Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b

ABSTRACT We present four new secondary eclipse observations for the ultrahot Jupiter WASP-121b acquired using the Hubble Space Telescope Wide Field Camera 3. The eclipse depth is measured to a median precision of 60 ppm across 28 spectroscopic channels spanning the 1.12–$1.64\, \mu {\rm m}$ wavelength range. This is a considerable improvement to the 90 ppm precision we achieved previously for a single eclipse observation using the same observing set-up. Combining these data with those reported at other wavelengths, a blackbody spectrum for WASP-121b is ruled out at >6σ confidence and we confirm the interpretation of previous retrieval analyses that found the data are best explained by a dayside thermal inversion. The updated spectrum clearly resolves the water emission band at 1.3–$1.6\, \mu {\rm m}$, with higher signal-to-noise than before. It also fails to reproduce a bump in the spectrum at $1.25\, \mu {\rm m}$ derived from the first eclipse observation, which had tentatively been attributed to VO emission. We conclude that the latter was either a statistical fluctuation or a systematic artefact specific to the first eclipse data set.

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An emission spectrum for WASP-121b measured across the 0.8–1.1 μm wavelength range using the Hubble Space Telescope

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1753 ◽

2019 ◽

Vol 488 (2) ◽

pp. 2222-2234 ◽

Cited By ~ 29

Author(s):

Thomas Mikal-Evans ◽

David K Sing ◽

Jayesh M Goyal ◽

Benjamin Drummond ◽

Aarynn L Carter ◽

...

Keyword(s):

Wavelength Range ◽

Hubble Space Telescope ◽

Thermal Dissociation ◽

Wide Field ◽

Statistical Fluctuation ◽

Space Telescope ◽

Thermal Inversion ◽

Eclipse Observations ◽

Best Fitting ◽

Fitting Model

Abstract WASP-121b is a transiting gas giant exoplanet orbiting close to its Roche limit, with an inflated radius nearly double that of Jupiter and a dayside temperature comparable to a late M dwarf photosphere. Secondary eclipse observations covering the 1.1–$1.6\, \mu{\rm m}$ wavelength range have revealed an atmospheric thermal inversion on the dayside hemisphere, likely caused by high-altitude absorption at optical wavelengths. Here we present secondary eclipse observations made with the Hubble Space Telescope Wide Field Camera 3 spectrograph that extend the wavelength coverage from $1.1\, \mu{\rm m}$ down to $0.8\, \mu{\rm m}$. To determine the atmospheric properties from the measured eclipse spectrum, we performed a retrieval analysis assuming chemical equilibrium, with the effects of thermal dissociation and ionization included. Our best-fitting model provides a good fit to the data with reduced $\chi ^2_\nu =1.04$. The data diverge from a blackbody spectrum and instead exhibit emission due to H− shortward of $1.1\, \mu{\rm m}$. The best-fitting model does not reproduce a previously reported bump in the spectrum at $1.25\,\mu{\rm m}$, possibly indicating this feature is a statistical fluctuation in the data rather than a VO emission band as had been tentatively suggested. We estimate an atmospheric metallicity of $[{\rm M}/{\rm H}]= {1.09}_{-0.69}^{+0.57}$, and fit for the carbon and oxygen abundances separately, obtaining $[{\rm C}/{\rm H}]= {-0.29}_{-0.48}^{+0.61}$ and $[{\rm O}/{\rm H}]= {0.18}_{-0.60}^{+0.64}$. The corresponding carbon-to-oxygen ratio is ${\rm C/O} = 0.49_{-0.37}^{+0.65}$, which encompasses the solar value of 0.54, but has a large uncertainty.

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Characterising Two Ultra-Hot Jupiters with the Hubble Space Telescope

10.5194/epsc2020-657 ◽

2020 ◽

Author(s):

Billy Edwards ◽

Quentin Changeat ◽

William Pluriel ◽

Niall Whiteford ◽

Kai Hou Yip ◽

...

Keyword(s):

Emission Spectrum ◽

Hubble Space Telescope ◽

Cloud Model ◽

Thermal Structure ◽

Emission Spectra ◽

Pressure Profile ◽

Wide Field ◽

Space Telescope ◽

Thermal Inversion ◽

Hot Jupiters

The Hubble Space Telescope&#8217;s Wide Field Camera 3 (WFC3) has been widely used for transmission and emission spectroscopy of exoplanet atmospheres, identifying the main molecular constituents, detecting the presence of clouds and probing their thermal structure. Hubble observations of the emission spectra of a number of ultra-hot Jupiters have led to somewhat surprising results. Initially, these very hot planets were predicted to have inverted temperature pressure profiles due to strong optical absorption by TiO/VO in the upper atmospheres. However, observations of their emission spectra have been inconclusive on their thermal structure and composition. While some datasets show rich spectral features, others can be fit with simple blackbody models. We will present the analysis of Hubble WFC3 transmission and emission spectra for two ultra-hot Jupiters: WASP-76 b and KELT-7 b. In each case, the data was reduced and fitted using the open-source codes Iraclis and Taurex3. Previous studies of the WFC3 transmission spectra of WASP-76 b found hints of TiO and VO or non-grey clouds. Accounting for a fainter stellar companion to WASP-76, we reanalyse this data and show that removing the effects of this background star changes the slope of the spectrum, resulting in these visible absorbers no longer being detected, removing the need for a non-grey cloud model to adequately fit the data but maintaining the strong water feature previously seen. However, our analysis of the emission spectrum suggests the presence of titanium oxide (TiO) and an atmospheric thermal inversion.&#160;Meanwhile, our study of KELT-7 b uncovers a rich transmission spectrum which suggests the presence of water and H-. In contrast, the extracted emission spectrum does not contain strong absorption features and, although it is not consistent with a simple blackbody, it can be explained by a varying temperature-pressure profile, collision induced absorption (CIA) and H-.&#160; These finding bring new insights into the nature of this intriguing class of planets but more data is required to fully understand them and thus we will also present the anticipated results of further characterisation.

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The distance to M31 in the era of precision cosmology

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312021473 ◽

2012 ◽

Vol 8 (S289) ◽

pp. 235-235

Author(s):

David Valls-Gabaud

Keyword(s):

Large Scale ◽

Near Infrared ◽

Hubble Space Telescope ◽

Three Dimensional ◽

Eclipsing Binaries ◽

Wide Field ◽

Acoustic Oscillations ◽

Data Set ◽

Red Giant ◽

Precision Cosmology

AbstractWith the advent of precision cosmology, where distances out to redshifts z < 0.6 can be measured to 2% precision on the basis of baryon acoustic oscillations, it appears essential to establish an accurate calibration of the primary and secondary indicators of the cosmological distance ladder. Here we review recent attempts at anchoring M31 very accurately using three independent methods, and discuss in detail the systematics that affect each. Two double-lined eclipsing binaries yield a distance to M31 which is precise to 4%. New Bayesian methods have been applied to determine the tip of the red-giant branch, even in sparsely populated colour–magnitude diagrams, and provide unique insights in the context of a precise three-dimensional distribution of the satellites in the M31 system. Over 2500 Cepheids have been identified in large-scale multi-colour surveys of M31, the largest homogeneous data set thus far obtained for any galaxy. A subset of 68 with periods longer than 10 days have been observed with the Wide-Field Camera 3 on board the Hubble Space Telescope, yielding the tightest-ever near-infrared period–luminosity relation, with a mean distance error of 1%. Combined with other measurements, the distance to M31 is now measured with a precision of 3%. Forthcoming improvements, and their implications, are also discussed.

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New insight into the stellar mass function of Galactic globular clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa969 ◽

2020 ◽

Vol 494 (3) ◽

pp. 4226-4243 ◽

Cited By ~ 2

Author(s):

H Ebrahimi ◽

A Sollima ◽

H Haghi ◽

H Baumgardt ◽

M Hilker

Keyword(s):

Globular Clusters ◽

Initial Conditions ◽

Hubble Space Telescope ◽

Relaxation Times ◽

Mass Range ◽

Mass Function ◽

Wide Field ◽

Data Set ◽

Orbital Parameters ◽

Galactic Globular Clusters

ABSTRACT We present the results of the analysis of deep photometric data of 32 Galactic globular clusters. We analysed 69 parallel field images observed with the Wide Field Channel of the Advanced Camera for Surveys of the Hubble Space Telescope which complemented the already available photometry from the globular cluster treasury project covering the central regions of these clusters. This unprecedented data set has been used to calculate the relative fraction of stars at different masses (i.e. the present-day mass function) in these clusters by comparing the observed distribution of stars along the cluster main sequence and across the analysed field of view with the prediction of multimass dynamical models. For a subsample of 31 clusters, we were able to obtain also the half-mass radii, mass-to-light ratios, and the mass fraction of dark remnants using available radial velocity information. We found that the majority of globular clusters have single power-law mass functions F(m) ∝ mα with slopes α > −1 in the mass range 0.2 < m/M⊙ < 0.8. By exploring the correlations between the structural/dynamical and orbital parameters, we confirm the tight anticorrelation between the mass function slopes and the half-mass relaxation times already reported in previous works, and possible second-order dependence on the cluster metallicity. This might indicate the relative importance of both initial conditions and evolutionary effects on the present-day shape of the mass function.

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Radial variation of the stellar mass functions in the globular clusters M15 and M30: clues of a non-standard IMF?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2759 ◽

2020 ◽

Vol 499 (2) ◽

pp. 2390-2400

Author(s):

M Cadelano ◽

E Dalessandro ◽

J J Webb ◽

E Vesperini ◽

D Lattanzio ◽

...

Keyword(s):

Globular Clusters ◽

Hubble Space Telescope ◽

Dynamical Evolution ◽

Mass Function ◽

Initial Mass Function ◽

Radial Variation ◽

Wide Field ◽

Data Set ◽

Central Regions ◽

Mass Segregation

ABSTRACT We exploit a combination of high-resolution Hubble Space Telescope and wide-field ESO-VLT observations to study the slope of the global mass function (αG) and its radial variation (α(r)) in the two dense, massive and post core-collapse globular clusters M15 and M30. The available data set samples the clusters’ main sequence down to ∼0.2 M⊙ and the photometric completeness allows the study of the mass function between 0.40 M⊙ and 0.75 M⊙ from the central regions out to their tidal radii. We find that both clusters show a very similar variation in α(r) as a function of clustercentric distance. They both exhibit a very steep variation in α(r) in the central regions, which then attains almost constant values in the outskirts. Such a behaviour can be interpreted as the result of long-term dynamical evolution of the systems driven by mass-segregation and mass-loss processes. We compare these results with a set of direct N-body simulations and find that they are only able to reproduce the observed values of α(r) and αG at dynamical ages (t/trh) significantly larger than those derived from the observed properties of both clusters. We investigate possible physical mechanisms responsible for such a discrepancy and argue that both clusters might be born with a non-standard (flatter/bottom-lighter) initial mass function.

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An Algorithm for the Removal of Cosmic Ray Artifacts in Spectral Data Sets

Applied Spectroscopy ◽

10.1177/0003702819839098 ◽

2019 ◽

Vol 73 (8) ◽

pp. 893-901

Author(s):

Sinead J. Barton ◽

Bryan M. Hennelly

Keyword(s):

Cosmic Ray ◽

Data Sets ◽

Biological Cells ◽

Statistical Classification ◽

Signal To Noise ◽

Multivariate Statistical ◽

Data Set ◽

Artefact Removal ◽

Single Capture ◽

Acquisition Method

Cosmic ray artifacts may be present in all photo-electric readout systems. In spectroscopy, they present as random unidirectional sharp spikes that distort spectra and may have an affect on post-processing, possibly affecting the results of multivariate statistical classification. A number of methods have previously been proposed to remove cosmic ray artifacts from spectra but the goal of removing the artifacts while making no other change to the underlying spectrum is challenging. One of the most successful and commonly applied methods for the removal of comic ray artifacts involves the capture of two sequential spectra that are compared in order to identify spikes. The disadvantage of this approach is that at least two recordings are necessary, which may be problematic for dynamically changing spectra, and which can reduce the signal-to-noise (S/N) ratio when compared with a single recording of equivalent duration due to the inclusion of two instances of read noise. In this paper, a cosmic ray artefact removal algorithm is proposed that works in a similar way to the double acquisition method but requires only a single capture, so long as a data set of similar spectra is available. The method employs normalized covariance in order to identify a similar spectrum in the data set, from which a direct comparison reveals the presence of cosmic ray artifacts, which are then replaced with the corresponding values from the matching spectrum. The advantage of the proposed method over the double acquisition method is investigated in the context of the S/N ratio and is applied to various data sets of Raman spectra recorded from biological cells.

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Testing the evolution of correlations between supermassive black holes and their host galaxies using eight strongly lensed quasars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2992 ◽

2020 ◽

Vol 501 (1) ◽

pp. 269-280

Author(s):

Xuheng Ding ◽

Tommaso Treu ◽

Simon Birrer ◽

Adriano Agnello ◽

Dominique Sluse ◽

...

Keyword(s):

Black Holes ◽

Hubble Space Telescope ◽

High Redshift ◽

Galactic Nuclei ◽

Host Galaxy ◽

Wide Field ◽

Host Galaxies ◽

Field Surveys ◽

Instrumental Resolution ◽

The Moment

ABSTRACT One of the main challenges in using high-redshift active galactic nuclei (AGNs) to study the correlations between the mass of a supermassive black hole ($\mathcal {M}_{\rm BH}$) and the properties of its active host galaxy is instrumental resolution. Strong lensing magnification effectively increases instrumental resolution and thus helps to address this challenge. In this work, we study eight strongly lensed AGNs with deep Hubble Space Telescope imaging, using the lens modelling code lenstronomy to reconstruct the image of the source. Using the reconstructed brightness of the host galaxy, we infer the host galaxy stellar mass based on stellar population models. $\mathcal {M}_{\rm BH}$ are estimated from broad emission lines using standard methods. Our results are in good agreement with recent work based on non-lensed AGNs, demonstrating the potential of using strongly lensed AGNs to extend the study of the correlations to higher redshifts. At the moment, the sample size of lensed AGNs is small and thus they provide mostly a consistency check on systematic errors related to resolution for non-lensed AGNs. However, the number of known lensed AGNs is expected to increase dramatically in the next few years, through dedicated searches in ground- and space-based wide-field surveys, and they may become a key diagnostic of black holes and galaxy co-evolution.

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Galaxy spin direction distribution in HST and SDSS show similar large-scale asymmetry

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2020.46 ◽

2020 ◽

Vol 37 ◽

Author(s):

Lior Shamir

Keyword(s):

Large Scale ◽

Spiral Galaxies ◽

Hubble Space Telescope ◽

Gravitational Interaction ◽

Large Data ◽

Sloan Digital Sky Survey ◽

Data Sets ◽

Dipole Axis ◽

Data Set ◽

The Asymmetry

Abstract Several recent observations using large data sets of galaxies showed non-random distribution of the spin directions of spiral galaxies, even when the galaxies are too far from each other to have gravitational interaction. Here, a data set of $\sim8.7\cdot10^3$ spiral galaxies imaged by Hubble Space Telescope (HST) is used to test and profile a possible asymmetry between galaxy spin directions. The asymmetry between galaxies with opposite spin directions is compared to the asymmetry of galaxies from the Sloan Digital Sky Survey. The two data sets contain different galaxies at different redshift ranges, and each data set was annotated using a different annotation method. The results show that both data sets show a similar asymmetry in the COSMOS field, which is covered by both telescopes. Fitting the asymmetry of the galaxies to cosine dependence shows a dipole axis with probabilities of $\sim2.8\sigma$ and $\sim7.38\sigma$ in HST and SDSS, respectively. The most likely dipole axis identified in the HST galaxies is at $(\alpha=78^{\rm o},\delta=47^{\rm o})$ and is well within the $1\sigma$ error range compared to the location of the most likely dipole axis in the SDSS galaxies with $z>0.15$ , identified at $(\alpha=71^{\rm o},\delta=61^{\rm o})$ .

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The Low-redshift Intergalactic Medium

Publications of the Astronomical Society of Australia ◽

10.1071/as99095 ◽

1999 ◽

Vol 16 (1) ◽

pp. 95-99 ◽

Cited By ~ 11

Author(s):

J. Michael Shull ◽

Steven V. Penton ◽

John T. Stocke

Keyword(s):

Galaxy Formation ◽

Large Scale ◽

Intergalactic Medium ◽

Hubble Space Telescope ◽

Characteristic Size ◽

Baryon Density ◽

Frequency Space ◽

Physical Conditions ◽

Low Metallicity ◽

Set Up

AbstractThe low-redshift Lyα forest of absorption lines provides a probe of large-scale baryonic structures in the intergalactic medium, some of which may be remnants of physical conditions set up during the epoch of galaxy formation. We discuss our recent Hubble Space Telescope (HST) observations and interpretation of low-z Lyα clouds toward nearby Seyferts and QSOs, including their frequency, space density, estimated mass, association with galaxies, and contribution to Ωb. Our HST/GHRS detections of ∼ 70 Lyα absorbers with Nhi ≥ 1012·6 cm−2 along 11 sightlines covering pathlength Δ(cz) = 114,000 km s−1 show f (>Nhi) α Nhi−0·63±0·04 and a line frequency dN/dz = 200 ± 40 for Nhi > 1012·6 cm−2 (one every 1500 km s−1 of redshift). A group of strong absorbers toward PKS 2155–304 may be associated with gas (400–800) kpc from four large galaxies, with low metallicity (≤0·003 solar) and D/H ≤ 2 × 10−4. At low-z, we derive a metagalactic ionising radiation field from AGN of J0 = × 10−23 erg cm−2 s−1 Hz−1 sr−1 and a Lyα-forest baryon density Ωb =(0·008 ± 0·004)[J−23N14b100]½ for clouds of characteristic size b = (100 kpc)b100.

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Colonial Origins of Maoist Insurgency in India

Journal of Conflict Resolution ◽

10.1177/0022002717727818 ◽

2017 ◽

Vol 62 (10) ◽

pp. 2232-2274 ◽

Cited By ~ 6

Author(s):

Shivaji Mukherjee

Keyword(s):

Ethnic Inequality ◽

Long Term Effects ◽

Security Threat ◽

Data Set ◽

Internal Security ◽

New Instrument ◽

Maoist Insurgency ◽

Rule Set ◽

Set Up ◽

Indirect Rule

What are the long-term effects of colonial institutions on insurgency? My article shows the historical origins of insurgency by addressing the puzzle of why the persistent Maoist insurgency, considered to be India’s biggest internal security threat, affects some districts along the central eastern corridor of India but not others. Combining archival and interview data from fieldwork in Maoist zones with an original district-level quantitative data set, I demonstrate that different types of British colonial indirect rule set up the structural conditions of ethnic inequality and state weakness that facilitate emergence of Maoist control. I address the issue of selection bias, by developing a new instrument for the British choice of indirect rule through princely states, based on the exogenous effect of wars in Europe on British decisions in India. This article reconceptualizes colonial indirect rule and also presents new data on rebel control and precolonial rebellions.

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