More Like this

1. Star-crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination

   Tang, S.-Y. ; Stahl, A.G. ; Prato, L. ; Schaefer, G.H. ; Johns-Krull, C.M. ; Skiff, B.A. ; Beichman, C ; Uyama, T. ( June 2023 , The Astrophysical journal)

   The stellar companion to the weak-line T Tauri star DI Tau A was first discovered by the lunar occultation technique in 1989 and was subsequently confirmed by a speckle imaging observation in 1991. It has not been detected since, despite being targeted by five different studies that used a variety of methods and spanned more than 20 yr. Here, we report the serendipitous rediscovery of DI Tau B during our Young Exoplanets Spectroscopic Survey (YESS). Using radial velocity data from YESS spanning 17 yr, new adaptive optics observations from Keck II, and a variety of other data from the literature, we derive a preliminary orbital solution for the system that effectively explains the detection and (almost all of the) non-detection history of DI Tau B. We estimate the dynamical masses of both components, finding that the large mass difference (q ∼ 0.17) and long orbital period (>35 yr) make the DI Tau system a noteworthy and valuable addition to studies of stellar evolution and pre-main sequence models. With a long orbital period and a small flux ratio (f2/f1) between DI Tau A and B, additional measurements are needed for a better comparison between these observational results and pre-main-sequence models. Finally, we report an average surface magnetic field strength (B¯) for DI Tau A, of ∼0.55 kG, which is unusually low in the context of young active stars. 

   more » « less
2. Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X

   https://doi.org/10.3847/1538-3881/acc865  

   Sikora, James ; Rowe, Jason ; Barat, Saugata ; Bean, Jacob L. ; Brady, Madison ; Désert, Jean-Michel ; Feinstein, Adina D. ; Gilbert, Emily A. ; Henry, Gregory ; Kasper, David ; et al ( May 2023 , The Astronomical Journal)

   The early K-type T-Tauri star, V1298 Tau (V= 10 mag, age ≈ 20–30 Myr) hosts four transiting planets with radii ranging from 4.9 to 9.6R_⊕. The three inner planets have orbital periods of ≈8–24 days while the outer planet’s period is poorly constrained by single transits observed with K2 and the Transiting Exoplanet Survey Satellite (TESS). Planets b, c, and d are proto–sub-Neptunes that may be undergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity (RV) modeling analysis, which includes recently obtained TESS photometry and MAROON-X RV measurements. Assuming circular orbits, we obtain a low-significance (≈2σ) RV detection of planet c, implying a mass of${19.8}_{-8.9}^{+9.3}{M}_{\oplus }$and a conservative 2σupper limit of <39M_⊕. For planets b and d, we derive 2σupper limits ofM_b< 159M_⊕andM_d< 41M_⊕, respectively. For planet e, plausible discrete periods ofP_e> 55.4 days are ruled out at the 3σlevel while seven solutions with 43.3 <P_e/d< 55.4 are consistent with the most probable 46.768131 ± 000076 days solution within 3σ. Adopting the most probable solution yields a 2.6σRV detection with a mass of 0.66 ± 0.26M_Jup. Comparing the updated mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e are consistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich core with a substantial (∼5% by mass) H₂envelope.

    

   more » « less
3. Photodynamical Modeling of the Fascinating Eclipses in the Triple-star System KOI-126

   https://doi.org/10.3847/1538-4357/ac31b8  

   Yenawine, Mitchell E. ; Welsh, William F. ; Orosz, Jerome A. ; Bieryla, Allyson ; Cochran, William D. ; Endl, Michael ; Latham, David W. ; Quinn, Samuel N. ; Short, Donald R. ; Windmiller, Gur ( January 2022 , The Astrophysical Journal)

   We explore the fascinating eclipses and dynamics of the compact hierarchical triple-star system KOI-126 (KIC 5897826). This system is composed of a pair of M-dwarf stars (KOI-126 B and C) in a 1.74 day orbit that revolve around an F star (KOI-126 A) every 34 days. Complex eclipse shapes are created as the M stars transit the F star, due to two effects: (1) the duration of the eclipse is a significant fraction of the M-star orbital period, so the prograde or retrograde motion of the M stars in their orbit lead to unusually short or long duration eclipses; (2) due to 3-body dynamics, the M-star orbit precesses with an astonishingly quick timescale of 1.74 yr for the periastron (apsidal) precession, and 2.73 yr for the inclination and nodal angle precession. Using the full Kepler data set, supplemented with ground-based photometry, plus 29 radial velocity measurements that span 6 yr, our photodynamical modeling yields masses ofM_A= 1.2713 ± 0.0047M_⊙(0.37%),M_B= 0.23529 ± 0.00062M_⊙(0.26%), andM_C= 0.20739 ± 0.00055M_⊙(0.27%) and radii ofR_A= 1.9984 ± 0.0027R_⊙(0.14%),R_B= 0.25504 ± 0.00076R_⊙(0.3%), andR_C= 0.23196 ± 0.00069R_⊙(0.3%). We also estimate the apsidal motion constant of the M dwarfs, a parameter that characterizes the internal mass distribution. Although it is not particularly precise, we measure a mean apsidal motion constant,$\overline{k_2}$, of${0.046}_{-0.028}^{+0.046}$, which is approximately 2σlower than the theoretical model prediction of 0.150. We explore possible causes for this discrepancy.

    

   more » « less
4. The Peak of the Fallback Rate from Tidal Disruption Events: Dependence on Stellar Type

   https://doi.org/10.3847/2041-8213/ad0388  

   Bandopadhyay, Ananya ; Fancher, Julia ; Athian, Aluel ; Indelicato, Valentino ; Kapalanga, Sarah ; Kumah, Angela ; Paradiso, Daniel A. ; Todd, Matthew ; Coughlin, Eric R. ; Nixon, C. J. ( January 2024 , The Astrophysical Journal Letters)

   A star completely destroyed in a tidal disruption event (TDE) ignites a luminous flare that is powered by the fallback of tidally stripped debris to a supermassive black hole (SMBH) of massM_•. We analyze two estimates for the peak fallback rate in a TDE, one being the “frozen-in” model, which predicts a strong dependence of the time to peak fallback rate,t_peak, on both stellar mass and age, with 15 days ≲t_peak≲ 10 yr for main sequence stars with masses 0.2 ≤M_⋆/M_⊙≤ 5 andM_•= 10⁶M_⊙. The second estimate, which postulates that the star is completely destroyed when tides dominate the maximum stellar self-gravity, predicts thatt_peakis very weakly dependent on stellar type, with$t_{\mathrm{peak}}=\left(23.2\pm 4.0\mathrm{days}\right){\left(M_{•}/{10}^6{M}_{\odot }\right)}^{1/2}$for 0.2 ≤M_⋆/M_⊙≤ 5, while$t_{\mathrm{peak}}=\left(29.8\pm 3.6\mathrm{days}\right){\left(M_{•}/{10}^6{M}_{\odot }\right)}^{1/2}$for a Kroupa initial mass function truncated at 1.5M_⊙. This second estimate also agrees closely with hydrodynamical simulations, while the frozen-in model is discrepant by orders of magnitude. We conclude that (1) the time to peak luminosity in complete TDEs is almost exclusively determined by SMBH mass, and (2) massive-star TDEs power the largest accretion luminosities. Consequently, (a) decades-long extra-galactic outbursts cannot be powered by complete TDEs, including massive-star disruptions, and (b) the most highly super-Eddington TDEs are powered by the complete disruption of massive stars, which—if responsible for producing jetted TDEs—would explain the rarity of jetted TDEs and their preference for young and star-forming host galaxies.

    

   more » « less
5. A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf

   https://doi.org/10.3847/2041-8213/ace618  

   Jencson, Jacob E. ; Pearson, Jeniveve ; Beasor, Emma R. ; Lau, Ryan M. ; Andrews, Jennifer E. ; Bostroem, K. Azalee ; Dong 董, Yize 一泽 ; Engesser, Michael ; Gomez, Sebastian ; Guolo, Muryel ; et al ( July 2023 , The Astrophysical Journal Letters)

   We analyze pre-explosion near- and mid-infrared (IR) imaging of the site of SN 2023ixf in the nearby spiral galaxy M101 and characterize the candidate progenitor star. The star displays compelling evidence of variability with a possible period of ≈1000 days and an amplitude of Δm≈ 0.6 mag in extensive monitoring with the Spitzer Space Telescope since 2004, likely indicative of radial pulsations. Variability consistent with this period is also seen in the near-IRJandK_sbands between 2010 and 2023, up to just 10 days before the explosion. Beyond the periodic variability, we do not find evidence for any IR-bright pre-supernova outbursts in this time period. The IR brightness ($M_{K_s}=-10.7$mag) and color (J−K_s= 1.6 mag) of the star suggest a luminous and dusty red supergiant. Modeling of the phase-averaged spectral energy distribution (SED) yields constraints on the stellar temperature ($T_{\mathrm{eff}}={3500}_{-1400}^{+800}$K) and luminosity ($\log L/L_{\odot }=5.1\pm 0.2$). This places the candidate among the most luminous Type II supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. Comparison with stellar evolution models gives an initial mass ofM_init= 17 ± 4M_⊙. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at$\dot{M}\approx 3\times {10}^{-5}$to 3 × 10⁻⁴M_⊙yr⁻¹for an assumed wind velocity ofv_w= 10 km s⁻¹, perhaps pointing to enhanced mass loss in a pulsation-driven wind.

    

   more » « less