Rapid Decreasing in the Orbital Period of the Detached White Dwarf?main Sequence Binary SDSS J143547.87+373338.5

SDSS J143547.87+373338.5 is a detached eclipsing binary that contains a white dwarf with a mass of 0.5 M⊙ and a fully convective star with a mass of 0.21 M⊙. The eclipsing binary was monitored photometrically from 2009 March 24 to 2015 April 10, by using two 2.4-m telescopes in China and in Thailand. The changes in the orbital period are analyzed based on eight newly determined eclipse times together with those compiled from the literature. It is found that the observed?calculated (O?C) diagram shows a downward parabolic change that reveals a continuous period decrease at a rate of dot{P}=-8.04× {10}-11 s s‑1. According to the standard theory of cataclysmic variables, angular momentum loss (AML) via magnetic braking (MB) is stopped for fully convective stars. However, this period decrease is too large to be caused by AML via gravitational radiation (GR), indicating that there could be some extra source of AML beyond GR, but the predicted mass-loss rates from MB seem unrealistically large. The other possibility is that the O?C diagram may show a cyclic oscillation with a period of 7.72 years and a small amplitude of 0.ͩ000525. The cyclic change can be explained as the light-travel-time effect via the presence of a third body because the required energy for the magnetic activity cycle is much larger than that radiated from the secondary in a whole cycle. The mass of the potential third body is determined to be {M}3{sin}{i}prime =0.0189(+/- 0.0016) M⊙ when a total mass of 0.71 M⊙ for SDSS J143547.87+373338.5 is adopted. For orbital inclinations {i}prime ≥slant 15uildrel{circ}over{.} 9, it would be below the stable hydrogen-burning limit of M3 ∼ 0.072 M⊙, and thus the third body would be a brown dwarf.Fil: Qian, S. B.. Chinese Academy of Sciences; República de ChinaFil: Han, Z. T.. Chinese Academy of Sciences; República de ChinaFil: Soonthornthum, B.. National Astronomical Research Institute of Thailand; TailandiaFil: Zhu, L. Y.. Chinese Academy of Sciences; República de ChinaFil: He, J. J.. Chinese Academy of Sciences; República de ChinaFil: Rattanasoon, S.. National Astronomical Research Institute of Thailand; TailandiaFil: Aukkaravittayapun, S.. National Astronomical Research Institute of Thailand; TailandiaFil: Liao, W. P.. Chinese Academy of Sciences; República de ChinaFil: Zhao, E. G.. Chinese Academy of Sciences; República de ChinaFil: Zhang, J.. Chinese Academy of Sciences; República de ChinaFil: Fernandez Lajus, Eduardo Eusebio. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; Argentin

Rapid decreasing in the orbital period of the detached white dwarf-main sequence binary SDSS J143547.87+373338.5

SDSS J143547.87+373338.5 is a detached eclipsing binary that contains a white dwarf with a mass of 0.5 Mo and a fully convective star with a mass of 0.21 Mo. The eclipsing binary was monitored photometrically from 2009 March 24 to 2015 April 10, by using two 2.4-m telescopes in China and in Thailand. The changes in the orbital period are analyzed based on eight newly determined eclipse times together with those compiled from the literature. It is found that the observed-calculated (O-C) diagram shows a downward parabolic change that reveals a continuous period decrease at a rate of s s-1. According to the standard theory of cataclysmic variables, angular momentum loss (AML) via magnetic braking (MB) is stopped for fully convective stars. However, this period decrease is too large to be caused by AML via gravitational radiation (GR), indicating that there could be some extra source of AML beyond GR, but the predicted mass-loss rates from MB seem unrealistically large. The other possibility is that the O-C diagram may show a cyclic oscillation with a period of 7.72 years and a small amplitude of 0.000525. The cyclic change can be explained as the light-travel-time effect via the presence of a third body because the required energy for the magnetic activity cycle is much larger than that radiated from the secondary in a whole cycle. The mass of the potential third body is determined to be Mo when a total mass of 0.71 Mo for SDSS J143547.87+373338.5 is adopted. For orbital inclinations , it would be below the stable hydrogen-burning limit of M3 ∼ 0.072 Mo, and thus the third body would be a brown dwarf.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

SDSS J001641-000925: The first stable red dwarf contact binary with a close-in stellar companion

SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of P ∼ 8 s yr-1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O-C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M3 sin i′ ∼ 0.14 M⊙. The orbital separation between the third body and the central binary is about 2.8AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

SDSS J001641-000925: The first stable red dwarf contact binary with a close-in stellar companion

SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of P ∼ 8 s yr-1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O-C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M3 sin i′ ∼ 0.14 M⊙. The orbital separation between the third body and the central binary is about 2.8AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Heat Conduction in κ\kappa-(BEDT-TTF)2_2Cu(NCS)2_2

The first study of thermal conductivity, $\kappa$, in a quasi-two-dimensional organic superconductor of the $\kappa$-(BEDT-TTF)$_2$X family reveals features analogous to those already observed in the cuprates. The onset of superconductivity is associated with a sudden increase in $\kappa$ which can be suppressed by the application of a moderate magnetic field. At low temperatures, a finite linear term - due to a residual electronic contribution- was resolved. The magnitude of this term is close to what is predicted by the theory of transport in unconventional superconductors.Comment: 5 pages, 4 figures include

Rapid decreasing in the orbital period of the detached white dwarf-main sequence binary SDSS J143547.87+373338.5

SDSS J143547.87+373338.5 is a detached eclipsing binary that contains a white dwarf with a mass of 0.5 Mo and a fully convective star with a mass of 0.21 Mo. The eclipsing binary was monitored photometrically from 2009 March 24 to 2015 April 10, by using two 2.4-m telescopes in China and in Thailand. The changes in the orbital period are analyzed based on eight newly determined eclipse times together with those compiled from the literature. It is found that the observed-calculated (O-C) diagram shows a downward parabolic change that reveals a continuous period decrease at a rate of s s-1. According to the standard theory of cataclysmic variables, angular momentum loss (AML) via magnetic braking (MB) is stopped for fully convective stars. However, this period decrease is too large to be caused by AML via gravitational radiation (GR), indicating that there could be some extra source of AML beyond GR, but the predicted mass-loss rates from MB seem unrealistically large. The other possibility is that the O-C diagram may show a cyclic oscillation with a period of 7.72 years and a small amplitude of 0.000525. The cyclic change can be explained as the light-travel-time effect via the presence of a third body because the required energy for the magnetic activity cycle is much larger than that radiated from the secondary in a whole cycle. The mass of the potential third body is determined to be Mo when a total mass of 0.71 Mo for SDSS J143547.87+373338.5 is adopted. For orbital inclinations , it would be below the stable hydrogen-burning limit of M3 ∼ 0.072 Mo, and thus the third body would be a brown dwarf.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Processing GOTO data with the Rubin Observatory LSST Science Pipelines I: Production of coadded frames

The past few decades have seen the burgeoning of wide field, high cadence surveys, the most formidable of which will be the Legacy Survey of Space and Time (LSST) to be conducted by the Vera C. Rubin Observatory. So new is the field of systematic time-domain survey astronomy, however, that major scientific insights will continue to be obtained using smaller, more flexible systems than the LSST. One such example is the Gravitational-wave Optical Transient Observer (GOTO), whose primary science objective is the optical follow-up of Gravitational Wave events. The amount and rate of data production by GOTO and other wide-area, high-cadence surveys presents a significant challenge to data processing pipelines which need to operate in near real-time to fully exploit the time-domain. In this study, we adapt the Rubin Observatory LSST Science Pipelines to process GOTO data, thereby exploring the feasibility of using this "off-the-shelf" pipeline to process data from other wide-area, high-cadence surveys. In this paper, we describe how we use the LSST Science Pipelines to process raw GOTO frames to ultimately produce calibrated coadded images and photometric source catalogues. After comparing the measured astrometry and photometry to those of matched sources from PanSTARRS DR1, we find that measured source positions are typically accurate to sub-pixel levels, and that measured L-band photometries are accurate to ∼50 mmag at mL∼16 and ∼200 mmag at mL∼18. These values compare favourably to those obtained using GOTO's primary, in-house pipeline, GOTOPHOTO, in spite of both pipelines having undergone further development and improvement beyond the implementations used in this study. Finally, we release a generic "obs package" that others can build-upon should they wish to use the LSST Science Pipelines to process data from other facilities

SDSS J001641-000925: The first stable red dwarf contact binary with a close-in stellar companion

SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of P ∼ 8 s yr-1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O-C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M3 sin i′ ∼ 0.14 M⊙. The orbital separation between the third body and the central binary is about 2.8AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Searching for electromagnetic counterparts to gravitational-wave merger events with the prototype Gravitational-wave Optical Transient Observer (GOTO-4)

We report the results of optical follow-up observations of 29 gravitational-wave (GW) triggers during the first half of the LIGO–Virgo Collaboration (LVC) O3 run with the Gravitational-wave Optical Transient Observer (GOTO) in its prototype 4-telescope configuration (GOTO-4). While no viable electromagnetic (EM) counterpart candidate was identified, we estimate our 3D (volumetric) coverage using test light curves of on- and off-axis gamma-ray bursts and kilonovae. In cases where the source region was observable immediately, GOTO-4 was able to respond to a GW alert in less than a minute. The average time of first observation was 8.79 h after receiving an alert (9.90 h after trigger). A mean of 732.3 square degrees were tiled per event, representing on average 45.3 per cent of the LVC probability map, or 70.3 per cent of the observable probability. This coverage will further improve as the facility scales up alongside the localization performance of the evolving GW detector network. Even in its 4-telescope prototype configuration, GOTO is capable of detecting AT2017gfo-like kilonovae beyond 200 Mpc in favourable observing conditions. We cannot currently place meaningful EM limits on the population of distant (⁠D^L=1.3 Gpc) binary black hole mergers because our test models are too faint to recover at this distance. However, as GOTO is upgraded towards its full 32-telescope, 2 node (La Palma & Australia) configuration, it is expected to be sufficiently sensitive to cover the predicted O4 binary neutron star merger volume, and will be able to respond to both northern and southern triggers