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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"

18102 results found.

  1. GRB 250830B: Swift-XRT afterglow detection
  2. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  3. GRB 250902A: SVOM/GRM observation
  4. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  5. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 250901A: SVOM/VT optical afterglow with VHF data
  7. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  8. GRB 250901A: LCO optical upper limit
  9. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  10. EP250831a: NOT optical observations and tentative afterglow candidate
  11. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  12. GRB 250901A: SVOM detection of a burst
  13. EP250901a: Mephisto optical upper limits
  14. EP250901a: Einstein Probe detection of an X-ray transient
  15. EP250831a: EP-WXT detection of a fast X-ray transient
  16. GRB 250831A: Swift-XRT counterpart detection
  17. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. GRB 250831A: SVOM/VT upper limit with VHF data
  19. GRB 250831A: SVOM detection of a soft burst
  20. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  21. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  22. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  23. GRB 250830B: Swift ToO observations
  24. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  25. EP250821a: SOAR observations
  26. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  27. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  28. GRB 250808B: SVOM detection of a burst through offline search
  29. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  30. EP250828a: Optical counterpart detection with Kinder observations
  31. EP250828a: Liverpool Telescope upper limits
  32. EP-WXT trigger 01709200800 : KAIT optical observations
  33. EP250828a: KAIT optical upper limit
  34. EP250827a: Swift/UVOT Detection
  35. EP250828a: NOT optical counterpart confirmation
  36. EP250828a: SVOM/VT optical candidate
  37. EP250828a: Seimei/TriCCS optical counterpart detection
  38. GRB 250828B: Swift detection of a burst
  39. EP250828a: Optical upper limit with Kinder observations
  40. EP250828a: Einstein Probe detection of an X-ray transient
  41. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  42. EP250827a: confirmation of optical rebrightening with LCO
  43. GRB 250826A: SVOM/GRM observation
  44. EP250827A: An optical rebrightening was detected by LCO.
  45. EP250827a: TRT optical observations
  46. EP250827a: Einstein Probe detection of an X-ray transient
  47. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  48. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  49. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  50. Fermi GRB 250824B: Global MASTER-Net observations report
  51. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  52. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  53. EP250821a: MeerKAT radio counterpart
  54. GRB 250823A: COLIBRÍ optical observations
  55. GRB 250823A: SVOM/VT optical observation
  56. GRB 250823A: Swift/UVOT Detection
  57. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  58. GRB 250823A: Enhanced Swift-XRT position
  59. GRB 250823A: LCOGT Optical Detection
  60. GRB 250823A: Swift detection of a burst
  61. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  62. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  63. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  64. GRB 250821A: Kilonova-Catcher optical upper limits
  65. GRB 250821A: VLT/FORS2 Optical Observation
  66. GRB 250821B: SVOM/GRM observation
  67. EP250821a: SVOM/VT optical observation
  68. GRB 250821A: NOT z-band upper limit
  69. GRB 250821A: KAIT optical upper limit
  70. GRB 250821A: Enhanced Swift-XRT position
  71. GRB 250821A: Swift/UVOT Upper Limits
  72. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  73. GRB 250821A: LCOGT Optical Upper Limits
  74. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  75. GRB 250821A: Swift detection of a burst
  76. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  77. EP250821a: Einstein Probe detection of an X-ray transient
  78. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  79. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  80. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  81. GRB 250814A: Swift/UVOT Upper Limits
  82. GRB 250813B: Swift/UVOT Upper Limit
  83. IPN triangulation of GRB 250816A (short)
  84. IPN triangulation of GRB 250814C (short)
  85. IPN triangulation of GRB 250804B (short)
  86. GRB 250818B: Kilonova-Catcher optical afterglow detection
  87. GRB 250818B: Swift/UVOT Detection
  88. GRB 250818B: SAO RAS optical observations
  89. GRB 250818B: KAIT optical observations
  90. GRB 250818A: Swift/UVOT Upper Limits
  91. GRB 250818A: Enhanced Swift-XRT position
  92. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  93. GRB 250814A: Further GRAWITA TNG NIR observations
  94. GRB 250818B: SVOM detection of a short burst
  95. GRB 250818A: Swift detection of a burst
  96. GRB 250816A: SVOM/GRM observation of a short burst
  97. GRB 250813B: Liverpool Telescope optical upper limits
  98. GRB 250814A: Further COLIBRÍ optical upper limit
  99. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  100. GRB 250814A: GRAWITA TNG NIR observations

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