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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"

32538 results found.

  1. GRB 250725A: Swift-BAT refined analysis
  2. Konus-Wind detection of GRB 250725A
  3. GRB 250725A: SVOM/GRM observation
  4. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  5. GRB 250725A: Swift/UVOT Upper Limits
  6. GRB 250725A: Fermi-LAT detection
  7. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  8. GRB 250725A: BOOTES-7 early optical detection
  9. GRB 250725A: SVOM/VT optical candidate
  10. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  11. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  13. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  14. SVOM J195836+32283 is not a real source
  15. SVOM J195836+32283/sb25072103: Second VT observation
  16. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  17. GRB 250721A: Fermi GBM Observation
  18. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  19. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  20. GRB 250713A : SVOM/ECLAIRs refined analysis
  21. GRB 250717B: SVOM/GRM observation
  22. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  23. GRB 250721A: Tiled Swift observations
  24. GRB 250721A: MAXI/GSC detection
  25. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  26. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  27. GRB 250717B: COLIBRÍ optical upper limit
  28. GRB 250718B: Fermi GBM Final Localization Correction
  29. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  30. GRB 250717B: Swift ToO observations
  31. GRB 270713A: Kitab and AbAO Optical Observations
  32. GRB 250717B: Fermi GBM Observation
  33. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  34. Konus-Wind detection of GRB 250716A
  35. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  36. GRB 250716A: Swift ToO observations
  37. GRB 250714A: SVOM/GRM observation
  38. Fermi GRB 250716A: Global MASTER-Net observations report
  39. Fermi GRB 250715A: Global MASTER-Net observations report
  40. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  41. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  42. GRB 250713A: Mephisto optical upper limits
  43. Fermi GRB 250714A: Global MASTER-Net observations report
  44. GRB 250713A: SVOM/VT optical upper limit
  45. GRB 250713A: NOT optical upper limits
  46. GRB 250713A: OHP/T193 upper limit
  47. GRB 250713A: SVOM/C-GFT upper limit
  48. GRB 250706B/C: 7DT Follow-up Observations
  49. GRB 250713A: EP-FXT counterpart detection
  50. EP250711a: COLIBRÍ continuous optical observations
  51. GRB 250706A: Swift-BAT refined analysis
  52. GRB 250702F: Swift-BAT refined analysis
  53. GRB 250628A: Swift-BAT refined analysis
  54. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  55. GRB 250713A: JinShan optical upper limits
  56. EP250711a: Global MASTER-Net observations report
  57. GRB 250711A: DDOTI Optical Upper Limit
  58. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  59. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  60. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  61. GRB 250711A: SVOM/GRM observation
  62. EP250711a: NOT optical counterpart candidate
  63. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  64. Fermi GRB 250711A: Global MASTER-Net observations report
  65. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  66. GRB 250704A: GRANDMA observations
  67. GRB 250704A: SVOM/ECLAIRs refined analysis
  68. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  69. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  70. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  71. GRB 250702B,D,E / EP250702a: ALMA detection
  72. IceCube-250708A: No Candidates from WINTER
  73. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  74. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  75. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  76. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  77. GRB 250706B/C: Insight-HXMT detection
  78. EP/WXT 01709181970: GOTO observations confirm stellar variability
  79. EP250704a/GRB 250704B: 10 GHz VLA detection
  80. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  81. IceCube-250706A: No Candidates from WINTER
  82. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  83. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  84. GRB 250704B / EP250704a: VLA radio detection
  85. Fermi GRB 250708A: Global MASTER-Net observations report
  86. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  87. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  89. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  90. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  91. EP250704a/GRB250704B : HCT optical and NIR upper limits
  92. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  93. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  94. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  95. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  96. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  97. GRB 250702F: radio detection with the VLA
  98. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  99. IceCube-250706A: EP-FXT follow-up observations
  100. Fermi-LAT Gamma-ray Observations of IceCube-250706A

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