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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"

20146 results found.

  1. GRB 250831A: SVOM/VT upper limit with VHF data
  2. GRB 250831A: SVOM detection of a soft burst
  3. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  4. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  5. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  6. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  7. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  8. GRB 250828B: Swift-BAT refined analysis
  9. EP250821a: SOAR observations
  10. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  11. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  12. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  13. GRB 250808B: SVOM detection of a burst through offline search
  14. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP250828a: Optical counterpart detection with Kinder observations
  16. EP250828a: Liverpool Telescope upper limits
  17. EP-WXT trigger 01709200800 : KAIT optical observations
  18. EP250828a: KAIT optical upper limit
  19. EP250827a: Swift/UVOT Detection
  20. EP250828a: NOT optical counterpart confirmation
  21. EP250828a: SVOM/VT optical candidate
  22. EP250828a: Seimei/TriCCS optical counterpart detection
  23. EP250828a: Optical upper limit with Kinder observations
  24. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  25. EP250828a: Einstein Probe detection of an X-ray transient
  26. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  27. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  28. EP250827a: confirmation of optical rebrightening with LCO
  29. EP250827a: GOTO observation of the optical afterglow
  30. GRB 250826A: SVOM/GRM observation
  31. EP250827A: An optical rebrightening was detected by LCO.
  32. EP250827a: TRT optical observations
  33. EP250827a: BOOTES-7 early optical dectection
  34. EP250827a: Las Cumbres independent detection of the optical counterpart
  35. EP250827a: Einstein Probe detection of an X-ray transient
  36. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  37. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  38. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  39. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  40. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  41. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  42. EP250821a: MeerKAT radio counterpart
  43. GRB 250823A: COLIBRÍ optical observations
  44. GRB 250823A: SVOM/VT optical observation
  45. GRB 250823A: Swift/UVOT Detection
  46. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  47. GRB 250818B: MeerKAT Detection
  48. GRB 250823A: Enhanced Swift-XRT position
  49. GRB 250823A: LCOGT Optical Detection
  50. GRB 250823A: Liverpool Telescope optical detection
  51. GRB 250823A: Swift detection of a burst
  52. Konus-Wind detection of GRB 250821B
  53. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  54. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  55. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  56. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  57. GRB 250821A: Kilonova-Catcher optical upper limits
  58. GRB 250821A: VLT/FORS2 Optical Observation
  59. GRB 250821B: SVOM/GRM observation
  60. EP250821a: SVOM/VT optical observation
  61. GRB 250821A: NOT z-band upper limit
  62. GRB 250821A: KAIT optical upper limit
  63. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  64. GRB 250821A: Enhanced Swift-XRT position
  65. GRB 250821A: Swift/UVOT Upper Limits
  66. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  67. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  68. GRB 250821A: LCOGT Optical Upper Limits
  69. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  70. GRB 250821A: Swift detection of a burst
  71. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  72. EP250821a: Einstein Probe detection of an X-ray transient
  73. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  74. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  75. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  76. GRB 250814A: Swift/UVOT Upper Limits
  77. GRB 250813B: Swift/UVOT Upper Limit
  78. IPN triangulation of GRB 250816A (short)
  79. IPN triangulation of GRB 250814C (short)
  80. IPN triangulation of GRB 250804B (short)
  81. GRB 250818B: Kilonova-Catcher optical afterglow detection
  82. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  83. GRB 250818B: Liverpool Telescope optical detections
  84. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  85. GRB 250818A: AstroSat CZTI detection
  86. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  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. GRB 250813B: SVOM/ECLAIRs refined analysis
  93. GRB 250818A: Fermi GBM Observation
  94. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  95. GRB 250814A: Further GRAWITA TNG NIR observations
  96. GRB 250818B: SVOM detection of a short burst
  97. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  98. GRB 250818A: Swift detection of a burst
  99. GRB 250816A: SVOM/GRM observation of a short burst
  100. SVOM/sb25081602: detection of a likely X-ray transient

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