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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"

18484 results found.

  1. GRB 250831A: SVOM detection of a soft burst
  2. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  3. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  4. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  5. GRB 250830B: Swift ToO observations
  6. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  7. EP250821a: SOAR observations
  8. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  9. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  10. GRB 250808B: SVOM detection of a burst through offline search
  11. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP250828a: Optical counterpart detection with Kinder observations
  13. EP250828a: Liverpool Telescope upper limits
  14. EP-WXT trigger 01709200800 : KAIT optical observations
  15. EP250828a: KAIT optical upper limit
  16. EP250827a: Swift/UVOT Detection
  17. EP250828a: NOT optical counterpart confirmation
  18. EP250828a: SVOM/VT optical candidate
  19. EP250828a: Seimei/TriCCS optical counterpart detection
  20. GRB 250828B: Swift detection of a burst
  21. EP250828a: Optical upper limit with Kinder observations
  22. EP250828a: Einstein Probe detection of an X-ray transient
  23. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  24. EP250827a: confirmation of optical rebrightening with LCO
  25. GRB 250826A: SVOM/GRM observation
  26. EP250827A: An optical rebrightening was detected by LCO.
  27. EP250827a: TRT optical observations
  28. EP250827a: Einstein Probe detection of an X-ray transient
  29. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  30. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  31. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  32. Fermi GRB 250824B: Global MASTER-Net observations report
  33. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  34. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  35. EP250821a: MeerKAT radio counterpart
  36. GRB 250823A: COLIBRÍ optical observations
  37. GRB 250823A: SVOM/VT optical observation
  38. GRB 250823A: Swift/UVOT Detection
  39. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  40. GRB 250823A: Enhanced Swift-XRT position
  41. GRB 250823A: LCOGT Optical Detection
  42. GRB 250823A: Swift detection of a burst
  43. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  44. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  45. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  46. GRB 250821A: Kilonova-Catcher optical upper limits
  47. GRB 250821A: VLT/FORS2 Optical Observation
  48. GRB 250821B: SVOM/GRM observation
  49. EP250821a: SVOM/VT optical observation
  50. GRB 250821A: NOT z-band upper limit
  51. GRB 250821A: KAIT optical upper limit
  52. GRB 250821A: Enhanced Swift-XRT position
  53. GRB 250821A: Swift/UVOT Upper Limits
  54. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  55. GRB 250821A: LCOGT Optical Upper Limits
  56. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  57. GRB 250821A: Swift detection of a burst
  58. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  59. EP250821a: Einstein Probe detection of an X-ray transient
  60. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  61. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  62. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  63. GRB 250814A: Swift/UVOT Upper Limits
  64. GRB 250813B: Swift/UVOT Upper Limit
  65. IPN triangulation of GRB 250816A (short)
  66. IPN triangulation of GRB 250814C (short)
  67. IPN triangulation of GRB 250804B (short)
  68. GRB 250818B: Kilonova-Catcher optical afterglow detection
  69. GRB 250818B: Swift/UVOT Detection
  70. GRB 250818B: SAO RAS optical observations
  71. GRB 250818B: KAIT optical observations
  72. GRB 250818A: Swift/UVOT Upper Limits
  73. GRB 250818A: Enhanced Swift-XRT position
  74. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  75. GRB 250814A: Further GRAWITA TNG NIR observations
  76. GRB 250818B: SVOM detection of a short burst
  77. GRB 250818A: Swift detection of a burst
  78. GRB 250816A: SVOM/GRM observation of a short burst
  79. GRB 250813B: Liverpool Telescope optical upper limits
  80. GRB 250814A: Further COLIBRÍ optical upper limit
  81. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  82. GRB 250814A: GRAWITA TNG NIR observations
  83. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  84. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  85. GRB250814A: TRT optical upper limits
  86. GRB 250814B: SVOM/GRM observation
  87. GRB 250814A: P200/WIRC observations of the afterglow candidate
  88. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  89. GRB 250814A: KAIT optical upper limit
  90. GRB 250814A: Swift-XRT refined Analysis
  91. GRB 250814A: Possible afterglow candidate from P200/WIRC
  92. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  93. GRB 250814A: J-band upper limit from WINTER
  94. GRB 250813B: NOT observations of the optical afterglow
  95. GRB 250814A: COLIBRÍ optical upper limit
  96. GRB 250813A: AstroSat CZTI detection
  97. GRB 250814A: DDOTI Optical Upper Limit
  98. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  99. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).

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