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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"

18283 results found.

  1. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  2. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  3. GRB 251117A: SVOM/GRM observation of a short burst
  4. GRB 251117A: Tiled Swift observations
  5. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  7. EP251023a: Assy AZT-20 optical observations
  8. EP251023a: UAFO and AbAO optical observations
  9. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  10. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  11. GRB 251025B: further Mondy optical observations
  12. GRB 251111A: Mondy optical upper limit
  13. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  15. GRB 251116B: LCO optical upper limits
  16. GRB 251116C: LCO optical upper limits
  17. GRB 251116B: SVOM detection of a burst
  18. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  19. GRB 251115A: Tiled Swift observations
  20. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  21. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  22. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  23. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  24. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  25. GRB 251112A: Swift/UVOT Upper Limits
  26. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  27. Swift Trigger 1413695: a possible GRB 251112A
  28. GRB251111A: 1.3m DFOT optical upper limit
  29. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  30. GRB 251111A: Swift-XRT afterglow detection
  31. GRB 251111A: SVOM/VT optical observations with X-band data
  32. GRB 251111A: SVOM/VT optical observations with VHF data
  33. GRB 251111A: LCO optical observation
  34. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  35. GRB 251106A: Swift/UVOT Upper Limits
  36. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  37. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  38. GRB 251102B: SVOM/GRM observation
  39. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  40. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  41. GRB 251106A: Swift-XRT afterglow detection
  42. GRB 251106A: Kilonova-Catcher optical upper limit
  43. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  44. GRB 251106A: MASTER optical observations
  45. GRB 251106A: SVOM detection of a burst
  46. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  47. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  48. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  49. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  50. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  51. GRB 251103B: Swift/UVOT Upper Limits
  52. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  53. GRB 251104A: SVOM detection of a burst
  54. GRB 251103A: WFST optical observations
  55. GRB 251103A: Xinglong 2.16m optical detection
  56. GRB 251103A: KAIT optical observations
  57. GRB 251103B: Nanshan/HMT optical upper limit
  58. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  59. GRB 251103B: MITSuME Akeno optical upper limits
  60. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  61. EP251102a: NIR observations with WINTER
  62. GRB 251103A: J-band detection with WINTER
  63. Swift GRB 251103B: Global MASTER-Net observations report
  64. GRB 251103B: GROWTH-India Telescope optical upper limits
  65. GRB 251103A: Kilonova-Catcher optical afterglow detection
  66. GRB 251103B: Enhanced Swift-XRT position
  67. GRB 251103B: Swift detection of a burst
  68. GRB 251103A: Swift/UVOT Detection
  69. GRB 251103A: Swift-XRT afterglow detection
  70. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. EP251102a: Einstein Probe detection of a fast X-ray transient
  72. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  73. GRB 251103A: LCO optical observation
  74. EP251102.890: COLIBRÍ optical counterpart candidate
  75. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  76. GRB 251103A: LCO optical afterglow detection
  77. GRB 251103A: NOT optical afterglow candidate
  78. GRB 251103A: SVOM detection of a bright burst
  79. GRB 251031A: Fermi GBM Observation
  80. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  81. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  82. GRB 251025C: SVOM/GRM observation
  83. GRB 251028A: SVOM/GRM observation
  84. GRB 251022A: Swift-XRT confirmation of fading
  85. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  86. GRB 251028B: Fermi/GBM observation
  87. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  88. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  89. GRB251026B: PRIME H-band upper limit
  90. GRB251025B: 3.6m DOT Optical Observations
  91. SVOM trigger sb25102702/GRB 251027A is not a GRB
  92. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  93. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  94. EP251027.145: COLIBRÍ optical upper limits
  95. GRB 251022A: SVOM/GRM observation
  96. GRB 251026B: Swift ToO observations
  97. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  98. GRB 251027A: LCO optical upper limit
  99. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 251023B / EP251023b: Mondy optical upper limit

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