Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe $UBV$ Color Evolution of Classical Novae. IV. Time-Stretched $(U-B)_0$-$(M_B-2.5log f_{rm s})$ and $(V-I)_0$-$(M_I-2.5log f_{rm s})$ Color-Magnitude Diagrams of Novae in Outburst
66
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Light curves and color evolutions of two classical novae can be largely overlapped if we properly squeeze or stretch the timescale of a target nova against that of a template nova by $t=t/f_{rm s}$. Then the brightness of the target nova is related to the brightness of the template nova by $(M[t])_{rm template} = (M[t/f_{rm s}] - 2.5 log f_{rm s})_{rm target}$, where $M[t]$ is the absolute magnitude and a function of time $t$, and $f_{rm s}$ is the ratio of timescales between the target and template novae. In the previous papers of this series, we show that many novae broadly overlap in the time-stretched $(B-V)_0$-$(M_V-2.5 log f_{rm s})$ color-magnitude diagram. In the present paper, we propose two other $(U-B)_0$-$(M_B-2.5log f_{rm s})$ and $(V-I)_0$-$(M_I-2.5log f_{rm s})$ diagrams, and show that their tracks overlap for 16 novae and for 52 novae, respectively. Here, $(U-B)_0$, $(B-V)_0$, and $(V-I)_0$ are the intrinsic $U-B$, $B-V$, and $V-I$ colors and not changed by the time-stretch, and $M_B$, $M_V$, and $M_I$ are the absolute $B$, $V$, and $I$ magnitudes. Using these properties, we considerably refine the previous estimates of their distance and reddening. The obtained distances are in reasonable agreement with those of {it Gaia} Data Release 2 catalogue.
rate research
Read More
We propose a modified color-magnitude diagram for novae in outburst, i.e., $(B-V)_0$ versus $(M_V-2.5 log f_{rm s})$, where $f_{rm s}$ is the timescaling factor of a (target) nova against a comparison (template) nova, $(B-V)_0$ is the intrinsic $B-V$ color, and $M_V$ is the absolute $V$ magnitude. We dub it the time-stretched color-magnitude diagram. We carefully reanalyzed 20 novae based on the time-stretching method and revised their extinctions $E(B-V)$, distance moduli in the $V$ band $(m-M)_V$, distances $d$, and timescaling factors $f_{rm s}$ against the template nova LV Vul. We have found that these 20 nova outburst tracks broadly follow one of the two template tracks, LV Vul/V1668 Cyg or V1500 Cyg/V1974 Cyg group, in the time-stretched color-magnitude diagram. In addition, we estimate the white dwarf masses and $(m-M)_V$ of the novae by directly fitting the absolute $V$ model light curves ($M_V$) with observational apparent $V$ magnitudes ($m_V$). A good agreement in the two estimates of $(m-M)_V$ confirms the consistency of the time-stretched color-magnitude diagram. Our distance estimates are in good agreement with the results of Gaia Data Release 2.
We have examined the outburst tracks of 40 novae in the color-magnitude diagram (intrinsic B-V color versus absolute V magnitude). After reaching the optical maximum, each nova generally evolves toward blue from the upper-right to the lower-left and then turns back toward the right. The 40 tracks are categorized into one of six templates: very fast nova V1500 Cyg; fast novae V1668 Cyg, V1974 Cyg, and LV Vul; moderately fast nova FH Ser; and very slow nova PU Vul. These templates are located from the left (blue) to the right (red) in this order, depending on the envelope mass and nova speed class. A bluer nova has a less massive envelope and faster nova speed class. In novae with multiple peaks, the track of the first decay is more red than that of the second (or third) decay, because a large part of the envelope mass had already been ejected during the first peak. Thus, our newly obtained tracks in the color-magnitude diagram provide useful information to understand the physics of classical novae. We also found that the absolute magnitude at the beginning of the nebular phase is almost similar among various novae. We are able to determine the absolute magnitude (or distance modulus) by fitting the track of a target nova to the same classification of a nova with a known distance. This method for determining nova distance has been applied to some recurrent novae and their distances have been recalculated.
Galaxy clusters are the largest gravitationally bound systems in the Universe and, as such, play an important role in cosmological studies. An important resource for studying their properties in a statistical manner are homogeneous and large image datasets covering diverse environments. In this sense, the wide-field images (1.4 deg^{2}) obtained by the Southern Photometric Local Universe Survey (S-PLUS) in 12 optical bands, constitute a valuable tool for that type of studies. In this work, we present a photometric analysis of pixel color-magnitude diagrams, corresponding to a sample of 24 galaxies of different morphological types located in the Fornax cluster.
We revise the Non-Gaussianity of canonical curvaton scenario with a generalized $delta N$ formalism, in which it could handle the generic potentials. In various curvaton models, the energy density is dominant in different period including the secondary inflation of curvaton, matter domination and radiation domination. Our method could unify to deal with these periods since the non-linearity parameter $f_{rm NL}$ associated with Non-Gaussianity is a function of equation of state $w$. We firstly investigate the most simple curvaton scenario, namely the chaotic curvaton with quadratic potential. Our study shows that most parameter space satisfies with observational constraints. And our formula will nicely recover the well-known value of $f_{rm NL}$ in the absence of non-linear evolution. From the micro origin of curvaton, we also investigate the Pseudo-Nambu-Goldstone curvaton. Our result clearly indicates that the second short inflationary process for Pseudo-Nambu-Goldstone curvaton is ruled out in light of observations. Finally, our method sheds a new way for investigating the Non-Gaussianity of curvaton mechanism, espeically for exploring the Non-Gaussianity in MSSM curvaton model.
The relative production rate of $B^{0}_{s}$ and $B^{0}$ mesons is determined with the hadronic decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^0 rightarrow D^{-}K^{+}$. The measurement uses data corresponding to 1.0 fb$^{-1}$ of $pp$ collisions at a centre-of-mass energy of $sqrt{s}=7$ TeV recorded in the forward region with the LHCb experiment. The ratio of production rates, $f_{s}/f_{d}$, is measured to be $0.238 pm 0.004 pm 0.015 pm 0.021 $, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain $f_{s}/f_{d} = 0.256 pm 0.020$. The dependence of $f_{s}/f_{d}$ on the transverse momentum and pseudorapidity of the $B$ meson is determined using the decays $B^{0}_{s} rightarrow D^{-}_{s}pi^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays $B^{0} rightarrow D^{-}K^{+}$ and $B^{0} rightarrow D^{-}pi^{+}$ is measured to be $0.0822 pm 0.0011 (textrm{stat}) pm 0.0025 (textrm{syst})$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
