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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"

32494 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  2. EP250302a: Optical Observations at CrAO and SAO RAS
  3. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  4. EP 250304A: Optical counterpart detection by LCO
  5. EP250302A: 1.3m DFOT optical afterglow detection
  6. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  7. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  8. Konus-Wind detection of GRB 250222A
  9. EP250304a: REM NIR upper limits
  10. IPN triangulation of GRB 250222A
  11. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  12. EP250302a: Mondy Continued Optical Observations
  13. EP250304a: VLT/X-shooter redshift z = 0.200
  14. EP250304a: Swift-XRT detection of a fading X-ray source
  15. EP250304a: TRT optical counterpart detection
  16. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  17. EP250304a: Global MASTER-Net observations report
  18. EP250302a: SVOM/VT optical observation
  19. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  20. EP250302a: SAO RAS optical observations
  21. EP250302a : GIT optical follow-up
  22. EP250302a: VLT/X-shooter redshift confirmation
  23. EP250225a: the candidate optical counterpart is an AGN
  24. EP250302a: Kinder optical follow-up observations
  25. EP250302a: Swift/UVOT detection
  26. EP250302a: NUTTelA-TAO Early Measurments
  27. EP250302a: optical observation from the INAF Asiago Observatory
  28. EP250302a: REM NIR upper limits
  29. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  30. EP250302a: Mondy Observations and Optical Light Curve
  31. EP250302a: VLT/MUSE optical redshift z = 1.131
  32. INTEGRAL: end of scientific operations
  33. EP250302A: VLT near-infrared observations
  34. EP250302A: VLT/X-shooter tentative redshift
  35. EP250302a: OHP/T193 optical and spectroscopic observations
  36. EP250302a: Global MASTER-Net observations report
  37. EP250302a: Xinglong F60B optical observation
  38. EP250302a: Swift-XRT observations of a fading X-ray source
  39. EP250302a: Einstein Probe detection of an X-ray transient
  40. EP250302a: SVOM/C-GFT optical observations
  41. GRB 250226A: GRANDMA Optical Observations
  42. EP250302a: Montarrenti Observatory optical detection
  43. Fermi GRB 250302A: Global MASTER-Net observations report
  44. EP250302a: FTW optical and NIR detection
  45. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  46. GRB 250225B: VLT near-infrared afterglow confirmation
  47. EP250228a: Optical observations with Kinder and Swift/UVOT
  48. Konus-Wind detection of GRB 250226A
  49. GRB 250225B: EIRSAT-1 GMOD Detection
  50. GRB 250226A: KAO Optical Upper Limit
  51. GRB 250226A: AbAO AS-32 Optical Upper Limit
  52. EP250227a: Global MASTER-Net observations report
  53. EP250223A: Upper limits from Fermi-GBM Observations
  54. EP250227a: TRT optical upper limit
  55. GRB 250225B: VLT/HAWKI near-infrared observations
  56. EP250227a: Optical upper limits with Kinder observations
  57. EP250227a: NOT optical observations
  58. EP250228a: updates on the EP observations
  59. GRB 250226A: Fermi GBM Observation
  60. EP250225a: EP-FXT follow-up observation
  61. EP250223a: J band upper limit by SYSU 80cm telescope
  62. EP250228a: Swift/XRT localisation
  63. EP250228a: Global MASTER-Net observations report
  64. GRB 250226A / EP250226a: LCO detection of the afterglow
  65. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  66. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  67. GRB 250225B: VLT/Xshooter imaging
  68. GRB 250205A / EP250205A: further radio observations with the VLA
  69. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  70. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  71. GRB 250225B: INTEGRAL SPI-ACS detection
  72. EP250225a: NOT optical candidate counterpart
  73. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  74. EP250226a / GRB 250226A: SVOM/VT optical observations
  75. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  76. EP250225a: TRT optical upper limits
  77. EP250226a/GRB 250226A: 1.6m Mephisto observations
  78. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  79. EP250226a/GRB 250226A: Kinder optical follow-up observations
  80. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  81. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  82. Fermi GRB 250226B: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  84. GRB 250225B: Fermi GBM Observation
  85. GRB 250221A: ATCA Detections and Upper Limits
  86. GRB 250225B: REM NIR upper limits
  87. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  88. Konus-Wind detection of GRB 250225B
  89. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  90. EP250223a: CrAO ZTSH optical observation
  91. GRB 250225B: VLT optical and near-infrared candidate counterpart
  92. GRB 250225B: VLT/FORS2 candidate optical afterglow
  93. GRB 250225B: SVOM/GRM observation of a long burst
  94. GRB 250226A: GECAM-B detection
  95. GRB 250221A: EP-FXT detection of the X-ray afterglow
  96. GRB 250214A: SVOM/GRM observation
  97. EP250226a/GRB 250226A: GSP detects optical counterpart
  98. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  99. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  100. EP250226a / GRB 250226A: TRT optical counterpart observation

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