J/ApJ/928/L8ivo://CDS.VizieR/J/ApJ/928/L8doi:10.26093/cds/vizier.19289008CDSDe K.Chakrabarty D.Soria R.Ashley M.C.B.Conroy C.Hankins M.J.,Kasliwal M.M.Lau R.M.Moore A.M.Simcoe R.Soon J.Travouillon T.2024-11-06T20:24:38Z2024-04-05T13:39:29ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frvariable-starsx-ray-binary-starsinfrared-astronomyspectroscopyphotometrygiant-starsThe symbiotic X-ray binary Sct X-1 was suggested to be the first known neutron star accreting from a red supergiant companion. Although known for nearly 50yr, detailed characterization of the donor remains lacking, particularly due to the extremely high reddening toward the source (A_V_>~25mag). Here, we present (i) improved localization of the counterpart using Gaia and Chandra observations, (ii) the first broadband infrared spectrum (~1-5{mu}m; R~2000) obtained with SpeX on the NASA Infrared Telescope Facility, and (iii) the J-band light curve from the Palomar Gattini-IR survey. The infrared spectrum is characterized by (i) deep water absorption features (H_2_O index ~40%), (ii) strong TiO, VO, and CO features, and (iii) weak/absent CN lines. We show that these features are inconsistent with known red supergiants but suggest an M8-9 III-type O-rich Mira donor star. We report the discovery of large-amplitude ({Delta}J~3.5mag) periodic photometric variability, suggesting a pulsation period of 621+/-36 (systematic) +/-8 (statistical) days, which we use to constrain the donor to be a relatively luminous Mira (M_K_=-8.6+/-0.3mag) at a distance of 3.6_-0.7_^+0.8^kpc. Comparing these characteristics to recent models, we find the donor to be consistent with a ~3-5M_{sun}_ star at an age of ~0.1-0.3Gyr. Together, we show that Sct X-1 was previously misclassified as an evolved high-mass X-ray binary; instead, it is an intermediate-mass system with the first confirmed Mira donor in an X-ray binary. We discuss the implications of Mira donors in symbiotic X-ray binaries and highlight the potential of wide-field infrared time-domain surveys and broadband infrared spectroscopy to unveil their demographics.2022ApJ...928L...8Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/928/L8CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2014)II/195 : Namelists of variable stars Nos.67-73 (Khopolov+, 1985-97)III/114 : Spectra of Late-Type Standards, 2.0-2.5 Microns (Kleinmann+ 1986)III/196 : Near-IR stellar spectra from 1.428 to 2.5 um (Lancon+ 1996)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/A+AS/146/217 : Library of Sp. (0.5 to 2.5um) of Cool Stars (Lancon+ 2000)J/ApJ/597/323 : Cool stars at the Galactic Center (Blum+, 2003)J/A+A/425/489 : Late-type stars in the inner Milky Way (Comeron+, 2004)J/MNRAS/376/313 : Carbon star in Magellanic Cloud (Groenewegen+, 2007)J/MNRAS/386/313 : IR observations of Mira variables (Whitelock+, 2008)J/AJ/152/164 : I-band light curves of OGLE LMC Miras (He+, 2016)J/ApJS/240/21 : Symbiotic stars with 2MASS, WISE & Gaia data (Akras+, 2019)J/MNRAS/483/5077 : Machine learning to identify symbiotic stars (Akras+, 2019)J/ApJ/872/43 : IR sp. of symbiotic stars. XII. V934 Her (Hinkle+, 2019)J/A+A/634/A133 : X-Shooter Spectral Library (XSL). DR2 (Gonneau+, 2020)J/ApJS/257/23 : Multiwavelength obs. of Miras in the LMC (Iwanek+, 2021)J/AJ/162/187 : IRTF spectral indices for giant stars (Messineo+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/928/L8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/928/L8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/928/L8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/928/L8https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/928/L8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/928/L8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayInfrareddefaultJ/ApJ/928/L8/fig1Palomar Gattini-IR (PGIR) J-band light curve of 2MASS J18352582-0736501recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[58425.1/59448.4] Modified Julian Date (JD-2400000.5)dtime.epochdoubleJmag[10.27/14.16] PGIR J-band magnitudemagphot.mag;em.IR.Jfloate_Jmag[0.02/1.3] Uncertainty in Jmagmagstat.error;phot.magfloatJ/ApJ/928/L8/fig2SpeX SXD and LXD_long spectra of 2MASS J18352582-0736501recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintModeSpex Mode, SXD or LXD_longinstr.setupcharlambda[9187.3/53689] Wavelength, Angstroms0.1nmem.wldoubleFlux[-2.9e-12/4.3e-12] Flux density, erg/s/cm2mW.m**-2phot.flux.density;em.IRdouble