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Observational constraints on the rastall gravity from rotation curves of low surface brightness galaxies

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arXiv 2019年

作者： Tang, Meirong Xu, Zhaoyi Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

The Rastall gravity is a modification of Einstein's general relativity, in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci curvature. It is in dispute whether the Rastall gravity is equivalent to the general relativity (GR). In this work, we constrain the theory using the rotation curves of Low Surface Brightness (LSB) spiral galaxies. Through fitting the rotation curves of LSB galaxies, we obtain the parameter β of the Rastall gravity. The β values of LSB galaxies satisfy Weak Energy Condition (WEC) and Strong Energy Condition(SEC). Combining the β values of type Ia supernovae and gravitational lensing of elliptical galaxies on the Rastall gravity, we conclude that the Rastall gravity is equivalent to the general relativity. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

Quasi-simultaneous spectroscopic and multi-band photometric observations of blazar S5 0716+714 during 2018-2019

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arXiv 2019年

作者： Feng, Hai-Cheng Liu, H.T. Bai, J.M. Xing, L.F. Li, Y.B. Xiao, M. Xin, Y.X. Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences 19B Yuquan Road Beijing100049 China

In order to study short timescale optical variability of γ-ray blazar S5 0716+714, quasi-simultaneous spectroscopic and multi-band photometric observations were performed from 2018 November to 2019 March with the 2.4 m optical telescope located at Lijiang Observatory of Yunnan Observatories. The observed spectra are well fitted with a power-law Fλ = Aλ−α (spectral index α > 0). Correlations found between α, A, A/A , Fλ, and Fλ/Fλ are consistent with the trend of bluer-when-brighter (BWB). The same case is for colors, magnitudes, color variation rates, and magnitude variation rates of photometric observations. The variations of α lead those of Fλ. Also, the color variations lead the magnitude variations. The observational data are mostly distributed in the I(+,+) and III(-,-) quadrants of coordinate system. Both of spectroscopic and photometric observations show BWB behaviors in S5 0716+714. The observed BWB may be explained by the shock-jet model, and its appearance may depend on the relative position of the observational frequency ranges with respect to the synchrotron peak frequencies, e.g., at the left of the peak frequencies. Fractional variability amplitudes are Fvar ∼ 40% for both of spectroscopic and photometric observations. Variations of α indicate variations of relativistic electron distribution producing the optical spectra. Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

EXPLORING THE CONVECTIVE CORE OF THE HYBRID δ SCUTI-γ DORADUS STAR COROT 100866999 WITH ASTEROSEISMOLOGY

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arXiv 2019年

作者： Chen, Xinghao Li, Yan Zhang, Xiaobin Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

We computed a grid of theoretical models to fit the δ Scuti frequencies of CoRoT 100866999 detected earlier from the CoRoT timeserials. The pulsating primary star is determined to be a main sequence star with a rotation period of 4.1+0−0..65 days, rotating slower than the orbital motion. The fundamental parameters of the primary star are determined to be M = 1.71+0−0..1304 M∙, Z = 0.012+0−0..004000, fov = 0.02+0−0..0002, Teff = 8024+249−297 K, L = 11.898+2−1..156847 L∙, log g = 4.166+0−0..013002, R = 1.787+0−0..040016 R∙, and Xc = 0.488+0−0..011020, matching well those obtained from the eclipsing light curve analysis. Based on the model fittings, p1 and p5 are suggested to be two dipole modes, and p3, p4, p6, and p7 to be four quadrupole modes. In particular, p4 and p7 are identified as two components of one quintuplet. Based on the best-fitting model, we find that p1 is a g mode and the other nonradial modes have pronounced mixed characters, which give strong constraints on the convective core. Finally, the relative size of the convective core of CoRoT 100866999 is determined to Rconv/R = 0.0931+0−0..00030013. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

Kepler-411: a four-planet system with an active host star

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arXiv 2019年

作者： Sun, Leilei Ioannidis, P. Gu, Shenghong Schmitt, J.H.M.M. Wang, Xiaobin Kouwenhoven, M.B.N. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Hamburger Sternwarte Universität Hamburg Gojenbergsweg 112 Hamburg21029 Germany Suzhou Dushu Lake Science and Education Innovation District Suzhou Industrial Park 111 Renai Rd. Suzhou215123 China

We present a detailed characterization of the Kepler-411 system (KOI 1781). This system was previously known to host two transiting planets: one with a period of 3 days (R = 2.4R *;Kepler-411b) and one with a period of 7.8 days (R = 4.4R *;Kepler-411c), as well as a transiting planetary candidate with a 58-day period (R = 3.3R *;KOI 1781.03) from Kepler photometry. Here, we combine Kepler photometry data and new transit timing variation (TTV) measurements from all the Kepler quarters with previous adaptive-optics imaging results, and dynamical simulations, in order to constrain the properties of the Kepler-411 system. From our analysis, we obtain masses of 25.6±2.6M * for Kepler-411b and 26.4±5.9 M * for Kepler-411c, and we confirm the planetary nature of KOI 1781.03 with a mass of 15.2±5.1M *, hence the name Kepler-411d. Furthermore, by assuming near-coplanarity of the system (mutual inclination below 30◦), we discover a nontransiting planet, Kepler-411e, with a mass of 10.8±1.1M * on a 31.5-day orbit, which has a strong dynamical interaction with Kepler-411d. With densities of 1.71 ± 0.39 g cm−3 and 2.32 ± 0.83 g cm−3, both Kepler-411c and Kepler-411d belong to the group of planets with a massive core and a significant fraction of volatiles. Although Kepler-411b has a sub-Neptune size, it belongs to the group of rocky *** Codes 85 Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

Circumstellar properties of Type Ia supernovae from the helium star donor channel

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arXiv 2019年

作者： Moriya, Takashi J. Liu, Dongdong Wang, Bo Liu, Zheng-Wei Division of Science National Astronomical Observatory of Japan National Institutes of Natural Sciences 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Centre for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

We investigate predicted circumstellar properties of Type Ia supernova progenitor systems with non-degenerate helium star donors. It has been suggested that systems consisting of a carbon+oxygen white dwarf and a helium star can lead to Type Ia supernova explosions. Binary evolution calculations for the helium star donor channel predict that such a progenitor system is in either a stable helium-shell burning phase or a weak helium-shell flash phase at the time of the Type Ia supernova explosion. By taking the binary evolution models from our previous study, we show that a large fraction of the progenitor systems with a helium star donor have low enough density to explain the current non-detection of radio emission from Type Ia supernovae. Most of the progenitor systems in the weak helium-shell flash phase at the time of the Type Ia supernova explosions, which may dominate the prompt (short delay time) Type Ia supernova population, have both low circumstellar density and a faint helium star donor to account for the non-detection of radio emission and a pre-explosion companion star in SN 2011fe and SN 2014J. We also find some progenitor systems that are consistent with the properties of the companion star candidate identified at the explosion location of Type Iax SN 2012Z. Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs

Photometric investigation on the W-subtype contact binary V1197 her

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arXiv 2019年

作者： Zhou, X. Soonthornthum, B. P.O. Box 110 Kunming650216 China National Astronomical Research Institute of Thailand 260 Moo 4 T. Donkaew A. MaerimChiangmai50180 Thailand Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang Dis-trict Beijing100012 China

Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at Thai National Observatory and the Wilson-Devinney (W-D) program is used to model the observational light curves. The photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q = 2.61 and fill-out factor to be f = 15.7 %. The temperature difference between the primary star and secondary star is only 140K in spite of the low degree of contact, which means that V1197 Her is not only in geometrical contact configuration but also already under thermal contact status. The orbital inclination of V1197 Her is as high as i = 82.7◦, and the primary star is completely eclipsed at the primary minimum. The totally eclipsing characteristic implies that the determined physical parameters are highly reliable. The masses, radii and luminosities of the primary star (star 1) and secondary star (star 2) are estimated to be M1 = 0.30(1)Mo, M2 = 0.77(2)Mo, R1 = 0.54(1)Ro, R2 = 0.83(1)Ro, L1 = 0.18(1)Lo and L2 = 0.38(1)Lo. The evolutionary status of the two component stars are drawn in the H - R diagram, which shows that the less massive but hotter primary star is more evolved than the secondary star. The period of V1197 Her is decreasing continuously at a rate of dP/dt = −2.58×10−7day·year−1, which can be explained by mass transfer from the more massive star to the less massive one with a rate of dMdt2 = −1.61 × 10−7Mo/year. The light curves of V1197 Her is reported to have the O’Connell effect. Thus, a cool spot is added to the massive star to model the asymmetry on light curves. Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

Search for intra-day optical variability in γ-ray–loud blazars s5 0716+714 and 3c 273

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arXiv 2019年

作者： Liu, H.T. Feng, Hai Cheng Xin, Y.X. Bai, J.M. Li, S.K. Wang, Fang Yunnan Observatories Chinese Academy of Sciences KunmingYunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences KunmingYunnan650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China School of Physics and Space Science China West Normal University Nanchong637009 China

We present the photometric observations of blazars S5 0716+714 and 3C 273 with high temporal resolution (30–60s) in the I or R bands. The observations were performed with a 1.02 m optical telescope from 2007 March 07 to 2012 May 16. The F-test, one-way analysis of variance (ANOVA) test, and z-transformed discrete correlation function (ZDCF) cross-correlation zero lag test are used to search for intra-day variability (IDV). Four and five reliable IDVs survive three tests for S5 0716+714 and 3C 273, respectively. IDVs are found for S5 0716+714 and 3C 273. A flare on 2008 May 08 has ∆I ≈ 0.06±0.01 mag in a duration of 0.54 hr for S5 0716+714. A flare on 2011 May 10 shows ∆R ≈ 0.05±0.01 mag in a duration of 0.40 hr for 3C 273. Sharp dips appear on 2011 May 9 for 3C 273, and show ∆R ≈ 0.05±0.01 mag. Under the assumptions that the IDV is tightly connected to black hole mass, M•, and that the flare durations are representative of the minimum characteristic timescales, we can estimate upper bounds to M•. In the case of the Kerr black holes, M• . 108.91Mo and M• . 109.02Mo are given for S5 0716+714 and 3C 273, respectively. These mass measurements are consistent with those measurements reported in the literatures. Also, we discuss the origins of optical variations found in this work. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

The W-subtype active contact binary PZ UMa with a possible more massive tertiary component

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arXiv 2019年

Two sets of multiple-color (B,V,Rc,Ic) light curves of PZ UMa were observed in dependently with the 2.4 meter telescope at the Thai National Observatory and the 1 meter telescope at Yunnan Observatories. The light curves were analyzed with the Wilson-Devinney program and the two sets of light curves produced consistent results, which show that PZ UMa is a W-subtype contact binary with an extreme mass ratio (M1/M2 = 0.18). The basic physical parameters of PZ UMa were determined to be M2 = 0.77(2)M, M1 = 0.14(1)M, R2 = 0.92(1)R, R1 = 0.43(1)R, L2 = 0.46(2)L and L1 = 0.15(3)L. The orbital period analysis of PZ UMa revealed a 13.22 year periodicity, which implies that there may be a tertiary component orbiting around the binary system. The mass and orbital radius of the tertiary component were calculated to be M3 = 0.88M and a3 = 3.67AU, if the orbit was coplanar with the central binary system. It is interesting that the minimum mass of the tertiary was calculated to be M3min = 0.84M, which means the tertiary component is even larger than the primary star and the secondary one of PZ UMa. PZ UMa is a late-type contact binary with stellar activity. The O’Connell effect appeared on its light curves when it was observed on April 2016. However, the O’Connell effect reversed when the target was observed again on December 2016. The changes of the O’Connell effect in such a short time-scale strongly support the occurrence of rapidly changing magnetic activity on this W UMa binary. Copyright © 2019, The Authors. All rights reserved.

关键词： Observatories

The outcomes of carbon-oxygen white dwarfs accreting CO-rich material

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arXiv 2018年

作者： Wu, Chengyuan Wang, Bo Liu, Dongdong Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Centre for Astronomical Mega-Science CAS Beijing100012 China

The double-degeneratemodel, involving the merger of double carbon-oxygenwhite dwarfs (CO WDs), is one of the two classic models for the progenitors of type Ia supernovae (SNe Ia). Previous studies suggested that off-centre carbon burning would occur if the mass-accretion rate (Macc) is relatively high during the merging process, leading to the formation of oxygen-neon (ONe) cores that may collapse into neutron stars. However, the off-centre carbon burning is still incompletely understood, especially when the inwardly propagating burning wave reaches the centre. In this paper, we aim to investigate the propagating characteristics of burning waves and the subsequently evolutionary outcomes of these CO cores. We simulated the long-term evolution of CO WDs that accrete CO-rich material by employing the stellar evolution code MESA on the basis of the thick-disc assumption. We found that the final outcomes of CO WDs strongly depend on Macc(Moyr-1) based on the thick-disc assumption, which can be divided into four regions: (1) explosive carbon ignition in the centre, then SNe Ia (Macc-6);(2) OSi cores, then neutron stars (2.45 × 10-6. Macc -6);(3) ONe cores, then e-capture SNe (4.5 × 10-6 Macc-5);(4) off-centre oxygen and neon ignition, then off-centre explosion or Si-Fe cores (Macc 1.05 × 10-5). Our results indicate that the final fates of double CO WD mergers are strongly dependent on the merging processes (e.g. slow merger, fast merger, composite merger, violent merger, etc.). Copyright © 2018, The Authors. All rights reserved.

关键词： Carbon