34 research outputs found
Period-Luminosity Relations for Galactic classical Cepheids in the Sloan bands
We present the first period-luminosity (PL) and period-Wesenheit (PW)
relations in the Sloan-Pans-STARRS gP1rP1iP1 bands for classical fundamental
mode Cepheids in the Milky Way. We used a relatively modest number of 76 stars
for the PL and 84-85 stars for the PW relations calibration. The data for the
project were collected with the network of 40-cm telescopes of Las Cumbres
Observatory, and Gaia Data Release 3 parallaxes were used for the calculations.
These gri-band PL and PW relations calibrations will be a useful tool for
distance determinations in the era of large sky surveys using the Sloan
photometric system, especially with the near-future start of the Large Synoptic
Survey of Space and Time (LSST).Comment: 31 pages, 7 figures, 3 tables, Accepted for publication in Ap
The Araucaria Project: A study of the classical Cepheid in the eclipsing binary system OGLE LMC562.05.9009 in the Large Magellanic Cloud
We present a detailed study of the classical Cepheid in the double-lined,
highly eccentric eclipsing binary system OGLE-LMC562.05.9009. The Cepheid is a
fundamental mode pulsator with a period of 2.988 days. The orbital period of
the system is 1550 days. Using spectroscopic data from three 4-8-m telescopes
and photometry spanning 22 years, we were able to derive the dynamical masses
and radii of both stars with exquisite accuracy. Both stars in the system are
very similar in mass, radius and color, but the companion is a stable,
non-pulsating star. The Cepheid is slightly more massive and bigger (M_1 = 3.70
+/- 0.03M_sun, R_1 = 28.6 +/- 0.2R_sun) than its companion (M_2 = 3.60 +/-
0.03M_sun, R_2 = 26.6 +/- 0.2R_sun). Within the observational uncertainties
both stars have the same effective temperature of 6030 +/- 150K. Evolutionary
tracks place both stars inside the classical Cepheid instability strip, but it
is likely that future improved temperature estimates will move the stable giant
companion just beyond the red edge of the instability strip. Within current
observational and theoretical uncertainties, both stars fit on a 205 Myr
isochrone arguing for their common age. From our model, we determine a value of
the projection factor of p = 1.37 +/- 0.07 for the Cepheid in the
OGLE-LMC562.05.9009 system. This is the second Cepheid for which we could
measure its p-factor with high precision directly from the analysis of an
eclipsing binary system, which represents an important contribution towards a
better calibration of Baade-Wesselink methods of distance determination for
Cepheids.Comment: Accepted to be published in Ap
Time-delay measurement of MgII broad line response for the highly-accreting quasar HE 0413-4031: Implications for the MgII-based radius-luminosity relation
We present the monitoring of the AGN continuum and MgII broad line emission
for the quasar HE 0413-4031 () based on the six-year monitoring by the
South African Large Telescope (SALT). We managed to estimate a time-delay of
days in the rest frame of the source using seven
different methods: interpolated cross-correlation function (ICCF), discrete
correlation function (DCF), -transformed DCF, JAVELIN, two estimators of
data regularity (Von Neumann, Bartels), and method. This time-delay is
below the value expected from the standard radius-luminosity relation. However,
based on the monochromatic luminosity of the source and the SED modelling, we
interpret this departure as the shortening of the time-delay due to the higher
accretion rate of the source, with the inferred Eddington ratio of .
The MgII line luminosity of HE 0413-4031 responds to the continuum variability
as , which is consistent with
the light-travel distance of the location of MgII emission at . Using the data of 10 other quasars, we confirm the
radius-luminosity relation for broad MgII line, which was previously determined
for broad H line for lower-redshift sources. In addition, we detect a
general departure of higher-accreting quasars from this relation in analogy to
H sample. After the accretion-rate correction of the light-travel
distance, the MgII-based radius-luminosity relation has a small scatter of only
dex.Comment: 39 pages (23 pages - Main text, 16 pages - Appendix), 21 figures, 14
tables; accepted for publication in the Astrophysical Journa
Time delay measurement of Mg II line in CTS C30.10 with SALT
We report 6 yr monitoring of a distant bright quasar CTS C30.10 (z = 0.90052)
with the Southern African Large Telescope (SALT). We measured the rest-frame
time-lag of days between the continuum variations and the response
of the Mg II emission line, using the Javelin approach. More conservative
approach, based on five different methods, imply the time delay of
days. This time delay, combined with other available
measurements of Mg II line delay, mostly for lower redshift sources, shows that
the Mg II line reverberation implies a radius-luminosity relation very similar
to the one based on a more frequently studied H line.Comment: submitted to ApJ; comments welcom
New genetic loci link adipose and insulin biology to body fat distribution.
Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms