arXiv subjects

M. Haas

Publications and source records attributed to M. Haas.

At least 19 recordsLinked to original sources

arXiv2026

Star formation quenching precedes morphological transformation in COSMOS-WEB's richest galaxy groups

We analyzed the 25 richest galaxy groups in COSMOS-Web at z = 0.18-3.65, identified via the AMICO algorithm. These groups contain 20-30 galaxies with high (>75%) membership probability. Our study reveals both passive-density and active-density relations: late-type galaxies (LTGs) prefer higher central overdensities than early-type galaxies (ETGs) across all groups, and many massive LTGs exhibit colors typical of quiescent galaxies. We identify red sequences (RS) in 5 groups, prominently established at z < 1, with early emergence in the RS locus up to z ~ 2.2. This suggests group environments represent a transitional phase where star formation quenching precedes morphological transformation, contrasting with the classical morphology-density relation in rich clusters. In the central regions (~33 arcsec / 100 kpc from centers), we identified 86 galaxies: 23 (~27%) ETGs and 63 (~73%) LTGs. High-mass galaxies (M_star > 10^10.5 M_sun) undergo rapid quenching over ~1 Gyr, becoming predominantly spheroidal ETGs. This indicates morphological transformation accelerates in massive systems during peak cosmic star formation. Intermediate-mass galaxies (10^9 < M_star/M_sun < 10^10.5) show mild quenching, while low-mass galaxies (M_star < 10^9 M_sun) remain largely star-forming; here, environmental processes suppress star formation without destroying disks, suggesting group quenching operates on longer timescales than mass quenching. Overall, mass-dependent quenching dominates the high-mass end, while environment shapes lower-mass systems. The HLAGN fraction for both groups and field increases with redshift, peaking at z ~ 2, with groups consistently showing higher fractions. We suggest AGN feedback partially drives rapid quenching in high-mass galaxies, while mergers may trigger AGN activity.

astro-ph.GA↗

arXiv2025

Emission-Line and Continuum Reverberation Mapping of the NLS1 Galaxy WPVS 48

WPVS 48 is a nearby narrow-line Seyfert 1 galaxy without previous analysis of the broad-line region (BLR) by means of optical spectroscopic reverberation mapping. By studying the continuum and emission line variability of WPVS 48, we aim to infer the BLR size as well as the mass of the central supermassive black hole (SMBH). We analyse data from a dedicated optical spectroscopic reverberation mapping campaign of WPVS 48 taken with the 10 m Southern African Large Telescope (SALT) at 24 epochs over a period of 7 months between December 2013 and June 2014. WPVS 48 shows variability throughout the campaign. We find a stratified BLR, where the variability amplitude of the integrated emission lines decreases with distance to the ionizing continuum source. Specifically, the variable emission of H$\alpha$, H$\beta$, H$\gamma$, He I $\lambda5876$ originates at distances of $16.0^{+4.0}_{-2.0}$, $15.0^{+4.5}_{-1.9}$, $12.5^{+3.5}_{-2.5}$ and $14.0^{+2.5}_{-2.1}$ light-days, respectively, to the optical continuum at 5100 A. The He II $\lambda 4686$ lag is $\lesssim 5$ days. Based on the high S/N spectra, we identify variable emission of N III $\lambda4640$ and C IV $\lambda4658$ in the line complex with He II $\lambda 4686$. We derive interband continuum delays increasing with wavelength up to $\sim 8$ days. These delays are consistent with an additional diffuse continuum originating at the same distance as the variable Balmer emission. We derive a central black hole mass of $(1.3_{-0.6}^{+1.1})\times10^7M_{\odot}$ based on the integrated line-widths and distances of the BLR and discuss corrections for the inclination angle. This gives an Eddington ratio $L/L_{\text{Edd}}\approx 0.39$ without correction for inclination.

astro-ph.GA↗

arXiv2025

Double-peaked Ca II traces a relativistic broad-line region disk in NGC 4593

Double-peaked emission lines are observed in a small percentage of active galactic nuclei (AGN). These lines allow the determination of properties of the line-emitting region, known as the broad-line region (BLR). We investigated the structure and kinematics of the BLR in the Seyfert galaxy NGC 4593 through an analysis of the NIR line blend of Ca II 8498, 8542, 8662, and O I 8446 observed in a 2019 VLT/MUSE spectrum. We performed a detailed decomposition of the near-infrared Ca II triplet and O I 8446 blend, extracting clean profiles of Ca II 8498, 8542, 8662 and O I 8446. We then fitted Ca 8662 with a relativistic elliptical line-emitting disk model. The line profiles are double-peaked with a FWHM of approx. 3700 km/s and exhibit a redward asymmetry with a red-to-blue peak ratio of 4:3. The Ca II triplet lines have an intensity ratio of 1:1:1 and show no evidence of a central narrow or intermediate-width component. The profiles of Ca II and O I are remarkably similar, suggesting a common region of origin. Given the 1:1:1 ratio of the Ca II triplet, this region is likely a high-density emission zone, and the Ca II 8662 profile is well described by a mildly eccentric, low-inclination relativistic disk with minimal internal turbulence. The profile represents one of the clearest kinematic signatures of a relativistic disk observed in BLR emission lines to date. The double-peaked profiles of the NIR Ca II triplet and O I 8446 in NGC 4593 represent the first detection of double-peaked Ca II and O I 8446 in a non-transient AGN spectrum. The minimal intrinsic turbulence (the lowest value reported for an AGN emission line to date) and absence of narrow or intermediate-width components in Ca II 8662 make it a powerful diagnostic tool of BLR structure and kinematics. Further investigations of the profiles of Ca II and O I in other AGN are recommended to better constrain BLR properties.

astro-ph.GA↗

arXiv2024

The transient event in NGC 1566 from 2017 to 2019 -- I. An eccentric accretion disk and a turbulent, disk-dominated broad-line region unveiled by double-peaked Ca II and O I lines

NGC 1566 is known for exhibiting recurrent outbursts, which are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported to be accompanied by a change in Seyfert classification from Seyfert 1.8 to Seyfert 1.2. We analyze data from an optical spectroscopic variability campaign of NGC 1566 taken with the 9.2m SALT between July 2018 and October 2019 and supplement our data set with optical to near-infrared spectroscopic archival data taken by VLT/MUSE in September 2015 and October 2017. We observe the emergence and fading of a strong power-law-like blue continuum as well as strong variations in the Balmer, HeI, HeII lines and the coronal lines [FeVII], [FeX] and [FeXI]. Moreover, we detect broad double-peaked emission line profiles of OI 8446 and the CaII 8498,8542,8662 triplet. This is the first time that genuine double-peaked OI 8446 and CaII 8498,8542,8662 emission in AGN is reported in the literature. All broad lines show a clear redward asymmetry with respect to their central wavelength and we find indications for a significant blueward drift of the total line profiles during the transient event. We show that the double-peaked emission line profiles are well approximated by emission from a low-inclination, relativistic eccentric accretion disk, and that single-peaked profiles can be obtained by broadening due to scale-height dependent turbulence. Small-scale features in the OI and CaII lines suggest the presence of inhomogeneities in the broad-line region. We conclude that the broad-line region in NGC 1566 is dominated by the kinematics of a relativistic eccentric accretion disk. The broad-line region can be modeled to be vertically stratified with respect to scale-height turbulence. The observed blueward drift might be attributed to a low-optical-depth wind launched during the transient event.

astro-ph.HE↗

arXiv2023

Light and colour of cirrus, translucent and opaque dust in the high-latitude area of LDN 1642

We have performed a 5-colour surface photometric study of the high-galactic-latitude area of dark nebula LDN 1642. Scattered light properties are presented of diffuse, translucent and opaque dust over the range of 3500 -- 5500 A. Far infrared absolute photometry at 200 um improves the precision of and provides a zero point to the extinction. The intensity of the scattered light depends on dust column density in a characteristic way: for optically thin dust the intensity first increases linearly, then turns to a saturation value; at still larger extinctions the intensity turns down to a slow decrease. The $A_V$ value of the saturated intensity maximum shifts in a systematic way, from $A_V\approx$ 1.5 mag at 3500 A, to $\sim 3$ mag at 5500 A. The intensity curves offer a straight-forward explanation for the behaviour of the scattered-light colours. At the intensity peak the colour agrees with the integrated starlight colour, while it is bluer at the low- and redder at the high-column-density side of the peak, respectively. These colour changes are a direct consequence of the wavelength dependence of the extinction. We have compared the colours of the LDN 1642 area with other relevant observational studies: high-latitude diffuse/translucent clouds, wide-field cirrus dust; and externally illuminated AGB-star envelopes. For extragalactic low-surface-brightness sources cirrus is an unwanted foreground contaminant. Our results for cirrus colours can help to distinguish cases where a diffuse plume or stream, apparently associated with a galaxy or a group or cluster, is more likely a local cirrus structure. Keywords: ISM: dust, extinction -- ISM: clouds, individual LDN 1642 -- Galaxy: solar neighbourhood -- Astronomical instruments, methods and techniques: methods -- Physical data and processes: scattering

astro-ph.GA↗

arXiv2023

Wavelength-resolved reverberation mapping of intermediate redshift quasars HE 0413-4031 and HE 0435-4312: Dissecting Mg II, optical Fe II, and UV Fe II emission regions

We present the wavelength-resolved reverberation mapping (RM) of combined MgII and UV FeII broad-line emissions for two intermediate redshifts (z$\sim$1), luminous quasars - HE 0413-4031 and HE 0435-4312, monitored by the SALT and 1-m class telescopes between 2012-2022. Through this technique, we aim to disentangle the Mg II and FeII emission regions and to build a radius-luminosity relation for UV FeII emission, which has so far remained unconstrained. Several methodologies have been applied to constrain the time delays for total MgII and FeII emissions. In addition, this technique is performed to quantify the inflow or outflow of broad-line region gas around the supermassive black hole and to disentangle the emission/emitting regions from lines produced in proximity to each other. The mean total FeII time delay is nearly equal to the mean total Mg II time delay for HE 0435-4312 suggesting a co-spatiality of their emissions. However, in HE 0413-4031, the mean FeII time delay is found to be longer than the mean MgII time delay, suggesting that FeII is produced at longer distances from the black hole. The UV Fe II R-L relation is updated with these two quasars and compared with the optical FeII relation, which suggests that the optical FeII region is located further than the UV FeII by a factor of 1.7-1.9 i.e. $R_{\rm FeII-opt}\sim(1.7-1.9)R_{\rm FeII-UV}$. We detected a weak pattern in the time delay vs. wavelength relation, suggesting that the MgII broad-line originates a bit closer to the SMBH than the UV FeII, however, the difference is not very significant. Comparison of MgII, UV, and optical FeII R-L relations suggests that the difference may be larger for lower-luminosity sources, possibly with the MgII emission originating further from the SMBH. In the future, more RM data will be acquired to put better constraints on these trends, in particular the UV FeII R-L relation.

astro-ph.GA↗

arXiv2022

Wavelength-resolved Reverberation Mapping of quasar CTSC30.10: Dissecting MgII and FeII emission regions

We present the results of the reverberation monitoring aimed at MgII broad line and FeII pseudocontinuum for the luminous quasar CTS C30.10 (z = 0.90052) with the Southern African Large Telescope covering the years 2012-2021. We aimed at disentangling the MgII and UV FeII variability and the first measurement of UV FeII time delay for a distant quasar. We used several methods for time-delay measurements and determined both FeII and MgII time delays as well as performed a wavelength-resolved time delay study for a combination of MgII and FeII in the 2700 - 2900 \AA restframe wavelength range. We obtain the time delay for MgII of $275.5^{+12.4}_{-19.5}$ days in the rest frame, while for FeII we have two possible solutions of $270.0^{+13.8}_{-25.3}$ days and $180.3^{+26.6}_{-30.0}$ in the rest frame. Combining this result with the old measurement of FeII UV time delay for NGC 5548 we discuss for the first time the radius-luminosity relation for UV FeII with the slope consistent with $0.5$ within uncertainties. Since FeII time delay has a shorter time-delay component but lines are narrower than MgII, we propose that the line delay measurement is biased towards the BLR part facing the observer, with the bulk of the Fe II emission may arise from the more distant BLR region, one that is shielded from the observer.

astro-ph.GA↗

arXiv2018

The broad line region and dust torus structure of the Seyfert 1 WPVS48

Optical and near-mid-infrared reverberation mapping data obtained at Universit\"{a}tssternwarte Bochum in Chile and with the Spitzer Space Telescope allow us to explore the geometry of both the H$\alpha$ BLR and the dust torus for the nearby Seyfert 1 galaxy WPVS\,48. On average, the H$\alpha$ variations lag the blue AGN continuum by about 18 days, while the dust emission variations lag by 70 days in the J+K and by 90 days in the L+M bands. The IR echoes are sharp, while the H$\alpha$ echo is smeared. This together favours a bowl-shaped toroidal geometry where the dust sublimation radius is defined by a bowl surface, which is virtually aligned with a single iso-delay surface, thus leading to the sharp IR echoes. The BLR clouds, however, are located inside the bowl and spread over a range of iso-delay surfaces, leading to a smeared echo.

astro-ph.GA↗

arXiv2018

ALMA resolves the stellar birth explosion in distant quasar 3C298

Galaxies are believed to experience star formation and black hole driven nuclear activity symbiotically. The symbiosis may be more extreme in the distant universe, as far-infrared photometry with the Herschel Space Observatory has found many cases of ultra-luminous cool dust emission in z>1 radio galaxies and quasars, which could have its origin in the central black hole activity, or in extreme starbursts. We here present strong evidence for an extreme circumnuclear starburst in the z=1.439 quasar 3C298. Our unparalleled 0.18 arcsecond resolution ALMA image at rest-frame 410micrometer wavelength shows that the ~40K dust in its host galaxy resides in an asymmetric circumnuclear structure. The morphology of this structure implies a starburst origin and a symbiotic physical relation with the AGN driven radio source. The symbiosis is likely to be a general property of distant massive galaxies.

astro-ph.GA↗

arXiv2018

Photodynamical analysis of the triply eclipsing hierarchical triple system EPIC 249432662

Using Campaign 15 data from the K2 mission, we have discovered a triply-eclipsing triple star system: EPIC 249432662. The inner eclipsing binary system has a period of 8.23 days, with shallow $\sim$3% eclipses. During the entire 80-day campaign, there is also a single eclipse event of a third-body in the system that reaches a depth of nearly 50% and has a total duration of 1.7 days, longer than for any previously known third-body eclipse involving unevolved stars. The binary eclipses exhibit clear eclipse timing variations. A combination of photodynamical modeling of the lightcurve, as well as seven follow-up radial velocity measurements, has led to a prediction of the subsequent eclipses of the third star with a period of 188 days. A campaign of follow-up ground-based photometry was able to capture the subsequent pair of third-body events as well as two further 8-day eclipses. A combined photo-spectro-dynamical analysis then leads to the determination of many of the system parameters. The 8-day binary consists of a pair of M stars, while most of the system light is from a K star around which the pair of M stars orbits.

astro-ph.SR↗

arXiv2018

Broad-line region structure and line profile variations in the changing look AGN HE1136-2304

A strong X-ray outburst was detected in HE1136-2304 in 2014. Accompanying optical spectra revealed that the spectral type has changed from a nearly Seyfert 2 type (1.95), classified by spectra taken 10 and 20 years ago, to a Seyfert 1.5 in our most recent observations. We seek to investigate a detailed spectroscopic campaign on the spectroscopic properties and spectral variability behavior of this changing look AGN and compare this to other variable Seyfert galaxies. We carried out a detailed spectroscopic variability campaign of HE1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014 December and 2015 July. The broad-line region (BLR) of HE1136-2304 is stratified with respect to the distance of the line-emitting regions. The integrated emission line intensities of Halpha, Hbeta, HeI 5876, and HeII 4686 originate at distances of 15.0 (+4.2,-3.8), 7.5 (+4.6,-5.7), 7.3 (+2.8,-4.4), and 3.0 (+5.3,-3.7) light days with respect to the optical continuum at 4570AA. The variability amplitudes of the integrated emission lines are a function of distance to the ionizing continuum source as well. We derived a central black hole mass of 3.8 (+-3.1) 10exp(7) M_solar based on the line widths and distances of the BLR. The outer line wings of all BLR lines respond much faster to continuum variations indicating a Keplerian disk component for the BLR. The response in the outer wings is about two light days shorter than the response of the adjacent continuum flux with respect to the ionizing continuum flux. The vertical BLR structure in HE1136-2304 confirms a general trend that the emission lines of narrow line active galactic nuclei (AGNs) originate at larger distances from the midplane in comparison to AGNs showing broader emission lines. Otherwise, the variability behavior of this changing look AGN is similar to that of other AGN.

astro-ph.GA↗

arXiv2018

Optical and UV surface brightness of translucent dark nebulae: Dust albedo, radiation field and fluorescence emission by H2

Photometry of the nebulae LDN1780, LDN1642 and LBN406 is used to derive scattering properties of dust and to investigate the presence of UV fluorescence emission by molecular hydrogen and the extended red emission (ERE). We used multi-wavelength optical photometry and imaging at ground-based telescopes and archival imaging and spectroscopic UV data from the spaceborn GALEX and SPEAR/FIMS instruments. We used Monte Carlo RT and both observational data and synthetic models for the ISRF in the solar neighbourhood. The line-of-sight extinctions through the clouds have been determined using near infrared excesses of background stars and the 200/250um far infrared emission by dust measured using the ISO and Herschel space observatories. The optical surface brightness of the target clouds can be explained in terms of scattered light. The dust albedo ranges from 0.58 at 3500A to 0.72 at 7500A. The SED of LDN1780 is explained in terms of optical depth and background scattered light effects instead of ERE. The FUV surface brightness of LDN 1780 cannot be explained by scattered light only. In LDN1780 H2 fluorescent emission in the wavelength range 1400A-1700A has been detected and analysed. Our albedo values agree with the predictions of the dust model of Weingartner and Draine and with the THEMIS CMM model for evolved core-mantle grains. The H2 fluorescent emission in LDN1780 shows a pronounced dichotomy with a preference for its southern side where enhanced illumination impinges from the Sco OB2 association and the O star zeta Oph. A good correlation is found between the H2 fluorescence and a previously mapped 21-cm excess emission. The H2 fluorescence emission in LDN1780 has been modelled using a PDR code; the resulting values for H2 column density and the total gas density are consistent with the estimates derived from CO observations and optical extinction along the line of sight.

astro-ph.GA↗

arXiv2018

Long-term optical, UV, and X-ray continuum variations in the changing-look AGN HE 1136-2304

A strong outburst in the X-ray continuum and a change of its Seyfert spectral type was detected in HE 1136-2304 in 2014. The spectral type changed from nearly Seyfert 2 type (1.95) to Seyfert 1.5 type in comparison to previous observations taken ten to twenty years before. In a subsequent variability campaign we wanted to investigate whether this outburst was a single event or whether the variability pattern following the outburst was similar to those seen in other variable Seyfert galaxies. In addition to a SALT spectral variability campaign, we carried out optical continuum as well as X-ray and UV (Swift) monitoring studies from 2014 to 2017. HE 1136-2304 strongly varied on timescales of days to months from 2014 to 2017. No systematic trends were found in the variability behavior following the outburst in 2014. A general decrease in flux would have been expected for a tidal disruption event. This could not be confirmed. More likely the flux variations are connected to irregular fluctuations in the accretion rate. The strongest variability amplitudes have been found in the X-ray regime: HE 1136-2304 varied by a factor of eight during 2015. The amplitudes of the continuum variability (from the UV to the optical) systematically decreased with wavelength following a power law F_var = a ${\times}$ {\lambda}^-c with c = 0.84. There is a trend that the B-band continuum shows a delay of three light days with respect to the variable X-ray flux. The Seyfert type 1.5 did not change despite the strong continuum variations for the period between 2014 and 2017.

astro-ph.GA↗

arXiv2017

Galaxy overdensities around 3C radio galaxies and quasars at $1<z<2.5$ revealed by Spitzer $3.6/4.5\mu$m and Pan-STARRS

Luminous radio sources are thought to lie in galaxy clusters or proto-clusters. The complete sample of 64 high-redshift 3C sources at $1 3\sigma$) within 30" ($\sim$250 kpc) projected distance from the radio source compared to the surrounding galaxy densities measured in the $50''-120''$ annulus. The Pan-STARRS/IRAC cut reveals higher average overdensities than the IRAC1/2 cut and also a decline of overdensities at $z>1.4$. To infer the nature of the cluster members, we rerun the analysis using a stronger IRAC1/2 cut $[3.6] - [4.5] < -0.1$ which removes $1<z<1.4$ passive ellipticals but not star-forming galaxies. For the strong cut, the overdensities, on average, completely disappear at $1<z<1.4$. We therefore suggest that the 4.5$\mu$m detected cluster member galaxies are mainly passive ellipticals.

astro-ph.GA↗

arXiv2017

Brightness variations of the FUor-type eruptive star V346 Nor

Decades after the beginning of its FU Orionis-type outburst, V346 Nor unexpectedly underwent a fading event of $\Delta{}K$ = 4.6 mag around 2010. We obtained near-infrared observations and re-analysed data from the VISTA/VVV survey to outline the brightness evolution. In our VLT/NaCO images, we discovered a halo of scattered light around V346~Nor with a size of about 0.04 arcsec (30 au). The VISTA data outlined a well-defined minimum in the light curve at late 2010/early 2011, and tentatively revealed a small-amplitude periodic modulation of 58 days. Our latest data points from 2016 demonstrate that the source is still brightening but has not reached the 2008 level yet. We used a simple accretion disk model with varying accretion rate and line-of-sight extinction to reproduce the observed near-infrared magnitudes and colors. We found that before 2008, the flux changes of V346 Nor were caused by a correlated change of extinction and accretion rate, while the minimum around 2010 was mostly due to decreasing accretion. The source reached a maximal accretion rate of ${\approx}10^{-4} M_{\odot}$ yr$^{-1}$ in 1992. A combination of accretion and extinction changes was already invoked in the literature to interpret the flux variations of certain embedded young eruptive stars.

astro-ph.SR↗

arXiv2016

The bimodal initial mass function in the Orion Nebula Cloud

Due to its youth, proximity and richness the Orion Nebula Cloud (ONC) is an ideal testbed to obtain a comprehensive view on the Initial Mass Function (IMF) down to the planetary mass regime. Using the HAWK-I camera at the VLT, we have obtained an unprecedented deep and wide near-infrared JHK mosaic of the ONC (90% completeness at K~19.0mag, 22'x28). Applying the most recent isochrones and accounting for the contamination of background stars and galaxies, we find that ONC's IMF is bimodal with distinct peaks at about 0.25 and 0.025 M_sun separated by a pronounced dip at the hydrogen burning limit (0.08 M_sun), with a depth of about a factor 2-3 below the log-normal distribution. Apart from ~920 low-mass stars (M < 1.4 M_sun) the IMF contains ~760 brown dwarf (BD) candidates and ~160 isolated planetary mass object (IPMO) candidates with M > 0.005 M_sun, hence about ten times more substellar candidates than known before. The substellar IMF peak at 0.025 M_sun could be caused by BDs and IPMOs which have been ejected from multiple systems during the early star-formation process or from circumstellar disks.

astro-ph.GA↗

arXiv2015

Light curves of the latest FUor: Indication of a close binary

We monitored the recent FUor 2MASS J06593158-0405277 (V960 Mon) since November 2009 at various observatories and multiple wavelengths. After the outburst by nearly 2.9 mag in $r$ around September 2014 the brightness gently fades until April 2015 by nearly 1 mag in $U$ and 0.5 mag in $z$. Thereafter the brightness at $λ>5000 Å$ was constant until June 2015 while the shortest wavelengths ($U, B$) indicate a new rise, similar to that seen for the FUor V2493 Cyg (HBC722). Our near-infrared (NIR) monitoring between December 2014 and April 2015 shows a smaller outburst amplitude ($\sim$2 mag) and a smaller (0.2 $-$ 0.3 mag) post-outburst brightness decline. Optical and NIR color-magnitude diagrams indicate that the brightness decline is caused by growing extinction. The post-outburst light curves are modulated by an oscillating color-neutral pattern with a period of about 17 days and an amplitude declining from $\sim$0.08 mag in October 2014 to $\sim$0.04 mag in May 2015. The properties of the oscillating pattern lead us to suggest the presence of a close binary with eccentric orbit.

astro-ph.SR↗

arXiv2015

Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP-40 and WASP-21 systems

As part of our ongoing effort to investigate transit timing variations (TTVs) of known exoplanets, we monitored transits of the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All of them are suspected to show TTVs due to the known properties of their host systems based on the respective discovery papers. During the past three years 46 transit observations were carried out, mostly using telescopes of the Young Exoplanet Transit Initiative. The analyses are used to refine the systems orbital parameters. In all cases we found no hints for significant TTVs, or changes in the system parameters inclination, fractional stellar radius and planet to star radius ratio. However, comparing our results with those available in the literature shows that we can confirm the already published values.

astro-ph.EP↗