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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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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28117 results found.

  1. EP250828a: SVOM/VT optical candidate
  2. EP250828a: Seimei/TriCCS optical counterpart detection
  3. EP250828a: Optical upper limit with Kinder observations
  4. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  5. EP250827a: LCO observations show fading optical counterpart
  6. EP250828a: Einstein Probe detection of an X-ray transient
  7. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  8. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  9. EP250827a: confirmation of optical rebrightening with LCO
  10. GRB 250826A: SVOM/GRM observation
  11. EP250827A: An optical rebrightening was detected by LCO.
  12. EP250827a: Swift-XRT counterpart detection
  13. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  14. EP250827a: TRT optical observations
  15. EP250827a: Gemini-South redshift z = 1.613
  16. EP250827a: Einstein Probe detection of an X-ray transient
  17. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  18. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  19. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  20. Fermi GRB 250824B: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  22. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  23. GRB 250823A: Swift-BAT refined analysis
  24. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  25. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  26. GRB 250823A: Swift-XRT refined Analysis
  27. EP250821a: MeerKAT radio counterpart
  28. GRB 250823A: COLIBRÍ optical observations
  29. GRB 250823A: SVOM/VT optical observation
  30. GRB 250823A: Swift/UVOT Detection
  31. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  32. GRB 250823A: Fermi GBM Observation
  33. GRB 250823A: Enhanced Swift-XRT position
  34. GRB 250823A: LCOGT Optical Detection
  35. GRB 250823A: Swift detection of a burst
  36. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  37. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  38. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  39. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  40. GRB 250806A: Gemini observations of host galaxy candidate
  41. GRB 250821A: Kilonova-Catcher optical upper limits
  42. EP250821a: Swift/XRT counterpart fading
  43. GRB 250821A: Swift-BAT refined analysis
  44. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  45. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  46. GRB 250821A: VLT/FORS2 Optical Observation
  47. GRB 250821B: SVOM/GRM observation
  48. EP250821a: SVOM/VT optical observation
  49. GRB 250821A: NOT z-band upper limit
  50. GRB 250821A: KAIT optical upper limit
  51. GRB 250821A: Swift-XRT refined Analysis
  52. GRB 250821B: Fermi GBM Detection
  53. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  54. GRB 250821A: Enhanced Swift-XRT position
  55. GRB 250821A: Swift/UVOT Upper Limits
  56. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  57. EP250821a: Swift XRT and UVOT counterpart detection
  58. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  59. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  60. GRB 250821A: LCOGT Optical Upper Limits
  61. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  62. GRB 250821A: Swift detection of a burst
  63. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  64. EP250821a: Einstein Probe detection of an X-ray transient
  65. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  66. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  67. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  68. GRB 250814A: Swift/UVOT Upper Limits
  69. GRB 250813B: Swift/UVOT Upper Limit
  70. IPN triangulation of GRB 250816A (short)
  71. IPN triangulation of GRB 250814C (short)
  72. IPN triangulation of GRB 250804B (short)
  73. GRB 250818B: Kilonova-Catcher optical afterglow detection
  74. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  75. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  76. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  77. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  78. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  79. GRB 250818B: Swift/UVOT Detection
  80. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  81. GRB 250818B: SAO RAS optical observations
  82. GRB 250818A: Swift-XRT refined Analysis
  83. GRB 250818B: EP-FXT counterpart detection
  84. GRB 250818A: Swift-BAT refined analysis
  85. GRB 250818B: KAIT optical observations
  86. GRB 250818A: Swift/UVOT Upper Limits
  87. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  88. GRB 250818A: Enhanced Swift-XRT position
  89. GRB 250813B: SVOM/ECLAIRs refined analysis
  90. GRB 250818A: Fermi GBM Observation
  91. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  92. GRB 250814A: Further GRAWITA TNG NIR observations
  93. GRB 250818B: Swift-XRT afterglow detection
  94. GRB 250818B: SVOM detection of a short burst
  95. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  96. GRB 250818A: Swift detection of a burst
  97. sb25081602: Swift-XRT observations
  98. GRB 250816A: SVOM/GRM observation of a short burst
  99. GRB 250814A: Swift-BAT refined analysis
  100. GRB 250813B: Liverpool Telescope optical upper limits

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