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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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28115 results found.

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

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