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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"

30495 results found.

  1. GRB 251116D: Insight-HXMT/HE detection
  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. GRB 251117A: Fermi-LAT detection
  6. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  7. GRB 251116C: Swift/BAT arcminute localization of a burst
  8. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  9. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  10. GRB 251116B: SVOM/VT optical upper limit
  11. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  12. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  13. GRB 251116D: Glowbug gamma-ray detection
  14. EP251023a: Assy AZT-20 optical observations
  15. EP251023a: UAFO and AbAO optical observations
  16. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  17. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  18. GRB 251116C: SVOM/VT optical upper limit
  19. GRB 251025B: further Mondy optical observations
  20. GRB 251111A: Mondy optical upper limit
  21. GRB 251116B: EP-FXT follow-up observation
  22. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  24. GRB 251116B: LCO optical upper limits
  25. GRB 251116C: LCO optical upper limits
  26. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  27. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  28. GRB 251115A: Tiled Swift observations
  29. GRB 251115A: Fermi-LAT detection
  30. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  31. Fermi GRB 251115A: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  33. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  34. GRB 251113A: Glowbug gamma-ray detection
  35. GRB 251113A: AstroSat CZTI detection
  36. GRB 251112A: Swift-BAT refined analysis
  37. Konus-Wind detection of GRB 251108C
  38. Konus-Wind detection of GRB 251103A
  39. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  40. IPN triangulation of GRB 251108C
  41. Fermi GRB 251114A: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  43. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  44. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  45. Fermi GRB 251113A: Global MASTER-Net observations report
  46. GRB 251111A: SVOM/ECLAIRs refined analysis
  47. GRB 251025B: SVOM/ECLAIRs refined analysis
  48. GRB 251112A: Swift/UVOT Upper Limits
  49. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  50. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  51. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  52. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  53. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  54. GRB251111A: 1.3m DFOT optical upper limit
  55. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  56. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  57. GRB 251111A: SVOM/VT optical observations with X-band data
  58. GRB 251111A: Swift-XRT observations
  59. GRB 251111A: EP-FXT counterpart detection
  60. GRB 251013C: Chandra X-ray observations and jet break detection
  61. GRB 251111A: SVOM/VT optical observations with VHF data
  62. GRB 251111A: KAIT optical upper limit
  63. GRB 251111A: LCO optical observation
  64. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  65. GRB 251103B: Swift-BAT refined analysis
  66. GRB 251106A: Swift/UVOT Upper Limits
  67. GRB 251105B: Insight-HXMT/HE detection
  68. GRB 251106B: Insight-HXMT detection
  69. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  70. GRB 251105A: AstroSat CZTI detection
  71. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  72. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  73. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  74. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  75. GRB 251102B: SVOM/GRM observation
  76. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  78. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  79. IPN triangulation of GRB 251105B (possible sGRB with EE)
  80. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  81. GRB 251106A: Swift-XRT afterglow detection
  82. GRB 251106A: Kilonova-Catcher optical upper limit
  83. Fermi GBM Sub-Threshold Detection of GRB 251106A
  84. GRB 251106A: Swift/BAT arcminute localization of a burst
  85. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  86. GRB 251106A: MASTER optical observations
  87. GRB 251103B: AstroSat CZTI detection
  88. GRB 251025C: TERI Gamma-ray detection
  89. GRB 251016B: TERI Gamma-ray detection
  90. GRB 251016A: TERI Gamma-ray detection of a short burst
  91. GRB 250920C: TERI Gamma-ray detection
  92. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  93. GRB 251105A: Fermi GBM Observation
  94. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  95. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  97. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  98. Fermi GBM Sub-Threshold Detection of GRB 251105B
  99. GRB 251103B: Swift/UVOT Upper Limits
  100. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate

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