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White Dwarfs with Infrared Excess from LAMOST Data Release 11

Keyi Wang, Qiong Liu, Siyi Xu, Alberto Rebassa-Mansergas

Abstract

Infrared (IR) excess observed around white dwarfs (WDs) is typically attributed to companions or debris disks. These systems are interesting because they offer a unique opportunity to study the late stages of stellar evolution and the interactions between WDs and surrounding material. The 11th data release (DR11) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) - one of the largest spectroscopic surveys to date - has recently provided spectra for 3092 WDs, many of which have yet to be systematically investigated for IR excess. In this study, we cross-correlated the LAMOST DR11 WD catalog with optical and IR surveys, including the Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), UKIRT Infrared Deep Sky Survey (UKIDSS), and Wide-field Infrared Survey Explorer (WISE). We performed spectral energy distribution fitting using the VOSA tool for 1818 WDs and identified 167 IR excess WD candidates. After excluding 23 sources with potential contamination within 6" and five additional sources identified through WISE ccf flag analysis, we identified 139 objects with candidate IR excess. These include 30 candidate WD + M dwarf binaries (18 new systems), 19 candidate WD + brown dwarf (BD) binaries (eight new systems), 66 candidate WD + dust disks (38 new systems), and 24 candidate either WD + BD or WD + dust disks (19 new systems). Given the limited spatial resolution of WISE, all candidate systems require follow-up IR observations for confirmation, such as high spatial resolution imaging or IR spectroscopy. This will help expand the parameter space of dust disks, allowing us to explore a broader range of possibilities.

White Dwarfs with Infrared Excess from LAMOST Data Release 11

Abstract

Infrared (IR) excess observed around white dwarfs (WDs) is typically attributed to companions or debris disks. These systems are interesting because they offer a unique opportunity to study the late stages of stellar evolution and the interactions between WDs and surrounding material. The 11th data release (DR11) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) - one of the largest spectroscopic surveys to date - has recently provided spectra for 3092 WDs, many of which have yet to be systematically investigated for IR excess. In this study, we cross-correlated the LAMOST DR11 WD catalog with optical and IR surveys, including the Sloan Digital Sky Survey (SDSS), Two Micron All-Sky Survey (2MASS), UKIRT Infrared Deep Sky Survey (UKIDSS), and Wide-field Infrared Survey Explorer (WISE). We performed spectral energy distribution fitting using the VOSA tool for 1818 WDs and identified 167 IR excess WD candidates. After excluding 23 sources with potential contamination within 6" and five additional sources identified through WISE ccf flag analysis, we identified 139 objects with candidate IR excess. These include 30 candidate WD + M dwarf binaries (18 new systems), 19 candidate WD + brown dwarf (BD) binaries (eight new systems), 66 candidate WD + dust disks (38 new systems), and 24 candidate either WD + BD or WD + dust disks (19 new systems). Given the limited spatial resolution of WISE, all candidate systems require follow-up IR observations for confirmation, such as high spatial resolution imaging or IR spectroscopy. This will help expand the parameter space of dust disks, allowing us to explore a broader range of possibilities.
Paper Structure (14 sections, 2 equations, 8 figures, 4 tables)

This paper contains 14 sections, 2 equations, 8 figures, 4 tables.

Table of Contents

  1. INTRODUCTION
  2. Data and Screening Process
  3. Selection of High Quality WD Sample
  4. Photometric Data Collection
  5. VOSA SED Fitting
  6. Results of Infrared Excess Characterization
  7. WISE Image and Flag Checking
  8. Two-component model fitting
  9. Discussion
  10. WD+M Dwarf Binary Candidates
  11. WD + BD Binary Candidates
  12. WD + BD or Dust Candidates
  13. WD + Dust Disk Candidates
  14. Conclusions

Figures (8)

  • Figure 1: Images of the WD 1441-007 (obsid: 441411232). The left panel shows the WISE W1 (3.4$\mu$m) image, the middle panel presents the UKIDSS K-band (2.2$\mu$m) image, and the right panel displays the Pan-STARRS z-band (optical) image.The field of view is 30$\arcsec$ × 30$\arcsec$ for each cutout, and the blue circle is centered at the LAMOST coordinate of the WD with a radius of 6$\arcsec$. Both Pan-STARRS and UKIDSS $K$-band images reveal contamination sources within 6$\arcsec$ of the WDs, indicating potential blending with nearby objects in these systems.
  • Figure 2: Gaia HR diagram of 1818 WDs with $P_{\rm wd} > 0.75$, showing WD+M (blue circles), WD+BD (red squares), WD+Dust (green triangles), and WD+BD or Dust (orange diamonds) systems with candidate IR excess identified from this study.
  • Figure 3: SEDs of three different types of IR excess sources. The SED fitting results of three types of IR excess sources are shown in panels (a)–(c), corresponding to a WD+M dwarf candidate, a WD+BD binary candidate, and a WD+dust candidate, respectively. (a) SED fitting result for the WD+M dwarf candidate (obsid: 140108109). The best-fit model (black line) combines a WD (Koester; $T_{\rm eff} = 12000$ K, $\log g = 7.5$; blue line) and an M-type companion (BT-Settl; $T_{\rm eff} \approx 2700$ K; gray line), yielding $\chi^2 = 2.9$. Photometry includes: SDSS or J-PAS(magenta squares), UKIDSS or 2MASS(cyan pentagons), WISE (red circles), and upper limits (yellow triangles). (b) SED fitting result for the WD+BD binary candidate (obsid: 1087109127). The best-fit model (black line) combines a WD (Koester; $T_{\rm eff} = 10750$ K, $\log g = 8$; blue line) and a BD companion (BT-Settl; $T_{\rm eff} \approx 2200$ K; gray line), yielding $\chi^2 = 3.8$. Photometry sources are the same as in panel (a). (c) SED fitting result for the WD+dust disk candidate (obsid: 381705107).The best-fit model (black line) combines a WD (Koester; $T = 14750$ K, $\log g = 8$; blue) and a dust component ($T = 850$ K; red dashed), yielding $\chi^2 = 2.2$. Photometry sources are the same as in panel (a).
  • Figure 4: Bolometric luminosity versus effective temperature for our WD+low-mass companion candidates (30 WD+M and 19 WD+BD systems). Black circles mark WD components, blue squares M-dwarf companions, and green triangles BD companions. Red curves show hydrogen-atmosphere (DA-type) WD evolutionary/cooling tracks for $M_{\rm WD}=0.2\,M_\odot$2018AA...614A..49C and $M_{\rm WD}=0.5,\,1.1,$ and $1.3\,M_\odot$2019AA...625A..87C. Also shown are low-mass main-sequence relations (0.40, 0.20, 0.10, 0.07 $M_\odot$; 2015AA...577A..42B) and BT-Settl BD sequences (0.04, 0.02, 0.01 $M_\odot$). Red markers denote potentially reliable candidates (11 WD+M and two WD+BD), flagged with a superscript "Y" in Tables \ref{['tab:wd+M_candidates']} and \ref{['tab:wd+BD_candidates']}.
  • Figure 5: Mass--cooling-age and $\log g$--$\log(T_{\mathrm{eff}})$ distributions for our WD+M-dwarf candidates. Left: WD mass versus cooling age for the SDSS WDMS reference sample from 2016MNRAS.458.3808R (grey dots; $N=915$ systems with valid WD parameters after our interpolation) overplotted with our 30 candidates (red squares). The candidates fall within the main locus traced by the reference sample and span a comparable range of masses and cooling ages. Right:$\log g$ versus $\log(T_{\mathrm{eff}})$ for the same two samples. Our candidates largely overlap the SDSS WDMS distribution, with a small number extending toward the edge of the reference locus.
  • ...and 3 more figures