneracy, which should enable similar degenerate solutions to be easily located in the future. A Bayesian estimate, based on a Galactic model, yields a host mass $M=0.25^{+0.30}_{-0.15} M_odot$ at a distance $D_L=5.9^{+1.3}_{-1.95}$ kpc. The lens-source relative proper motion is relatively fast, $mu=9$ mas/yr, which implies that the host mass and distance can be determined by high-resolution imaging after about 10 years. The same observations could in principle resolve the discrete degeneracy in $q$, but this will be more challenging.","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"43-61"},"PeriodicalIF":2.2,"publicationDate":"2018-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47078077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.32023/0001-5237/68.3.8
S. Ninkovič
{"title":"Ratio of the Mean Random Velocity Squares Revisited","authors":"S. Ninkovič","doi":"10.32023/0001-5237/68.3.8","DOIUrl":"https://doi.org/10.32023/0001-5237/68.3.8","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69520847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-01-01DOI: 10.32023/0001-5237/68.2.2
K. Sziládi, J. Vinkó, L. Szabados
{"title":"Metallicity estimates for double-mode cepheids from photometry","authors":"K. Sziládi, J. Vinkó, L. Szabados","doi":"10.32023/0001-5237/68.2.2","DOIUrl":"https://doi.org/10.32023/0001-5237/68.2.2","url":null,"abstract":"","PeriodicalId":44887,"journal":{"name":"Acta Astronomica","volume":"68 1","pages":"111-123"},"PeriodicalIF":2.2,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69520799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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