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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"

26042 results found.

  1. Trigger_18947: Swift ToO observations (retracted)
  2. GRB 241113B: EP-FXT afterglow detection
  3. LIGO/Virgo/KAGRA S241125n: DDOTI Optical Upper Limits
  4. LIGO/Virgo/KAGRA S241125n: Gaoyazi/GOT optical observations
  5. LIGO/VIRGO/KAGRA S241125n: GROWTH-India telescope optical observations
  6. LIGO/Virgo S241125n: Swift XRT observations, 5 X-ray sources
  7. EP241125a: EP detection of an X-ray transient
  8. LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on a Optical Counterpart at the BAT Position
  9. LIGO/Virgo/KAGRA S241125n: Upper limits from Fermi-GBM Observations
  10. LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
  11. LIGO/Virgo/KAGRA S241125n: Kinder optical upper limit in the BAT error region
  12. LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
  13. LIGO/Virgo/KAGRA S241125n: No counterpart candidates in INTEGRAL SPI-ACS prompt observation, comparisong with Swift/BAT counterpart
  14. LIGO/Virgo/KAGRA S241125n: Updated Sky localization and Coincidence with External Event
  15. LIGO/Virgo/KAGRA S241125n: Swift/BAT-GUANO candidate counterpart
  16. GRB 241113B: SVOM/VT optical afterglow observations
  17. Konus-Wind detection of GRB 241117A
  18. IPN triangulation of GRB 241117A
  19. GRB 241026A: VIRT Optical Upper Limit
  20. GRB 241025A: VIRT Optical Upper Limit
  21. GRB 241120A: Mondy and AbAO optical observations
  22. GRB 241113A: Possible ATCA Radio detection
  23. GRB 241115A: CALET Gamma-Ray Burst Monitor detection
  24. GRB 241112B: Mephisto further optical observations
  25. GRB 241115a: PRIME near-infrared upper limits
  26. GRB 241117A: Swift/BAT-GUANO localization skymap of a burst
  27. LIGO/Virgo/KAGRA S241116cq: Upper limits from Swift/BAT-GUANO
  28. GRB 241115B: Fermi GBM Observation
  29. GRB 241115B: Swift/BAT-GUANO localization skymap of a long burst
  30. GRB 241115C: Fermi GBM Observation
  31. GRB 241115A: Swift-XRT afterglow detection
  32. EP241115a/GRB 241115D: Optical upper limits with Kinder observations
  33. GRB 241113B: Mephisto upper limits
  34. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  35. EP241113a: Swift XRT weak detection
  36. GRB 241115A: Fermi GBM Observation
  37. GRB 241115A: LCOGT Optical Upper Limits
  38. GRB 241115C: Swift/BAT-GUANO localization skymap of a burst
  39. Swift GRB 241115A: Global MASTER-Net observations report
  40. GRB 241115A: Swift detection of a burst
  41. EP 241113a: LBT possible optical counterpart
  42. GRB 241113B: KAIT Optical Afterglow Candidate
  43. GRB 241113A: Swift-BAT refined analysis
  44. GRB 241113A: PRIME near-infrared upper limits
  45. GRB 241113A: J-band observations with WINTER
  46. GRB 241113B: Swift-XRT observations
  47. GRB 241113A: 1.6m Mephisto and 50cm array optical upper limits
  48. GRB 241113A: KAIT optical observations
  49. GRB 241113A: Swift-XRT refined Analysis
  50. GRB 241113A: Swift/UVOT Detection
  51. GRB 241113A: REM detection of the optical/NIR afterglow
  52. Konus-Wind detection of GRB 241107A (short/hard)
  53. GRB 241113B: Swift ToO observations
  54. GRB 241113A: LCO optical observations
  55. GRB 241113A: Enhanced Swift-XRT position
  56. GRB241113A: LCOGT (40-cm) optical counterpart detection
  57. GRB 241113A: MASTER010615.66-224018.2 optical counterpart detection
  58. GRB 241113A: Swift detection of a burst with an optical counterpart
  59. Swift GRB241113.33: Global MASTER-Net observations report
  60. GRB 241112B: AbAO optical upper limit
  61. GRB 241107A: GROWTH-India telescope optical upper limit
  62. GRB 241112B: Optical afterglow detection confirmation in revisiting the Mephisto data
  63. GRB 241112B: Swift-XRT afterglow detection
  64. GRB 241112B: LCO optical detection of the SVOM/VT candidate
  65. GRB 241112B: SVOM/VT afterglow detection
  66. GRB 241107A: Swift/BAT candidate arcminute localization of a short burst
  67. GRB 241112B: Swift ToO observations
  68. GRB 241107A: INTEGRAL IBIS localization
  69. GRB 241105A: VLT/FORS2 refined spectroscopic redshift z = 2.681
  70. IPN triangulation of GRB 241107A (short/hard)
  71. GRB 241025A: VZLUSAT-2 detection
  72. GRB 241030B: TESS detection of optical counterpart
  73. EP241107a: AbAO optical upper limit
  74. GRB 241108A: Further COLIBRÍ Upper Limits on the Optical Counterpart
  75. GRB 241108A: Swift-XRT observations
  76. EP241107A: MASTER optical observations of xray transient
  77. EP241107a: KAIT optical observations
  78. GRB 241108A: Swift ToO observations
  79. GRB 241030A: TESS observations
  80. EP241107a: Kinder optical follow-up observations
  81. EP241107a: AKO Optical Afterglow Follow-Up Observations
  82. GRB 241105A: EP-FXT follow-up observations
  83. GRB 241105A: SVOM/GRM observation
  84. GRB 241105a: PRIME near-infrared upper limits
  85. GRB 241105A: ePESSTO+ NTT optical afterglow detection
  86. EP241107a: GIT optical observations
  87. EP241107a: AKO Optical Afterglow Detection
  88. GRB 241025A: LBT optical observations
  89. GRB241105A: Gemini-South Optical Afterglow Detection
  90. GRB 241105A: VLT/FORS2 optical afterglow rapid fading
  91. GRB 241105A: Swift/UVOT Detection
  92. GRB 241105A: Swift/BAT-GUANO refined analysis of short burst with extended emission
  93. GRB 241030A: optical afterglow detection from the INAF Asiago Observatory
  94. GRB 241105A: BOOTES-7 optical detection
  95. GRB 241030A: Mondy optical observations
  96. GRB 241105A: Fermi GBM Observation of a Short Burst with Extended Emission
  97. GRB 241105A: SVOM/VT optical afterglow observations
  98. GRB 241105A: Swift-XRT afterglow detection
  99. GRB 241104A: Swift-XRT observations
  100. GRB 241105A: Swift ToO observations

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