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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').
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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.

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

32509 results found.

  1. EP251118a: NOT candidate optical counterpart
  2. GRB 251118A: Swift ToO observations
  3. EP251118a: Einstein Probe detected of a fast X-ray transient
  4. Fermi GRB 251118B: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  6. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  7. GRB 251116C: SVOM/ECLAIRs refined analysis
  8. GRB 251116B: SVOM/ECLAIRs refined analysis
  9. GRB 251117A: AstroSat CZTI detection
  10. GRB 251114B: Insight-HXMT/HE detection
  11. GRB 251114B: GECAM-B detection of a short burst
  12. GRB 251117A: Fermi GBM observation
  13. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  14. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  15. GRB 251116D: Insight-HXMT/HE detection
  16. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 251117A: SVOM/GRM observation of a short burst
  18. GRB 251117A: Tiled Swift observations
  19. GRB 251117A: Fermi-LAT detection
  20. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  21. GRB 251116C: Swift/BAT arcminute localization of a burst
  22. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  23. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  24. GRB 251116B: SVOM/VT optical upper limit
  25. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  26. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  27. GRB 251116D: Glowbug gamma-ray detection
  28. EP251023a: Assy AZT-20 optical observations
  29. EP251023a: UAFO and AbAO optical observations
  30. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  31. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  32. GRB 251116C: SVOM/VT optical upper limit
  33. GRB 251025B: further Mondy optical observations
  34. GRB 251111A: Mondy optical upper limit
  35. GRB 251116B: EP-FXT follow-up observation
  36. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  38. GRB 251116B: LCO optical upper limits
  39. GRB 251116C: LCO optical upper limits
  40. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  41. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  42. GRB 251115A: Tiled Swift observations
  43. GRB 251115A: Fermi-LAT detection
  44. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  45. Fermi GRB 251115A: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  47. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  48. GRB 251113A: Glowbug gamma-ray detection
  49. GRB 251113A: AstroSat CZTI detection
  50. GRB 251112A: Swift-BAT refined analysis
  51. Konus-Wind detection of GRB 251108C
  52. Konus-Wind detection of GRB 251103A
  53. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  54. IPN triangulation of GRB 251108C
  55. Fermi GRB 251114A: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  57. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  58. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  59. Fermi GRB 251113A: Global MASTER-Net observations report
  60. GRB 251111A: SVOM/ECLAIRs refined analysis
  61. GRB 251025B: SVOM/ECLAIRs refined analysis
  62. GRB 251112A: Swift/UVOT Upper Limits
  63. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  64. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  65. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  66. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  67. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  68. GRB251111A: 1.3m DFOT optical upper limit
  69. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  70. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  71. GRB 251111A: SVOM/VT optical observations with X-band data
  72. GRB 251111A: Swift-XRT observations
  73. GRB 251111A: EP-FXT counterpart detection
  74. GRB 251013C: Chandra X-ray observations and jet break detection
  75. GRB 251111A: SVOM/VT optical observations with VHF data
  76. GRB 251111A: KAIT optical upper limit
  77. GRB 251111A: LCO optical observation
  78. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  79. GRB 251103B: Swift-BAT refined analysis
  80. GRB 251106A: Swift/UVOT Upper Limits
  81. GRB 251105B: Insight-HXMT/HE detection
  82. GRB 251106B: Insight-HXMT detection
  83. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  84. GRB 251105A: AstroSat CZTI detection
  85. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  86. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  87. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  88. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  89. GRB 251102B: SVOM/GRM observation
  90. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  92. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  93. IPN triangulation of GRB 251105B (possible sGRB with EE)
  94. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  95. GRB 251106A: Swift-XRT afterglow detection
  96. GRB 251106A: Kilonova-Catcher optical upper limit
  97. Fermi GBM Sub-Threshold Detection of GRB 251106A
  98. GRB 251106A: Swift/BAT arcminute localization of a burst
  99. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  100. GRB 251106A: MASTER optical observations

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