skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


This content will become publicly available on November 1, 2025

Title: Revealing the Elusive Companion of the Red Giant Binary 2MASS J05215658+4359220 from UV HST and Astrosat/UVIT Data
Abstract Black hole (BH) demographics in different environments is critical in view of recent results on massive star binarity, and of the multimessenger detectability of compact object mergers. But the identification and characterization of noninteracting BHs are elusive, especially in the sparse field stellar population. A candidate noninteractive BH + red giant (RG) binary system, 2MASS J05215658+4359220, was identified by T. A. Thompson et al. We obtained Astrosat/UVIT far-ultraviolet (FUV) imaging and Hubble Space Telescope (HST) UV−optical imaging and spectroscopy of the source to test possible scenarios for the optically elusive companion. HST/STIS spectra from ≈1600 to 10230 Å are best fit by the combination of two stellar sources, a RG withTeff= 4250 ± 150 K, logg= 2.0,RRG∼ 27.8R⊙(assuming a single-temperature atmosphere), and a subgiant companion withTeff= 6000 K,Rcomp= 2.7R⊙, orTeff= 5270 K,Rcomp= 4.2R⊙using models with one-tenth or one-third solar metallicity, respectively, logg= 3.0, extinctionEB−V= 0.50 ± 0.2, adopting the Data Release 3 Gaia distanceD= 2463 ± 120 pc. No FUV data existed prior to our programs. STIS spectra give an upper limit of 10−17erg cm−2s−1Å−1shortwards of 2300 Å; an upper limit of ≳25.7 ABmag was obtained in two UVIT FUV broad bands. The nondetection of FUV flux rules out a compact companion such as a hot white dwarf. The STIS spectrum shows strong Mgiiλ2800 Å emission, typical of chromospherically active RGs. The masses inferred by comparison with evolutionary tracks, ∼1M⊙for the RG and between 1.1 and 1.6M⊙for the subgiant companion, suggest past mass transfer, although the RG currently does not fill its Roche lobe. WFC3 imaging in F218W, F275W, F336W, F475W, and F606W shows an unresolved source in all filters.  more » « less
Award ID(s):
2307146
PAR ID:
10599726
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
The Astrophysical Journal
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
976
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
131
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; (, The Astrophysical Journal)
    Abstract We assess the impact of Caiiλλ3934, 3969 and Naiλλ5891, 5897 absorption arising in the interstellar medium (ISM) on the Sloan Digital Sky Survey-IV MaNGA Stellar Library (MaStar) and produce corrected spectroscopy for 80% of the 24,162-star catalog. We model the absorption strength of these transitions as a function of the stellar distance, Galactic latitude, and dust reddening based on high-spectral resolution studies. With this model, we identify 6342 MaStar stars that have negligible ISM absorption (WISM(CaiiK) < 0.07 Å andWISM(Nai5891) < 0.05 Å). For 12,110 of the remaining stars, we replace their NaiD profile (and their Caiiprofile for effective temperaturesTeff> 9000 K) with a coadded spectrum of low-ISM stars with similarTeff, surface gravity, and metallicity. For 738 additional stars withTeff> 9000 K, we replace these spectral regions with a matching ATLAS9-based BOSZ model. This results in a mean reduction inW(CaiiK) (W(NaiD)) of 0.4–0.7 Å (0.6–1.1 Å) for hot stars (Teff> 7610 K), and a mean reduction inW(NaiD) of 0.1–0.2 Å for cooler stars. We show that interstellar absorption in the simple stellar population (SSP) model spectra constructed from the original library artificially enhancesW(CaiiK) by ≳20% at young ages (<400 Myr); dramatically enhances the strength of stellar NaiD in starbursting systems (by ≳50%); and enhances stellar NaiD in older stellar populations (≳10 Gyr) by ≳10%. We provide SSP spectra constructed from the cleaned library and discuss the implications of these effects for stellar population synthesis analyses constraining the stellar age, [Na/Fe] abundance, and initial mass function. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al (, The Astrophysical Journal)
    Abstract The Ovi1032, 1038 Å line is a key probe of cooling gas in the circumgalactic medium (CGM) of galaxies but has been observed to date primarily in absorption along single sight lines. We present deep Hubble Space Telescope (HST) Solar Blind Channel of the Advanced Camera for Surveys observations of the compact, massive starburst Makani. Makani hosts a 100 kpc, [Oii]-emitting galactic wind driven by two episodes of star formation over 400 Myr. We detect Oviand Lyαemission across the [Oii] nebula with similar morphology and extent, out tor≈ 50 kpc. Using differential narrowband imaging, we separate Lyαand Oviand show that the Oviemission is comparable in brightness to [Oii], withLO VI= 4 × 1042erg s−1. The similar hourglass morphology and size of [Oii] and Oviimplicate radiative cooling atT= 105.5K in a hot–cold interface. This may occur as theT> 107K CGM—or the hot fluid driving the wind—exchanges mass with theT≈ 104K clouds entrained in (or formed by) the wind. The optical/UV line ratios may be consistent with shock ionization, although uncertain attenuation and Lyαradiative transfer complicate the interpretation. The detection of Oviin Makani lies at the bleeding edge of the UV imaging capabilities of HST and provides a benchmark for future emission-line imaging of the CGM with a wide-area UV telescope. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084 b, and TOI-4184b. We characterized the host stars by combining spectra fromShane/Kast andMagellan/FIRE, spectral energy distribution analysis, and stellar evolutionary models. In addition, we used Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science images, and statistical validation packages to support the planetary interpretation. We performed a global analysis of multi-colour photometric data from TESS and ground-based facilities in order to derive the stellar and planetary physical parameters for each system. We find that TOI-2084 band TOI-4184 bare sub-Neptune-sized planets with radii ofRp= 2.47 ± 0.13R⊕andRp= 2.43 ± 0.21R⊕, respectively. TOI-2084 b completes an orbit around its host star every 6.08 days, has an equilibrium temperature ofTeq= 527 ± 8 K and an irradiation ofSp= 12.8 ± 0.8S⊕. Its host star is a dwarf of spectral M2.0 ± 0.5 at a distance of 114 pc with an effective temperature ofTeff= 3550 ± 50 K, and has a wide, co-moving M8 companion at a projected separation of 1400 au. TOI-4184 b orbits around an M5.0 ± 0.5 type dwarf star (Kmag= 11.87) each 4.9 days, and has an equilibrium temperature ofTeq= 412 ± 8 K and an irradiation ofSp= 4.8 ± 0.4S⊕. TOI-4184 is a metal poor star ([Fe/H] = −0.27 ± 0.09 dex) at a distance of 69 pc with an effective temperature ofTeff= 3225 ± 75 K. Both planets are located at the edge of the sub-Jovian desert in the radius-period plane. The combination of the small size and the large infrared brightness of their host stars make these new planets promising targets for future atmospheric exploration with JWST. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    We present JWST/NIRSpec integral field data of the quasar PJ308-21 atz = 6.2342. As shown by previous ALMA and HST imaging, the quasar has two companion sources, interacting with the quasar host galaxy. The high-resolution G395H/290LP NIRSpec spectrum covers the 2.87 − 5.27 μm wavelength range and shows the rest-frame optical emission of the quasar with exquisite quality (signal-to-noise ratio ∼100 − 400 per spectral element). Based on the Hβline from the broad line region, we obtain an estimate of the black hole massMBH, Hβ ∼ 2.7 × 109 M⊙. This value is within a factor ≲1.5 of the Hα-based black hole mass from the same spectrum (MBH, Hα ∼ 1.93 × 109 M⊙) and is consistent with a previous estimate relying on the Mg IIλ2799 line (MBH, MgII ∼ 2.65 × 109 M⊙). All theseMBHestimates are within the ∼0.5 dex intrinsic scatter of the adopted mass calibrations. The high Eddington ratio of PJ308-21λEdd, Hβ ∼ 0.67 (λEdd, Hα ∼ 0.96) is in line with the overall quasar population atz ≳ 6. The relative strengths of the [O III], Fe II, and Hβlines are consistent with the empirical “Eigenvector 1” correlations as observed for low redshift quasars. We find evidence for blueshifted [O III]λ5007 emission with a velocity offset Δv[O III] = −1922 ± 39 km s−1from the systemic velocity and a full width at half maximum (FWHM)FWHM([O III]) = 2776−74+75km s−1. This may be the signature of outflowing gas from the nuclear region, despite the true values of Δv[O III]andFWHM([O III]) likely being more uncertain due to the blending with Hβand Fe IIlines. Our study demonstrates the unique capabilities of NIRSpec in capturing quasar spectra at cosmic dawn and studying their properties in unprecedented detail. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Astronomy & Astrophysics)
    Context. A low-mass companion potentially in the brown dwarf mass regime was discovered on a ~12 yr orbit (~5.5 au) around HD 167665 using radial velocity (RV) monitoring. Joint RV–astrometry analyses confirmed that HD 167665B is a brown dwarf with precisions on the measured mass of ~4–9%. Brown dwarf companions with measured mass and luminosity are valuable for testing formation and evolutionary models. However, its atmospheric properties and luminosity are still unconstrained, preventing detailed tests of evolutionary models. Aims. We further characterize the HD 167665 system by measuring the luminosity and refining the mass of its companion and reassessing the stellar age. Methods. We present new high-contrast imaging data of the star and of its close-in environment from SPHERE and GRAVITY, which we combined with RV data from CORALIE and HIRES and astrometry from HIPPARCOSandGaia. Results. The analysis of the host star properties indicates an age of 6.20 ± 1.13 Gyr. GRAVITY reveals a point source near the position predicted from a joint fit of RV data and HIPPARCOS–Gaiaproper motion anomalies. Subsequent SPHERE imaging confirms the detection and reveals a faint point source of contrast of ∆H2= 10.95 ± 0.33 mag at a projected angular separation of ~180 mas. A joint fit of the high-contrast imaging, RV, and HIPPARCOSintermediate astrometric data together with theGaiaastrometric parameters constrains the mass of HD 167665B to ~1.2%, 60.3 ± 0.7MJ. The SPHERE colors and spectrum point to an early or mid-T brown dwarf of spectral type T4−2+1. Fitting the SPHERE spectrophotometry and GRAVITY spectrum with synthetic spectra suggests an effective temperature of ~1000–1150 K, a surface gravity of ~5.0–5.4 dex, and a bolometric luminosity log(L/L⊙)=−4.892−0.028+0.024dex. The mass, luminosity, and age of the companion can only be reproduced within 3σby the hybrid cloudy evolutionary models of Saumon & Marley (2008, ApJ, 689, 1327), whereas cloudless evolutionary models underpredict its luminosity. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email