The Galactic Bulge exploration I.: The period-absolute\,magnitude-metallicity relations for RR~Lyrae stars for GBPG_{\rm BP}, VV, GG, GRPG_{\rm RP}, II, JJ, HH, and KsK_{\rm s} passbands using GaiaGaia DR3 parallaxes

We present a new set of period-absolute magnitude-metallicity (PMZ) relations for single-mode RR Lyrae stars calibrated for the optical $G_{\rm BP}$, $V$, $G$, $G_{\rm RP}$, near-infrared $I$, $J$, $H$, and $K_{\rm s}$ passbands. We compiled a large dataset (over $100$ objects) of fundamental and first-overtone RR~Lyrae pulsators consisting of mean intensity magnitudes, reddenings, pulsations properties, iron abundances, and parallaxes measured by the \textit{Gaia} astrometric satellite in its third data release. Our newly calibrated PMZ relations encapsulate the most up-to-date ingredients in terms of both data and methodology. They are aimed to be used in conjunction with large photometric surveys targeting the Galactic bulge, including the Optical Gravitational Lensing Experiment (OGLE), the Vista Variables in the V\'ia L\'actea Survey (VVV), and the \textit{Gaia} catalog. In addition, our Bayesian probabilistic approach provides accurate uncertainty estimates of the predicted absolute magnitudes of individual RR Lyrae stars. Our derived PMZ relations provide consistent results when compared to benchmark distances to Globular clusters NGC\,6121 (also known as M4), NGC\,5139 (also known as omega Cen), and Large and Small Magellanic Clouds, which are stellar systems rich in RR~Lyrae stars. Lastly, our $K_{\rm s}$-band PMZ relations match well with the previously published PMZ relations based on Gaia data and accurately predict the distance toward the prototype of this class of variables, the eponymic RR~Lyr itself.Comment: Accepted for publication in A&

Blazhko modulation in the infrared

We present first direct evidence of modulation in the K band of Blazhko-type RR Lyrae stars that are identified by their secular modulations in the I-band data of Optical Gravitational Lensing Experiment-IV. A method has been developed to decompose the K-band light variation into two parts originating from the temperature and the radius changes using synthetic data of atmosphere-model grids. The amplitudes of the temperature and the radius variations derived from the method for non-Blazhko RRab stars are in very good agreement with the results of the Baade-Wesselink analysis of RRab stars in the M3 globular cluster confirming the applicability and correctness of the method. It has been found that the Blazhko modulation is primarily driven by the change in the temperature variation. The radius variation plays a marginal part, moreover it has an opposite sign as if the Blazhko effect was caused by the radii variations. This result reinforces the previous finding based on the Baade-Wesselink analysis of M3 (NGC 5272) RR Lyrae, that significant modulation of the radius variations can only be detected in radial-velocity measurements, which relies on spectral lines that form in the uppermost atmospheric layers. Our result gives the first insight into the energetics and dynamics of the Blazhko phenomenon, hence it puts strong constraints on its possible physical explanations

Near infrared and optical emission of WASP-5 b

CONTEXT: Thermal emission from extrasolar planets makes it possible to study important physical processes in their atmospheres and derive more precise orbital elements. AIMS: By using new near infrared and optical data, we examine how these data constrain the orbital eccentricity and the thermal properties of the planet atmosphere. METHODS: The full light curves acquired by the TESS satellite from two sectors are used to put upper limit on the amplitude of the planet's phase variation and estimate the occultation depth. Two, already published and one, yet unpublished followup observations in the 2MASS K (Ks) band are employed to derive a more precise occultation light curve in this near infrared waveband. RESULTS: The merged occultation light curve in the Ks band comprises 4515 data points. The data confirm the results of the earlier eccentricity estimates, suggesting circular orbit: e=0.005+/-0.015. The high value of the flux depression of (2.70+/-0.14) ppt in the Ks band excludes simple black body emission at the 10 sigma level and disagrees also with current atmospheric models at the (4-7) sigma level. From the analysis of the TESS data, in the visual band we found tentative evidence for a near noise level detection of the secondary eclipse, and placed constraints on the associated amplitude of the planet's phase variation. A formal box fit yields an occultation depth of (0.157+/-0.056) ppt. This implies a relatively high geometric albedo of Ag=0.43+/-0.15 for fully efficient atmospheric circulation and Ag=0.29+/-0.15 for no circulation at all. No preference can be seen either for the oxygen-enhanced, or for the carbon-enhanced atmosphere models.Comment: After the 2nd referee report. Wrong citation of e*cos(w) by Baskin et al. (2013) has been corrected. Appendix B is supplied by another figur

VVV-WIT-01: highly obscured classical nova or protostellar collision?

© 2020 The Author(s).A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H-Ks=5.2). It peaked before March 2010, then faded by ~9.5 mag over the following two years. The 1.6-22 µm spectral energy distribution in March 2010 was well fit by a highly obscured black body with T ~ 1000 K and AKs ~ 6.6 mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062-0.294. The chance projection probability is small for any single event (p ≈ 0.01 to 0.02) which suggests a physical association, e.g. a collision between low mass protostars. However, black body emission at T ~ 1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve, due to condensation of dust ~30-60 days after the explosion. Radio follow up with the Australia Telescope Compact Array (ATCA) detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p=0.13 to 0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.Peer reviewedFinal Published versio

Gamma Dor and Gamma Dor - Delta Sct Hybrid Stars In The CoRoT LRa01

A systematic search for gamma Dor and gamma Dor - delta Scuti hybrid pulsators was conducted on the CoRoT LRa01 Exo-archive yielding a total of 418 gamma Dor and 274 hybrid candidates. After an automatic jump correction 194 and 167 respectively, show no more obvious jumps and were investigated in more detail. For about 25\% of these candidates classification spectra from the Anglo-Australian Observatory (AAO) are available. The detailed frequency analysis and a check for combination frequencies together with spectroscopic information allowed us to identify I) 34 gamma Dor stars which show very different pulsation spectra where mostly two modes dominate. Furthermore, a search for regularities in their oscillation spectra allowed to derive recurrent period spacings for 5 of these gamma Dor stars. II) 25 clear hybrid pulsators showing frequencies in the gamma Dor and delta Sct domain and are of A-F spectral type.Comment: Proceedings of the 4th HELAS International Conference held in Lanzarote, 201

The Emergence of the Infrared transient VVV-WIT-06

We report the discovery of an enigmatic large-amplitude (ΔKs> 10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT-06) is located at R.A. = 17:07:18.917, decl. = -39:06:26.45 (J2000), corresponding to Galactic coordinates l = 347.14539, b = 0.88522. It exhibits a clear eruption, peaking at Ks = 9 mag during 2013 July and fading to Ks ~ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of {FWHM} ~ 3000 k/s). We estimate a total extinction of A_V=10--15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to Ks> 18.5 mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (I) the closest Type I SN observed in about 400 years, (II) an exotic high-amplitude nova that would extend the known realm of such objects, or (III) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered.Peer reviewe

Near-infrared and optical emission of WASP-5 b

Context. Thermal emission from extrasolar planets makes it possible to study important physical processes in their atmospheres and derive more precise orbital elements.Aims. By using new near-infrared (NIR) and optical data, we examine how these data constrain the orbital eccentricity and the thermal properties of the planet atmosphere.Methods. The full light curves acquired by the TESS satellite from two sectors are used to put an upper limit on the amplitude of the phase variation of the planet and estimate the occultation depth. Two previously published observations and one followup observation (published herein) in the 2MASS K (Ks) band are employed to derive a more precise occultation light curve in this NIR waveband.Results. The merged occultation light curve in the Ks band comprises 4515 data points. The data confirm the results of the earlier eccentricity estimates, suggesting a circular orbit of: e = 0.005 +/- 0.015. The high value of the flux depression of (2.70 +/- 0.14) ppt in the Ks band excludes simple black body emission at the 10 sigma level and also disagrees with current atmospheric models at the (4-7)sigma level. From analysis of the TESS data, in the visual band we find tentative evidence for a near-noise-level detection of the secondary eclipse, and place constraints on the associated amplitude of the phase variation of the planet. A formal box fit yields an occultation depth of (0.157 +/- 0.056) ppt. This implies a relatively high geometric albedo of A(g) = 0.43 +/- 0.15 for fully efficient atmospheric circulation and A(g) = 0.29 +/- 0.15 for no circulation at all. No preference can be seen for either the oxygen-enhanced or the carbon-enhanced atmosphere models