Supernova Remnant CTB Research Articles

PSR B1951+32: A Bow Shock-confined X-Ray Nebula, a Synchrotron Knot, and an Optical Counterpart Candidate

The radio pulsar PSR B1951+32 and the supernova remnant CTB 80 provide a rich laboratory for the study of neutron stars and supernova remnants. Here, we present ground-based optical and near-infrared observations of them, along with X-ray observations with Chandra and a reanalysis of archival data obtained with the Hubble Space Telescope. The X-ray observations reveal a cometary pulsar wind nebula that appears to be confined by a bow shock produced by the high-velocity motion of the pulsar, making PSR B1951+32 a rare pulsar exhibiting both an Hα bow shock and a shocked X-ray pulsar wind nebula. The distribution of Hα and radio continuum emission is indicative of a contact discontinuity of the shocked pulsar winds and shocked ambient medium at ~0.05 pc. On the other hand, the optical synchrotron knot of PSR B1951+32 likely has a flat spectrum in the optical and near-infrared wave bands, and our astrometry is consistent with only one of the two reported optical counterpart candidates for the pulsar.

A Spectral Analysis of the Central Component of CTB 80

Based on observations of the extended supernova remnant CTB 80 carried out with the Giant Metrewave Radio Telescope (GMRT, India) at 240 and 618 MHz we have analyzed the spectral behavior of the ∼ 10′ nebula formed near the pulsar PSR B1951+32, finding signatures of the interaction of the pulsar with the surrounding plasma.

New High-Resolution Radio Observations of the Supernova Remnant CTB 80

We report new high resolution and high sensitivity radio observations of the extended supernova remnant (SNR) CTB 80 (G69.0+2.7) at 240 MHz, 324 MHz, 618 MHz, and 1380 MHz. The imaging of CTB 80 at 240 MHz and 618 MHz was performed using the Giant Metrewave Radio Telescope (GMRT) in India. The observations at 324 MHz and 1380 MHz were obtained using the Very Large Array (VLA, NRAO) in its C and D configurations. The new radio images reveal faint extensions for the asymmetric arms of CTB 80. The arms are irregular with filaments and clumps of size 1' (or 0.6 pc at a distance of 2 kpc). The radio image at 1380 MHz is compared with IR and optical emission. The correspondence IR/radio is excellent along the N arm of CTB 80. Ionized gas observed in the [SII] line perfectly matches the W and N edges of CTB 80. The central nebula associated with the pulsar PSR B1951+32 was investigated with an angular resolution of 10" x 6". The new radio image obtained at 618 MHz shows with superb detail structures in the 8' x 4' E-W ``plateau'' nebula that hosts the pulsar on its western extreme. A twisted filament, about 6' in extent (~3.5 pc), trails behind the pulsar in an approximate W-E direction. In the bright ``core'' nebula (size \~45"), located to the W of the plateau, the images show a distortion in the morphology towards the W; this feature corresponds to the direction in which the pulsar escapes from the SNR with a velocity of ~240 km/s. Based on the new observations, the energetics of the SNR and of the PWN are investigated.

The Distance to the Supernova Remnant CTB 87 and the Radial Velocity of the Perseus Arm towardl = 75o, Derived from Hiand CO Observations

We present the results of an analysis of H I data from the Canadian Galactic Plane Survey and new CO observations in the direction of the radio-bright, filled-center supernova remnant (SNR) CTB 87. Our CO (1-0) and CO (3-2) data reveal evidence for associated molecular material surrounding parts of CTB 87 at a systemic velocity of vLSR ≈ -58 km s-1. There is no evidence of interacting H I or the existence of a stellar wind bubble around the SNR. This indicates a supernova explosion of Type II and a B2 or later type progenitor star. We established a new distance of 6.1 ± 0.9 kpc based on the extinction-distance relation introduced by Foster & Routledge, which agrees with a location within the Perseus spiral arm. Our result contradicts previous distance estimates based on H I absorption measurements, which indicated a distance of about 12 kpc, using a flat rotation curve. This discrepancy arises from a significant shift of the radial velocities in the direction of CTB 87 due to a spiral shock. The new distance reduces the derived physical size and the luminosity of CTB 87 by factors of 2 and 4, respectively. The properties of this plerionic SNR are then more similar to those of the other SNRs of its kind except the Crab Nebula, which is an exceptionally luminous object.

The Distance to Supernova Remnant CTB 109 Deduced from Its Environment

We conducted a study of the environment around the supernova remnant (SNR) CTB 109. We found that the SNR is part of a large complex of H II regions extending over an area of 400 pc along the Galactic plane at a distance of about 3 kpc at the closer edge of the Perseus spiral arm. At this distance, CTB 109 has a diameter of about 24 pc. We demonstrated that including spiral shocks in the distance estimation is an ultimate requirement to determine reliable distances to objects located in the Perseus arm. The most likely explanation for the high concentration of H II regions and SNRs is that the star formation in this part of the Perseus arm is triggered by the spiral shock.

The Supernova Remnant CTB 104A: Magnetic Field Structure and Interaction with the Environment

We present new, high-resolution 1420 and 408 MHz continuum images and H I and 12CO (J = 1-0) spectral line maps of the diffuse supernova remnant (SNR) CTB 104A (G93.7-0.3). Analysis of the complex continuum emission reveals no significant spectral index variations across the remnant. Three prominences around CTB 104A are found to be related to the SNR, while one extension to the east is identified as an H II region associated with a background molecular shell. Small-scale polarization and rotation measure (RM) structures are turbulent in nature, but we find a well-ordered RM gradient across the remnant, extending from southeast to northwest. This gradient does not agree with the direction of the global Galactic magnetic field but does agree with a large-scale RM anomaly inferred from RM data by Clegg et al. We show that the observed morphology of CTB 104A is consistent with expansion in a uniform magnetic field, and this is supported by the observed RM distribution. By modeling the RM gradient with a simple compression model we have determined the magnetic field strength within the remnant as B0 ≈ 2.3 μG. We have identified signatures of the interaction of CTB 104A with the surrounding neutral material and determined its distance, from the kinematics of the H I structure encompassing the radio emission, as 1.5 kpc. We also observed clear breaks in the H I shell that correspond well to the positions of two of the prominences, indicating regions where hot gas is escaping from the interior of the SNR.

The peculiar supernova remnant CTB 80

Deep CCD exposures of the peculiar supernova remnant CTB 80 in the light of the H +( Nii), (S ii), (O ii), and (O iii) lters have been obtained. These images reveal signicant shock heated emission in the area of the remnant. An extended bright diuse nebula in the south{east part of CTB 80 overlaps soft X-ray emission from ROSAT but it does not appear to be related to the remnant under study. New diuse and lamentary structures are detected to the south, south{east, and north of PSR 1951+32, most likely associated with CTB 80. Especially, the sulfur line image shows emission in the north along the outer boundary of the IRAS and HI shells. The (O iii) emission is lamentary, suggesting shock velocities greater than 100 km s 1 but its spatial extent is quite limited. Lower shock velocities are expected in the north and north{east areas of the remnant, since (O ii) emission is present, while (O iii) line emission is not detected. The comparison between the (O iii )a nd (Oii) line images further suggest the presence of signicant inhomogeneities in the interstellar medium. The flux{calibrated images do not indicate the presence of incomplete recombination zones, and we estimate that the densities of the preshock clouds should not exceed a few atoms per cm 3 . The typical projected angular widths of the observed laments are30 00 . Typical surface brightness values of the long (O iii) lament in the south are12 10 17 erg s 1 cm 2 arcsec 2 while the (O ii) image is characterized by fluxes of 10{20 10 17 erg s 1 cm 2 arcsec 2 . The area covered by the optical radiation along with the radio emission at 1410 MHz suggest that CTB 80 occupies a larger angular extent than was previously known.

3EG J2016+3657: Confirming an EGRET Blazar behind the Galactic Plane

We recently identified the blazar-like radio source G74.87+1.22 (B2013+370) as the counterpart of the high-energy gamma-ray source 3EG J2016+3657 in the Galactic plane. However, since most blazar identifications of EGRET sources are only probabilistic in quality even at high Galactic latitude, and since there also exists a population of unidentified Galactic EGRET sources, we sought to obtain additional evidence to support our assertion that 3EG J2016+3657 is a blazar. These new observations consist of a complete set of classifications for the 14 brightest ROSAT X-ray sources in the error circle, of which B2013+370 remains the most likely source of the gamma-rays. We also obtained further optical photometry of B2013+370 itself which shows that it is variable, providing additional evidence of its blazar nature. Interestingly, this field contains, in addition to the blazar, the plerionic supernova remnant CTB 87, which is too distant to be the EGRET source, and three newly discovered cataclysmic variables, all five of these X-ray sources falling within 16' of each other. This illustrates the daunting problem of obtaining complete identifications of EGRET sources in the Galactic plane.

Thermal X-ray emission of the extended lobe near 1E 2259+586 with CTB 109

A “jet-like” lobe runs northeastward from the pulsar 1E2259+586 to the shell within the supernova remnant CTB 109, and it was previously suspected to be an “X-ray jet” in a binary system analogous to SS433/W50 (Gregory & Fahlman, 1983). We report X-ray spectra of the lobe relative to elsewhere in the remnant using ASCA and ROSAT, and comparison with other X-ray jets. X-ray emission from the “jet-like” lobe is thermal with dominant lines of Ne IX, Ne X, Mg XI, and Si XIII, and has softer emission than elsewhere in the remnant. The spectral fit for the lobe indicates that the plasma is in ionization non-equilibrium and its best fit is T s ∼10 6.5 K and n o t∼48,000 cm −3yr. This lobe contrasts with the double lobes in W50 where non-thermal X-ray emission is found (Yamauchi et al., 1994). If the lobe in CTB109 is a jet, it would be similar to the Vela jet because it was recently discovered to have thermal X-rays (Markwardt & Ögelman, 1995). The Vela jet is connected with the pulsar, providing the loss mechanism for most of the pulsar's rotational energy, and it has high pressure of the “cocoon” of shocked jet material. On the contrary, the “jet-like” lobe in CTB 109 is not connected with 1E 2259+586 in the ROSAT image (Rho & Petre, 1997) and does not have higher pressure than elsewhere in the remnant. Therefore, this lobe may not be a supersonic beam; it is neither powered by nor related to the central pulsar. We suggest this lobe was produced by Rayleigh-Taylor instability due to a reflected shock arising from the blast wave-molecular cloud interaction.

ROSATObservations of the Supernova Remnant CTB 1

We present ROSAT PSPC observations of the supernova remnant CTB 1 (G116.9 +0.2). The remnant is detected for the first time in the X-ray region. The X-ray morphology places the remnant into the class of center-filled remnants with a centrally peaked X-ray emission profile and accompanying optical and radio shells. The emission is consistent with a thermal plasma with T = 3 × 106 K and absorption NH = 7 × 1021 cm-2. A "breakout" along the northeast rim of the remnant is coincident with the position of an X-ray pulsar. A much larger feature appears to be a partial shell which may be associated with a previous supernova remnant that swept the area around CTB 1 clean. The appearance of the remnant is most easily explained by evaporating clouds. Projection effects caused by an asymmetric remnant are discussed as another, less plausible, explanation.

X‐Ray Imaging and Spectroscopy of the Supernova Remnant CTB 109 and Its Associated Pulsar 1E 2259+586

X‐Ray Imaging and Spectroscopy of the Supernova Remnant CTB 109 and Its Associated Pulsar 1E 2259+586

Optical Imaging and Spectroscopy of the Galactic Supernova Remnants CTB 1 (G116.9+0.2), G116.5+1.1, and G114.3+0.3

Optical Imaging and Spectroscopy of the Galactic Supernova Remnants CTB 1 (G116.9+0.2), G116.5+1.1, and G114.3+0.3

Historical Supernovae and Supernova Remnants

The oldest historical supernova (SN), recorded by ancient Chinese in 14th Century B.C. on pieces of tortoise shells or bones, is identified with the aid of modern space γ-ray observations. Hard X-rays with energy up to 20 keV were observed from IC 443 by the X-ray satellite Ginga. We infer from these observations the age of IC 443 is ∼ 1000 — 1400 yrs. The result supports the hypothesis that IC 443 is the remnant of the historical SN 837 that occurred during the Tang Dynasty. The association between the supernova remnant (SNR) CTB 80 and SN 1408 has been hotly debated for about ten years and is briefly reviewed and discussed here. A new picture is presented to explain this association. High energy emission from historical SNRs can persist in a multiphase interstellar medium (ISM). As a result, the study of the relationship between SNRs and ancient guest stars has gained new vitality.

Discovery of a Candidate Isolated Neutron Star in a New Supernova Remnant Near CTB 1

We have discovered a neutron star candidate in the region near the supernova remnant CTB 1 (G116.9+0.2). The source is located near the center of a previously unknown shell of soft X-ray emission (G117.7+0.6), which is consistent with a middle-aged supernova remnant. The X-ray emission is periodic at the 99% confidence level with a period of 0.24181 s. The thermal X-ray emission is probably residual heat of formation from the cooling neutron star. We cannot entirely rule out a less likely possibility that the X-rays have an origin in the magnetosphere. A comparison of the neutron star age and temperature with cooling theories is presented.

ROSAT observations of the unusual supernova remnant CTB 80 containing the pulsar PSR 1951 + 32

view Abstract Citations (68) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ROSAT Observations of the Unusual Supernova Remnant CTB 80 Containing the Pulsar PSR 1951+32 Safi-Harb, Samar ; Ogelman, Hakki ; Finley, John P. Abstract The unusal supernova remnant CTB, 80 containing the 39.5 ms pulsar PSR 1951 + 32, has been observed with the Position Sensitive Proportional Counter (PSPC) and the High Resolution Imager (HRI) aboard ROSAT. The HRI image, centered on the pulsar, is composed of a bright compact core of approximately 1 arcminute radius containing the pulsar and a compact nebula, as well as a diffuse nebula extending approximately 5 arcminutes eastward of the pulsar. The PSPC allowed us to model the spectra of the point source, the compact nebula and the 5 arcminute diffuse nebula. For a power-law spectrum with photon index Gamma approximately 2 and an interstellar column density of NH approximately 3 x 1021/cm21 the derived luminosities are approximately 2.3 x 1033 d2.52 ergs/s from the pointlike source, approximately 3.9 x 1033 d2.52 ergs/s from the compact nebula, and approximately 1.8 x 1033 d2.52 ergs/s from the 5 arcminutes diffuse nebula. In addition, the 2 deg diameter circular field of view of the PSPC reveals a hard emission feature southeast of the pulsar with a conical geometry extending out to the edge of the detector. The spectrum from this region is well described by a two-temperature Raymond-Smith thermal plasma with an average temperature of approximately 107 K and a luminosity of approximately 1034d2.52 ergs/s. Pulsations from the 39.5 ms pulsar, PSR 1951 + 32, are detected at the 99% confidence level. The implied pulsed fration is approximately 35% with a complicated energy-dependent behavior. The compact core and the extended diffuse nebula can be explained as synchrotron radiation from the relativistic pulsar wind confined by the ram pressure of the surrounding inhomgeneous medium. The conelike feature detected southeast of PSR 1951 + 32 is consistent with emission from an optically thin SNR in the radiative cooling phase of its evolution. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175212 Bibcode: 1995ApJ...439..722S Keywords: Interstellar Matter; Pulsars; Supernova Remnants; X Ray Astronomy; Brightness; Data Reduction; Flux Density; Radio Observation; Rosat Mission; X Ray Spectra; Astrophysics; ISM: INDIVIDUAL ALPHANUMERIC: CTB 80; ISM: SUPERNOVA REMNANTS; STARS: PULSARS: INDIVIDUAL ALPHANUMERIC: PSR 1951; 32; X-RAYS: ISM full text sources ADS | data products SIMBAD (2) HEASARC (1)

CO study of the giant molecular cloud towards supernova remnant

view Abstract Citations (5) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CO Study of the Giant Molecular Cloud Towards Supernova Remnant CTB 87 Cho, Se-Hyung ; Kim, K. T. ; Fukui, Y. Abstract We present the results of CO observations of the giant molecular cloud towards supernova remnant (SNR) CTB 87. Most of the CO emission is concentrated in three clumpy regions n(H2) approximately 103 cubic centimeters, each incorporating two subclumps. Both the x-ray and radio continuum emissions from the SNR lie between the two subclumps of clumpy region A. The estimated total mass of molecular gas is 1.2x106 solar mass, similar to other sites of a massive-star formation region, where Crab-like SNR like CTB 87 can be formed. However, the line profiles, line widths and velocity structures of clumpy region A, where the SNR is projected, show a typical feature of the dense part of giant molecular clouds. Therefore, we do not find any indication of interaction of the SNR with the molecular cloud. Publication: The Astronomical Journal Pub Date: August 1994 DOI: 10.1086/117097 Bibcode: 1994AJ....108..634C Keywords: Carbon Monoxide; Molecular Clouds; Molecular Gases; Radio Emission; Star Formation; Supernova Remnants; Infrared Astronomy Satellite; Spectral Line Width; Astrophysics; SUPERNOVA REMNANTS; ISM: CLOUDS; SUPERNOVAE: INDIVIDUAL: CTB 87 full text sources ADS | data products SIMBAD (4)

Interaction between the Supernova Remnant CTB 80 and the Ambient Interstellar Medium: H i and CO Observations

view Abstract Citations (22) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interaction between the Supernova Remnant CTB 80 and the Ambient Interstellar Medium: H i and CO Observations Koo, Bon-Chul ; Yun, Min-Su ; Ho, Paul T. P. ; Lee, Youngung Abstract We performed VLA H I 21 cm line and 12CO J = 1-0 line observations of the old supernova remnant (SNR) CTB 80. The clumpy structure of the fast, υexp ∼ 72 km s-1, expanding SNR shell detected by Koo et al. (1990) is found to be due to fast-moving H I clumps, which have a dense, nH ∼ 100 cm-3, core surrounded by a relatively diffuse envelope. These clumps are most likely the preexisting "cold clouds" in the ambient interstellar medium (ISM) that had been swept-up and accelerated by the SN blast wave. CO observations show that most of the molecular gas in this region is confined into two large filamentary clouds. There is no certain evidence for the interaction between the SNR and the molecular cloud. By analyzing the Arecibo H I data of Koo et al., we found that the ISM around CTB 80 is far from being uniform and homogeneous. Instead, it seems to be composed of a large cold cloud, a warm neutral medium pervaded by small cold clouds, and a tenuous hot tunnel, which is close to the McKee & Ostriker's three-phase ISM model. We discuss how the ambient ISM shaped the morphology of CTB 80 in H I, infrared, and radio continuum. Publication: The Astrophysical Journal Pub Date: November 1993 DOI: 10.1086/173303 Bibcode: 1993ApJ...417..196K Keywords: ISM: GENERAL; ISM: INDIVIDUAL ALPHANUMERIC: CTB 80; ISM: SUPERNOVA REMNANTS; RADIO LINES: ISM full text sources ADS | data products SIMBAD (8)

The semicircular shell of CTB 109

The radio and X-ray images of the supernova remnant CTB 109 have the morphology of a semicircular shell. It is shown that such a structure is a natural result of a supernova explosion that occurred 3,000 yr ago near an interface between the diffuse interstellar medium and a dense molecular cloud. The calculated X-ray, infrared, and radio fluxes agree fairly well with the observed values.

Detection of an expanding H I shell in the old supernova remnant CTB 80

An expanding H I shell associated with the SNR CTB 80 has been detected. The expansion velocity and size indicate that the H I shell is an SNR shell. The center, shape, and mass of the shell match those of the IR shell detected by Fesen et al. (1988), supporting the idea that the pulsar has caught up with the SW portion of the shell and has produced its peculiar radio morphology. The shell's large 60 to 100 micron ratio implies that the larger grains may have been preferentially destroyed by the shock.

Optical observations of the morphology and kinematics of the compact core of the peculiar supernova remnant CTB 80

Optical observations of the morphology and kinematics of the compact core of the peculiar supernova remnant CTB 80