Surface Brightness Scale of Galactic Cepheids

1999 ◽  
Vol 190 ◽  
pp. 561-562
Author(s):  
G. P. Di Benedetto
Keyword(s):  
Surface Brightness ◽  
Variable Stars ◽  
Giant Stars ◽  
Near Ir

An accurate calibration of the surface brightness scaleSVas a function of the near-IR color (V–K) has been recently measured for non-variable Galactic dwarf and giant stars. It can be shown that this correlation can be applied to theSVscale of Galactic Cepheid variable stars, which are of major cosmological interest.

scholarly journals Surface Brightness Scale of Galactic Cepheids

1999 ◽  
Vol 190 ◽  
pp. 561-562
Author(s):  
G. P. Di Benedetto
Keyword(s):  
Surface Brightness ◽  
Variable Stars ◽  
Giant Stars ◽  
Near Ir

An accurate calibration of the surface brightness scale SV as a function of the near-IR color (V – K) has been recently measured for non-variable Galactic dwarf and giant stars. It can be shown that this correlation can be applied to the SV scale of Galactic Cepheid variable stars, which are of major cosmological interest.

Precise distances to red giant stars with seismic data using the near-IR surface-brightness relation

2017 ◽  
Vol 13 (S334) ◽  
pp. 368-369
Author(s):  
Jesper Storm ◽  
Dariusz Graczyk ◽  
Marica Valentini ◽  
Friedrich Anders ◽  
Cristina Chiappini ◽  
...  
Keyword(s):  
Bayesian Methods ◽  
Seismic Data ◽  
Surface Brightness ◽  
Scaling Relations ◽  
Giant Stars ◽  
Large Samples ◽  
Near Ir ◽  
Red Giant Stars ◽  
Red Giant ◽  
Good Agreement

AbstractThe Kepler and CoRoT satellites have determined precise asteroseismic radii for large samples of red giant stars. Combining these data with data from spectroscopic and photometric surveys has led to precise distance determinations using comprehensive Bayesian methods. Here we determine angular diameters and thus distances using the interferometrically calibrated near-IR surface-brightness method finding good agreement with previous results. The method can easily be reversed when accurate Gaia parallaxes for these stars become available to calibrate the asteroseismic scaling relations.

Slow variability and circumstellar shells of red variable stars

1987 ◽  
Vol 122 ◽  
pp. 541-542
Author(s):  
T. Lloyd Evans
Keyword(s):  
Variable Stars ◽  
Circumstellar Dust ◽  
Infrared Photometry ◽  
Constant Ratio ◽  
Giant Stars ◽  
Long Period ◽  
Period Variations ◽  
Cyclic Variations ◽  
Circumstellar Shells ◽  
The Mean

Infrared photometry shows that while all RV Tauri stars have circumstellar dust shells, the RVb stars with slow cyclic variations in mean light as well as the 30–100 day variations common to all RV stars have more hot dust close to the star (Lloyd Evans 1985). Many M giant stars which are variables of semiregular type also show long-period variations in the mean light (O'Connell 1933; Payne-Gaposchkin 1954), with a roughly constant ratio between the two periods. Payne-Gaposchkin (1954) found P2/P1 ~9.4 for red variables of type M and P2/P1 ~19.4 for stars of type F-K, most of which are FV Tauri stars. Re-analysis using the more extensive data available now indicates P2/P1 ~10 for the M giants and P2/P1 ~15 for the FV Tauri stars. The nature of the long-period variability is unknown (Wood 1975).

scholarly journals Variability Survey of ω Centauri in the Near-IR: Period-Luminosity Relations

2015 ◽  
Vol 12 (S316) ◽  
pp. 351-352
Author(s):  
C. Navarrete ◽  
M. Catelan ◽  
R. Contreras Ramos ◽  
F. Gran ◽  
J. Alonso-García ◽  
...  
Keyword(s):  
Time Series ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Variable Stars ◽  
Star Cluster ◽  
Wide Field ◽  
Time Series Study ◽  
Near Ir ◽  
Series Study

Abstractω Centauri is by far the most massive globular star cluster in the Milky Way, and possibly the remnant of a dwarf galaxy. As such, it contains a large number of variable stars of different classes. Here we report on an extensive, wide-field time-series study of ω Cen in the J and KS bands, which has allowed us to study the near-IR period-luminosity relations for different variability classes, including the first such relations for the SX Phoenicis stars.

scholarly journals The Swift Bulge Survey: optical and near-IR follow-up featuring a likely symbiotic X-ray binary and a focused wind CV

2020 ◽  
Vol 492 (3) ◽  
pp. 4344-4360 ◽  
Author(s):  
A W Shaw ◽  
C O Heinke ◽  
T J Maccarone ◽  
G R Sivakoff ◽  
J Strader ◽  
...  
Keyword(s):  
White Dwarf ◽  
Near Infrared ◽  
Substantial Contribution ◽  
Galactic Centre ◽  
First Year ◽  
X Ray ◽  
Giant Stars ◽  
Near Ir ◽  
Star Binary

ABSTRACT The nature of very faint X-ray transients (VFXTs) – transient X-ray sources that peak at luminosities $L_X\lesssim 10^{36} {\rm \, erg \, s^{-1}}$ – is poorly understood. The faint and often short-lived outbursts make characterizing VFXTs and their multiwavelength counterparts difficult. In 2017 April we initiated the Swift Bulge Survey, a shallow X-ray survey of ∼16 square degrees around the Galactic centre with the Neil Gehrels Swift Observatory. The survey has been designed to detect new and known VFXTs, with follow-up programmes arranged to study their multiwavelength counterparts. Here we detail the optical and near-infrared follow-up of four sources detected in the first year of the Swift Bulge Survey. The known neutron star binary IGR J17445-2747 has a K4III donor, indicating a potential symbiotic X-ray binary nature and the first such source to show X-ray bursts. We also find one nearby M-dwarf (1SXPS J174215.0-291453) and one system without a clear near-IR counterpart (Swift J175233.9-290952). Finally, 3XMM J174417.2-293944 has a subgiant donor, an 8.7 d orbital period, and a likely white dwarf accretor; we argue that this is the first detection of a white dwarf accreting from a gravitationally focused wind. A key finding of our follow-up campaign is that binaries containing (sub)giant stars may make a substantial contribution to the VFXT population.

scholarly journals Surface photometry of cD envelopes

2006 ◽  
Vol 2 (S235) ◽  
pp. 213-213
Author(s):  
S. N. Kemp ◽  
V. Guzmán Jiménez ◽  
P. Ramírez Beraud ◽  
F. J. Hernández Ibarra ◽  
J. A. Pérez Grana
Keyword(s):  
Star Formation ◽  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Cluster Member ◽  
Surface Photometry ◽  
X Ray ◽  
Cooling Flows ◽  
Near Ir ◽  
San Pedro ◽  
Cd Galaxies

We have carried out deep BVR surface photometry of 6 cD and cD-like galaxies using the 2.1-m telescope at San Pedro Mártir, cD galaxies are supergiant galaxies (M>1013M⊙) with enormous halos (>100 kpc in radius) surrounding a giant elliptical galaxy, found generally at the centre of rich clusters (Oemler 1976, Schombert 1988). The surface brightness profiles of their halos (envelopes) break from the r1/4 law, containing more light at large radii (Schombert (1988)), although a detailed 1 and 2 dimensional analysis of their morphology has yet to be carried out. There have been four main theories as to the origin of cD envelopes (Schombert (1988) and references within), a) stripping of stars from other cluster member galaxies, b) formation of galaxy and envelope at the same time during the formation of the cluster, c) mergers of cluster members, which do not easily explain the high velocity dispersions in the envelopes (~ 1000 km s−1), d) cooling flows: accumulation of cooling X-ray-emitting ICM gas around the central galaxy. Very red envelopes have been found around some cD's, and star formation biased towards lowmass stars in cooling flows were invoked to explain these red halos, but the expected very bright near-IR halos were not detected (Joy et al. 1995 and references within). Previous detailed studies of cD galaxies (e.g. Mackie 1992) found a range of colour gradients.

scholarly journals Stellar Over-Densities in the Outer Halo of the Milky Way

2010 ◽  
Vol 27 (1) ◽  
pp. 45-55 ◽  
Author(s):  
Stefan C. Keller
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Local Density ◽  
Spatial Scales ◽  
Sloan Digital Sky Survey ◽  
Tidal Disruption ◽  
Giant Stars ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Model Predictions

AbstractThis study presents a tomographic survey of a subset of the outer halo (10–40 kpc) drawn from the Sloan Digital Sky Survey Data Release 6. Halo substructure on spatial scales of >3 degrees is revealed as an excess in the local density of sub-giant stars. With an appropriate assumption of a model stellar isochrone it is possible for us to then derive distances to the sub-giant population. We describe three new candidate halo substructures; the 160- and 180-degree over-densities (at distances of 17 and 19 kpc respectively and radii of 1.3 and 1.5 kpc respectively) and an extended feature at 28 kpc that covers at least 162 deg2, the Virgo Equatorial Stream. In addition, we recover the Sagittarius dwarf galaxy (Sgr) leading-arm material and the Virgo Over-Density.The derived distances, together with the number of sub-giant stars associated with each substructure, enables us to derive the integrated luminosity for the features. The tenuous, low surface brightness of the features strongly suggests an origin from the tidal disruption of an accreted galaxy or galaxies. Given the dominance of the tidal debris of Sgr in this region of the sky we investigate if our observations can be accommodated by tidal disruption models for Sgr. The clear discordance between observations and model predictions for known Sgr features means it is difficult to tell unambiguously if the new substructures are related to Sgr or not. Radial velocities in the stellar over-densities will be critical in establishing their origins.

scholarly journals Modeling the Hα Emission Surrounding Spica Using the Lyman Continuum from a Gravity-darkened Central Star

2021 ◽  
Vol 923 (1) ◽  
pp. 10
Author(s):  
Jason P. Aufdenberg ◽  
Joseph M. Hammill
Keyword(s):  
Surface Brightness ◽  
Central Star ◽  
Model Atmosphere ◽  
Stellar Atmosphere ◽  
Primary Star ◽  
Near Ir ◽  
Lyman Continuum ◽  
Sky Survey ◽  
Hα Emission ◽  
Star Binary

Abstract The large, faint Hα emission surrounding the early B-star binary Spica has been used to constrain the total hydrogen recombination rate of the nebula and indirectly probe the Lyman continuum luminosity of the primary star. Early analysis suggested that a stellar atmosphere model, consistent with Spica A’s spectral type, has a Lyman continuum luminosity about two times lower than required to account for the measured Hα surface brightness within the nebula. To more consistently model both the stellar and nebular emission, we have used a model atmosphere for Spica A that includes the effects of gravity darkening as input to photoionization models to produce synthetic Hα surface brightness distributions for comparison to data from the Southern Hα Sky Survey Atlas. This paper presents a method for the computation of projected surface brightness profiles from 1D volume emissivity models and constrains both stellar and nebular parameters. A mean effective temperature for Spica A of ≃24,800 K is sufficient to match both the observed absolute spectrophotometry, from the far-UV to the near-IR, and radial Hα surface brightness distributions. Model hydrogen densities increase with the distance from the star, more steeply and linearly toward the southeast. The northwest matter-bounded portion of the nebula is predicted to leak ∼17% of Lyman continuum photons. Model H ii region column densities are consistent with archival observations along the line of sight.

scholarly journals Radial velocities, metallicities, and distances of Cepheids in M31 and M33

2004 ◽  
Vol 193 ◽  
pp. 99-102
Author(s):  
Amy D. Forestell ◽  
Thomas G. Barnes ◽  
Christopher Sneden ◽  
Thomas J. Moffett
Keyword(s):  
High Resolution ◽  
Surface Brightness ◽  
Local Group ◽  
Variable Stars ◽  
Radial Velocities ◽  
Distance Scale ◽  
Distance Measurements ◽  
Using Data ◽  
Extragalactic Distance Scale

AbstractCepheid variable stars are fundamental to the calibration of the extragalactic distance scale. We present radial velocities, preliminary metallicities, and preliminary surface brightness distances of Cepheids in Local Group galaxies M31 and M33 using data obtained with the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. These data are the first step toward surface brightness distance measurements and metallicity calibrations of these extragalactic Cepheids.

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