The PRime-focus Infrared Microlensing Experiment (PRIME): First Results

We present spectra of the optical transient of GRB 021004 obtained with the Hobby-Eberly Telescope starting 15.48 hr, 20.31 hr, and 4.84 days after the ?-ray burst and a spectrum obtained with the H. J. Smith 2.7 m Telescope starting 14.31 hr after the ?-ray burst. GRB 021004 is the first burst afterglow for which the spectrum is dominated by absorption lines from high-ionization species with multiple velocity components separated by up to 3000 km s-1. We argue that these absorption lines are likely to come from shells around a massive progenitor star. The high velocities and high ionizations arise from a combination of acceleration and flash ionization by the burst photons and the wind velocity and steady ionization by the progenitor. We also analyze the broadband spectrum and the light curve so as to distinguish the structure of gas within 0.3 pc of the burster. We delineate six components in the medium surrounding the ?-ray burst along the line of sight: (1) The z 2.293 absorption lines arise from the innermost region closest to the burst, where the ionization will be highest and the 3000 km s-1 velocity comes from the intrinsic velocity of a massive star wind boosted by acceleration from the burst flux. For a mass-loss rate of ~ 6 ? 10-5 M? yr-1, this component also provides the external medium with which the jet collides over radial distances 0.004-0.3 pc to create the afterglow light. (2) A second cloud or shell produces absorption lines with a relative velocity of 560 km s-1. This component could be associated with the shell created by the fast massive star wind blowing a bubble in the preceding slow wind at a radial distance on the order of 10 pc or by a clump at ~0.5 pc accelerated by the burst. (3) More distant clouds within the host galaxy that lie between 30 and 2500 pc and have been ionized by the burst will create the z 2.33 absorption lines. (4-6) If the three bumps in the afterglow light curve at 0.14, 1.1, and 4.0 days are caused by clumps or shells in the massive star wind along the line of sight, then the radii and overdensities of these are 0.022, 0.063, and 0.12 pc and 50%, 10%, and 10%, respectively. The immediate progenitor of the ?-ray burst could be either a WC-type Wolf-Rayet star with a high-velocity wind or a highly evolved massive star the original mass of which was too small for it to become a WN-type Wolf-Rayet star. In summary, the highly ionized lines with high relative velocities most likely come from shells or clumps of material close to the progenitor, and these shells were plausibly produced by a massive star soon before its collapse.

Type Ia supernovae (SNe Ia) are more precise standardizable candles when measured in the near-infrared (NIR) than in the optical. With this motivation, from 2012 to 2017 we embarked on the RAISIN program with the Hubble Space Telescope (HST) to obtain rest-frame NIR light curves for a cosmologically distant sample of 37 SNe Ia (0.2 ≲ z ≲ 0.6) discovered by Pan-STARRS and the Dark Energy Survey. By comparing higher-z HST data with 42 SNe Ia at z < 0.1 observed in the NIR by the Carnegie Supernova Project, we construct a Hubble diagram from NIR observations (with only time of maximum light and some selection cuts from optical photometry) to pursue a unique avenue to constrain the dark energy equation-of-state parameter, w. We analyze the dependence of the full set of Hubble residuals on the SN Ia host galaxy mass and find Hubble residual steps of size ∼0.06-0.1 mag with 1.5σ−2.5σ significance depending on the method and step location used. Combining our NIR sample with cosmic microwave background constraints, we find 1 + w = −0.17 ± 0.12 (statistical + systematic errors). The largest systematic errors are the redshift-dependent SN selection biases and the properties of the NIR mass step. We also use these data to measure H 0 = 75.9 ± 2.2 km s−1 Mpc−1 from stars with geometric distance calibration in the hosts of eight SNe Ia observed in the NIR versus H 0 = 71.2 ± 3.8 km s−1 Mpc−1 using an inverse distance ladder approach tied to Planck. Using optical data, we find 1 + w = −0.10 ± 0.09, and with optical and NIR data combined, we find 1 + w = −0.06 ± 0.07; these shifts of up to ∼0.11 in w could point to inconsistency in the optical versus NIR SN models. There will be many opportunities to improve this NIR measurement and better understand systematic uncertainties through larger low-z samples, new light-curve models, calibration improvements, and eventually by building high-z samples from the Roman Space Telescope.

Type Ia supernovae (SN Ia) are more nearly standard candles when measured in the near-infrared (NIR) than in the optical. With this motivation, from 2012-2017 we embarked on the RAISIN program with the Hubble Space Telescope (HST) to obtain rest-frame NIR light curves for a cosmologically distant sample of 37 SN Ia ($0.2<z<0.7$) discovered by Pan-STARRS and the Dark Energy Survey. By comparing higher-$z$ HST data with 43 SN Ia at $z<0.1$ observed in the NIR by the Carnegie Supernova Project, we construct a Hubble diagram exclusively from NIR observations to pursue a unique avenue to constrain the dark energy equation of state parameter, $w$. We analyze the dependence of the full set of Hubble residuals on the SN Ia host galaxy mass and find Hubble residual steps of size $\sim$0.08-0.12 mag with 2- to 3-$\sigma$ significance depending on the method and step location used. Combining our NIR sample with Cosmic Microwave Background (CMB) constraints, we find $1+w=-0.04\pm0.12$ (statistical$+$systematic errors). The largest systematic errors are the redshift-dependent SN selection biases and the properties of the NIR mass step. We also use these data to measure ${\rm H}_0=75.4\pm 2.4~{\rm km~s^{-1}~Mpc^{-1}}$ from stars with geometric distance calibration in the hosts of 8 SNe Ia observed in the NIR versus ${\rm H}_0=65.9\pm3.4~{\rm km~s^{-1}~Mpc^{-1}}$ using an inverse distance ladder approach tied to Planck. Using optical data we find $1+w=-0.01\pm0.09$ and with optical and NIR data combined, we find $1+w=0.03\pm0.08$; these shifts of up to $\sim$0.07 in $w$ could point to inconsistency in the optical versus NIR SN models. There will be many opportunities to improve this NIR measurement and better understand systematic uncertainties through larger low-$z$ samples, new light-curve models, calibration improvements, and eventually building high-$z$ samples from the Roman Space Telescope.

The Wide-Field InfraRed Survey Telescope (WFIRST) is a NASA space mission in study for launch in 2024. It has a 2.4 m telescope, wide-field IR instrument operating in the 0.7 - 2.0 micron range and an exoplanet imaging coronagraph instrument operating in the 400 - 1000 nm range. The observatory will perform galaxy surveys over thousands of square degrees to J=27 AB for dark energy weak lensing and baryon acoustic oscillation measurements and will monitor a few square degrees for dark energy SN Ia studies. It will perform microlensing observations of the galactic bulge for an exoplanet census and direct imaging observations of nearby exoplanets with a pathfinder coronagraph. The mission will have a robust and well- funded guest observer program for 25% of the observing time. WFIRST will be a powerful tool for time domain astronomy and for coordinated observations with gravitational wave experiments. Gravitational wave events produced by mergers of nearby binary neutron stars (LIGO-Virgo) or extragalactic supermassive black hole binaries (LISA) will produce electromagnetic radiation that WFIRST can observe.

The Korea Microlensing Telescope Network (KMTNet) is a wide-field photometric system installed by the Korea Astronomy and Space Science Institute (KASI). Here, we present the overall technical specifications of the KMTNet observation system, test observation results, data transfer and image processing procedure, and finally, the KMTNet science programs. The system consists of three 1.6 m wide-field optical telescopes equipped with mosaic CCD cameras of 18k by 18k pixels. Each telescope provides a 2.0 by 2.0 square degree field of view. We have finished installing all three telescopes and cameras sequentially at the Cerro-Tololo Inter-American Observatory (CTIO) in Chile, the South African Astronomical Observatory (SAAO) in South Africa, and the Siding Spring Observatory (SSO) in Australia. This network of telescopes, which is spread over three different continents at a similar latitude of about -30 degrees, enables 24-hour continuous monitoring of targets observable in the Southern Hemisphere. The test observations showed good image quality that meets the seeing requirement of less than 1.0 arcsec in I-band. All of the observation data are transferred to the KMTNet data center at KASI via the international network communication and are processed with the KMTNet data pipeline. The primary scientific goal of the KMTNet is to discover numerous extrasolar planets toward the Galactic bulge by using the gravitational microlensing technique, especially earth-mass planets in the habitable zone. During the non-bulge season, the system is used for wide-field photometric survey science on supernovae, asteroids, and external galaxies.

The cool stellar populations of early-type galaxies have been examined through an analysis of red (6800-9200A) and near-infrared (K-band) spectra of the nuclear regions of 17 E/S0 galaxies in the Virgo cluster, ten Coma cluster members and seven field galaxies. The Virgo galaxy sample spans about 4.5 mag. in K-band luminosity. To characterize the red stellar populations of these galaxies, the strengths of the Ca II triplet at lambda-lambda 8498, 8542, 8662A, the Na I doublet at lambda-lambda 8183, 8195A, the Mg I lambda 8807A line, several molecular bands of TiO and VO, and the CO band with bandhead near 2.29 microns have been measured from the spectra. The variations in the colors and spectral features of E/S0 galaxies as a function of luminosity are described and compared to the radial changes seen in the integrated light of the Galactic bulge as a function of galactocentric distance. The Virgo galaxy observations were used to define the behavior of the colors and spectral indices of early-type galaxies as a function of luminosity. A comparison to the Coma and field galaxies was hindered by the low signal-to-noise ratio of the Coma galaxy data and the lack of published photometry for three of the field galaxies; however, the Coma and field zgalaxies did not exhibit any trends which were statistically different than those seen in the Virgo galaxies. In general, the spectral features which varied significantly with K-band luminosity also showed statistically significant correlations with V-K and J-K color. Specifically, (1) the CO band, the TiO bands and the Na I index (the doublet itself is unresolved in the spectra obtained here) strengthen with redder colors and higher luminosities, (2) the Mg I line and the lines of the Ca II triplet do not vary significantly in strength among galaxies of different color or brightness, and (3) the VO band was not detected in any galaxy. In addition, the redshift correction to the CIT photometric CO index was found to be well-fit by the relation KCO = +5.23z. Using previously published photometry and spectroscopy of stars in the Galactic Bulge, the radial variations in the bulge's stellar population have been estimated by constructing models of the integrated light of Baade's Window (BW), located at b}= -3.9 degrees, and a Galactic bulge field near b = -8 degrees. A close examination of the BW color-magnitude diagram (CMD) and the resulting BW model indicate that: (1) the isochrone which best traces the "average" distribution of stars in the BW CMD has [Fe/H] = -0.23 and an age of 8.0 Gyr; (2) the I-band fluctuation magnitude of the BW stellar population is consistent with current estimates of the distance to the Galactic center; (3) the stellar population in Baade's Window is quite complex, consisting of either a purely "bulge" population with a large spread in its properties (such as metallicity) or a mixture of separate populations, possibly halo and bulge; (4) most, if not all, of the observed characteristics of the BW population which have usually been attributed to an overall increased metallicity in BW stars can be better explained by selective enrichment of Ti and perhaps variations in the relative abundances of the CNO elements without a corresponding Fe enhancement; and (5) the integrated light of BW is very similar to the integrated light of the nucleus of a low-luminosity early-type galaxy and is giant-dominated for lambda > 5500A. Three major conclusions were drawn from the radial variations seen in the integrated light models of the Galactic bulge. First, extrapolating the derived radial gradients to the inner bulge, it appears that the differences between the BW model and a luminous E/S0 galaxy cannot be attributed solely to the fact that BW represents a region of the Galactic bulge much further from the center of the galaxy than the analogous regions which the spectra of the early-type galaxies sample. Second, the two indices which measure spectral features in the vicinity of the Na I lines increase steeply with redder colors in the E/S0 galaxies but appear to decrease with color in the Galactic bulge; this effect is not understood but may be caused by some deficiency in the modelling. Spectral synthesis of this region of the spectrum would be extemely useful in disentangling the Na I doublet from other contaminating species (e.g. TiO, nearby atomic lines and the CN bands prevalent in K giants). Third, differences in the slopes of the TiO/color trends in E/S0 galaxies and in the Galactic bulge may indicate that the [Ti/Fe] ratio is changing differently in these two instances. The overall trends exhibited by the Virgo E/S0 galaxies are most consistent with the following scenario: the integrated light of early-type galaxies is dominated by giant stars having an average [Fe/H] > -0.3, but the chemical composition of this population changes with the luminosity of the galaxy-- either the overall metallicity increases or specific elements are selectively enriched with redder colors and increasing luminosity. If it is assumed that the radial stellar population gradients in the Galactic bulge are similar to those in early-type galaxies, then the bulge models indicate that these stellar population variations are different than those which occur among the nuclei of E/S0 galaxies of differing luminosity.

A large fraction of Type Ia supernova (SN Ia) observations over the next decade will be in the near-infrared (NIR), at wavelengths beyond the reach of the current standard light-curve model for SN Ia cosmology, SALT3 (∼2800–8700 Å central filter wavelength). To harness this new SN Ia sample and reduce future light-curve standardization systematic uncertainties, we train SALT3 at NIR wavelengths (SALT3-NIR) up to 2 μm with the open-source model-training software SALTshaker, which can easily accommodate future observations. Using simulated data, we show that the training process constrains the NIR model to ∼2%–3% across the phase range (−20 to 50 days). We find that Hubble residual (HR) scatter is smaller using the NIR alone or optical+NIR compared to optical alone, by up to ∼30% depending on filter choice (95% confidence). There is significant correlation between NIR light-curve stretch measurements and luminosity, with stretch and color corrections often improving HR scatter by up to ∼20%. For SN Ia observations expected from the Roman Space Telescope, SALT3-NIR increases the amount of usable data in the SALT framework by ∼20% at redshift z ≲ 0.4 and by ∼50% at z ≲ 0.15. The SALT3-NIR model is part of the open-source SNCosmo and SNANA SN Ia cosmology packages.

We present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006–2014. Six events are likely to be due to planets with Einstein radius crossing times t E < 0.5 days, and the shortest has t E = 0.057 ± 0.016 days and an angular Einstein radius of θ E = 0.90 ± 0.14 μas. We measure the detection efficiency depending on both t E and θ E with image-level simulations for the first time. These short events are well modeled by a power-law mass function, dex−1 star−1 with for M/M ⊙ < 0.02. This implies a total of FFPs or very wide orbit planets of mass 0.33 < M/M ⊕ < 6660 per star, with a total mass of star−1. The number of FFPs is times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of α ∼ 0.9, which would imply a total mass of star−1. This model predicts that Roman Space Telescope will detect FFPs with masses down to that of Mars (including with 0.1 ≤ M/M ⊕ ≤ 1). The Sumi et al. large Jupiter-mass FFP population is excluded.

We have obtained spatially resolved spectra of the triply imaged QSO APM08279+5255 using the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). We study the line of sight equivalent width (EW) differences and velocity shear of high and low ionization absorbers (including a damped Lyman alpha [DLA] system identified in a spatially unresolved ground based spectrum) in the three lines of sight. The combination of a particularly rich spectrum and three sight-lines allow us to study 27 intervening absorption systems over a redshift range , probing proper transverse dimensions of 30 pc up to 2.7 kpc. We find that high ionization systems (primarily C IV absorbers) do not exhibit strong EW variations on scales <0.4 kpc; their fractional EW differences are typically less than 30%. When combined with previous work on other QSO pairs, we find that the fractional variation increases steadily with separation out to at least ~ kpc. Conversely, low ionization systems (primarily Mg II absorbers) show strong variations (often >80%) over kpc scales. A minimum radius for strong ( Å) Mg II systems of >1.4 kpc is inferred from absorption coincidences in all lines of sight. For weak Mg II absorbers (EW Å), a maximum likelihood analysis indicates a most probable coherence scale of 2.0 kpc for a uniform spherical geometry, with 95% confidence limits ranging between 1.5 and 4.4 kpc. The weak Mg II absorbers may therefore represent a distinct population of smaller galaxies compared with the strong Mg II systems which we know to be associated with luminous galaxies whose halos extend over tens of kpc. Alternatively, the weak systems may reside in the outer parts of larger galaxies, where their filling factor may be lower. By cross-correlating spectra along different lines of sight, we infer shear velocities of typically less than 20 km s-1 for both high and low ionization absorbers. Finally, for systems with weak absorption that can be confidently converted to column densities, we find constant N(C IV)/N(Si IV) across the three lines of sight. Similarly, the [Al/Fe] ratios in the DLA are consistent with solar relative abundances over a transverse distance of ~ kpc.

Context. Galaxy interactions and mergers can lead to supermassive black hole (SMBH) binaries, which become active galactic nucleus (AGN) pairs when the SMBHs start accreting mass. If there is a third galaxy involved in the interaction, then a triple-AGN system can form. Aims. Our goal is to investigate the nature of the nuclear emission from the galaxies in the interacting pair NGC 7733–NGC 7734 using archival VLT/MUSE integral field spectrograph data and study its relation to the stellar mass distribution traced by near-infrared (NIR) observations from the South African Astronomical Observatory (SAAO). Methods. We conducted NIR observations using the SAAO and identified the morphological properties of bulges in each galaxy. We used MUSE data to obtain a set of ionized emission lines from each galaxy and studied the ionization mechanism. We also examined the relation of the galaxy pair with any nearby companions with far-ultraviolet observations using the UVIT. Results. The emission line analysis from the central regions of NGC 7733 and NGC 7734 shows Seyfert and low ionization nuclear emission-line regions type AGN activity. The galaxy pair NGC 7733−34 also shows evidence of a third component, which has Seyfert-like emission. Hence, the galaxy pair NGC 7733−34 forms a triple-AGN system. We also detected an extended narrow-line region associated with the nucleus of NGC 7733.

We simulate the yield of small (0.5–4.0 R ⊕) transiting exoplanets around single mid-M and ultracool dwarfs (UCDs) in the Nancy Grace Roman Space Telescope Galactic Bulge Time Domain Survey. We consider multiple approaches for simulating M3–T9 sources within the survey fields, including scaling local space densities and using Galactic stellar population synthesis models. These approaches independently predict ∼100,000 single mid-M dwarfs and UCDs brighter than a Roman F146 magnitude of 21 that are within the survey fields. Assuming planet occurrence statistics previously measured for early-to-mid-M dwarfs, we predict that the survey will discover small transiting planets around these sources, each to a significance of 7.1σ or greater. Significant departures from this prediction would test whether the occurrence rates of small planets increase or decrease around mid-M dwarfs and UCDs compared to early-M dwarfs. We predict the detection of habitable, terrestrial planets (R p < 1.23 R ⊕) in the survey. However, atmospheric characterization of these planets will be challenging with current or near-future space telescope facilities due to the faintness of the host stars. Nevertheless, accurate statistics for the occurrence of small planets around mid-M dwarfs and UCDs will enable direct tests of predictions from planet formation theories and will determine our understanding of planet demographics around the objects at the bottom of the main sequence. This understanding is critical given the prevalence of such objects in our galaxy, whose planets may therefore comprise the bulk of the galactic census of exoplanets.

We present the results of a photometric and spectroscopic study of stars in four fields toward the inner disk and Galactic bulge. The fields are located symmetrically about the minor axis of the Milky Way at (l, b) = (-248, -60), (-87, -60), (+84, -60), and (+244, -61). We measured radial velocities and strengths of selected absorption-line indexes and derived the average reddening to each field, individual metallicities and photometric parallaxes for each star, and mean azimuthal rotation velocities and velocity dispersions for each field. We found that the stars are not strongly peaked in distribution at the tangent point or at bulgelike distances along any of the lines of sight. In each field, we find that velocity dispersion decreases as [Fe/H] increases, a correlation noted in many previous works. We also find that both velocity dispersion and [Fe/H] vary along each line of sight in a manner consistent with progressively sampling different populations (thin disk, bulge, thick disk, halo) at increasing distance; hence, the observed metallicity?velocity dispersion correlation is likely the result, at least in part, of the superposition of multiple populations viewed along the line of sight. We find that the disk stars in the (-248, -60) field are approaching the solar position at ~50 km s-1 faster than the stars in the (+244, -61) field are moving away. Similarly, inner disk stars from the two inner fields have a velocity asymmetry of ~35 km s-1. The velocity dispersions in these fields are also asymmetric; the -l fields have lower values than predicted for a circularly rotating exponential disk, while the +l fields have higher values. These kinematic asymmetries suggest that a barlike asymmetry exists in the inner disk of similar geometric positioning as the bar detected in the Galactic bulge. Comparison of the line-of-sight kinematics in our (+84, -60) field with the values of Minniti for a field at (+8?, +7?) indicates that the kinematics of the outer bulge is symmetric about the Galactic major axis. From the stars at bulgelike distances in our inner fields, we calculated a rotational velocity, and azimuthal velocity dispersion for the bulge. By linearly interpolating the values in the two fields, we found the projected mean rotation of the bulge to be 53.3 ? 0.3 km s-1 kpc-1, or 9.0 ? 0.5 km s-1 deg-1, in general agreement with other values from the literature.

Mission concepts for NASA's Wide Field Infrared Survey Telescope (WFIRST)^1,2, ESA's Euclid^3,4 mission, as well as next-generation ground-based surveys require large mosaic focal planes sensitive in both visible and near infrared (NIR) wavelengths. We have developed space-qualified detectors, readout electronics and focal plane design techniques that can be used to intermingle CCDs and NIR detectors on a single, silicon carbide (SiC) cold plate. This enables optimized, wideband observing strategies. The CCDs, developed at Lawrence Berkeley National Laboratory, are fully-depleted, pchannel devices that are backside illuminated and capable of operating at temperatures down to 120K. The NIR detectors are 1.7 &mu;m and 2.0 &mu;m wavelength cutoff H2RG&reg; HgCdTe, manufactured by Teledyne Imaging Sensors under contract to LBNL. Both the CCDs and NIR detectors are packaged on 4-side abuttable SiC pedestals with a common mounting footprint supporting a 44 mm mosaic pitch. Both types of detectors have direct-attached readout electronics that convert the detector signal directly to serial, digital data streams and allow a flexible, low cost data acquisition strategy to enable large data rates. A mosaic of these detectors can be operated at a common temperature that achieves the required dark current and read noise performance necessary for dark energy observations. We report here the qualification testing and performance verification for a focal plane that accommodates a 4x8 array of CCDs and HgCdTe detectors.

Galaxies have long been known to form large clusters, and cosmologists are interested in characterizing this clustering as a way of studying the large-scale structure of the universe. This work is motivated by a data catalog consisting of information on lines of sight from Earth to distant quasi-stellar objects (QSO's) and the carbon IV absorbers that lie on them. The absorbers are believed to be gas clouds near galaxies too far away to be easily observed. Thus, the absorber catalog provides a unique and interesting way to examine the large-scale structure of the universe. On large scales previous studies have mainly used pairs of absorbers on the same lines of sight to obtain estimates describing the clustering of absorbers. It is clear that absorbers on different lines of sight contain information about the degree of clustering. We develop an adaptation of the rigid motion corrected estimator of the reduced second-moment function for the absorber catalog taking into account the across-line-of-sight information. We show how to compute this estimator efficiently using the weights for an isotropic estimator proposed in a recent study. We also show how the modified versions of the rigid motion estimators can be obtained. Simulations suggest that using the modified rigid motion correction estimator may reduce standard errors by 5–20%% on scales from 50 to 250 h−1 Mpc for a set of 100 lines of sight.

We present the reddening (E(V-I)) and Extinction maps in V-band (A_V) and I-band (A_I) for 48 Optical Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields, covering a range of $-11^\circ <l< 11^\circ$, with the total area close to 11 square degrees. These measurements are based on two-band photometry of Red Clump Giant (RCG) stars in OGLE-II VI maps of GB. We confirm the anomalous value of the ratio of total to selective extinction $R_{VI} = A_V / E(V-I) = 1.9 \sim 2.1$, depending on the line of sight, as measured by Udalski (2003). By using the average value of $R_{VI}=1.964$ with the standard deviation sdev=0.085, we measured E(V-I), A_V and A_I, and we obtained extinction and reddening maps with a high spatial resolution of $ 26.7''\sim 106.8''$, depending on the stellar density of each field. We assumed that average, reddening corrected colours of red clump giants are the same in every field. The maps cover the range 0.42<E(V-I)<3.5, 0.83<A_V<6.9 and 0.41<A_I<3.4 mag respectively. The zero points of these maps are calibrated by using V-K colours of 20 RR Lyrae ab variables (RRab) in Baade's window. The apparent reddening corrected I-band magnitudes of the RCGs change by +0.4 mag while the Galactic coordinate l varies from $+5^{\circ}$ to $-5^{\circ}$, indicating that these stars are in the Galactic Bar. The reddening corrected colour of RRab and RCGs in GB are consistent with colours of local stars, while in the past these colours were claimed to be different.