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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"

17205 results found.

  1. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  2. EP251023a: Assy AZT-20 optical observations
  3. EP251023a: UAFO and AbAO optical observations
  4. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  5. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  6. GRB 251025B: further Mondy optical observations
  7. GRB 251111A: Mondy optical upper limit
  8. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  10. GRB 251116B: LCO optical upper limits
  11. GRB 251116C: LCO optical upper limits
  12. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  13. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  14. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  15. The EP-WXT trigger 01709248221 is likely a flaring star
  16. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  17. GRB 251112A: Swift/UVOT Upper Limits
  18. GRB 251112A: Swift-XRT refined Analysis
  19. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  20. Swift Trigger 1413695: a possible GRB 251112A
  21. GRB251111A: 1.3m DFOT optical upper limit
  22. GRB 251111A: Swift-XRT afterglow detection
  23. GRB 251111A: SVOM/VT optical observations with X-band data
  24. GRB 251111A: EP-FXT counterpart detection
  25. GRB 251111A: SVOM/VT optical observations with VHF data
  26. GRB 251111A: LCO optical observation
  27. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  28. GRB 251106A: Swift/UVOT Upper Limits
  29. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  30. GRB 251102B: SVOM/GRM observation
  31. The EP-WXT trigger 01709248051 is likely a flaring star
  32. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  33. GRB 251106A: Swift-XRT afterglow detection
  34. GRB 251106A: Kilonova-Catcher optical upper limit
  35. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  36. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  37. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  38. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  39. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  41. GRB 251103B: Swift/UVOT Upper Limits
  42. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  43. GRB 251103A: WFST optical observations
  44. EP251102a: update of EP-FXT follow-up observation
  45. GRB 251103A: Xinglong 2.16m optical detection
  46. GRB 251103A: KAIT optical observations
  47. GRB 251103B: Nanshan/HMT optical upper limit
  48. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  49. GRB 251103B: MITSuME Akeno optical upper limits
  50. GRB 251103B: Swift-XRT refined Analysis
  51. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  52. EP251102a: NIR observations with WINTER
  53. GRB 251103A: J-band detection with WINTER
  54. GRB 251103B: GROWTH-India Telescope optical upper limits
  55. GRB 251103A: Kilonova-Catcher optical afterglow detection
  56. GRB 251103B: Enhanced Swift-XRT position
  57. GRB 251103B: Swift detection of a burst
  58. GRB 251103A: Swift/UVOT Detection
  59. GRB 251103A: Swift-XRT afterglow detection
  60. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. EP251102a: Einstein Probe detection of a fast X-ray transient
  62. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  63. GRB 251103A: LCO optical observation
  64. EP251102.890: COLIBRÍ optical counterpart candidate
  65. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  66. GRB 251103A: LCO optical afterglow detection
  67. GRB 251103A: NOT optical afterglow candidate
  68. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  69. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  70. GRB 251025C: SVOM/GRM observation
  71. GRB 251028A: SVOM/GRM observation
  72. GRB 251022A: Swift-XRT confirmation of fading
  73. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  74. GRB 251026A/EP251026a: EP-FXT follow-up observation
  75. The EP-WXT trigger 01709247588 is likely a flaring star
  76. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  77. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  78. GRB251026B: PRIME H-band upper limit
  79. GRB251025B: 3.6m DOT Optical Observations
  80. SVOM trigger sb25102702/GRB 251027A is not a GRB
  81. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  82. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  83. EP251027.145: COLIBRÍ optical upper limits
  84. GRB 251022A: SVOM/GRM observation
  85. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  86. GRB 251027A: LCO optical upper limit
  87. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  88. GRB 251023B / EP251023b: Mondy optical upper limit
  89. GRB 251017A: INASAN-Kislovodsk optical observations
  90. GRB 251026A: Mondy optical upper limit
  91. GRB 251025B: Mondy optical observations
  92. GRB 251025B: Kilonova-Catcher optical afterglow detection
  93. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  94. EP251023a: Mondy optical observations
  95. GRB 251025B: MAO/AZT-22 optical observations
  96. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  97. GRB 251025B: J-band detection with WINTER
  98. GRB 251026A: SVOM/C-GFT upper limit
  99. IceCube-251025A: DDOTI Optical Upper Limit
  100. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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