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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

17192 results found.

  1. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  2. The EP-WXT trigger 01709248221 is likely a flaring star
  3. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  4. GRB 251112A: Swift/UVOT Upper Limits
  5. GRB 251112A: Swift-XRT refined Analysis
  6. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  7. Swift Trigger 1413695: a possible GRB 251112A
  8. GRB251111A: 1.3m DFOT optical upper limit
  9. GRB 251111A: Swift-XRT afterglow detection
  10. GRB 251111A: SVOM/VT optical observations with X-band data
  11. GRB 251111A: EP-FXT counterpart detection
  12. GRB 251111A: SVOM/VT optical observations with VHF data
  13. GRB 251111A: LCO optical observation
  14. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  15. GRB 251106A: Swift/UVOT Upper Limits
  16. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  17. GRB 251102B: SVOM/GRM observation
  18. The EP-WXT trigger 01709248051 is likely a flaring star
  19. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  20. GRB 251106A: Swift-XRT afterglow detection
  21. GRB 251106A: Kilonova-Catcher optical upper limit
  22. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  23. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  24. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  25. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  26. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  28. GRB 251103B: Swift/UVOT Upper Limits
  29. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  30. GRB 251103A: WFST optical observations
  31. EP251102a: update of EP-FXT follow-up observation
  32. GRB 251103A: Xinglong 2.16m optical detection
  33. GRB 251103A: KAIT optical observations
  34. GRB 251103B: Nanshan/HMT optical upper limit
  35. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  36. GRB 251103B: MITSuME Akeno optical upper limits
  37. GRB 251103B: Swift-XRT refined Analysis
  38. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  39. EP251102a: NIR observations with WINTER
  40. GRB 251103A: J-band detection with WINTER
  41. GRB 251103B: GROWTH-India Telescope optical upper limits
  42. GRB 251103A: Kilonova-Catcher optical afterglow detection
  43. GRB 251103B: Enhanced Swift-XRT position
  44. GRB 251103B: Swift detection of a burst
  45. GRB 251103A: Swift/UVOT Detection
  46. GRB 251103A: Swift-XRT afterglow detection
  47. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  48. EP251102a: Einstein Probe detection of a fast X-ray transient
  49. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  50. GRB 251103A: LCO optical observation
  51. EP251102.890: COLIBRÍ optical counterpart candidate
  52. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  53. GRB 251103A: LCO optical afterglow detection
  54. GRB 251103A: NOT optical afterglow candidate
  55. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  56. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  57. GRB 251025C: SVOM/GRM observation
  58. GRB 251028A: SVOM/GRM observation
  59. GRB 251022A: Swift-XRT confirmation of fading
  60. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  61. GRB 251026A/EP251026a: EP-FXT follow-up observation
  62. The EP-WXT trigger 01709247588 is likely a flaring star
  63. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  64. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  65. GRB251026B: PRIME H-band upper limit
  66. GRB251025B: 3.6m DOT Optical Observations
  67. SVOM trigger sb25102702/GRB 251027A is not a GRB
  68. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  69. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  70. EP251027.145: COLIBRÍ optical upper limits
  71. GRB 251022A: SVOM/GRM observation
  72. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  73. GRB 251027A: LCO optical upper limit
  74. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 251023B / EP251023b: Mondy optical upper limit
  76. GRB 251017A: INASAN-Kislovodsk optical observations
  77. GRB 251026A: Mondy optical upper limit
  78. GRB 251025B: Mondy optical observations
  79. GRB 251025B: Kilonova-Catcher optical afterglow detection
  80. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  81. EP251023a: Mondy optical observations
  82. GRB 251025B: MAO/AZT-22 optical observations
  83. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  84. GRB 251025B: J-band detection with WINTER
  85. GRB 251026A: SVOM/C-GFT upper limit
  86. IceCube-251025A: DDOTI Optical Upper Limit
  87. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  88. GRB 251026A: SVOM detection of a long burst
  89. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  90. GRB 251023A: SVOM/GRM observation
  91. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  92. GRB 251025B: GROWTH-India Telescope optical observations
  93. GRB 251024A: Swift/UVOT Upper Limits
  94. GRB 251025B: Swift-XRT afterglow detection
  95. GRB 251025A (sb25102501): stellar flare confirmed
  96. GRB 251025B: SVOM/VT optical observations with VHF data
  97. GRB 251025B: SVOM/C-GFT optical counterpart detection
  98. GRB 251025B: SVOM detection of a burst
  99. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  100. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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