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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"

27320 results found.

  1. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  2. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  3. GRB250101A: Radio upper limits from VLA observations
  4. GRB 250305A: SVOM/GRM observation of a burst
  5. The EP-WXT trigger 01709132323 is likely a flaring star
  6. EP250304A: Upper limits from Fermi-GBM Observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  8. EP250302a: Optical Observations at CrAO and SAO RAS
  9. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  10. EP 250304A: Optical counterpart detection by LCO
  11. EP250302A: 1.3m DFOT optical afterglow detection
  12. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  13. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP250304a: REM NIR upper limits
  15. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  16. EP250302a: Mondy Continued Optical Observations
  17. EP250304a: Swift-XRT detection of a fading X-ray source
  18. EP250304a: TRT optical counterpart detection
  19. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  20. EP250304a: Einstein Probe detection of an X-ray transient
  21. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  22. EP250302a: SAO RAS optical observations
  23. EP250302a : GIT optical follow-up
  24. EP250225a: the candidate optical counterpart is an AGN
  25. EP250302a: Kinder optical follow-up observations
  26. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  27. EP250302a: Swift/UVOT detection
  28. EP250302a: optical observation from the INAF Asiago Observatory
  29. EP250302a: REM NIR upper limits
  30. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  31. EP250302a: Mondy Observations and Optical Light Curve
  32. EP250302a: VLT/MUSE optical redshift z = 1.131
  33. EP250302A: VLT near-infrared observations
  34. EP250302A: VLT/X-shooter tentative redshift
  35. EP250302a: OHP/T193 optical and spectroscopic observations
  36. EP250302a: Swift-XRT observations of a fading X-ray source
  37. EP250302a: Einstein Probe detection of an X-ray transient
  38. EP250302a: SVOM/C-GFT optical observations
  39. GRB 250226A: GRANDMA Optical Observations
  40. EP250302a: Montarrenti Observatory optical detection
  41. EP250302a: Nanshan/HMT optical counterpart detection
  42. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  43. GRB 250225B: VLT near-infrared afterglow confirmation
  44. EP250228a: Optical observations with Kinder and Swift/UVOT
  45. Konus-Wind detection of GRB 250226A
  46. GRB 250225B: EIRSAT-1 GMOD Detection
  47. GRB 250226A: KAO Optical Upper Limit
  48. GRB 250226A: AbAO AS-32 Optical Upper Limit
  49. EP250227a: Global MASTER-Net observations report
  50. EP250223A: Upper limits from Fermi-GBM Observations
  51. EP250227a: TRT optical upper limit
  52. GRB 250225B: VLT/HAWKI near-infrared observations
  53. EP250227a: Optical upper limits with Kinder observations
  54. EP250227a: NOT optical observations
  55. EP250227a: Einstein Probe detected of a fast X-ray transient
  56. EP250228a: updates on the EP observations
  57. GRB 250226A: Fermi GBM Observation
  58. EP250223a: J band upper limit by SYSU 80cm telescope
  59. EP250228a: Swift/XRT localisation
  60. EP250228a: Einstein Probe detection of an X-ray transient
  61. GRB 250226A / EP250226a: LCO detection of the afterglow
  62. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  64. GRB 250225B: VLT/Xshooter imaging
  65. GRB 250205A / EP250205A: further radio observations with the VLA
  66. EP250225a: NOT optical candidate counterpart
  67. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  68. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  69. EP250225a: TRT optical upper limits
  70. EP250226a/GRB 250226A: 1.6m Mephisto observations
  71. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  72. EP250226a/GRB 250226A: Kinder optical follow-up observations
  73. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  74. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  76. GRB 250225B: Fermi GBM Observation
  77. GRB 250225B: REM NIR upper limits
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  79. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  80. EP250223a: CrAO ZTSH optical observation
  81. GRB 250225B: VLT optical and near-infrared candidate counterpart
  82. GRB 250225B: SVOM/GRM observation of a long burst
  83. EP250226a/GRB 250226A: GSP detects optical counterpart
  84. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  85. EP250226a / GRB 250226A: TRT optical counterpart observation
  86. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  87. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  88. EP250225a: GSP optical upper limit
  89. EP250223a: GMG Optical Observation
  90. EP250225a: Einstein Probe detected of a fast X-ray transient
  91. GRB 250225B: Swift detection of a burst
  92. EP250223a: GROWTH-India Telescope optical observations
  93. GRB 250221A: Swift-BAT refined analysis
  94. EP250215A: J band upper limit by SYSU 80cm telescope
  95. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  97. EP250223a: Kinder optical follow-up observations
  98. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  99. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  100. GRB 250119B: VZLUSAT-2 detection

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