Showing papers by "Varoujan Gorjian published in 2021"
Dartmouth College1, University of North Carolina at Chapel Hill2, University of Texas at Austin3, University of Tokyo4, University of Wisconsin-Madison5, American Museum of Natural History6, Cadi Ayyad University7, Smithsonian Institution8, University of Kansas9, University of Arizona10, American Association of Variable Star Observers11, Massachusetts Institute of Technology12, Western Connecticut State University13, University of New Mexico14, Swarthmore College15, George Mason University16, Keele University17, University of Toronto18, Université de Montréal19, NASA Exoplanet Science Institute20, Jet Propulsion Laboratory21, University of California, Riverside22, Max Planck Society23, California Institute of Technology24, Ames Research Center25, Goddard Space Flight Center26, Princeton University27
TL;DR: In this article, the authors presented the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424), a member of the 120-Myr-old Pisces-Eridanus stream (Psc--Eri).
Abstract: Young exoplanets can offer insight into the evolution of planetary atmospheres, compositions, and architectures. We present the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424). TOI 451 is a member of the 120-Myr-old Pisces--Eridanus stream (Psc--Eri). We confirm membership in the stream with its kinematics, its lithium abundance, and the rotation and UV excesses of both TOI 451 and its wide binary companion, TOI 451 B (itself likely an M dwarf binary). We identified three candidate planets transiting in the TESS data and followed up the signals with photometry from Spitzer and ground-based telescopes. The system comprises three validated planets at periods of 1.9, 9.2 and 16 days, with radii of 1.9, 3.1, and 4.1 Earth radii, respectively. The host star is near-solar mass with V=11.0 and H=9.3 and displays an infrared excess indicative of a debris disk. The planets offer excellent prospects for transmission spectroscopy with HST and JWST, providing the opportunity to study planetary atmospheres that may still be in the process of evolving.
31 citations
Massachusetts Institute of Technology1, Space Telescope Science Institute2, Wayne State University3, Virginia Tech4, University of California, Irvine5, University of Wyoming6, Spectral Sciences Incorporated7, University of St Andrews8, Chinese Academy of Sciences9, Netherlands Institute for Space Research10, Leiden University11, Durham University12, Spanish National Research Council13, Georgia State University14, University of California, Berkeley15, University of Haifa16, INAF17, University of Padua18, University of Kentucky19, Herzberg Institute of Astrophysics20, Tel Aviv University21, University of Leicester22, National Autonomous University of Mexico23, Jet Propulsion Laboratory24, University of Arizona25, York University26, Peking University27, University of Belgrade28, University of Hamburg29, Brigham Young University30, Ohio State University31, Western Michigan University32, Academy of Sciences of the Czech Republic33, University of Southampton34, University of Nevada, Las Vegas35, Universidade Federal do Rio Grande do Sul36, University of California, Los Angeles37, University of Copenhagen38, Shanghai Jiao Tong University39
TL;DR: In this paper, the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817 were presented, showing that the X-ray spectrum is highly absorbed, and there are new blueshifted,broad and narrow UV absorption lines, which suggest that a dust-free, ionized, cobalt-obscurer located at the inner broad line region partially covers the central source.
Abstract: We present the first results from the ongoing, intensive, multi-wavelength
monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN
was, in part, selected for its historically unobscured nature, we discovered
that the X-ray spectrum is highly absorbed, and there are new blueshifted,
broad and narrow UV absorption lines, which suggest that a dust-free, ionized
obscurer located at the inner broad line region partially covers the central
source. Despite the obscuration, we measure UV and optical continuum
reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin
accretion disk, and measure reverberation lags associated with the optical
broad line region, as expected. However, in the first 55 days of the campaign,
when the obscuration was becoming most extreme, we observe a de-coupling of the
UV continuum and the UV broad emission line variability. The correlation
recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured
state. The short CIV and Ly alpha lags suggest that the accretion disk extends
beyond the UV broad line region.
30 citations
Université de Montréal1, California Institute of Technology2, McGill University3, York University4, American Museum of Natural History5, Goddard Space Flight Center6, Max Planck Society7, University of Ottawa8, University of Kansas9, NASA Exoplanet Science Institute10, University of California, Los Angeles11, University of Tokyo12, University of California, Berkeley13, University of Hawaii14
TL;DR: In this article, the authors presented the results of an extensive 4-year Keck/HIRES radial-velocity (RV) follow-up program of the WASP-107 system and provided a detailed study of the physics governing the accretion of its gas envelope.
Abstract: With a mass in the Neptune regime and a radius of Jupiter, WASP-107b presents a challenge to planet formation theories. Meanwhile, the planet's low surface gravity and the star's brightness also make it one of the most favorable targets for atmospheric characterization. Here, we present the results of an extensive 4-year Keck/HIRES radial-velocity (RV) follow-up program of the WASP-107 system and provide a detailed study of the physics governing the accretion of its gas envelope. We reveal that WASP-107b's mass is only 1.8 Neptune masses ($M_b = 30.5 \pm 1.7$ $M_\oplus$). The resulting extraordinarily low density suggests that WASP-107b has a H/He envelope mass fraction of $> 85$% unless it is substantially inflated. The corresponding core mass of $<4.6$ $M_\oplus$ at 3$\sigma$ is significantly lower than what is traditionally assumed to be necessary to trigger massive gas envelope accretion. We demonstrate that this large gas-to-core mass ratio most plausibly results from the onset of accretion at $\gtrsim 1$ AU onto a low-opacity, dust-free atmosphere and subsequent migration to the present-day $a_b = 0.0566 \pm 0.0017$ AU. Beyond WASP-107b, we also detect a second more massive planet ($M_c \sin i = 0.36 \pm 0.04$ $M_{J}$) on a wide eccentric orbit ($e_c = 0.28 \pm 0.07$) which may have influenced the orbital migration and spin-orbit misalignment of WASP-107b. Overall, our new RV observations and envelope accretion modeling provide crucial insights into the intriguing nature of WASP-107b and the system's formation history. Looking ahead, WASP-107b will be a keystone planet to understand the physics of gas envelope accretion.
23 citations
Spanish National Research Council1, Catholic University of the Most Holy Conception2, University of Grenoble3, University of Kansas4, University of Tokyo5, Vanderbilt University6, Chalmers University of Technology7, Smithsonian Institution8, Ames Research Center9, University of California, Riverside10, California Institute of Technology11, Université de Montréal12, University of New Mexico13, University of Geneva14, University of California, Santa Cruz15, Goddard Space Flight Center16, George Mason University17, Swarthmore College18, University of Liège19, National Scientific and Technical Research Council20, European Southern Observatory21, University of Porto22, Massachusetts Institute of Technology23, Space Telescope Science Institute24, Princeton University25
TL;DR: In this article, the authors used TESS, Spitzer, ground-based light curves, and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b.
Abstract: Context. The NASA mission TESS is currently doing an all-sky survey from space to detect transiting planets around bright stars. As part of the validation process, the most promising planet candidates need to be confirmed and characterized using follow-up observations. Aims. In this article, our aim is to confirm the planetary nature of the transiting planet candidate TOI-674b using spectroscopic and photometric observations. Methods. We use TESS, Spitzer, ground-based light curves, and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b. We perform a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. Results. We confirm and characterize TOI-674b, a low-density super-Neptune transiting a nearby M dwarf. The host star (TIC 158588995, V = 14.2 mag, J = 10.3 mag) is characterized by its M2V spectral type with M = 0.420 ± 0.010 M , R = 0.420 ± 0.013 R , and Teff = 3514 ± 57 K; it is located at a distance d = 46.16 ± 0.03 pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of 1.977143 ± 3 × 10-6 days, a planetary radius of 5.25 ± 0.17 R , and a mass of 23.6 ± 3.3 M implying a mean density of ρp =0.91 ± 0.15 g cm-3. A non-circular orbit model fit delivers similar planetary mass and radius values within the uncertainties. Given the measured planetary radius and mass, TOI-674b is one of the largest and most massive super-Neptune class planets discovered around an M-type star to date. It is found in the Neptunian desert, and is a promising candidate for atmospheric characterization using the James Webb Space Telescope.
20 citations
Spanish National Research Council1, Catholic University of the Most Holy Conception2, University of Grenoble3, University of Kansas4, University of Tokyo5, Vanderbilt University6, Chalmers University of Technology7, Smithsonian Institution8, Ames Research Center9, University of California, Riverside10, California Institute of Technology11, Université de Montréal12, University of New Mexico13, University of Geneva14, University of California, Santa Cruz15, Goddard Space Flight Center16, George Mason University17, Swarthmore College18, University of Liège19, National Scientific and Technical Research Council20, European Southern Observatory21, University of Porto22, Massachusetts Institute of Technology23, Space Telescope Science Institute24, Princeton University25
TL;DR: In this article, the authors used TESS, Spitzer, ground-based light curves and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b.
Abstract: We use TESS, Spitzer, ground-based light curves and HARPS spectrograph radial velocity measurements to establish the physical properties of the transiting exoplanet candidate TOI-674b. We perform a joint fit of the light curves and radial velocity time series to measure the mass, radius, and orbital parameters of the candidate. We confirm and characterize TOI-674b, a low-density super-Neptune transiting a nearby M dwarf. The host star (TIC 158588995, $V = 14.2$ mag, $J = 10.3$ mag) is characterized by its M2V spectral type with $\mathrm{M}_\star=0.420\pm 0.010$ M$_\odot$, $\mathrm{R}_\star = 0.420\pm 0.013$ R$_\odot$, and $\mathrm{T}_{\mathrm{eff}} = 3514\pm 57$ K, and is located at a distance $d=46.16 \pm 0.03$ pc. Combining the available transit light curves plus radial velocity measurements and jointly fitting a circular orbit model, we find an orbital period of $1.977143 \pm 3\times 10^{-6}$ days, a planetary radius of $5.25 \pm 0.17$ $\mathrm{R}_\oplus$, and a mass of $23.6 \pm 3.3$ $\mathrm{M}_\oplus$ implying a mean density of $\rho_\mathrm{p} = 0.91 \pm 0.15$ [g cm$^{-3}$]. A non-circular orbit model fit delivers similar planetary mass and radius values within the uncertainties. Given the measured planetary radius and mass, TOI-674b is one of the largest and most massive super-Neptune class planets discovered around an M type star to date. It is also a resident of the so-called Neptunian desert and a promising candidate for atmospheric characterisation using the James Webb Space Telescope.
17 citations
Dartmouth College1, University of North Carolina at Chapel Hill2, University of Texas at Austin3, University of Tokyo4, University of Wisconsin-Madison5, American Museum of Natural History6, Cadi Ayyad University7, Smithsonian Institution8, University of Kansas9, University of Arizona10, American Association of Variable Star Observers11, Massachusetts Institute of Technology12, Western Connecticut State University13, University of New Mexico14, Swarthmore College15, George Mason University16, Keele University17, University of Toronto18, Université de Montréal19, NASA Exoplanet Science Institute20, Jet Propulsion Laboratory21, University of California, Riverside22, Max Planck Society23, California Institute of Technology24, Ames Research Center25, Goddard Space Flight Center26, Princeton University27
TL;DR: In this article, the authors presented the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424), a member of the 120-Myr-old Pisces-Eridanus stream (Psc--Eri).
Abstract: Young exoplanets can offer insight into the evolution of planetary atmospheres, compositions, and architectures. We present the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424). TOI 451 is a member of the 120-Myr-old Pisces--Eridanus stream (Psc--Eri). We confirm membership in the stream with its kinematics, its lithium abundance, and the rotation and UV excesses of both TOI 451 and its wide binary companion, TOI 451 B (itself likely an M dwarf binary). We identified three candidate planets transiting in the TESS data and followed up the signals with photometry from Spitzer and ground-based telescopes. The system comprises three validated planets at periods of 1.9, 9.2 and 16 days, with radii of 1.9, 3.1, and 4.1 Earth radii, respectively. The host star is near-solar mass with V=11.0 and H=9.3 and displays an infrared excess indicative of a debris disk. The planets offer excellent prospects for transmission spectroscopy with HST and JWST, providing the opportunity to study planetary atmospheres that may still be in the process of evolving.
16 citations
TL;DR: The K2-138 system with the most currently known planets was verified in this paper, where the authors verified the sixth planet's orbital period of $41.966 ± 0.006$ days and measure a radius of $3.44+0.32−0.31.
Abstract: $K2$ greatly extended $Kepler$'s ability to find new planets, but it was typically limited to identifying transiting planets with orbital periods below 40 days. While analyzing $K2$ data through the Exoplanet Explorers project, citizen scientists helped discover one super-Earth and four sub-Neptune sized planets in the relatively bright ($V=12.21$, $K=10.3$) K2-138 system, all which orbit near 3:2 mean motion resonances. The $K2$ light curve showed two additional transit events consistent with a sixth planet. Using $Spitzer$ photometry, we validate the sixth planet's orbital period of $41.966\pm0.006$ days and measure a radius of $3.44^{+0.32}_{-0.31}\,R_{\oplus}$, solidifying K2-138 as the $K2$ system with the most currently known planets. There is a sizeable gap between the outer two planets, since the fifth planet in the system, K2-138 f, orbits at 12.76 days. We explore the possibility of additional non-transiting planets in the gap between f and g. Due to the relative brightness of the K2-138 host star, and the near resonance of the inner planets, K2-138 could be a key benchmark system for both radial velocity and transit timing variation mass measurements, and indeed radial velocity masses for the inner four planets have already been obtained. With its five sub-Neptunes and one super-Earth, the K2-138 system provides a unique test bed for comparative atmospheric studies of warm to temperate planets of similar size, dynamical studies of near resonant planets, and models of planet formation and migration.
8 citations
Posted Content•
TL;DR: In this article, the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817 were presented, showing that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad and narrow UV absorption lines.
Abstract: We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission line variability. The correlation recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region.
7 citations
TL;DR: In this paper, the mass and density of a K-dwarf Wolf 503 (HIP 67285) was determined using radial velocity measurements from four instruments, and a joint radial velocity-transit fit was conducted to constrain the eccentricity at $0.41 ± 0.05.
Abstract: Using radial velocity measurements from four instruments, we report the mass and density of a $2.043\pm0.069 ~\rm{R}_{\oplus}$ sub-Neptune orbiting the quiet K-dwarf Wolf 503 (HIP 67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence $K2$ campaign 17 photometry and conduct a joint radial velocity-transit fit to constrain the eccentricity at $0.41\pm0.05$. The addition of a transit observation by $Spitzer$ also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, $6.26^{+0.69}_{-0.70}~\rm{M}_{\odot}$, in combination with the updated radius measurements, gives Wolf 503 b a bulk density of $\rho = 2.92\pm ^{+0.50}_{-0.44}$ $\rm{g}~\rm{cm}^{-3}$. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial $\rm{H}_2\rm{O}$ mass fraction ($45^{+19.12}_{-16.15}\%$) or a modest H/He envelope ($0.5\pm0.28\%$). The low H/He mass fraction, along with the old age of Wolf 503 ($11\pm2$ Gyrs), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host ($J=8.3$ mag) makes it an attractive target for transmission spectroscopy.
2 citations
Posted Content•
TL;DR: In this article, the mass and density of a K-dwarf Wolf 503 (HIP 67285) was determined using radial velocity measurements from four instruments, and a joint radial velocity-transit fit was conducted to constrain the eccentricity at $0.41 ± 0.05.
Abstract: Using radial velocity measurements from four instruments, we report the mass and density of a $2.043\pm0.069 ~\rm{R}_{\oplus}$ sub-Neptune orbiting the quiet K-dwarf Wolf 503 (HIP 67285). In addition, we present improved orbital and transit parameters by analyzing previously unused short-cadence $K2$ campaign 17 photometry and conduct a joint radial velocity-transit fit to constrain the eccentricity at $0.41\pm0.05$. The addition of a transit observation by $Spitzer$ also allows us to refine the orbital ephemeris in anticipation of further follow-up. Our mass determination, $6.26^{+0.69}_{-0.70}~\rm{M}_{\odot}$, in combination with the updated radius measurements, gives Wolf 503 b a bulk density of $\rho = 2.92\pm ^{+0.50}_{-0.44}$ $\rm{g}~\rm{cm}^{-3}$. Using interior composition models, we find this density is consistent with an Earth-like core with either a substantial $\rm{H}_2\rm{O}$ mass fraction ($45^{+19.12}_{-16.15}\%$) or a modest H/He envelope ($0.5\pm0.28\%$). The low H/He mass fraction, along with the old age of Wolf 503 ($11\pm2$ Gyrs), makes this sub-Neptune an opportune subject for testing theories of XUV-driven mass loss while the brightness of its host ($J=8.3$ mag) makes it an attractive target for transmission spectroscopy.
TL;DR: The K2-138 system with the most currently known planets was verified in this paper, where the authors verified the sixth planet's orbital period of $41.966 ± 0.006$ days and measure a radius of $3.44+0.32−0.31.
Abstract: $K2$ greatly extended $Kepler$'s ability to find new planets, but it was typically limited to identifying transiting planets with orbital periods below 40 days. While analyzing $K2$ data through the Exoplanet Explorers project, citizen scientists helped discover one super-Earth and four sub-Neptune sized planets in the relatively bright ($V=12.21$, $K=10.3$) K2-138 system, all which orbit near 3:2 mean motion resonances. The $K2$ light curve showed two additional transit events consistent with a sixth planet. Using $Spitzer$ photometry, we validate the sixth planet's orbital period of $41.966\pm0.006$ days and measure a radius of $3.44^{+0.32}_{-0.31}\,R_{\oplus}$, solidifying K2-138 as the $K2$ system with the most currently known planets. There is a sizeable gap between the outer two planets, since the fifth planet in the system, K2-138 f, orbits at 12.76 days. We explore the possibility of additional non-transiting planets in the gap between f and g. Due to the relative brightness of the K2-138 host star, and the near resonance of the inner planets, K2-138 could be a key benchmark system for both radial velocity and transit timing variation mass measurements, and indeed radial velocity masses for the inner four planets have already been obtained. With its five sub-Neptunes and one super-Earth, the K2-138 system provides a unique test bed for comparative atmospheric studies of warm to temperate planets of similar size, dynamical studies of near resonant planets, and models of planet formation and migration.